E 

171 

S66k 

no. 12 

c.2 

MHT 

Feedback 

Mechanisms 

IN THE HISTORICAL 

COLLECTIONS OF THE 

NATIONAL MUSEUM OF 

HISTORY AND TECHNOLOGY 

By Otto Mayr 

SMITHSONIAN INSTITUTION PRESS 

CITY OF WASHINGTON 

1971 



FEEDBACK MECHANISMS 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY NUMBER 12 

Feedback Mechanisms 

IN THE HISTORICAL COLLECTIONS OF THE 

NATIONAL MUSEUM OF HISTORY AND TECHNOLOGY 

By Otto Mayr 

ISSUED 

w 

SMITHSONIAN INSTITUTION PRESS 

CITY OF WASHINGTON 

1971 
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For sale by the Superintendent of Documents, U.S. Government Printing Office 

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TO MY FATHER 
Acknowledgments 

This book could not have been prepared without the support of a great 

many members of the staff of the National Museum of History and Technology. 

To begin with, I received indispensable help from all the curators in whose collections I found feedback mechanisms—as well as from those in whose collections 

I searched in vain. I hope to be forgiven for not naming all these curators individually: the list would be too long. 

Specifically, I am indebted to Virginia Beets, Silvio A. Bedini, and Robert G. 

Tillotson, of the Office of the Director, for help in administrative problems; to 

Jack Goodwin and Charles G. Berger, of the Library, for miracles in procuring 

needed books; and to Henry A. Alexander and Richard B. Farrar, of the Photographic Services Division, for producing the many excellent photos so quickly 

in spite of a heavy workload. 

A few have contributed even more directly. Robert P. Multhauf, while 

Director of the Museum, originally suggested the project and arranged the means 

for its accomplishment. Robert M. Vogel, Curator of Heavy Machinery and Civil 

Engineering, carefully read the manuscript and suggested a number of corrections. Part of the photographs were taken by Charles L. Granquist, of the Division of Mechanical and Civil Engineering; his photographs are identified by the 

initials CLG. The manuscript was typed by Mrs. Catherine St. C. Scott and Mrs. 

Eva Y. Elliott. Also a tribute is due to my wife Louise, who has endured the 

hardships involved in projects such as this, as always, with humor and grace. 
Preface 

Among the seemingly endless variety of machinery that might be listed 

under the heading automatic control, feedback mechanisms stand out as a distinct group because, although differing widely in outward appearance, they all 

function according to a single principle. The significance of the principle of feedback is all the greater as it is not limited to technology. Since 1948, when Norbert 

Wiener adopted it as one of the unifying concepts of the new science of cybernetics, it has come to be regarded as an invaluable tool in such diverse disciplines 

as biology, economics, and sociology. 

The interdisciplinary validity, for which the concept is admired, has been 

anticipated in technology at a much earlier period, when feedback was employed 

to solve problems of control, for example, in the mechanical, hydraulic, thermal, 

and electrical media. It might be of interest therefore to outline the history of 

feedback control by means of cataloging—systematically and in chronological 

order—the historical feedback devices contained in the collections of one of the 

world's great technological museums, the National Museum of History and Technology of the Smithsonian Institution. 

This catalog is limited to feedback mechanisms; other forms of automatic 

control, for example open-loop and programmed control, are disregarded without 

further explanation. The material to be described has definite boundaries also 

in space and time. In space, it is limited to the collections of the Smithsonian 

Institution's National Museum of History and Technology, collections which are 

partly exhibited and partly stored in various storage spaces; in time, it is limited 

to items that can be described, at least by lenient standards, as historical. How 

old must an item be to qualify? Objects that are being mass-produced and commercially marketed at the present are clearly inadmissible. On the other hand, 

certain developments—such as in the field of computers—may have to be considered historical even if they have occurred relatively recently. A cutoff date 

convenient for our purposes then seems to be the end of World War II, a date 

we will disregard, however, when appropriate. 

In an effort to make visible the more important lines of development of historical feedback devices, the material is presented in the form of a continuous 

narrative. This has led to an arrangement which is pragmatic rather than strictly 

systematic. Sometimes feedback devices are classified according to the controlled 

variable (e.g., speed, pressure, temperature) ; sometimes it has been more expedient to list them under the branch of technology where they were employed 

(e.g., automotive or textile). The necessary cross-references will be provided by 

the index. 

To describe individual objects, we have to consider two kinds of information: First, information concerning its external history has been presented, at 
Viii SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

least in concise form, as far as available, but the scope of this catalog did not 

permit the additional research required to close numerous gaps. Second, complicated technical objects such as we deal with here require technical description. 

Readers who may feel that too much space is devoted to purely technical matters 

should take into account that the historical significance of the objects cataloged 

here lies precisely in the technological ideas represented by them. 

The sources used and references to additional material have been indicated 

as usual in footnotes. Further information may be found at two general sources. 

One is the archives of the individual divisions of the Museum. For access to these, 

researchers should consult the respective curators directly. The other concerns 

the patent models which form a considerable part of this material. The patented 

inventions are described in detail in the patent specifications, and further material may be found in the case files of the United States Patent Office and the 

National Archives. 

The imaginative reader may miss in this catalog some items that he would 

have expected to find. This may be due to any one of three reasons: his definition 

of feedback may differ from the author's; the item may have been accidentally 

overlooked; or the item may actually not be represented in the collection. With 

regard to definition, the following practice has been followed. At the start, feedback was defined once and for all; thereafter only devices thus defined were 

accepted, others were disregarded without discussion. In a few cases, where whole 

groups of relevant objects were excluded for special reasons, as in the cases of 

safety valves, float-feed carburetors, or electronic devices, this was explained at 

the appropriate places. Second, feedback devices are rendered elusive by the interdisciplinary nature of the concept. Feedback is employed in many disguises, and 

it is represented in practically all divisions of the Museum. In spite of a serious 

effort to make this catalog exhaustive, it is only too possible that one or another 

item may have escaped the cataloging. Finally, the collection itself must not be 

expected to be complete. Feedback devices usually are inconspicuously attached 

to some larger machine or process which they have the function to regulate. 

Having rarely been collected for their own sake, they are represented unevenly. 

Our collection, for example, contains more than a hundred speed governors but 

only a few historical temperature controllers. All items listed have actually been 

identified in the collections. 

Each individual object is identified by two numbers, the catalog number 

(NMHT) and the accession number. The catalog numbers are assigned individually to specimens by each particular Museum division according to systems 

which vary between different divisions. The accession numbers indicate the accession files in the Registrar's office and are uniform for all of the Museum. The 

accession files contain all correspondence and other documents relating to the 

transaction by which the specimen reached the Museum, often containing valuable detailed information. A single accession number may refer to more than one 

object. As a help in finding the objects cataloged herein, we have included a 

Location Guide at the back of the book. 
Contents 

Page 

ACKNOWLEDGMENTS vi 

PREFACE vii 

1. INTRODUCTION 1 

Definition of Feedback Control 1 

T h e Origins of Feedback Control 2 

2. STEAM ENGINE GOVERNORS 4 

T h e Classical Centrifugal Governor of James Watt 4 

Automatic Cutoff Control 7 

Charles T. Porter's Loaded Governor 13 

Mid-Nineteenth Century Patent Models 16 

Valve-Mounted Governors 27 

Shaft Governors 33 

3. SPEED REGULATION OF OTHER PRIME MOVERS 39 

Governors of Waterwheels and Turbines 39 

Mechanical Servo Governors 39 

Hydraulic Servo Governors 43 

Speed Regulation of Steam Turbines 45 

Speed Regulation of Internal Combustion Engines 49 

4. FRICTION GOVERNORS 64 

Chronographs 64 

Phonographs 66 

Telegraphs 69 

5. AUTOMATIC CONTROL OF STEAM BOILERS 70 

6. PRESSURE REGULATORS 73 

7. TEMPERATURE CONTROL 77 

8. FEEDBACK CONTROL ON TEXTILE MACHINERY 79 

9. FEEDBACK CONTROL ON LAND VEHICLES 83 

Railway Technology 83 

Steam Automobiles 83 

Speed Governors on Trucks and Tractors 86 

Automobile Thermostats 88 

Float Feed Carburetors 89 

Pressure Control by Relief Valves 90 

Voltage and Current Regulation 90 

Power Steering 92 
X SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Page 

10. FEEDBACK CONTROL ON WATERCRAFT 93 

Servo Steering Devices "^ 

Feedback Control in Torpedoes °6 

T h e Whitehead and the Bliss-Leavitt Torpedoes 96 

T h e Howell Torpedo ^" 

Other Torpedoes in the Museum's Collection 100 

Gyroscopic Compasses 101 

T h e Sperry Gyropilot 102 

11. FEEDBACK IN ELECTRICAL TECHNOLOGY 105 

T h e Regulation of Electric Arc Lamps 105 

Early Arc Lamps 105 

Systems of Arc Lighting 107 

Miscellaneous Arc Lamp Regulators 117 

Feedback Control on Electric Machines 119 

Constant Current Regulation in Arc Lighting Systems 119 

Speed Control of Motors 123 

12. ELECTRONIC COMPUTERS 125 

Analog Computer for Process Control Analysis 125 

Digital Process Control Computer 126 

LOCATION GUIDE 127 

INDEX 131 
CHAPTER 1 

Introduction 

Definition of Feedback Control 

The objects cataloged here may be referred 

to as governors, regulators, servomotors, or by 

a variety of other terms, and they may differ 

greatly in outward appearance and practical 

application. The only thing they have in common is that their operation is based on the 

principle of feedback. Feedback has been described by Norbert Wiener as "the property of 

being able to adjust future conduct by past 

performance."x The American Institute of 

Electrical Engineers, more formally, has given 

this definition: "A Feedback Control System 

is a control system which tends to maintain a 

prescribed relationship of one system variable 

to another by comparing functions of these 

variables and using the difference as a means 

of control."

 2 We shall now try to rephrase 

these statements in order to obtain workable 

criteria for identifying feedback devices. 

The first characteristic of feedback control 

is its purpose. Feedback devices have the function of automatically carrying out a command, 

that is, to control a machine or process in 

such manner that a controlled variable is 

maintained at equal level with a command 

variable coming from a higher authority, 

usually a human operator. For example, a 

home thermostat has the task of making the 

room temperature equal to a desired value 

1. Norbert Wiener, The Human Use of Human 

Beings: Cybernetics and Society, 2nd edition (Garden 

City, New York, 1954), p. 33. 

2. A.I.E.E. Committee Report, "Proposed Symbols 

and Terms for Feedback Control Systems," Electrical 

Engineering 70 (1951):905-909. 

represented by a dial setting. An automobile 

power steering unit must point the front 

wheels into the direction indicated by the 

steering wheel. A steam engine governor has 

to maintain the engine speed at a value set 

by the operator. Feedback devices will carry 

out such commands in spite of external disturbances, such as, in the case of the thermostat, changing outside temperature; in the 

case of power steering, varying vehicle speed 

and road surface; or, for the steam engine, 

changes in steam conditions and load. The 

command, or desired value, is commonly called 

input (on the thermostat it is the dial setting; 

in power steering, the angular position of the 

steering wheel). The actual value of the controlled variable is the output (actual room 

temperature, or front wheel position). 

Second, feedback devices act in a cause-andeffect chain that forms a closed loop. If, for 

example, in the home temperature control 

system, due to an outside temperature decrease, 

the actual room temperature drops below the 

desired value, the thermostat will turn on the 

furnace, adding heat to the room until the difference between actual and desired temperature has disappeared. The effect of the 

weather change then travels around the whole 

loop: through the response of the temperaturesensing element of the thermostat, the room 

temperature drop actuates the furnace. This, 

by causing a heat addition and hence a temperature rise in the room, reverses the response 

of the thermostat. After traveling once around 

the loop, the original effect returns with the 

opposite sign. Starting as a temperature drop, 

it returns as a temperature increase. This 

;$MI1HSU.J;AI 

INSTITUTION JUL -: u !• j / 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

change of sign is the basis of the stability of 

feedback control (often called, therefore, 

more precisely negative feedback). Closedloop systems lacking this change of sign, that 

is, systems with positive feedback, are unstable. They are equivalent to what is commonly known as the vicious circle. A block 

diagram of a feedback control system in 

general is shown in Figure 1. 

Command 

input 

Reference Actuating 

input signal 

Reference 

selector 

Fe< 

\ic • 

1 

>dback— 

J 

Dynamic 

unit 

Feedback 

element 

Desired 

output 

FIGURE 1.—Block diagram of a feedback control system. Reprinted from DAzzo and Houpis, Feedback 

Control System Analysis and Synthesis (New York, 

I960), p. 2. Used with permission of McGraw-Hill Book 

Company. 

In addition to the two criteria obtained so 

far, we need, however, a third criterion. In 

nature as well as in technology, a variety of 

systems can be found with the property of 

self-regulation: such systems display a certain 

measure of stability under the influence of external disturbances. Mathematically, such 

systems can be described in terms of closed 

loops with negative feedback. Genuine feedback control systems are distinguished from 

these by that they incorporate a physically 

distinct element with only the function of 

sensing the output, that is, generating a 

feedback signal. This signal is then sent to 

a comparator element (sometimes difficult to 

identify), in order to be compared with the 

command signal. 

The Origins of Feedback Control 

The oldest feedback device—the float 

valve—dates from antiquity.3 Vitruvius reports 

3. For a detailed study of the early history of feedback control, see Otto Mayr, The Origins of Feedback 

Control (Cambridge, Massachusetts, 1970). 

M ^oaaat ^=^• 0 W 

FIGURE 2.—Water clock of Ktesibios (1st half third 

century B.C.) as reconstructed by Hermann Diels. Reprinted from Hermann Diels, Antike Technik, 3rd 

edition (Leipzig, 1924), fig. 71. 

that Ktesibios of Alexandria (first half of the 

third century B.C.), a mechanician at the 

court of King Ptolemy II Philadelphus, employed in one of his water clocks a levelregulating device (Figure 2) very similar to 

the float valve in today's automobile carburetor. Three centuries later, his fellow townsman, Heron of Alexandria, in his book 

Pneumatica, described several examples of 

another type of float valve equally familiar 

to us, the level regulator in WC water tanks. 

It should not surprise us that inventions of 

such refinement occurred at that particular 

place and time. The period between the lives 

of Ktesibios and Heron witnessed the culmination of Greek natural science and Roman 

technology, and Alexandria was then the intellectual center of the world. Knowledge of 

Alexandrian technology was inherited by the 
NUMBER 12 3 

Islamic world. Arabic builders of water clocks 

employed float valves as late as 1206. In 

Europe, however, this invention remained unknown until the eighteenth century when float 

valves were reinvented in England to regulate 

the levels in domestic water tanks and steam 

boilers. 

It was also England where the first feedback 

device of purely European origin was invented. In about 1620 Cornelis Drebbel, a 

Dutch engineer in the service of King James 

I, constructed a chemical laboratory furnace 

with an automatic temperature regulator 

(Figure 88), an invention little noticed by 

his contemporaries. In the following two 

centuries, this invention matured gradually. 

It was presented to a wider public in 1839, 

when Andrew Ure in his "Dictionary of Arts" 

described several versions of a bimetallic temperature regulator which he termed thermostat. 

Another early, if simple, feedback device 

is the safety valve of the classical steam boiler. 

T h e claim that it employs feedback rests on 

this argument: Consisting of a weight-loaded 

valve in the boiler wall, it compares the actual 

pressure (force on the inside area of the valve) 

with the desired pressure (weight). If the 

actual pressure exceeds the desired pressure, 

the valve will release steam until equilibrium 

is restored. Its inventor, Denis Papin, had 

originally intended it as a pressure regulator 

for his pressure cooker of 1681, but within 

only a few decades it became a standard accessory for steam boilers. 

Professional groups with remarkable influence upon eighteenth-century technology 

were the English and Scottish millwrights. 

Not only did they produce a disproportionately high number of great engineers, but 

among their many bold and ingenious inventions are several mechanisms employing feedback. Th e earliest of these is the fantail 

patented by Edmund Lee in 1745, a small 

auxiliary wind wheel attached to the cap of 

a windmill at right angles to the main wheel, 

with the function of always keeping the mill 

directed into the wind. In time the fantail 

became a characteristic feature of British windmills. A number of their inventions were 

devoted to the problem of speed regulation. 

A rather simple solution was found in mounting the windmill sails flexibly, so that they 

could recoil under a strong wind, thus 

presenting less area. Such schemes were proposed by E. Lee (1745), A. Meikle (1772), 

J. Barber (1773), B. Heame (1787), and 

finally, most successfully, by W. Cubitt in 

1807. Genuine feedback control of speed, in 

contrast to these, would require some distinct 

speed-sensing device, such as a centrifugal fan 

blowing air against a flexible baffle which 

would be deflected through a distance proportional to fan speed (R. Hilton, 1787), 

or the simpler and more successful centrifugal 

pendulum. A first application of the centrifugal pendulum on windmills (the "lift tenter") 

did not involve speed control; its only purpose was to maintain a constantly fine quality 

of flour by counteracting a natural tendency 

of the millstones to separate at higher speeds. 

English patents of 1787 and 1789 also describe 

genuine feedback systems, where centrifugal 

pendulums control the speed of windmills by 

directly adjusting the sail area. Such arrangements, however, never became popular. In 

general, the millwrights' discovery of the 

possibilities of the centrifugal pendulum had 

its greatest success not in their own limited 

field but in connection with James Watt's new 

steam engine. 
CHAPTE R 2 

Steam Engine Governors 

The Classical Centrifugal Governor of 

James Watt 

The Newcomen steam engine as well as 

the earlier versions of James Watt's engine 

worked with a purely reciprocal power stroke, 

which was adequate for pumping water out 

of coal mines but a severe limitation in finding 

new applications for the engine. In order to 

make the steam engine marketable as a prime 

mover for mills, James Watt and Matthew 

Boulton developed a new rotary steam engine, 

the first unit of which was sold in 1783. As 

a public demonstration of the capabilities of 

this engine, they next took part in building 

in London a large progressive steam mill, the 

Albion Mill. This mill apparently forms the 

connection through which the millwrights' 

invention of the centrifugal pendulum was 

passed on to the steam engine builders. 

Supervisor of construction and, later, of operation of the Albion Mill was the 23-year-old 

John Rennie, who had served his apprenticeship under Andrew Meikle, a noted Scottish 

millwright, and who was to become famous 

himself as a builder of bridges. At the Albion 

Mill, Matthew Boulton saw for the first time 

the "lift tenter," which he described in a 

letter to James Watt in May 1788. It seems 

that this suggestion fell upon fertile ground; 

the earliest known references to the centrifugal 

governor among the Boulton & Watt papers 

date from November 1788, half a year after 

this letter. Little later, the first governor was 

in operation on the famous "Lap" engine 

(the original is at the Science Museum in 

London) ; our Museum exhibits a quarterscale model (Figure 3) of the "Lap" engine 

(NMHT 323494; Accession 249295; built in 

1963 by C. A. Mills, Ruislip, England). Within 

a few years, the centrifugal governor became 

a standard component of the steam engine. 

James Watt, incidentally, never took out a 

patent for his governor; in his judgment it 

was not a new invention but merely an adaptation of the millwrights' lift tenter.4 

The function of the governor is to maintain a constant speed in spite of external 

disturbances such as changes in load or steam 

pressure. Two massive metal spheres ("flyballs") on long metal rods, suspended from 

a common pivot point and rotating at a speed 

proportional to that of the engine, swing outward with rising speed. Appropriate mechanical linkages connect the pendulum with the 

steam inlet valve in such a way that the steam 

supply is throttled with rising speed, and increased with falling speed, so that, under a 

given load condition, the engine will reach a 

certain equilibrium of speed. In equilibrium, the opening of the valve—as determined 

by the centrifugal displacement of the flyweights—is just sufficient to admit the amount 

of steam required to maintain this speed. If 

a load increase causes the speed to drop, the 

action of the flyballs will increase the valve 

opening by an amount proportional to the 

speed change, with the result of bringing the 

speed back toward the equilibrium valve. 

A particular type of feedback control represented by the simple centrifugal governor 

is called "proportional control." Its mode of 

4. H. W. Dickinson and Rhys Jenkins, James Watt 

and the Steam Engine (Oxford, 1927), pp. 220-223. 
NUMBER 12 

FIGURE 3.—Model of James Watt's "Lap" Engine of 1788. The detail view shows the centrifugal 

governor with its drive and its connections to the steam valve (top left). (NMHT 323494. 

Smithsonian photo P-64116.) 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

operation involves an operational shortcoming, illustrated by the example of the governor. Upon a load change, the corrective 

action—namely, the increase in steam flow— 

is directly caused by the drop in speed, and 

it could not be maintained without a lasting 

speed deviation. In proportional control systems, this error can never be completely 

eliminated, because the control action is 

based on it, although for sensitive systems it 

may be very small. The problem of the "proportional offset" has some historical significance. In the nineteenth century, a good 

deal of inventive effort was devoted to the 

search for "isochronous" or "astatic" governors that would be free from this defect, and 

a large amount of theoretical literature discussed the feasibility of such governors. 

In Watt's original arrangement, the centrifugal pendulum was a considerable distance 

removed from the throttle valve, which necessitated linkages of sometimes great length. 

Since the pendulum rotated at a very low 

speed the necessary centrifugal force had to 

be generated by making the flyballs very 

heavy, which had the unwanted side effect of 

making the system slow to respond to changes 

in speed. The restituting force—that is, the 

force which returned the pendulum to its 

rest position—was provided by the weight of 

the flyballs alone. This arrangement remained 

in use for roughly half a century. 

The oldest centrifugal governor in our collections belongs to the steam engine built by 

Thomas Holloway in 1819, believed to be 

the oldest American-built stationary steam 

engine extant (NMHT 319405; Accession 

239089). The 10-hp condensing engine served 

in a Philadelphia brewery until 1872. The 

machine is not fully preserved, but the large 

governor (48" high, 32" spread) is complete 

(Figure 4). Driven by rope and pulley, it 

was mounted on the floor above the engine, 

as shown on a small model built in 1964 in 

the Museum (NMHT 323716; Accession 

252392). As in James Watt's original design, 

the centrifugal motion of the flyballs is transmitted to the throttle valve by a lazy-tongs 

linkage. The governor is driven by a step 

pulley with three different diameters. This reFIGURE 4.—Steam engine built in 1819 by John Holloway of Philadelphia. In the arrangement shown, the 

governor is not connected to the engine. Originally it 

was installed on the floor above the engine. (NMHT 

319405. Smithsonian photo 72169.) 

sembles the arrangement on a 1798 drawing 

from the Boulton k Watt shops and is meant 

to be a provision for changing the controlled 

speed of the engine (actually, it changes 

mainly the proportional sensitivity, not the 

reference level of speed) .

5 

Almost as old, but considerably better preserved, is Mathias W. Baldwin's large steam 

engine of 1829, built by the famous Philadel5. Ibid., pi. 81. 
NUMBER 12 

drive train and removed from the bystander, 

had to be mounted a great distance away 

from the throttle valve, connected by linkages hidden under the frame of the machine. 

Later in the career of the engine, the original 

governor was replaced by a spring-loaded 

governor forming an integral unit with the 

throttle valve. Th e present arrangement is a 

conjectural reconstruction of the original 

governor, executed in the Museum's shops in 

1965. 

Further examples of similar governors of 

traditional design are, briefly, those of the 

steam engine model of 1838 marked "Bancks, 

441 Strand, London, fecit" (NMH T 316139; 

Accession 225132), and the cutaway engine 

model (Figure 6), used for classroom demonstration at Johns Hopkins University (NMH T 

322259; Accession 246694; marked "P. D. 

Lugenbeel, 1860"). Also probably used for 

purposes of demonstration was the simple 

kinematic model of a centrifugal pendulum 

(NMH T 261315; Accession 51116; unmarked; steel, 14"X10"). 

FIGURE 5.—Governor of steam engine built by Mathias 

W. Baldwin in Philadelphia, 1829. (NMHT 314822. 

Smithsonian photo 72173.) 

phia locomotive manufacturer to provide 

power for his own machine shop (NMH T 

314822; Accession 210004). By employing an 

unusual yoke-type connecting rod he was able 

to reduce the engine size substantially. Th e 

governor (Figure 5), otherwise conventional, 

is linked to the throttle valve by a peculiar 

forked bar straddling the engine shaft.6 

A good illustration of the traditional arrangement of the centrifugal governor is 

given by the Harlan 8c Hollingsworth 40-hp 

beam engine, built in 1850, and used from 

1851 to 1927 to operate a Charleston, S. C, 

railroad shop (NMH T 314791; Accession 

209703). Th e large slow-moving governor, 

requiring a place at once accessible to the 

6. Early Engineering Reminiscences (1815-1840) of 

George Escol Sellers, ed. Eugene S. Ferguson, United 

States National Museum Bulletin 238 (Washington, 

D.C, 1965), pp. 181-182, fig. 78. 

Automatic Cutoff Control 

In the middle of the nineteenth century, 

after Watt's governor had remained essentially unchanged for the first half century of 

its existence, the question of steam engine 

regulation was reexamined. In hundreds of 

new patents, modifications of every feature 

of the governor were suggested. Th e first improvement of importance, however, did not 

affect the governor itself but its final control 

element, the valve gear. Traditionally the 

governor regulated the engine speed by adjusting a throttle valve that changed the flow 

rate of the live steam entering the engine. 

T h e throttle valve thus purposely caused a 

pressure drop, that is, a loss in available 

energy. Th e inefficiency of this method was 

eventually recognized, and inventors explored 

a more economic alternative; instead of supplying the steam continuously at reduced 

pressure, it was suggested that it be supplied 

at full pressure, intermittently, during only 

part of the stroke. Th e first step in this de-
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 6.—Cutaway model of a conventional nineteenth-century steam engine showing the 

governor linked to a throttling valve mounted directly on the valve chest. (NMHT 322259. 

Smithsonian photo P-63299-A.) 

velopment was to construct valve gear that 

permitted the supply of steam to the cylinder 

to be cut off at some point before the end of 

the work stroke and to make this point variable. At low load the point of cutoff was 

adjusted to occur sooner than under heavy 

load. Since the steam in the cylinder was 

permitted to expand between cutoff and exhaust, it could deliver more work. The second step was to make the point of cutoff 

automatically adjustable by the governor. 

Solutions to this problem were proposed in 

numerous schemes by such inventors as 

Zachariah Allen in 1834, and Horatio Allen, 

J. J. Meyer, and F. E. Sickels, all in 1841.7 

The first truly successful automatic cutoff 

valve gear was built by George Henry Corliss 

(1817-1888) of Providence, R. I., in 1848. 

The application for his basic patent (U.S. 

Patent 6162 of 10 March 1849) was accompanied by a patent model, now in our 

Museum, that was patterned after a walking 

beam engine which he had actually built in 

1848 for the Wamsutta Mills in New Bedford, Mass. (NMHT 308646; Accession 

89797; walnut, 24"X6"X22").8 Figure 7 

shows the steam cylinder on the right with 

the horizontal stems of the inlet and exhaust 

valves, both at top and bottom; in the center 

is the governor, underneath it is the detaching mechanism, and farther below is the 

wrist plate which is driven in a rocking motion by an eccentric on the crankshaft (left). 

Like all successful early cutoff mechanisms, 

the Corliss arrangement is a detachable (also 

termed releasing or drop-off) cutoff gear—in 

contrast to the more recent positive cutoff, as 

on the Porter-Allen engine—and it affects 

only the inlet valves, while the cycle of the 

exhaust valves is fixed. The governor is not 

positively connected with the inlet valves; 

but by means of an ingenious trigger mechanism it can disconnect the linkage that 

opens the inlet valve at an earlier or later 

7. Conrad Matschoss, Die Entwicklung der Dampfmaschine, 2 vols. (Berlin, 1908), 1:466-473; II: 1-9. 

8. Frank A. Taylor, Catalogue of the Mechanical 

Collections of the Division of Engineering, United 

States National Museum, Smithsonian Institution, 

United States National Museum Bulletin 173 (Washington, D.C, 1939), pp. 71-72, pi. 17:2. 
NUMBER 12 

FIGURE 7.—George H. Corliss's patent model of 1849 describing his basic patent of automatic 

cutoff control. (NMHT 308646. Smithsonian photo 31694.) 

point during the engine stroke. If the engine 

runs too fast, the governor releases the inlet 

valve earlier thus admitting less steam; if the 

engine runs too slowly, say due to an increase in load, conversely more steam is admitted. 

Subsequently Corliss took out numerous 

further patents on releasing mechanisms 

which varied only in detail. Their basic 

principle can be studied best on the model 

of a Corliss cutoff valve with governor (Figure 8), dating probably from the 1860s 

(NMHT 309817; Accession 109438; unmarked; bronze and steel, 24"X9"X17").9 

The exceptionally well-made operational 

model, apparently not a patent model, was 

presented in 1930 by the Franklin Machine 

Company, Providence, R.I., a successor to the 

former Corliss Engine Works. Details on 

purpose and history of the model are unknown. Perhaps it was used in sales or in 

patent litigation as an illustration of the 

Corliss automatic cutoff control. (It seems to 

form a set with another model representing 

a thoroughly conventional throttle valve governor: NMHT 309818; Accession 190438; 

Figure 9) .

10

 Figure 8 shows in the middle 

the crank-operated governor, on the far left 

the slide valve (in closed position), to its 

right a dashpot, and in the middle below 

the governor the releasing mechanism. The 

slide valve is connected with a coil spring 

hidden underneath the frame, which on release closes the valve. The dashpot softens 

9. Ibid., pp. 74-75. 10. Ibid., p. 79 
10 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 8.—Model demonstrating automatic cutoff control, probably made at the Corliss Engine 

Works. (NMHT 309817. Smithsonian photo 44533-B.) 

the impact of this motion. Slightly to the 

right of the center is a block which is kept 

in a horizontal reciprocating sliding motion 

by the eccentric (top) through the linkages 

on the far right. Pressed upward by a leaf 

spring, the horizontal rod (bottom center) 

latches from below into the sliding block, 

transmitting the reciprocating motion to the 

slide valve. Th e governor is equipped to cut 

this motion of the valve short. When with 

increasing speed the arms of the pendulum 

rise, the inclined block under the governor 

slides downward in proportion, entering the 

path of a cam on the reciprocating connecting rod. As the cam strikes the inclined 

block, it is pushed downward, disengaging 

from the sliding block, thus cutting short the 

travel of the slide valve. Th e farther the inclined block extends downward, the earlier 

the moment of cutoff will occur, accordingly 

admitting less steam to the cylinder and decelerating the engine. 

From the great numbe r of automatic cutoff mechanisms that Corliss had invented and 

patented, a standard arrangement finally 

emerged which, from the last quarter of the 

nineteenth century on, was adopted by many 

American steam engine builders. In our 

Museum this is represented, besides a number of engine models, by a full-scale steam 

engine. 

Built around 1885 by Jacob Naylor at the 

"People's Works " in Philadelphia, this horizontal engine (Figure 10) served as the 

prime mover for a school machine shop 

(NMH T 314818; Accession 210004; about 50 

h p at 60 r.p.m. and 75 p.s.i.). Still a lowspeed engine, betrayed by the large size of 

the conventional governor (each pendulum 

arm is two feet long) , it is equipped with 

Corliss cutoff gear of late design, where the 

original sliding blocks have been replaced by 

rotary knockoff cams concentric with the 

steam valve spindles. In the usual fashion, 
NUMBER 12 11 

FIGURE 9.—Model demonstrating conventional throttling control, probably made at the Corliss Engine 

Works. (NMHT 309818. Smithsonian photo 44576.) 

the cutoff gear is located on the side of the 

engine cylinder (Figure 10) . Th e four valves, 

all of rotary design, are actuated by the circular wrist plate, which is maintained in a 

rocking motion by the eccentric through a 

horizontal connecting rod. Th e exhaust 

valves at the bottom of the cylinder are positively connected with the wrist plate, while 

the inlet valves are actuated only indirectly 

through the releasing cutoff mechanism. Th e 

two conspicuous dashpots below have the function of cushioning the closing movement of 

the inlet valves.11 

Further examples of Corliss cutoff control 

are the following engine models: 

1. Model of a horizontal Corliss mill engine 

(NMH T 327675; Accession 268278; 

bronze and steel, 4H/ 2 "X16"X16"), built 

in the 1870s at the Corliss Engine Works 

for purposes of demonstration and promotion. It is equipped with a fully operational governor-controlled cutoff with 

crab-claw releasing gear. 

2. Model of a horizontal Reynolds-Corliss 

engine as manufactured in the 1890s by 

the Edw. P. Allis Co. of Milwaukee, built 

around 1900 by Howell M. Winslow 

(NMH T 311991; Accession 157370; scale 

1"=1'). 

3. Model of an unspecified horizontal Corliss engine (NMH T 329211; Accession 

279374; overall size 19"x38"X23i/ 2 " ; 

marked "Built by Harry H. Catching, 

Lexington, Ky., 1958: A Hobby Project"). Governor and automatic cutoff 

gear are fully operational. 

4. Model of a large Corliss double pumping 

engine of 1870, a forerunner of the famous Centennial engine of 1876.12

 Th e 

model was reportedly built at the Corliss 

Engine Works (NMH T 309820; Accession 109438; scale 1"=1'). Each side of 

the engine is controlled by a separate 

governor, acting on its own cutoff gear. 

As engines equipped with automatic cutoff control were 30% to 50% more efficient 

than comparable conventional ones, Corliss's 

patents proved to be extremely lucrative. 

They were promptly contested by the steam 

engine builders, Thurston, Greene & Co., also 

of Providence, Rhode Island, who had acquired the rights to F. E. Sickels's patents, 

and who involved Corliss in an extended 

suit of patent litigation. A courtroom exhibit 

(Figure 11) of Corliss's opponents is the 

model of a Greene automatic cutoff engine 

of 1857 (NMH T 316013; Accession 223475; 

37i/ 2 "X1734"X 293^"; 6" stroke; brass and 

steel). It bears a brass plate reading: "i/2 H p 

model of Greene steam engine built by Ben11. Robert Henry Thurston, A History of the 

Growth of the Steam Engine, 2nd edition (New York, 

1884), pp. 319-321. 

12. Taylor, Catalogue of Mechanical Collections, 

pp. 75-76, pi. 18:1. 
12 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 10.—Corliss-type steam engine built about 1885 by Jacob Naylor at the "People's Works" 

in Philadelphia. The photograph shows the connections between the governor and the releasing 

cutoff gear mounted to the side of the cylinder. (NMHT 314818. Smithsonian photo 72170.) 
NUMBER 12 13 

FIGURE 11.—Model of a Greene steam engine used as a courtroom exhibit in patent litigation 

between Corliss and Greene, 1857. (NMHT 316013. Smithsonian photo 45519-A.) 

jamin Francis Thurston, Patent Att'y 1829-

1890. Used to familiarize himself with all 

technical details involved in the so-called 

Corliss Steam Engine Cutoff Cases." Noble 

T. Greene had in 1855 introduced an automatic cutoff gear similar in effect to that of 

Corliss but different in the mechanical execution. B. F. Thurston represented Greene in 

the ensuing protracted and costly litigation 

which ended with an injunction against the 

Greene engine effective up to 1869.13 

An NMHT exhibit label describes the operation of the Greene cutoff as follows: 

In Greene's engine, latches on a sliding bar driven by 

the steam eccentric opened the steam valves as the bar 

moved to and fro. The latches had a slight vertical 

movement, controlled by the governor; the higher the 

latches, the longer they held the valves open. A separate eccentric drove the exhaust valves so that the 

steam eccentric could be set to allow cutoff almost to 

the end of the stroke. (With a single eccentric, cutoff cannot occur after about half stroke). 

The governor on this model was reconstructed in the 1930s at the Brown University Machine Shop under supervision of 

Professor Wm. Kenerson. 

Charles T. Porter's Loaded Governor 

The invention of Corliss's automatic cutoff 

gear had left the traditional governor unchanged. The first significant improvement 

to the governor itself since its invention was 

the work of an outsider in the engineering profession. Charles T. Porter (1826-1910) of 

New York, who became famous as "the 

father of the high speed steam engine," was 

by training a lawyer. One of his first inventions, the revolutionary "loaded governor" 

(1858), was made quite intuitively. In his 

memoirs, Porter has referred to this as "the 

surprising combination of sensitiveness and 

stability in the action of this governor which 

has led to its general use, and at which I 

myself have never ceased to wonder because 

I was ignorant of its cause."

 14 

On the traditional governor, the centrifugal motion of the revolving flyballs serves as 

a measure of speed. According to the laws of 

the centrifugal pendulum, the displacement 

of the flyballs is a function only of speed and 

is independent of the mass of the balls. The 

function is nonlinear: the ratio between dis13. Thurston, History of Steam Engine, pp. 321-323. 

14. Charles Talbot Porter, Engineering Reminiscences (New York, 1908), p. 23. 
14 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

placement and speed, that is, the governor 

sensitivity, decreases with rising speeds. A 

simple calculation can show that the optimum range of operation of the traditional 

governor lies at speeds well below 100 

r.p.m.15 Such slow-moving pendulums possess 

little kinetic energy—i.e., little power for the 

control action—unless the balls are made 

very heavy. Increases in inertia, however, 

slow down the system's response to disturbances, at the cost of stability as well as accuracy. Lack of responsiveness was indeed the 

main shortcoming of the traditional pendulum governor. 

On his governor, Porter sharply reduced 

the size of the flyballs and increased instead 

the speed by a factor of approximately ten. 

Thus he obtained a governor motion that 

was at once powerful and responsive. To 

make the device sufficiently sensitive, he 

balanced the centrifugal forces by a counterweight which was at first mounted nonrotating from a lever, later arranged in the 

characteristic manner concentrically on the 

governor spindle. The sensational improvements in stability and steady-state accuracy 

of Porter's governor soon forced all other 

manufacturers of governors to review their 

designs.16 

The model of C. T. Porter's first loaded 

governor, 1858 (NMHT 251289; Accession 

48865; U.S. Patent 20894 of 13 July 1858; 

11"X12"X12"; brass and steel), was submitted to the U.S. Patent Office as part of 

Porter's patent application.17 Figure 12 

shows clearly the above-mentioned features. 

In contrast to Porter's commercial model 

where the counterpoise is located on the 

governor's axis of rotation, here the weight 

is arranged on the lever connecting the governor with the steam valve. 

Porter's loaded governor in its standard 

form can be seen on the high-speed PorterAllen steam engine (Figure 13), 1881 

(NMHT 315891; Accession 222964; full-size 

15. Robert Henry Thurston, A Manual of the Steam 

Engine, 3rd ed., 2 vols. (New York, 1897), 11:378. 

16. Porter, Engineering Reminiscences, pp. 16-33. 

17. Taylor, Catalogue of Mechanical Collections, pp. 

81-82. 

FIGURE 12.—Patent model of Charles T. Porter's loaded 

governor, 1858. The counterpoise is on the right of 

the horizontal lever, not in the familiar manner on 

the governor axis. (NMHT 251289. Smithsonian photo 

30368.) 

engine of 80 hp at 300 r.p.m.), which was 

installed as one of eight in Philadelphia's 

first electric company, the Brush Electric 

Light Co., to drive an electric generator for 

street lighting.18 The governor's most characteristic feature, the central counterpoise, 

rests loosely on the axis, so that its angular 

inertia will not retard the governor's responses to sudden load changes. Besides the 

governor, the most notable feature of the 

Porter-Allen high-speed engine is the automatic cutoff gear patented by John F. Allen 

in 1862.19 In contrast to the release cutoff as 

used by Sickels and Corliss—unsuitable for 

high speed because for valve closure it requires a fixed amount of time independent 

of engine speed—in Allen's gear the variable 

cutoff is positively controlled. The governor 

acts on a sliding link between eccentric and 

steam valve which can vary the length of 

18. Porter, Engineering Reminiscences, pp. 42-57, 

304-305. 

19. Matschoss, Entwicklung der Dampfmaschine, 

11:193-199. 
NUMBER 12 

15 

FIGURE 13.—Porter-Allen high-speed steam engine, 1881. The Porter governor with its characteristic central counterpoise varies the stroke of the eccentric by adjusting the link to the right of the 

governor. (NMHT 315891. Smithsonian photo 72176.) 

valve travel. The speed of the valve motion 

is therefore directly dependent upon the engine speed. 

The influence of Porter s invention was by 

no means limited to America. A European 

version of the loaded governor can be seen 

on a steam engine built by Sulzer Brothers, 

Winterthur, Switzerland, in 1884. The engine 

is part of a steam-driven Linde-Wolf refrigeration compressor (NMHT 328660; Accession 
16 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

274467). The governor is not only loaded by 

a large weight on its axis but also by a stack 

of small weights at the end of a lever below 

the governor. The controlled engine speed 

can be adjusted by adding or removing these 

weights. The governor acts on releasing-type 

automatic cutoff gear. 

Another engine in the Porter-Allen tradition, although it lacks the typical Porter governor, is the steam pumping engine designed 

by Erasmus Darwin Leavitt for the Louisville, Kentucky, waterworks. In order to make 

the governor sufficiently powerful in spite 

of the extremely low engine speed (18 r.p.m.) 

the governor is geared to run at four times 

the engine speed, and, unlike the Porter governor, it has no central weight but two heavy 

flyweights instead. An external lever connects 

the governor with a dashpot. The desired 

speed can be adjusted by suspending weights 

from this lever. The output lever of the governor controls, through appropriate linkages, 

the lead angle of the camshaft which, in 

turn, actuates the valves on both cylinders 

of the engine. The Louisville pumping engine is represented in the Museum not only 

by a fully operational 12:1 model (NMHT 

324000; Accession 254418; built 1963 by 

Harry H. Catching), but also by a set of 

original engineering drawings (NMHT 

320975) prepared between 1884 and 1892 

under the direction of E. D. Leavitt and C. 

Hermany. 

In exceptional cases, steam engine governors also were equipped with hydraulic servomotors. This is illustrated by the model of 

the gigantic 7500 hp double-compound steam 

engine, built 1902-04 by Allis-Chalmers, generating electricity for the Interborough 

Rapid Transit subway of New York (NMHT 

320023; Accession 242871; model built by 

Severn-Lamb, Ltd., 1960-62). The model 

shows a Porter governor acting on Corlisstype variable cutoff gear through a hydraulic 

servomotor. A second governor, of similar 

form but direct-acting, serves to prevent overspeed. An actual specimen of this overspeed 

governor is in the collection (NMHT 

315709; Accession 197529). The original 

servo-powered governor shown in the model 

was later replaced by a more modern AllisChalmers hydraulic servo regulator which is 

also in the collection (NMHT 315708; Accession 197529; size 5'5" [over drive shaft] 

X30'X4'8"; see drawing Allis-Chalmers 481— 

163 of 1-11-1962). 

Mid-Nineteenth Century Patent Models 

A successful invention as Porter's governor 

had hundreds of competitors. A striking feature of nineteenth-century American technology is the enormous outburst of inventive 

energy. Engine governors were only one subject of many to which Yankee inventors devoted their ingenuity, but their examples 

illustrate the phenomenon clearly enough. 

Between 1836 and 1902, the number of 

United States patents granted for speedgoverning devices—not counting shaft governors—is far in excess of one thousand. Up 

to the 1880s, the United States Patent Office 

required each patent application to be accompanied by a model of the invention; 

when the huge collection of patent models 

that had thus accumulated was reduced in 

1908 and liquidated in 1926, the Smithsonian 

Institution had first choice in selection of 

models. The patent models of governors described herein represent only a small and selected sample of the ingenuity concentrated 

on the subject of speed control. The models 

contain a great diversity of ideas, some of 

which proved impractical while others anticipated designs that were successful later on. 

The following patent models are described 

in chronological order. 

The earliest of these models (Figure 14) 

represents the U.S. Patent 8447 entitled 

"Apparatus for Regulating the Speed of Engines" of H. A. Luttgens, granted on 21 October 1851 (NMHT 251288; Accession 48865; 

steel and brass; 63/4"x9"X 14i/2"; the crank 

is inscribed "H. A. Luttgens").20 It is a 

complicated mechanism exhibiting—for the 

first time within the limits of our collections 

—three different innovations: (1) it provides 

20. Taylor, Catalogue of Mechanical Collections, 

pp. 80-81. 
NUMBER 12 17 

FICURE 14.—Patent model of steam engine governor by 

H. A. Luttgens, 1851. (NMHT 251288. Smithsonian 

photo 69392.) 

positive cutoff control by varying the throw 

of the eccentric, anticipating the more successful Porter-Allen engine of ten years later; 

(2) it contains a mechanical servo-power 

drive, by which the energy for the control 

action is supplied not by the governor itself 

but by the crankshaft of the engine; (3) it 

employs the integral or reset mode of control. 

A conventional flyball governor is mounted 

on a structure holding two parallel horizontal shafts one above the other, of which 

the lower one is the crankshaft of the engine. 

T h e variable-throw eccentric is mounted below the governor directly on the crankshaft. 

T h e shafts are connected by two drive belts 

and two pairs of pulleys. Th e belt on the 

governor side serves to drive the upper 

shaft and, through a pair of bevel gears, the 

governor. Th e other belt, driven from above 

by a slightly larger pulley, runs at a somewhat higher speed. Through a friction clutch 

it drives the outer part of a planetary gear 

transmission on the crankshaft, which is also 

acted upon by a belt brake connected with 

the output lever of the governor. A complicated mechanism on the crankshaft, of 

which this planetary gear transmission is 

part, drives, through a pair of small bevel 

gears, the eccentric from and to the shaft. 

T h e direction of this motion depends on the 

resultant of the opposing torques produced 

by the friction clutch and the brake or, indirectly, on the position of the governor. 

When the brake is not engaged, the friction 

clutch tends to drive the transmission forward in such a direction as to reduce the 

throw of the eccentric, which results in a 

later cutoff and hence acceleration of the engine. On the other hand, at excessive speed, 

the rising governor balls will actuate the 

brake, producing a torque in the opposite 

direction, which will increase the throw of 

the eccentric. Equilibrium will be established 

when, both torques being equal, the throw 

of the eccentric will remain constant. 

As already mentioned, one of the novelties 

of this governor is the application of the 

integral mode of control. On the classical 

governor a difference between actual and desired speed leads to a change in valve position. This governor, in contrast, responds 

to an error not by a one-time adjustment but 

by an adjusting movement that continues until the steady-state error has disappeared. 

Corrective action is proportional not to the 

error (as in proportional control) but to the 

time integral of the error. Integral control 

then has the advantage of high steady-state 

accuracy, which is offset, however, by poor 

dynamic behavior. In later years it has become popular only in combination with porportional control. Nothing is known of the 

practical fate of Luttgens' governor. 

T h e invention described in the patent for 

a "Governor for Steam Engines" of G. S. 

Stearns and W. Hodgson, 1852 (NMH T 

251287; Accession 48865; U. S. Patent 9236 

of 31 August 1852; steel and brass; 6"X13"X 

17"), is of a comparatively simple nature 
18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 15.—Patent model of steam engine governor by 

G. S. Stearns and W. Hodgson, 1852. (NMHT 251287. 

Smithsonian photo 30367.) 

(Figure 15) .

21

 In it the motion of a traditional centrifugal pendulum is transmitted by 

rack and pinion rather than by the usual 

pivoted levers. The advantages claimed for 

this design are simplicity and cheapness. 

An invention of much greater significance 

is represented by the patent model of 

Thomas Silver's marine steam engine governor (Figure 16) of 1855 (NMHT 325611; 

Accession 249602; iron and wood; 9" diam. X 

12" high; with brass plate "Tho's. Silver 

Philad'a."). 

All the governors encountered in this collection so far work by taking for each particular speed a distinct position in which the 

centrifugal force on the flyballs is balanced 

by gravity forces. This reliance on gravity has 

an obvious disadvantage, for such gravity 

governors can operate only when mounted 

vertically on a platform that is free from any 

accelerations. Demands for a governor independent of the orientation of its axis first 

FIGURE 16.—Patent model of Thomas Silver's marine 

steam engine governor, 1855 (NMHT 235611. Smithsonian photo 69390.) 

arose in connection with marine steam engines. On a rolling and pitching ship the 

traditional gravity governor was clearly useless, whereas ungoverned marine engines had 

a dangerous tendency to race whenever the 

propeller or paddle wheel was lifted out of 

the water in heavy seas. 

One of the earliest marine steam engine 

governors was invented by Thomas Silver 

(1813-1888)22 of Philadelphia (U.S. patent 

13202 of 3 July 1855). In order to eliminate 

gravity effects, Silver first simply extended the 

two arms of the conventional pendulum upward, and at the upper ends of these arms 

he added symmetrically two other flyballs to 

balance out the weight of the original ones. 

Second, he connected the governor slide to a 

helical spring mounted concentrically on the 

governor axis. This spring served to 

counteract the centrifugal forces. Silver had 

21. Ibid., p. 81. 

22. Dictionary of American Biography, under "Silver, Thomas." 
NUMBER 12 19 

FIGURE 17.—Patent model of H. N. Throop's governor 

for marine steam engines, 1857. (NMHT 325612. 

Smithsonian photo 69388.) 

considerable successM with this invention 

and its subsequent elaborations. His governor was used on numerous merchant steamers; it was adopted by the navies of France 

and Britain, but not by the United States 

Navy. 

A spring-loaded marine governor, too, is 

the "Governor for Steam Engines" of H. N. 

Throop (Figure 17), 1857 (NMHT 325612; 

Accession 249602; U.S. Patent 18997 of 29 

December 1857; iron and wood, 9i/2"X 

5i/2"Xl0i/2", unmarked). Gravity forces 

are neutralized by symmetric mounting of the 

flyballs, while a spring on the axis provides 

the centripetal force. The playful appearance of the device conceals a feature of remarkable subtlety. The patent specification 

explains: 

It will be observed that in my governor the weights 

do not move out from and into the axle in a radial 

line; but in moving out, they fall back of such a line 

to any desired extent, depending on the arrangement 

of the spring or springs and the length of the connections, or in other words, depending on the limits prescribed for the weights to move in, toward and from 

the axle. If the paddle wheel or screw to which an 

engine is attached is, by the uneven surface of the 

water and the plunging of the vessel, suddenly and 

frequently thrown out of the water, as is often the 

case, leaving no resistance to the power and motion of 

the engine, except the inertia of the wheels or screw, 

the motion of the engine and the spindle of the 

governor is instantly increased; but the weights of the 

governor, on account of their inertia, will not readily 

participate in such increased motion, consequently 

they are left behind or fall back of the radial line, 

with a movement outward, aided in some degree by 

the centrifugal force due to the increased motion of 

the engine; thus instantly closing the valve. 

The governor's action is based on two 

separate physical effects. Centrifugal force 

displaces the flyballs outward in proportion 

to engine speed. In addition to this radial 

motion, the flyballs are also capable of tangential motion when the engine is decelerated or accelerated. The resulting governor 

action then is proportional to the speed itself and to the rate of change of speed (i.e., 

the first derivative of speed with respect to 

time), a characteristic known in modern 

control engineering as "proportional plus 

derivative response." In employing inertia 

effects, Throop's governor anticipates the 

shaft governors popular at the end of the 

nineteenth century. 

The patent model representing the "Im23. Thurston, Manual of Steam Engine, 11:391. 

FIGURE 18.—Patent model of S. H. Miller's steam 

engine governor, 1860. (NMHT 325613. Photo CLG.) 
20 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

provement in Governors for Steam-Engines" 

of S. H. Miller, 1860 (NMHT 325613; Accession 249602; U.S. Patent 29986 of 11 

September 1869; steel, brass, and wood, 9"X 

9"X10"), again belongs to the class of 

spring-loaded marine governors capable of 

operating in any axial position (Figure 18). 

It is a governor of basically conventional design. Leaf springs oppose the centrifugal 

forces on the flyballs which are arranged to 

travel on a linear radial path. 

The patent model of the steam engine 

governor (Figure 19) of Oliver A. Kelley 

and Estus Lamb, 1865 (NMHT 308667; Accession 89797; U. S. Patent 46111 of 31 January 1865; steel and brass, 6" diam. X 12" 

high; marked "Oliver A. Kelley & Estus Lamb, 

1864"), is remarkable not only for the exquisite quality of its construction but also for 

the concept it embodies.24 It represents an 

early—within this collection the first— 

governor combining the superior dynamic 

behavior of proportional control with the 

high steady-state accuracy of the integral response (discussed earlier in connection with 

the Luttgens governor, Figure 14). Since this 

feat is accomplished by purely mechanical 

means, the governor is somewhat complicated. The proportional action is obtained 

in the same way as on a conventional governor. A sleeve linked to the flyball in the 

usual way slides up and down on the governor shaft in proportion to engine speed. An 

arm attached to this sleeve reaches out 

through a slot in the casing of the governor. 

This arm is connected to a vertical spindle 

carrying on its threaded lower part a nut 

attached to the arm moving the valve. Thus 

the valve is moved directly in proportion to 

the position of the flyballs. Superimposed to 

this motion is another more complicated one. 

The vertical spindle is connected through a 

pair of bevel gears to a ratchet wheel, which 

when rotated will drive the nut on the spindle 

up or down, thus moving the valve without 

further change in position of the flyballs. By 

an intricate triggering device, connected to 

,'? € 

24. Taylor, Catalogue of Mechanical Collections, 

p. 82. 

FIGURE 19.—Patent model of steam engine governor 

by Oliver A. Kelley and Estus Lamb, 1864. (NMHT 

308667. Smithsonian photo 69391.) 

the sliding arm of the governor through an 

S-shaped cam, the ratchet wheel is driven 

forward or backward according to whether 

the engine runs too slow or too fast. The 

governor will respond to a disturbance immediately by proportional action; the remaining steady-state error will set the ratchet 

wheel in motion, driving the nut up or down 

along the spindle until the steady-state error 

is eliminated. The governor of Kelley and 
NUMBER 12 21 

Lamb is in conception quite rational, indeed 

it anticipates a form of control very common 

nowadays. Whether it had practical success is 

not known. 

The advantages claimed by the patent 

specification for the "Improvement in SteamEngine Governors" of T. S. La France, 1866 

(NMHT 325614; Accession 249602; U.S. Patent 56956 of 7 August 1866; simple wooden 

model; 5"X7"X13"; marked "T. S. La 

France. Elmira N.Y."), are simplicity and 

cheapness of construction. A loaded governor 

with two small flyballs and a large central 

counterpoise on its axis (Figure 20), it is 

FIGURE 20.—Patent model for steam engine governor 

by T. S. La France, 1866. (NMHT 325614. Photo 

CLG.) 

'*Mrz%m%?< y.-m. ••„ 

FIGURE 21.—Patent model of Andrew J. Peavey's vane 

governor, 1870. (NMHT 308678. Photo CLG.) 

clearly inspired by Porter's governor from 

which it differs only in the arrangement of 

mechanical connections, and in that it is additionally loaded by an axial helical spring. 

Late in the nineteenth century a new class 

of governors became popular that employed 

various hydraulic rather than purely mechanical effects as their method of sensing 

speed. One of these is represented in the patent model (apparently a full-scale prototype) 

of the vane governor (Figure 21) of Andrew 

J. Peavey, 1870 (NMHT 308678; Accession 

89797; U.S. Patent 106400 of 16 August 

1870; steel and brass, 5"X6"x7i/ 2 "; marked: 

"ANDREW J. PEAVEY. BOSTON, 

MASS.").25 Its design is based on the assumption that the drag on an object immersed 

in a moving fluid is proportional to 

the relative velocity. The governor (Figure 

22) consists of a closed cylinder in which oil 

is set into motion by a paddle wheel driven 

at a speed proportional to that of the engine. 

The oil impinges against a gravity-loaded 

vane immersed in it, which is deflected from 

its rest position by an angle proportional to 

25. Ibid., pp. 82-83. 
22 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Qmreriior. 

Ad./Off//00. Ifrfe/i/er/J?up:/£/3p. 

TVQ;. V 

"?i.Qf;.^ 

^'yXsx^t^^a^/j^^^^ .......... \wvtvXov. . 

FIGURE 22.—The interior of A. J. Peavey's vane governor. Reprinted from U. S. Patent No. 

106400 of Aug. 16, 1870, Patent Specifications. 
NUMBER 12 23 

FIGURE 23.—Hydraulic governor by the "Mason Regulator Co." installed on a steam driven 

Frick refrigerator compressor. (NMHT 319243. Photo CLG.) 
24 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

the velocity of the oil. The vane is connected 

to the valve gear of the steam engine by 

suitable linkages. 

A similar hydraulic governor (Figure 23), 

although not a patent model, is that of the 

Mason Regulator Co. installed on the steamdriven "Frick" refrigeration compressor of 

1898 (NMHT 319243; Accession 236002; the 

governor is marked "MASON REGULATOR 

CO. BOSTON, MASS. U.S.A. PAT. MAR. 

27, 1883. FEB. 10, '85"; size without linkages 

4i/2" diam. X 6" high). It consists of an 

oiltight cylinder containing a piston pump, 

which is driven from the eccentric of the 

steam engine and discharges into a closed 

space under a diaphragm. The output oil 

pressure of the pump, as a measure of engine 

speed, displaces the weight- and spring-loaded 

diaphragm, causing a motion that is transmitted to the throttle valve by mechanical 

connections. 

Other governors of this type were manufactured, for example, by Stillman B. Allen 

of Boston (originally the "Huntoon" governor) , by J. B. Duff of New York, and by 

Jenkins & Lee of Philadelphia. They all had 

one serious disadvantage. Not only did these 

governors consume power, but they also converted the lost energy into heat which 

changed the oil viscosity and thus impaired 

their accuracy. In 1919, therefore, W. Trinks 

in his textbook on governors classified this 

type of governor as "discarded."

 26 

The patent model of William Yates, 1876, 

represents a conventional governor (Figure 

24) with its belt drive (NMHT 321888; Accession 245986; U.S. Patent 174888 of 14 

March 1876; brass on wood base, 11"X5"X 

9"; unmarked). The invention patented here 

is only an external accessory to the governor, 

a belt-idler operated valve-stop. Most governors were driven by leather belts. If the belt 

slipped off or broke, the governor would stop, 

opening the steam valve wide and causing 

the engine to race at uncontrolled high 

speed. The safety device described here eliminates this danger. An idler pulley running 

FIGURE 24.—Patent model of William Yates of a steam 

engine governor with a belt-idler operated valve-stop, 

1876. (NMHT 321888. Photo CLG.) 

on the belt is connected with a triggering 

mechanism in the valve stem. If the belt slips 

off or breaks, the idler drops, disengaging 

the valve stem from the governor. Under the 

effect of a counterweight (the horizontal bar 

above the valve body; the weight itself has 

been lost) the throttle valve is promptly 

closed. A further advantage of the invention 

26. Willibald Trinks, Governors and the Governing 

of Prime Movers (New York, 1919), p. 144. 

FIGURE 25.—Patent model of steam engine governor 

by John Knowlson, 1876. (NMHT 325615. Phot, CLG.) 
NUMBER 12 

is claimed that it also serves as a belt tightener. 

The patent model of John Knowlson, 

1876 (NMHT 325615; Accession 249602; 

cast iron and brass, H$4"X10i4"xlli/ 2 " ; 

marked "J. KNOWLSON. TROY. N.Y."), 

represents two separate patents, one on 

valve gear (U.S. Patent 176141 of 18 

25 

April 1876), the other on steam engine governors (U.S. Patent 177404 of 16 May 1876). 

The model (Figure 25) shows governor, valve 

gear, crankshaft, and crosshead of a positivecutoff steam engine, where the point of cutoff is changed by a sliding link controlled 

by the governor, similar to the Porter-Allen 

engine. The centrifugal governor consists of 

FICURE 26.—Patent model of engine governor by Johann Georg Bodemer, 1876. (NMHT 309243. 

Smithsonian photo 69389.) 
26 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

two weights sliding radially on horizontal 

bars, acting on the sliding link by chains 

passing through the hollow governor shaft. 

The centrifugal force on the flyweights is 

balanced by a leaf spring connected to the 

lower end of the chain, although the patent 

specification also mentions the possibility 

of simple counterpoises. The advantages 

claimed for this governor are "simplicity in 

operation, durability for continued work, and 

efficiency in action under all circumstances," 

especially with cutoff engines, claims that 

were not confirmed by commercial success. 

The exquisitely made patent model of 

J. G Bodemer, 1876 (NMHT 309243; Accession 89798; U.S. Patent 176591 of 24 April 

1876; steel and brass, 10i/2"X6"X 12"; 

marked "Modell von Bock & Handrick Dresden 550"), displays a prodigious, although 

perhaps impractical, amount of mechanical 

ingenuity (Figure 26) P Designed as a governor for hydraulic turbines, its output device is a belt shifter controlling the motion 

of the turbine valve driven by an independent source of power. It consists of a conventional loaded governor acting upon the belt 

shifter through two separate control mechanisms, of which the more sensitive one can 

be superimposed optionally upon the basic 

mechanism. Each is actuated by a pin riding 

in an S-shaped slotted cam attached to the 

slide of the governor, determining which one 

of three possible positions—forward, neutral, 

or reverse—the belt shifter will occupy. The 

power required to move the belt shifter is 

supplied directly from the mainshaft of the 

governor, through a complicated friction 

drive set in motion according to the governor 

output. 

A governor of this design was shown at the 

Centennial Exhibition at Philadelphia in 

1876. A simplified version of Bodemer's governor was used to regulate the turbines of 

the inventor's own plant.28 Johann Georg 

Bodemer (1842-1916), son of a wealthy textile manufacturer in Zschopau, Saxony, incidentally, was married to a daughter of 

Donald McKay, the well-known New England ship builder.29 

Despite its exotic appearance, the gyroscopic governor (Figure 27) of Joseph Reid, 

1879, serves the same purpose as the common centrifugal governor (NMHT 309242; 

Accession 89797; U.S. Patent 220867 of 21 

October 1879; steel with brass gears; 714" 

X5"X12"; marked "JOSEPH REID MONROE LA.") .

30

 As a speed-sensing device it 

employs a gyroscope geared to perform two 

separate simultaneous motions, rotation and 

precession, both proportional to engine 

speed. The gyroscope's axis of rotation is in29. Neue Deutsche Biographie, under "Bodemer, 

Johann Georg." 

30. Taylor, Catalogue of Mechanical Collections, 

p. 85. 

27. Taylor, Catalogue of Mechanical Collections, 

p. 84. 

28. Dingler's Polytechnisches Journal 222 (1876):505-

524, pi. 11. 

FIGURE 27.—Patent model of gyroscopic engine governor by Joseph Reid, 1879. (NMHT 309242. Photo 

CLG.) 
NUMBER 12 27 

FIGURE 28.—Patent model of steam engine governor 

by George H. Corliss, 1882. (NMHT 308715. Smithsonian photo 69393.) 

clined from the vertical axis of rotation; it 

is pivoted freely but held down by spring 

force. With increasing speed the gyroscope's 

axis tends to rise toward the vertical; the 

resulting motion is transmitted by suitable 

linkages to a horizontal lever, which is to be 

connected to the control valve. The patent 

includes a stop motion for the case of a breaking drive pulley. The particular advantage 

claimed for the gyroscopic governor is sensitivity to changes of speed. 

George Corliss's diminutive patent model 

of 1882, a governor for steam engines (Figure 28), represents one of the last of his 

many inventions (NMHT 308715; Accession 

89797; U.S. Patent 262209 of 8 August 1882; 

steel and brass on wood base; size of 

the governor proper 3"X2"X5i/2"; unmarked) .

31

 The governor is driven by a 

friction drive: a friction roller connected 

with the engine and capable of axial motion 

runs perpendicularly against a disc at the 

bottom of the governor shaft. The governor 

slide is connected not only to the control 

valve, but also, through appropriate linkages, to the axle of the friction roller. When 

the flyballs rise, due to increasing speed, the 

friction roller is moved toward the center of 

the friction disc, driving the governor at a 

higher gear ratio, hence increasing the control response that results from a given speed 

deviation. The effect of the mechanism is 

then nothing more than to increase the 

proportional sensitivity of a conventional governor, a feat that could have been accomplished by much simpler means. The device 

had no known influence on further developments. 

Valve-Mounted Governors 

In the last third of the nineteenth century 

two standard types of governor were established which endured as long as steam engines were used: the first was a simple pulleydriven centrifugal governor mounted directly 

on a throttle valve; it was applied mainly on 

the numerous small steam engines which did 

not justify costly and elaborate automatic 

cutoff gear. Steam engines of larger size, in 

contrast, were the domain of shaft governors 

that were always combined with automatic 

cutoff. The valve-mounted governors were 

produced in large quantities at low prices 

by companies specializing in this field. The 

basic designs were adopted in the 1860s or 

1870s, and were, with few changes, retained 

until the end of the steam engine era. 

An early example of this type is the Judson 

governor, still employing the traditional centrifugal pendulum with heavy flyballs, designed for low engine speeds. From 1850 on, 

Junius Judson and his associate William A. 

Cogswell took out numerous patents for ac31. Ibid., pp. 78-79. 
28 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 29.—Patent model of steam engine governor 

by Junius Judson and William A. Cogswell, 1875. 

(NMHT 309244. Photo CLG.) 

cessories to their basic governor, one of which 

is represented by the patent model of 1875 

(NMHT 309244; Accession 89797; U.S. Patent 169815 of 9 November 1875; marked 

"Judson Patent'd Dec. 5, 1871" and "120 

Rev's"; mounted on D/4" valve; overall 

height 19").32 The patent model (Figure 

29) consists of a governor from the actual 

production line to which an elastic clutch 

was added in the drive shaft as the patented 

feature. In order to prevent irregularities in 

the running of the engine from being transmitted to the governor, the belt pulley is 

mounted elastically on the drive shaft by 

means of a spiral spring concealed in the 

interior of the shaft. 

A Judson governor installed in operating 

position on an actual engine is exhibited 

(Figure 30) on the J. I. Case portable steam 

engine of 1869 (NMHT 62A10; Accession 

246139; governor mounted on H/2" valve). 

The governor is equipped with a dashpot 

and with an arrangement for changing the 

32. Ibid., pp. 83-84. 

controlled speed by suspending weights of 

different sizes from a lever which acts on the 

governor spindle. The dashpot, in general, 

is an inelegant but sometimes unavoidable 

expedient for quieting down engines with 

an inclination toward instability. 

Another Judson governor, of the simplest 

type, and showing considerable wear, dates 

probably from the same period (NMHT 

318460; Accession 234834). 

The stationary steam engine built in. 1864 

by the United States Military Railroad Department, Alexandria, Virginia, is equipped 

with a large unidentified governor (Figure 

31) closely resembling Judson's design 

(NMHT 310241; Accession 113602; unmarked; governor on 4" throttle valve; overall height 38"). Attached to it is a spring 

device for varying speed. 

A similar valve-mounted governor, of diminutive size but operational, is displayed on 

the Jerrehian toy steam engine of about 1870 

(NMHT 325908; Accession 258277). 

Also into the Judson class belongs the 

simple valve-mounted governor on the rotary 

steam engine built by Henry J. Hendey in 

about 1870 (NMHT 314511; Accession 

203480). 

Far more progressive than the Judson governor was the spring governor invented in 

1862 by Thomas R. Pickering (U.S. Patent 

36621 of 7 October 1862). Here the traditional pendulum is replaced by three centrifugal weights on vertical leaf springs 

parallel to the axis of the governor, an arrangement that has become characteristic for 

Pickering governors. These springs made the 

governor independent of gravity effects and 

hence of the vertical position. Combined 

with flyballs of reduced size, the springs enabled the governor to function at high 

speeds. In a design of unrivaled simplicity, 

avoiding all pivots and moving linkages, the 

Pickering governor was highly accurate and 

almost indestructible. It has been used in a 

wide range of applications, from steam turbines to chronometric regulators, and it is 

still being manufactured. 

The Museum possesses two specimens of 

early Pickering governors. The older one is 
NUMBER 12 29 

FIGURE 30.—Judson governor installed on the J. I. Case portable steam engine of 1869. (NMHT 

62A10. Photo CLG.) 

installed on an Otis steam elevator machine 

of 1875 (NMHT 318170; Accession 232978; 

marked, partly illegibly, "No. 3938; 360 

REV."; mounted on 2i/2" valve). Very similar to it is a unit (Figure 32) dating probably 

from the 1880s (NMHT 310289; Accession 

115810; marked "THE PICKERING GOVERNOR PORTLAND. CONN. U.S.A. 

SHAFT REV. 380"; serial no. 535798; 

mounted on a 2" valve, overall height 27"). 

Contrasted by these is a Pickering governor 

of 1931 (NMHT 310290; Accession 115810; 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 31.—Stationary steam engine built by the United States Military Railroad Department, 

1864, shown at its former location in the Arts and Industries Building. (NMHT 310241. Smithsonian photo 31026.) 

marked "MADE BY PICKERING GOV'R 

CO, PORTLAND, CONN. U.S.A. SHAFT 

REV. 600"; serial no. 535755B; mounted on 

2" valve, overall height 30").33 While the 

basic design conception is the same, the outward appearance (Figure 33) is drastically 

changed by a bell-shaped protective hood 

over the rotating parts of the governor. It is 

equipped with a "Ball Ranger" speed changer 

which adjusts the initial spring force on the 

governor, making the desired speed widely 

adjustable above and below the nominal 600 

revolutions per minute. 

The design of the Waters Governor Company of Boston, one of Pickering's competitors, is represented by a specimen (Figure 

34) dating presumably from the 1880s 

(NMHT 325525; Accession 258280; unmarked; mounted on a 1" valve, of which 

the body has been lost; overall height 17"). 

33. Ibid., p. 86. 

It employs two centrifugal weights restrained 

each by a C-shaped leaf spring so as to permit only radial motion (U.S. Patent 110703 

of Charles Waters, 3 January 1871). A provision for speed adjustment was standard 

equipment, while the stop motion for belt 

failure was optional. 

An unmarked governor that also appears 

to be a Waters product is installed on the 

Baxter combination steam engine and boiler 

of 1868 (NMHT 325905; Accession 257094) , 

to which it was added at an unknown later 

date. 

A similar Waters governor is installed on 

a Frick "Eclipse" portable steam engine, 

built in 1877 (NMHT 58A9; Accession 

222811; name plate partly illegible "Waters 

Pat 1871 Boston, Mass."; governor 

mounted on li/ 2 " valve). 

Another manufacturer specializing in governors since the 1860s was the Gardner Governor Co. of Quincy, Illinois. The Gardner 
NUMBER 12 31 

FIGURE 32.—Pickering steam engine governor, 1880s. 

(NMHT 310289. Photo CLG.) 

spring governor (Figure 35) in the Museum's 

collection was probably built in the 1930s 

(NMHT 329758; Accession 228958; mounted 

on 3^" valve; overall height 14"; marked "s/4 

GARDNER GOV. CO. QUINCY ILL. 

339730: 600 REV."). It is typical for a highspeed steam engine governor of mature design. Two flyweights mounted at the end of 

leaf springs are arranged parallel to the axis; 

their centrifugal motion is transmitted to the 

stem of the steam valve by a conventional 

set of linkages. Provisions are made both for 

changing the controlled speed—even while 

the engine is running—and for automatically 

closing the valve in case of belt failure. 

A special-purpose regulator derived from a 

FIGURE 33.—Pickering steam engine governor, 1931. 

(NMHT 310290. Photo CLG.) 
32 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 34.—Waters steam engine governor, 1880s. 

(NMHT 325525. Photo CLG.) 

FIGURE 35.—Gardner steam engine governor, 1930s. 

(NMHT 329758. Photo CLG.) 

conventional steam engine governor is the 

"Erie" compressor governor (Figure 36) 

built by the Jarecki Manufacturing Company about 1910-1920 (NMHT 326536; AcFIGURE 36.—Governor for steam-driven air compressor 

built by the Jarecki Mfg. Co., about 1920. (NMHT 

326536. Photo CLG.) 

cession 262282; mounted on a 2i/2" valve; 

overall height 29"; marked "JARECKI 

MFG. CO. ERIE PA. i/2 ERIE GOVERNOR 

275 REV. NO. [illegible], PAT. NOV. 14 

'99, DEC. 25 1900, NOV. 25 1901, NOV. 22 

1904, MAY 22, 1906"). Its purpose is to hold 

the output pressure of a steam-driven air 

compressor constant, while causing the steam 

engine to run at the lowest possible speed. 

Two flyweights, shaped as hemispheres, form 

a single 5-inch diameter sphere when the governor is at rest, separating at higher speeds. 

Their centrifugal force is balanced by a coil 

spring located outside of the governor body. 

As an unusual feature the governor contains 

a pressure-sensing device piped directly to 

the compressor output, generating a force on 

the valve stem in the same manner and direction as the centrifugal force of the flyweights. If the compressor output pressure 

rises above the desired value, the governor 
NUMBER 12 

responds by reducing the steam supply of the 

driving engine, and hence the compressor 

speed. The governor is equipped with an 

automatic safety stop of which the idler arm 

has been lost. 

Although not valve mounted, a governor 

best listed at this point is that of the Willans 

central-piston compound engine of 1905 

(NMHT 328723; Accession 275434; the engine is directly connected to a 240 V, 100 

amp. D.C. generator, speed 470 r.p.m.). A 

centrifugal spring governor is mounted under a protective shroud directly on the crankshaft. It is connected by a long vertical rod 

to the throttle valve in the steam inlet line. 

Throttling control on a high-performance 

engine such as this could be justified only if 

the engine operated rather constantly near 

full load. 

Shaft Governors 

First patented in 1839 by Jacob D. Custer 

of Norristown, Pennsylvania (U.S. Patent 

1179 of 21 June 1839), the shaft governor 

became popular in America in the 1870s, and 

a little later also in Europe where it was 

always regarded as a specifically American 

invention. In contrast to the cheap and 

simple valve-mounted governor, the shaft 

governor was an ingenious and complicated 

mechanism that had to be designed as an 

integral part of the individual steam engine. 

Its advantages were accuracy and economy 

of operation. 

Shaft governors were used exclusively with 

automatic cutoff control. The older of the 

two forms of such control, that by detachable 

cutoff gear, employed for example by George 

H. Corliss, was limited to low engine speeds. 

Operation at higher speeds required positive 

cutoff, where the inlet valve gear was linked 

positively to the eccentric during the whole 

engine cycle. Various such mechanisms were 

invented that were based on the conventional 

flyball governor, the best known was the 

Porter-Allen arrangement. The same task, 

however, could be accomplished far more 

simply by the shaft governor. Located within 

the flywheel, the basic centrifugal shaft governor employs several—usually two—centrifugal weights arranged symmetrically and 

balanced by springs. The weights are linked 

with the eccentric in such a way that when 

they move outward due to increasing speed, 

the throw of the eccentric is reduced causing 

earlier cutoff and hence a return to equilibrium speed.34 

Many shaft governors are based on the 

combined action of centrifugal force and inertia. The control response is proportional 

not only to the speed, as measured in terms 

of centrifugal force on the flyweights, but 

also to the rate of change of speed. This is 

accomplished by mounting the weights so 

that they will travel, relative to the flywheel, 

not on a purely radial path but rather on a 

path lying somewhere between the radial and 

the tangential direction. If then, for example, 

the engine is suddenly accelerated, the 

flyweights by their inertia are thrown backward, with the same effect upon the speedcontrol system as though they were moved 

outward due to centrifugal force. An early 

American patent describing such a governor 

was that of H. N. Throop, 1857 (Figure 17), 

but the idea of an inertial governor in general had already been published by Werner 

and William Siemens in 1845. Governors 

based on the inertial effect alone are unsuited for speed control, because they lack a 

sensing element for the controlled variable, 

speed, and therefore do not form a closed 

feedback loop. Pure inertia governors tend to 

maintain indiscriminately the momentary 

speed, but they cannot be set to hold the 

speed constant at any particular value, nor 

are they able to respond to very slow changes 

in speed.35 Shaft governors, however, that 

combine the inertial action with the conventional centrifugal action—i.e., that provide 

"proportional plus derivative control"—have 

been highly successful because of their responsiveness and accuracy. 

One of the first industrially successful shaft 

governors (Figure 37), patented in 1870 by 

Daniel A. Woodbury of Rochester, N.Y., is 

34. Trinks, Governors, pp. 61-76. 

35. Ibid., pp. 9-10, 139-140. 
34 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 37.—Patent model of shaft governor by Daniel 

A. Woodbury, 1870. (NMHT 251290. Smithsonian 

photo 30362.) 

represented in our Museum by the original 

patent model (NMHT 251290; Accession 

48865; U.S. Patent 107746 of 27 September 

1870; 12" diam. flywheel on 9"X12"X7" 

wood base) ,

36

 Within the flywheel two 

weights are mounted at the ends of leaf 

springs in such a way that they are free to 

move in radial direction only. The governor 

then is purely centrifugal. The flyweights are 

connected by a pair of S-shaped links to a 

mechanism at the hub of the wheel which 

reduces the throw of the eccentric as the flyweights move outward, and vice versa. 

Another centrifugal shaft governor (Figure 

38) is the patent model of Joseph W. 

Thompson and Nathan Hunt of Salem, Ohio, 

1878 (NMHT 308700; Accession 39797; U.S. 

Patent 204924 of 18 June 1878; steel flywheel 6" diam.; marked "BUCKEYE ENG. 

CO. SALEM, O.") ,

37

 Two weights, mounted 

on parallel pivoted levers permitting only 

radial motion, are balanced by two coil 

83. 

36. Taylor, Catalogue of Mechanical Collections, p. 

5. 

37. Ibid., p. 85, pi. 19:2. 

FIGURE 38.—Patent model of shaft governor by Joseph 

W. Thompson and Nathan Hunt, 1878. (NMHT 

308700. Smithsonian photo 32595-A.) 

springs. The weights are linked with the eccentric, adjusting not the throw but rather 

the lead angle of the eccentric with reference 

to the crankshaft, which equally results in a 

variation of the point of cutoff. The governor 

sensitivity and the desired speed can be adjusted by varying the spring tension and by 

changing the distance of the weights from 

the pivot point. The Thompson-Hunt shaft 

governor was usually combined with the 

famous "Buckeye" steam engine, a successful high-speed engine; it became one of the 

most popular constructions of shaft governors. 

Simple centrifugal shaft governors are furthermore to be found on two small steam 

engines, both dating from the 1880s, namely 

the self-contained boiler-engine unit (Figures 

79 and 80) built by the Shipman Engine 

Co. of Boston (NMHT 315712; Accession 

221209), and the Boesch model (fully operational) of a high-speed engine (Figure 39) 

of the Harrisburg Foundry and Machine Co. 

(NMHT 325664; Accession 255732). 
NUMBER 12 35 

FIGURE 39.—Model of Harrisburg steam engine. (NMHT 325664. Photo CLG.) 

A shaft governor actuated by inertia and 

centrifugal forces (Figure 40) is employed 

on the Westinghouse Automatic compound 

engine of 1896 (NMHT 322556; Accession 

249412; engine no. 1015; 45 hp with 125 p.s.i. 

at 375 r.p.m.; flywheel 42" diam. X IO14"). 

This single-acting, high-speed compound 

engine, invented by Henry Herman Westinghouse (1853-1933, brother of George Westinghouse) in 1888, was progressive in several 

ways. The engine is modern in appearance 

with its two cylinders housed in a single vertical block; it was of unprecedented economy, 

both in operation, due to combining the compound arrangement with high speed, and, by 

virtue of mass production, in initial cost.38 

The compactly designed shaft governor is 

contained in an oil-filled sealed compartment 

at the hub of the flywheel. In an arrangement somewhat reminiscent of the Buckeye 

governor, two flyweights, counteracted by 

heavy helical springs, are linked with the 

eccentric to adjust its throw. The inertia 

effect is obtained simply by mounting the 

flyweights so that they can swing tangentially as well as radially.39 

The Westinghouse Junior Automatic, a 

simplified smaller version of this engine, 

built about 1900 (NMHT 309924; Accession 

111907; serial no. 2909), is equipped with a 

shaft governor of similar but much simpler 

design, also employing both inertia and centrifugal force.40 

Also regulated by a centrifugal-inertia governor is a steam engine built by the Ball 

38. Thurston, Manual of Steam Engine, 11:393-394; 

Matschoss, Entwicklung der Dampfmaschine, 11:214-

218. 

39. "The New Westinghouse Compound Engine 

Governor," Iron Age (2 July 1891):6-7. 

40. Taylor, Catalogue of Mechanical Collections, p. 

54, pi. 14:2. 
36 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 40.—Westinghouse "automatic" compound steam engine, 1896. 

(NMHT 322556. Photo CLG.) 
NUMBER 12 37 

FIGURE 41.—Skinner "Universal Unaflow" steam engine, 1926. (NMHT 319477. Photo CLG.) 

Engine Co. of Erie, Pa., in 1896 (NMHT 

322557; Accession 249412; serial 3350; 40 

KW at 300 r.p.m.). Its designer, Frank H. 

Ball, experimented with a variety of shaft 

governors without arriving at a standard 

type. The present governor employs two flyweights, of which one responds to inertia 

effects and the other to changes of centrifugal 
38 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

force, each balanced by helical springs. By 

means of suitable linkages the flyweights 

change the lead angle of the eccentric. A 

dashpot is installed to damp out oscillations 

of the flyweights. 

The Museum's latest steam engine controlled by a shaft governor is the Skinner 

"Universal Unaflow" engine built in 1926 

(NMHT 319477; Accession 237917; 25-75 

hp with 150 p.s.i. at 250 r.p.m.; engine serial 

no. 10737; flywheel 62" diam. X 11"). The 

Skinner inertia governor (Figure 41) is distinguished by its simplicity of construction. 

It has only three moving parts: a large swinging beam pivoted near its center on a spoke 

of the flywheel; a heavy spring fixed to the 

rim of the flywheel; and a link connecting 

both. The mass of the swinging beam is distributed in such a manner that it will respond 

to inertia forces far more strongly than to 

changes in centrifugal force. Since the eccentric is an integral part of the beam, any 

motion of the beam is equivalent of shifting 

the eccentric. 
CHAPTE R 3 

Speed Regulation of Other Prime Movers 

Governors for Waterwheels and 

Turbines 

The conditions of operation of a waterwheel governor are very different from those 

of the steam engine. On the steam engine 

the various mechanical control elements are 

well lubricated and of relatively light weight. 

The operating medium, steam, is elastic and 

of little inertia, responding to control actions 

instantly and without dangerous pressure 

surges. The conditions under which waterwheels operate are rather the opposite. The 

final control elements, restrictions in water 

passages, are massive and heavy, and so are 

the mechanisms actuating them upon signals 

from the governor. Water, being incompressible and heavy, responds to attempts to 

change its velocity with pressure changes 

which can be destructive. These differences are reflected in governor design. 

Practically all steam engine governors described here so far take the energy for moving the final control element directly from 

the centrifugal governor, that is, from the 

sensing element; they are therefore directacting governors. Waterwheel governors, on 

the other hand, are indirect-acting—or servopowered: the energy for moving the control 

gates is provided by a source from outside of 

the governor. 

MECHANICAL SERVO GOVERNORS.41—A representative of the class of purely mechanical 

41. Into this class belong also the patent models by 

H. A. Luttgens (1851), O. A. Kelley and E. Lamb 

(1865), and J. G. Bodemer (1876), see Figures 14, 19, 

26. 

waterwheel governors is the Rodney Hunt 

governor (Figure 42) of about 1900 (NMHT 

318011; Accession 228784; marked "DOUBLE 

ACTING REGULATOR NO. 2. MADE BY 

R. HUNT MCH CO. ORANGE MASS."; 

short-base design; size 32"X21"X34"). The 

governor is described exhaustively in United 

States Patent 307758 (11 November 1884) of 

Charles E. Gibbs, which covers some improvements over a conventional design known as 

the "Scholfield" governor, named after N. 

Scholfield who received United States patents 

on waterwheel governors on 17 November 

1836 and 21 July 1857. Its principle of operation is: a shaft with two eccentrics set at 

180° to each other is continuously rotated 

by the waterwheel. The eccentrics keep in 

constant motion two reciprocating arms, to 

the ends of each are attached two ratchet 

pawls, facing in opposite directions. The ratchet arms move along the circumference of 

two large ratchet wheels fixed on the shaft 

positioning the control gate. The centrifugal 

governor, through suitable mechanical connections, determines which one of the pawls 

will engage the ratchet wheels. If the actual 

speed is equal to the desired speed, both sets 

of pawls are held back. If the speed is too 

low, the pawls that face forward are brought 

into action, turning the ratchet wheels forward and thus opening the water gate, while 

in the opposite case the action is reversed. 

The innovations described in Gibbs' patent 

of 1884 are: a lever attached to the governor 

spindle with a sliding weight for varying the 

controlled speed; a friction brake on the output shaft to avoid backlash; and a limiting 

39 
40 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 42.—Rodney Hunt water turbine governor, about 1900. (NMHT 318011. Smithsonian 

photo 72199.) 

device which disengages the governor action 

when the gate reaches its fully open or closed 

position. 

Other examples of mechanical servo governors are the earlier Woodward governors. 

The Woodward "Type 3" water turbine governor (Figure 43a) of 1903 (NMHT 315896; 

Accession 221844; serial no. 1309, used on a 

50 hp, 23" Trump turbine), a modification 

of the basic invention of Amos Woodward 

(U.S. Patent 103813, 31 May 1870), is described in detail in the U.S. Patent 432105 of 

Amos and Elmer E. Woodward of 15 July 

1890. It functions as follows: 

On the upright shaft are two friction pans a and b 

[Figure 43b]. These pans are loose on the shaft, the 

upper one being supported in position by a groove in 

the hub and the lower one by an adjustable stepbearing. Between these pans, and beveled to fit them, 

is a double-faced friction wheel c, which is keyed to 

the shaft. This shaft and friction wheel run continuously and have a slight endwise movement. They are 

supported by lugs on the ball arm and therefore rise 

and fall as the position of the balls varies with the 

speed. 

When the speed is normal, the inner or friction 
NUMBER 12 41 

FIGURE 43a.—Woodward "Type 3' 

water turbine governor, 1903. 

(NMHT 315896. Smithsonian 

photo 45926-J.) 

FIGURE 43&.—Sectional Drawing of 

Woodward "Type 3" mechanical 

waterwheel governor. Reprinted 

from Daniel W. Mead, Water 

Power Engineering, 2nd ed. (New 

York, 1915), fig. 288. Used with permission of McGraw-Hill Company. 
42 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 44.—Woodward "Model D" water turbine governor, about 1905-1910. (NMHT 320331. 

Photo Woodward Governor Co.) 

wheel revolves freely between the two outer wheels 

or pans which remain stationary. When a change of 

speed occurs, the friction wheel is brought against the 

upper or lower pan as the speed is either slow or fast. 

This causes the latter to revolve and, by means of 

the bevel gears, turn the gates in the proper direction 

until the speed is again normal. As the gate opens the 

nut d, travels along the screw e, which is driven 

through gearing by the main governor shaft and as 

the gate reacts, the nut d, coming in contact with the 

lever f, throws the vertical shaft upward and the governor out of commission." 

This governor, like the previously described Rodney Hunt governor, was well 

suited to serve in mills and factories where 

changes in load were neither frequent nor 

42. Daniel W. Mead, Water Power Engineering, 2nd 

edition (New York, 1915), pp. 462-463. 

rapid. But, employing only the "integral response"—its output is proportional to the 

time integral of the speed deviation—it had 

unfavorable dynamic characteristics; it was 

slow and prone to instability. 

To correct these deficiencies, the Woodward Company developed their "compensating" governor, patented by Elmer E. 

Woodward in 1901 (U.S. Patent 679353, 30 

July 1901). The Museum has a specimen of 

this type—a Model D (Figure 44)—built 

about 1905-1910 (NMHT 320331; Accession 

243909; serial no. 2624; size 50"X20"X40"). 

It is directly derived from the basic Woodward governor described above; its distinction 

is a closed feedback loop within its own action, which converts the integral-response 
NUMBER 12 43 

governor into a proportional governor. This is 

done briefly as follows: On the integralresponse governor, upon an error signal, a 

mechanism will be set off which moves the 

water gate at constant speed in the corrective 

direction until the actual and desired speeds 

are equal. On the "compensating" governor, 

another mechanism containing the characteristic "friction wheel compensator" is added 

to the effect that the corrective action limits 

itself in such a way that the output change 

will be directly proportional to the input 

deviation. Governors of this type can be adjusted for much higher sensitivity without a 

risk of instability.43 

HYDRAULIC SERVO GOVERNORS.—The hydraulic servomotor emerged as a rival to the 

mechanical servo relay. In the 1860s such 

devices had been used in automatic steering 

devices of ships,44 but soon they were also 

employed on the governors of water turbines 

where large actuating forces were required. 

Inserted between the governor and the control valve, the servomotor has the function 

to relay the governor output signal to the 

final control element with the utmost fidelity, 

but greatly amplified in force. As the principle sketches (Figures 45 and 46) show, its 

model is obviously the steam engine, with 

the "pilot valve" corresponding to the valve 

gear, and the "power cylinder" to the working cylinder of a double-acting engine. The 

working medium is a high-pressure fluid, 

possibly steam, water, or air, more commonly 

oil, entering at the supply port between the 

two small pistons of the pilot valve. If the 

pilot valve is moved upward by the governor, 

the high-pressure fluid will act on the upper 

side of the power piston causing it to move 

downward, while the space below it is vented. 

Conversely, a downward motion of the pilot 

valve will result in an upward motion of the 

power piston. 

Servomotors designed according to Figure 

45, however, are quite unsatisfactory, for a 

small governor action will lead to a complete 

opening or closing of the control valve, hence 

to a violent deceleration or acceleration of 

43. Ibid., pp. 463-466. 

44. H. G. Conway, "Some Notes on the Origins of 

Mechanical Servo Mechanisms," Transactions of the 

Newcomen Society 29(1953-55):55-75. 

FIGURE 45.—Governor linked to hydraulic servomotor 

without feedback. This arrangement would tend to be 

unstable. Reprinted from W. Trinks, Governors and 

the Governing of Prime Movers (New York, 1919), p. 

174, by permission of D. Van Nostrand Company. 

~-<D 

Pilot -z. 

Vol TJt - ^ 

FIGURE 46.—Governor and hydraulic servomotor, stability by feedback linkage 3-4-5. Reprinted from W. 

Trinks, Governors and the Governing of Prime Movers (New York, 1919), p. 176, by permission of D. Van 

Nostrand Company. 
44 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 47.—Lombard "Type F" water turbine governor 

with hydraulic servomotor, 1912. (NMHT 320136. 

Smithsonian photo X2337.) 

the machine, and finally to an increased governor action: in short, to instability. This is 

avoided by adding to the servomotor the expedient of feedback (see Figure 46). The 

lever connecting the governor with the pilot 

valve is extended to the rod of the power 

piston. This has the result that the motion 

of the power piston becomes proportional to 

that of the governor slide. The feedback 

lever, then, is equivalent to the compensating 

mechanism of the Woodward mechanical 

governors. Added to the feedback lever are 

often dashpots, springs, sliding links, etc., in 

many different arrangements, all with the 

objective of modifying the dynamic characteristics of the governor. Despite their widely 

varying appearance, hydraulic servo gover-

. 

FIGURE 48.—Woodward "Type LR" water turbine 

governor with hydraulic servomotor, about 1914. 

(NMHT 315858. Smithsonian photo 45926-L.) 

nors can always be reduced to the simple 

scheme described above.45 

The Lombard Governor Co. of Ashland, 

Massachusetts, began the manufacture of hydraulic governors in 1894. The Lombard 

"Type F" waterwheel governor (Figure 47) 

45. Trinks, Governors, pp. 170-194. 
NUMBER 12 45 

in our collection (built in 1912; NMHT 

320136; Accession 241096; serial no. 2113; 

size 44"X18"X62") was the smallest model 

made by this company; it is powered not by 

oil but by high-pressure water simply taken 

in from the river upstream of the turbine. 

The whole regulating apparatus is mounted 

on an iron table. The four-ball Pickeringtype governor at the top controls through a 

vertical pilot valve the horizontal power cylinder. The piston rod carries a rack that 

drives a gear segment to move the turbine 

gate and the conspicuous feedback levers 

which modify the opening of the pilot valve. 

The Museum (Division of Mechanical and 

Civil Engineering) has also a considerable 

archival collection of linen drawings, mostly 

on governor installation, of the Lombard 

Governor Co. 

The next stage in the development of hydraulic servo governors is represented by a 

Woodward "Type L-R" governor (Figure 

48) of approximately 1914 (NMHT 315858; 

Accession 221780; name plate "WOODWARD WATER WHEEL GOVERNOR 

TYPE L-R; FT.LBS. 1,250; SIZE 5 X 4.75; 

No. 4100—WOODWARD GOVERNOR 

CO., ROCKFORD, ILL. U.S.A. PATENTS: 

MAY 31, 1870; AUG. 11, 1890; JULY 15, 

1890; DEC. 15, 1896; JULY 30, 1901; AUG. 

11, 1914"; size 32"X16"X66"). Powered by 

high-pressure oil, this governor is designed 

as a single compact unit. Its most interesting 

feature is the double relay. To make the 

governor more sensitive, fast-acting, and 

powerful, the pilot valve had acquired such 

size that it could not be moved without great 

effort. Another smaller pilot valve was therefore superimposed, which treated the first pilot valve as though it was the power piston. 

Both servomotors are enclosed in feedback 

loops by means of linkages connecting the 

two piston rods in a suitable manner with 

the governor spindle. The governor is 

equipped with numerous accessories, such as 

a belt safety stop, adjustments for sensitivity, 

a hand wheel for manual control, and a small 

electric motor, the synchronizing motor, to 

adjust the tension on the speeder spring remotely from the switchboard in order to 

vary the turbine speed.46 

Speed Regulation of Steam Turbines 

Charles A. Parsons, the inventor of the 

first practical steam turbine, employed on his 

earlier models a most unconventional method 

of speed control. It is demonstrated on his 

fifth turbine (Figures 49-51), constructed in 

1884 or 85, now in the collection of the 

National Museum of History and Technology (NMHT 311875; Accession 153831; 

built by Clark, Chapman, Parsons & Co., 

Gateshead-on-Tyne, England; 10 electr. hp at 

18,000 r.p.m.). Its speed-sensing device, a 

centrifugal fan F, creates on its suction side 

a vacuum which is considered roughly proportional to the speed. Simultaneously, the 

vacuum generated by the fan also serves to 

circulate lubricating oil. A large springloaded leather diaphragm L, connected to 

the vacuum, is linked by a rigid rod to the 

throttle valve V in such a fashion as to reduce the steam flow to the turbine with increasing speed. Coupled with this purely 

mechanical system of speed control is an electrical fine adjustment. A metal pipe Y connected to the vacuum system has its opening 

at the top of the generator G. A springloaded baffle pivoting in front of the opening is actuated by the magnetic field of the 

dynamo, so that with increasing output voltage the vent hole is closed, causing an increase of vacuum and hence a decrease in 

turbine speed. In the case of decreasing generator output the vent is opened, so that the 

vacuum will sink, resulting in an opening of 

the throttle valve. Parsons claimed that "So 

accurate is the addition, that, when the load 

is gradually varied from nothing up to the 

maximum, the variation in volts at the terminal is less than one per cent." On the 

turbine exhibited, the diaphragm and the ro46. Ibid., pp. 181-184. 
FIGURE 49.—Parsons steam turbine, about 1885. (NMHT 311875. Smithsonian photo 34043-C.) 

FIGURE 50.—Drawing of a Parsons steam turbine similar to NMHT 311875. Reprinted from the 

Proceedings of the Institution of Mechanical Engineers, 1888, pi. 85. 

FIGURE 51.—Governor details of a Parsons steam 

turbine. Reprinted from the Proceedings of the 

Institution of Mechanical Engineers, 1888, pi. 86. 
NUMBER 12 47 

tary baffle on the yoke of the generator are 

missing.47 

In 1889 Parsons terminated his relationship with Clarke, Chapman & Co. and 

founded a firm of his own at Newcastle-uponTyne. Since the former company retained the 

rights to his patents, he had to resort to inventing a totally new steam turbine, the 

radial-flow turbine, as well as a new method 

of governing. The latter, which has become 

known as "gust-governing," has been implemented in a number of different ways; its 

basic principle was to admit the steam not in 

a steady flow but intermittently in periodic 

"gusts." Its advantage was that the control 

mechanism, avoiding static friction by being 

continuously in motion, would be more responsive to small deviations of speed. In some 

47. Charles A. Parsons, "Description of the Compound Steam Turbine and Turbo-Electric Generator," 

Proceedings, Institution of Mechanical Engineers 

(1888):485; Robert H. Parsons, The Development of 

the Parsons Steam Turbine (London, 1936), pp. 7-8. 

designs the duration of the "gust" was directly 

controlled by the governor; in others, as for 

example on the Parsons turbogenerator of 

1905 (Figure 52), an oscillatory motion generated by an eccentric was simply superimposed on the action of a conventional 

system by proportional control (NMHT 

322000; Accession 243961; serial no. 1025; 

steam pressure 100 p.s.i.g., no superheat, vacuum 27" hg.; designed for an output of 20 

KW, 110 volt A.C., 182 amp., at frequency 

of 83i/3 CPS, speed 5000 r.p.m.; 2-pole generator compound-wound with compensating 

coils). The governor employed here consists 

of a shunt solenoid mounted on the alternator. The core of the solenoid, suspended 

from above by a spring, is drawn downward 

with rising current output, that is, increasing speed. It is directly connected with the 

steam inlet valve, so that a downward motion 

of the core leads to the closing of the throttle 

valve. The special feature of Parsons' "gustgoverning" is the following: the pivot point 

FICURE 52.—Parsons steam turbine of 1905. (NMHT 322000. Smithsonian photo 72172.) 
48 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

of the lever connecting the core of the solenoid with the control valve is not fixed but 

oscillates vertically, being driven by an eccentric geared to the turbine shaft. This oscillation, independent in period and frequency 

of the governor action, serves only to keep 

the control system "alive"—i.e., in constant 

action—in order to avoid the sticking of any 

elements after prolonged periods of equilibrium. The frequency of steam blasts was initially about 160 to 180 per minute, later 

approximately twice that. Another notable 

feature of this system is the throttle valve: it 

is servo powered, using as a source of power 

steam that has leaked through the bushings 

of the throttle valve. When finally, about 

1919-1920, "gust-governing" was displaced 

by oil-powered hydraulic systems because of 

the stricter requirements of high-pressure 

steam, its passing was regretted by many engineers.48 

The early turbines of Gustav de Laval 

(1845-1913), the Swedish steam turbine pioneer, were regulated more conventionally 

than those of Parsons. Laval's turbines were 

first put into series production in 1892. The 

10-hp unit exhibited in our Museum was 

shown at the World's Columbian Exposition 

at Chicago, 1893 (NMHT 314843; Accession 

210798; capable of 10 to 20 hp at turbine 

speeds of about 20,000 to 30,000 r.p.m.; drives 

D.C. generator through reduction gear). The 

same turbine also served as a patent model, 

persuading the U.S. Patent Office to grant 

48. Robert H. Parsons, The Development of the 

Parsons Steam Turbine, pp. 16-17, 41, 145; Robert M. 

Neilson, The Steam Turbine, 2nd edition (London, 

1903), pp. 170-174. 

FIGURE 53.—Model of a Lenoir gas engine of about 1860. (NMHT 315042. Smithsonian photo 

43952-A.) 
NUMBER 12 49 

de Laval in 1894 a patent he had applied for 

in 1888. A flyweight governor mounted on the 

low-speed shaft of the reduction transmission 

is somewhat difficult to recognize, because it 

is totally enclosed in a small cylindrical capsule. In traditional fashion the governor acts 

through a simple arrangement of levers on 

the throttle valve in the steam inlet line. 

Similar is the speed control system of the 

Terry steam turbine of 1910 (NMHT 

314820; Accession 210004; serial no. 467; 58 

hp at 2500 r.p.m.). A flyweight governor 

mounted on the turbine shaft is directly connected to a throttle valve in the steam line. 

An example of more modern turbine regulation is the three-stage Curtis turbine built 

by the General Electric Co. in 1927 (NMHT 

309881; Accession 106194; type DS-53-3; 

serial no. 38769; 50/100 hp, 500/7800 

r.p.m.). The centrifugal governor is integrated into an oil-powered servo system. It 

positions a horizontal beam in the steam 

chest to which all the valves for the individual inlet nozzles are attached. Also included 

are a synchronizing motor for remote speed 

adjustment and an overspeed-shutdown 

mechanism to prevent dangerously high 

speeds. 

Speed Regulation of Internal 

Combustion Engines 

During the second half of the nineteenth 

century, the internal combustion engine became an important rival to the steam engine. 

At first its speed was controlled by governors derived directly from the steam engine, but soon distinctive new types emerged 

that took into account the peculiarities of 

the new engine. 

The speed-control system on the model of 

a Lenoir gas engine of about 1860 (model 

made at the Museum in 1957 after an engine built by the Lenoir Gas Engine Co. of 

London; NMHT 315042; Accession 214268) 

is clearly patterned (Figure 53) after that of 

the steam engine. A governor in the style of 

Watt's original design actuates a throttle 

valve in the fuel gas intake line. ConFIGURE 54.—Otto & Langen atmospheric gas engine, 

1872. The governor (top) acts on the exhaust valve 

(bottom). (NMHT 314658. Photo CLG.) 

trolled in the same manner is the Buick 

gasoline engine of 1902 (NMHT 319024; Accession 236000; a vertical single-cylinder fourstroke watercooled stationary engine, marked 

"THE BUICK MFG. CO., H.P.4, NO. 567, 

DETROIT, MICH."). A centrifugal governor behind the flywheel acts on a throttle 

valve in the intake line between carburetor 

and cylinder. This method of speed control 

is still in use. The Lorimer gasoline engine 

"Sturdy Scott" of the 1940s (NMHT 328394; 

Accession 272466; single cylinder vertical stationary engine of 8 hp at 600 r.p.m.) is 

equipped with a centrifugal governor acting 

on a throttle in the intake manifold (type 
50 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

"GC 1107.2.8," by Pierce Governor Co., Anderson, Indiana), which is, with minor modifications, still being produced.49 

A small step toward an independent mode 

of control was taken in the atmospheric freepiston gas engine of Otto 8c Langen, 1872 

(NMHT 314658; Accession 207779; i/2 hp; 

marked "PATENT LANGEN & OTTO 

GASMOTOREN FABRIK DEUTZ NO. 

537"). Its governor (Figure 54), according 

to the special character of the power stroke 

of this engine, acts on a throttling valve located in the exhaust line. 

The majority of speed-control systems for 

internal combustion engines can be divided 

into two classes: proportional control, where 

the rate of fuel intake can be varied continuously in relation to the speed by various 

proportioning devices; and "hit-and-miss" control, where in the case of part-load operation 

whole power strokes are omitted. Of both, 

the hit-and-miss method was the cheaper and 

49. A. L. Dyke, Automobile and Gasoline Engine 

Encyclopedia, 22nd edition (Chicago, 1952), p. 947. 

the shorter lived one. It was best suited for 

four-stroke engines using gas or gasoline, 

where for proper functioning an optimum 

fuel-air mixture was critical. 

The system of hit-and-miss governing is well 

demonstrated on the "Silent" Otto gas engine 

of about 1880 (NMHT 323495; Accession 

250990; a single-cylinder horizontal fourstroke gas engine of 2 hp at around 180 r.p.m., 

built since 1876 by the "Gasmotoren-Fabrik 

Deutz," serial no. 4417). In the side view of 

the engine (Figure 55) the governor is located 

on the lower left. Its appearance is somewhat 

untypical because the revolving flyballs are 

covered, presumably for reasons of safety, by 

a bowl-shaped hood. The top of the governor 

is connected by a bell crank to a small sleeve 

sliding on the horizontal lay shaft which 

powers the governor and slide valve. This 

sleeve, free to move horizontally but constrained to rotate with the shaft, carries a 

narrow cam which opens the gas inlet valve 

during a certain part of the suction stroke. 

At excessive speeds the slide moves to the 

FIGURE 55.—"Silent Otto" gas engine, about 1880. The centrifugal governor is protected by a 

bowl-shaped hood (left, bottom). (NMHT 323495. Smithsonian photo P65778.) 
NUMBER 12 

51 

FIGURE 56.—Centrifugal governor on Hart-Parr agricultural tractor, 1903. 

(NMHT 60A74. Photo CLG.) 
52 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 57.—Vertical Otto gas engine, about 1895 with a "pendulum" governor (incomplete, 

bottom). (NMHT 311902. Photo CLG.) 
NUMBER 12 53 

right so far that the cam will miss the valve 

lifter. The engine, receiving no fuel during 

the whole cycle, is thus decelerated until it 

runs again at the desired speed. Because of 

its inherent irregularity, large flywheels were 

needed in this method of control; on the other 

hand it was inexpensive, simple of construction, and above all highly economical with 

regard to fuel consumption.50 

The same control system is also employed 

on two other "Otto" engines in the Museum's 

collections, both of the same type as the above 

one, and both built in Philadelphia by 

Schleicher, Schumm & Co. or their successor, 

the "Otto Gas Engine Works" (1. NMHT 

309556; Accession 104812; built in 1882; 

serial no. 554; rated 4 hp at 160 r.p.m.61 

2. NMHT 323697; Accession 242800; built 

around 1910, serial no. 6690; 9.5 hp at 300 

r.p.m.), and on a White & Middleton gasoline 

engine of 1897 (NMHT 325904; Accession 

256985). 

Similar to this is also the speed regulation 

of the two-cylinder four-stroke kerosene engine 

on the huge Hart-Parr agricultural tractor of 

1903 (NMHT 60A74; Accession 230442). 

Again a centrifugal governor (Figure 56) acts 

on a system of latches which make the fuel inlet valves inoperative at above-normal speeds. 

A hit-and-miss system of very unusual character is the "pendulum" governor—not to be 

confused with the centrifugal pendulum— 

which measures velocity not in terms of centrifugal force but by the inertia effect of a 

pendulum suspended from some reciprocating 

member of the engine. On the vertical "Otto" 

gas engine (Figures 57 and 58) of about 1895 

(NMHT 311902; Accession 156547; Otto Gas 

Engine Works, Philadelphia, serial no. 4765; 

2 hp at 300 r.p.m.) the pendulum is suspended 

at the bottom of the eccentric rod in such 

a manner that at normal speed it will engage 

and open the gas intake valve once every 

50. Dugald Clerk and G. A. Burls, The Gas, Petrol, 

and Oil Engine, 2 vols., 2nd edition (New York, 1913), 

11:362-363; Friedrich Sass, Geschichte des deutschen 

Verbrennungsmotorenbaues. von 1860 bis 1918 (Berlin, 

1962), pp. 45-46. 

51. Taylor, Catalogue of Mechanical Collections, p. 

156. 

FIGURE 58.—Contemporary drawing of a vertical Otto 

engine similar to NMHT 311902, showing the "pendulum" governor in working condition. Reprinted 

from The Otto Gas Engine Works, Catalog of the 

"Otto" Gas Engine (Philadelphia, no date [about 

1897]), p. 9. 

cycle. At excessive speeds, however, the latch 

on the pendulum will, due to its inertia, miss 

the valve, and the engine will run without 

fuel until it has returned to normal speed. 

The pendulum governor on this particular 

engine is not complete. 

Another variation on the theme of hit-andmiss control is demonstrated on a small stationary "Domestic" gasoline engine of about 

1905 (NMHT 329792; Accession 282826; 

marked "MADE BY DOMESTIC ENGINE 

AND PUMP CO. SHIPPENSBURG, PENN-
54 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

SYLVANIA. No. 682 H.P. H/2"). A shaft 

governor of the simplest possible construction 

—a weight sliding radially along a shaft fixed 

to one spoke of the flywheel—acts through a 

variable-throw eccentric on the exhaust valve 

which it arrests at overspeed in its open 

position, thus preventing the engine from 

drawing in fresh fuel. When the speed has 

returned to its normal value, the exhaust valve 

will be released again. Hit-and-miss control 

similar to this—where a centrifugal governor 

acts simultaneously upon the exhaust valve 

and the ignition circuit—is employed on an 

Olds gasoline engine (Figure 59) of about 

1910 (NMHT 315111; Accession 216224; 

marked "SELF CONTAINED GASOLINE 

ENGINE, NO. 8482-3A PATENTED. MANUFACTURED BY OLDS GASOLINE ENGINE WORKS, LANSING, MICH., USA"), 

and on the "Aermotor gasoline engine, also 

of about 1910 (NMHT 316806; Accession 

228815). 

In spite of its economy, hit-and-miss regulation eventually lost its popularity. It was 

far too inaccurate for generation of electricity. 

Besides it was somewhat unreliable, and the 

discontinuity of its operation made large flywheels necessary. In the beginning of the 

FICURE 59.—Olds gasoline engine, about 1910. The right flywheel carries a simple shaft governor 

which actuates the "hit-and-miss" control through the horizontal rod on the lower right of the 

cylinder. (NMHT 315111. Smithsonian photo 45926-A.) 
NUMBER 12 55 

twentieth century it was gradually replaced. 

The systems of speed control that prevailed 

employed the proportional response, where 

the corrective action was proportional to the 

deviation of the actual from the desired speed. 

The simplest case—throttling control—has 

already been discussed. The remaining examples of this in the Museum's collection all 

have one feature in common: all employ 

centrifugal governors acting on some proportioning mechanism by which the amount of 

fuel per cycle introduced into the cylinder can 

be varied. 

The oldest of these regulators is installed 

on the Brayton oil engine (Figure 60) of 

about 1877 (NMHT 313703; Accession 

192653; rated 2 hp at 250 r.p.m.; used for driving an arc-light dynamo at Brown University). 

A spring-loaded centrifugal governor on a 

horizontal spindle determines the axial position of a cam sliding axially and rotating with 

the spindle. A roller running on the cam actuates a valve lifter of the fuel intake valve. The 

FIGURE 61.—Atkinson "Cycle" gas engine, 1889. 

(NMHT 310371. Smithsonian photo 31381-A.) 

cam is shaped three-dimensionally, its width 

varying along the axis, so that the period of 

valve opening depends on the axial position 

of the cam. With increasing speeds the governor then moves the cam in such a direction 

that the period of fuel admission is shortened.52 

The speed control of the Atkinson "Cycle" 

four-stroke gas engine (Figure 61) of 1889 is 

similar (NMHT 310371; Accession 117006; 

2 hp; serial no. 416).53 A spring governor 

controls the opening of the gas intake valve 

by inserting a stepped wedge more or less far 

between the valve lifter and the rotating cam. 

The Hornsby-Akroyd hot-bulb oil engine 

(Figure 62), about 1893-1895 (NMHT 

309637; Accession 106378; 4 hp at 225 r.p.m.; 

serial no. 1501), is equipped with a loaded 

governor acting on a bypass valve in the oil 

supply line, which at overspeed diverts some 

of the fuel oil back to the oil tank in the base 

plate of the engine. 

On the Mietz 8c Weiss one-cylinder twostroke hot-bulb oil engine, about 1906 

(NMHT 319407; Accession 236710), a cenFIGURE 60.—Brayton oil engine, about 1877. (NMHT 

313703. Smithsonian photo 56027.) 

52. R. C. Carpenter and H. Diederichs, Internal 

Combustion Engines, 3rd edition (New York, 1910), 

p. 250. 

53. Taylor, Catalogue of Mechanical Collections, p. 

157. 
56 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 62.—Hornsby-Akroyd hot-bulb oil engine (about 1893) with a Porter-type governor 

(foreground). (NMHT 309637. Smithsonian photo 6092.) 

trifugal shaft governor adjusts the length of 

stroke of the fuel pump according to the load 

by means of shifting the eccentric on the main 

shaft.54 

Diesel engines were usually controlled by 

conventional flyball governors acting on some 

proportioning mechanism in the fuel-oil pump 

which varied the amount of fuel injected into 

the cylinder at every stroke. The earliest example of this in our collection is the M.A.N. 

single-cylinder vertical Diesel engine of 1903 

(NMHT 314945; Accession 211077; type 

"DM 8", 8 hp at 270 r.p.m., marked 

"Vereinigte Maschinenbaufabrik Augsburg 

und Mascbinenbaugesellschaft Niirnberg 

A.G., Werk Augsburg, No. 443 Warme-Motor 

'Patent Diesel' 1903"). The fuel pump is a 

plunger pump where the discharge valve is 

uncontrolled, while the suction valve is directly linked with the governor (Figure 63), 

so that the engine speed determines the duration of opening of the suction valve of the 

fuel pump. The fuel pump is a replica built 

in the Museum after original drawings (not 

operational).55 

On the three-cylinder Diesel engine built 

by the American Diesel Engine Co. in 1905 

(NMHT 316726; Accession 227588; serial no. 

151; 120 hp at 220 r.p.m.), a flyball governor 

(Figure 64) similarly controls the opening 

time of the suction valve of the fuel pump, 

54. Carpenter and Diederichs, Internal Combustion 

Engines, p. 384. 

55. Hugh Giildner, The Design and Construction of 

Internal-Combustion Engines, trans. H. Diederichs 

(New York, 1910), pp. 267, 362; F. E. Junge, "Technical Aspects of Oil as Fuel," Power (18 February 1908), 

p. 255, fig. 46. 
NUMBER 12 57 

FIGURE 63.—Upper part of M.A.N. Diesel engine of 1903 with governor (top, enclosed) and fuel 

valve. (NMHT 314945. Photo CLG.) 

although not by the linear motion of a linkage 

but rather through the rotation of a cam.56 

56. Giildner, Internal Combustion Engines, pp. 430-

433. 

In contrast to the two preceding systems 

where the speed of Diesel engines is regulated 

by manipulating the suction valves of the 

fuel injection pump, the governor (Figure 
58 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FICURE 64.—Three-cylinder "American Diesel" engine, 1905; detail view of governor and fuel 

pump. (NMHT 316726. Photo CLG.) 
NUMBER 12 59 

FIGURE 65.—Three-cylinder "Atlas-Imperial" Diesel engine, 1921; detail view of governor (enclosed in engine block) and mechanism for varying the valve-stroke. (NMHT 316578. Photo 

CLG.) 
60 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

65) of the three-cylinder Atlas-Imperial marine 

engine, 1921, adjusts the opening period of 

the injection nozzle directly (NMHT 316578; 

Accession 223429; serial no. 8003; 55 hp at 

320 r.p.m.). This is accomplished by inserting, 

to a variable degree, wedges between the valve 

lifter rods and the valve actuating cams. A 

pressure regulator in the fuel supply line 

keeps the supply pressure constant in the 

event of changes in fuel consumption. The 

desired engine speed can be easily adjusted by 

a control lever changing the initial tension of 

the governor spring. 

The fuel injection pumps for automotive Diesel engines were often equipped with 

built-in governors. On Bosch fuel injection 

pumps, of which the Museum has specimens 

(Figures 66 and 67) of 1935 and 1944 (1. 

NMHT 311017; Accession 135324; type PE 

4 D; marked "P200/1000 BC1: PHV1/1Z." 2. 

NMHT 312825; Accession 167594; marked 

"American Bosch GV A250/800B19 NS."), the 

governors served to regulate the idling speed 

and to prevent overspeed, while in the normal 

working range the speed was controlled manually through the throttle lever. To accomplish 

this, the governor spring consists of a very soft 

spring and a very stiff spring arranged in 

series; the soft spring is in action at low idling 

speeds with the throttle lever at rest. In the 

normal working range the governor is inactive: 

the soft spring is fully compressed while the 

stiff spring is still uncompressed. The latter 

will respond only to the high centrifugal forces 

occurring at overspeed. The quantity of fuel 

injected is controlled by an ingenious method 

of changing the pump stroke directly: each 

plunger has on its side a conical groove so 

that its discharge per stroke depends on the 

plunger's angular position with respect to 

the inlet port. All plungers are connected 

through a rack-and-pinion arrangement with 

the output arm of the centrifugal governor. 

With increasing speed, the governor will rotate 

FIGURE 66.—Bosch "Type PE4D" fuel injection pump, 1935. The side of the governor is visible 

through the second opening from the left. (NMHT 311017. Photo CLG.) 
NUMBER 12 61 

the plungers in such a manner that by shortening their effective stroke it will decrease the 

discharge rate of the fuel injection pump. 

In a more recent type of internal combustion 

engine governor, the function of speed regulation is completely separated from that of 

supplying fuel. These governors are compactly 

designed black boxes with only two external 

connections: an input link to the drive shaft 

and an output lever to some proportioning 

device in the fuel supply system. As direct 

descendants of the hydraulic water turbine 

governors, they include hydraulic servomotors 

powered by self-contained, high-pressure oil 

systems. 

The Museum has three specimens of this 

type of governor. The oldest is a Woodward 

"Model SI" (Figure 68) from the early 1940s 

(NMHT 330029; Accession 288883; cutaway; 

5i/2"X8i/2"X 15i/2"; on display stand 5i/2" 

high). The speed-sensing device is an arrangement of conventional spring-loaded 

flyballs, acting upon the pilot valve of a hydraulic servomotor. As will be recalled (Figure 46), in order to have proportional 

response, a hydraulic servomotor requires a 

feedback connection between the power piston 

and the pilot valve. On the Woodward "SI" 

governor, the feedback link is hydraulic, consisting of special hydraulic pistons both on the 

power piston and on the pilot valve, both 

working in cylinders connected by a pipe. The 

governor is capable, however, of more than 

merely proportional response. The feedback 

pipeline contains a needle valve providing a 

small opening to the oil sump. Through it oil 

can enter or leave the enclosed space of the 

feedback connection, so that the relationship 

between power piston and pilot valve is no 

longer rigid but instead flexible, adapting 

FIGURE 67.—American Bosch fuel injection pump, 1944. (NMHT 312825. Smithsonian photo 

48438-L.) 
62 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 68.—Woodward "Model SI" engine governor 

with hydraulic servomotor, self-contained, about 1940. 

(NMHT 330029. Photo CLG.) 

itself to the needs of the governor. As a result, 

the governor provides "proportional plus 

integral" control, that is, unlike a purely proportional regulator, it can keep the speed 

precisely constant regardless of load changes; 

or, in the words of its manufacturer, it is 

"isochronous." The desired speed can be set 

on a geared dial which determines the initial 

compression of the spring balancing the 

flyballs.57 

Slightly more recent is the governor "Model 

B117" (Figure 69) by the Marquette Metal 

57. Woodward Governor Company, S.I. Governor, 

Dial Control; Bulletin 01030 (Rockford, Illinois, 1945). 

FIGURE 69.—Marquette "Model BI 17" engine governor 

with hydraulic servomotor, self-contained, 1940s. 

(NMHT 330028. Photo CLG.) 

Products Co., Cleveland Ohio (NMHT 330028 

Accession 288883; cutaway; 73/£"X67/8"X 

I514"; on turntable, 7i/2" high). In its function as well as in its principles of design it is 

similar to the preceding Woodward Model 

"SI." Differences are only in details of construction. 
NUMBER 12 

A further development of this conception 

of prime-mover governor is the Woodward 

"Model UG8" dating from about 1950 

(NMHT 315897; Accession 221844; cutaway; 

5L4"X53/4

/

'xi2i/2

,/; on display stand, 7i/2" 

high). It differs from the earlier Woodward 

unit by a more refined mechanical design, 

and by providing for several additional 

adjustments. A "compensating adjusting 

pointer" changes the proportional sensitivity; 

a "load limit control" knob permits limit of 

the output to less than full stroke; the "speed 

droop control" knob permits elimination of 

the integral response, for a purely proportional 

response is preferable when several engines 

run on the same shaft or are paralleled in an 

electrical system.58 

58. Woodward Governor Company, UG-8 Governor, 

Dial Control; Bulletin 03004 C (Rockford, Illinois, 

no date). 
CHAPTER 4 

Friction Governors 

Chronographs 

A descendant of the classical steam governor, distinguished by extreme simplicity of 

conception, is the friction governor. Like 

its ancestor, it employs centrifugal flyweights to sense speed, but corrective action is 

taken simply by braking; it is usually driven 

by falling weights or wound-up springs. Such 

governors have been applied where constant 

speed is required for purposes related to timekeeping, as, for example, to propel recorder 

charts, to rotate the turn tables of phonographs 

and the beacons of light towers, and to turn 

equatorial telescopes synchronously with the 

rotation of the earth. The friction governor is also noteworthy for a historical reason. 

Early telescope regulators at Greenwich Observatory displayed some curious oscillatory 

phenomena which Astronomer Royal George 

Biddell Airy (1801-1892) felt challenged to 

investigate. His results, published in 1840 and 

1850 in two frequently quoted papers, mark 

the beginnings of the theory of automatic 

control.59 

The oldest friction governor in the 

Museum's collection is part of the clockwork 

for an equatorial telescope, a 5-inch refractor 

by Trough ton 8c Simms, which was acquired 

by the Georgetown College Observatory in 

1849 (NMHT 316096; Accession 224215; 

brass, 6"X3i/ 2 "X9"; unmarked). The gover59. George Biddell Airy, "On the Regulator of the 

Clockwork for Effecting Uniform Motion of Equatorials," Memoirs of the Royal Astronomical Society 

11 (1840):249-267; Supplement to the above, Memoirs 

of the Royal Astronomical Society 20 (1850): 115-119. 

nor (Figure 70), consisting of three pendulums suspended from a rotating triangular 

plate, is mounted on top of a rectangular box 

housing the gear train and the cable drum of 

the weight drive. A conical hood covers the 

governor. At overspeed, the centrifugal pendulums swing outward and press against the 

walls of the cover. The resulting friction leads 

to a reduction in speed. A more modern counterpart to this is the driving clock (Figure 71) 

FIGURE 70.—Friction governor used on Troughton & 

Simms equatorial telescope of 1849. Not shown is the 

conical hood normally placed over the flyweights 

to provide a friction surface. (NMHT 316096. Smithsonian photo 71696.) 

64 
NUMBER 12 65 

FIGURE 71.—Friction governor used to drive a large 

telescope at Princeton University, 1920s. (NMHT 

327711. Smithsonian photo 70536.) 

of the 23-inch refractor from the old Halsted 

Observatory, Princeton University, built in the 

1920s by John W. Fecker of Pittsburgh 

(NMHT 327711; Accession 283654; steel, 

2H/2"X28"X43"; unmarked). It differs from 

the preceding one only in size. The governor 

consists of two flyballs of 5-inch diameter 

which at overspeeds actuate a large disk brake. 

Besides the gear train, a cable drum for the 

weight drive, and various provisions for adjustments, the rectangular frame of the clockwork houses a V^-hp electric motor for 

winding up the driving weight. 

Chronographs, forerunners of the modern 

self-writing laboratory recorder, consisted of a 

paper-covered drum, rotating at a known 

constant speed which was usually maintained 

by a centrifugal governor. The chronograph 

by the Washington instrument makers Fauth 

2c Co. dates probably from the 1880s (NMHT 

315243; Accession 217937; drum 14" long, 

mounted on iron base 12"X22"; unmarked) . 

The two-arm friction governor is mounted 

above the weight-drive mechanism on one side 

of the drum. A similar but somewhat more 

recent chronograph (Figure 72), also probably by Fauth (NMHT 322455; Accession 

248006; unmarked), is also weight-driven and 

equipped with a governor of the same design 

as the previous one. 

Two detached clockworks, approximately 

from the turn of the century, offer no clue 

whether they were used on chronographs or 

on equatorials. The governor on the first 

(NMHT 328889; Accession 277637; brass; 

73/4"X4i/2"x9"; unmarked) is of the same 

construction as those on the two abovementioned Fauth chronographs. It is mounted 

on a rectangular gear box which contains 

neither a weight- nor a spring-drive. The other 

clockwork (NMHT 322282; Accession 250512; 

brass; 5i/2"X3"X U%"; marked "G. Boulitte, 

Ing'r Const'r, 15 Rue Bobillet, Paris") is 

driven by a wound-up spring. It is regulated 

by a Pickering-type governor of three leaf 

springs, the lower collar of which presses at 

overspeed against a brake. 

An interesting variation of the basic concept 

of the friction governor (Figure 73) is used 

on a Wiechert seismograph of about 1910 

(NMHT 326987; Accession 265135; 34"X34" 

X52"; marked "Spindler k Hoyer Gottingen"). The governor regulating the speed of 

its chronograph consists of two pendulum 

arms each carrying a flyweight as well as a 

metal vane. When these arms swing outward 

with rising speed, the corresponding increase 

in aerodynamic resistance provides the necessary braking effect, which on the previous 

governors was due to solid friction. 

A chronograph of about 1940 (NMHT 

316276; Accession 224564; marked "Elektrosignal G.m.b.H., Berlin 017, 220 Typ 05.5, 

Gerat 1 + 1") contains a spring-driven clockwork with a Pickering-type friction governor 

which is remarkable only for its extremely 

small size; it is approximately 3/^-inch long 
66 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 72.—Chronograph, probably by Fauth & Co., Washington, about 1890. (NMHT 322455. 

Smithsonian photo 71859.) 

and l/g-inch in diameter. The spring-driven 

clockwork invented in 1942 by C. G. Abbot, 

a former Secretary of the Smithsonian Institution (NMHT 314888; Accession 211900; 

brass; 6"X5"X5" ; unmarked; U.S. Patent 

2367254), employs a spring-loaded friction 

governor in order to be able to run with equal 

accuracy in all orientations of its axis. 

Phonographs 

A new opportunity for friction governors 

presented itself with the introduction of the 

phonograph: the quality of tone reproduction 

depended on accurate speed control.60 The 

Museum's collection contains more than one 

hundred phonographs and related devices, 

most of which are equipped with such governors.61

 Instead of listing these all individually, we shall describe here only four repre60. Edward W. Kellogg, "A Review of the Quest for 

Constant Speed," R.C.A. Review 2 (1937):220-239. 

61. For a detailed treatment of early phonographs, 

see James L. Andem, A Practical Guide to the Use of 

the Edison Phonograph (Cincinnati, 1892), especially 

pp. 17-21; Roland Gelatt, The Fabulous Phonograph 

(Philadelphia, 1955); Oliver Read and Walter L. 

Welch, From Tinfoil to Stereo: Evolution of the 

Phonograph (Indianapolis, 1959). 

sentative specimens displayed in the Hall of 

Timekeeping and Light Machinery, where the 

governors are easily visible to the viewer. The 

FIGURE 73.—Centrifugal vane governor on Wiechert 

seismograph, about 1910. (NMHT 326987. Smithsonian 

photo 72264.) 
NUMBER 12 67 

FIGURE 74.—Bell & Tainter "Type P" gramophone with friction governor (rear). (NMHT 1015. 

Smithsonian photo 42171-A.) 

FIGURE 75.—Berliner gramophone equipped with governor (left) invented by Alfred C. Clark, 

1898. (NMHT 253757. Smithsonian photo 42171-E.) 
68 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Bell Sc Tainte r Graphophone (Figure 74) of 

1887 (NMH T 1015; Accession 6139; built by 

the American Graphophone Co., Type B, old 

style; serial no. 04192) is equipped with a 

friction governor functioning in the same 

way as the chronograph governor described 

before. It is mounted separately from the recording and reproducing apparatus (marked 

"Patented July 20, 1886"; size 6i/ 2 "Xl0i/ 2 " 

X6"). 

Edison's successful phonograph of 1887 is 

represented by a specimen built about 1899 

at Edison's shop especially for the Smithsonian 

Institution (NMH T 202871; Accession 

35337). Th e electrically driven phonograph 

employs a small two-ball friction governor 

modeled after Pickering's design. This arrangement was adopted in many phonographs, as, for example, in the coin-operated, 

spring-powered Graphophone "Model B" of 

the Columbia Phonograph Co., about 1897 

(NMH T 314989; Accession 212922; serial no. 

185552). Th e three-ball Pickering-type friction governor is visible through the glass 

cover in the rear of the machine. 

T h e governor on Alfred C. Clark's patent 

model of an improved version of the Berliner 

Gramophone, 1898 (NMH T 253757; Accession 49940), is clearly derived from the steam 

engine shaft governor (Figure 75). In case of 

overspeed it separates the recording and reproducing mechanism from the hand drive. 

FIGURE 76.—Governor of Siemens & Halske printing telegraph, 1901. (NMHT 327954. Smithsonian photo 74616.) 
NUMBER 12 69 

Alfred C. Clark, of Berliner's retail store in 

Philadelphia, obtained for this governor the 

United States Patent 597875 of 25 January 

1898. 

Telegraphs 

Governors were also used in certain systems 

of printing telegraphs based on synchronous 

rotation of corresponding parts at both the 

transmitter and the receiver. For example, 

the Hughes-type printing telegraph manufactured by Siemens 8c Halske employed a 

spring-loaded centrifugal friction governor 

(Figure 76). Our Museum has two specimens 

of this device (1. NMH T 319765; Accession 

238390; about 1897; governor serial no. 1257. 

2. NMH T 327954; Accession 271855; 1901; 

governor serial no. 3506) .

62 

Thoma s A. Edison, for similar purposes, 

employed a simple, small centrifugal governor which at overspeed would break the 

battery connection to the electric motor driving the apparatus. Examples of this are the 

patent model (Figure 77) of his printing tele62. Theodor Karrass, Geschichte der Telegraphie 

(Braunschweig, 1909), pp. 294, 302. 

FIGURE 77.—Patent model of Thomas A. Edison's 

Gold and Stock printing telegraph, 1873. (NMHT 

252616. Smithsonian photo 71882.) 

graph (U.S. Patent 140488 of 1 July 1873; 

NMH T 252616; Accession 49064) and a 

patent model entitled "Telephonic Telegraph" (U.S. Patent 198087 of 11 December 

1877; NMH T 252617; Accession 49064). 
CHAPTER 5 

Automatic Control of Steam Boilers 

Since their earliest period steam boilers have 

provided opportunities of application for a 

variety of feedback devices. The oldest of 

these is the safety valve first described in 1681 

by Denis Papin as a pressure regulator for 

pressure cookers but used by him as a steam 

boiler safety valve as early as 1707. It soon 

became an indispensable accessory of steam 

engines. Despite its simplicity—it consists of 

a weight-loaded valve in the boiler wall 

which is forced open by excessive steam pressure until the surplus steam is released—it 

represents a closed loop with negative feedback. Virtually all steam boilers in the 

Museum's collection, full-size specimens and 

scale models, possess safety valves. Since all 

are based on the same principle and show little historical development, these safety valves 

are too numerous to warrant individual listing. As a single representative of this class we 

may mention the safety valve (Figure 78) used 

by John Stevens on the water tube boiler of 

his experimental rack locomotive in 1825 

(NMHT 180029; Accession 20760).63 It is a 

simple disk valve held closed by a spherical 

lead weight suspended from the end of a 

pivoted lever. The desired boiler pressure can 

be adjusted by sliding the weight inward or 

outward along the lever. 

In the middle of the eighteenth century 

another feedback device was added to the 

boiler. The float valve, employed to keep the 

water level in the boiler automatically 

constant, was first described in a patent 

of James Brindley of 1758 (English Patent 

730); toward the end of the century this invention was widely accepted.64

 Unfortunately 

this invention is represented in the collections 

of the Museum by only a single device, the 

float level regulator of the Shipman "Automatic" steam engine.65 

A little later, feedback devices were applied 

to regulate the steam pressure by adjusting 

the rate of combustion. The arrangements 

proposed usually consisted of a pressuresensing device linked to a damper in the chimney, reducing the draft in case of excessive 

steam pressure. Matthew Murray of Leeds, 

England, patented such a system in 1799 

(English Patent 2327) ; a similar one was 

FIGURE 78.—Safety valve for water tube boiler by John 

Stevens, 1825. (NMHT 180029. Smithsonian photo 

2720.) 

63. Taylor, Catalogue of Mechanical Collections, 

pp. 109-110, 119. 

64. Mayr, Origins of Feedback Control, pp. 76-81. 

65. For typical examples of level control on steam 

boilers, see George F. Gebhardt, Steam Power Plant 

Engineering, 5th ed. (New York, 1917), pp. 640-644; 

and Terrell Croft, Steam Power Plant Auxiliaries and 

Accessories (New York, 1922), pp. 203-204. 

70 
NUMBER 12 71 

employed by Boulton 8c Watt about 1803;

 66 

more recent ones are described by Gebhardt.67 

In other cases the rate of combustion was 

66. H. W. Dickinson and Rhys Jenkins, James Watt 

and the Steam Engine (Oxford, 1927), p. 239. 

67. Gebhardt, Steam Power Plant Engineering, pp. 

178-179. 

controlled not by varying the draft but by 

changing the rate of fuel input directly. 

Both these types of boiler control, a float 

valve level regulator and a steam pressure 

control system, are represented on the Shipman "Automatic Steam Engine" (Figure 

79) built about 1885 by the Shipman Engine 

FIGURE 79.—Shipman "Automatic Steam Engine," about 1885. 

(NMHT 315712. Smithsonian photo 45572.) 
72 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

i 

FIGURE 80.—Shipman "Automatic Steam Engine," de 

tail view of level control system and shaft governor 

(Photo CLG.) 

Manufacturing Co. of Rochester, N.Y., and 

Boston (NMHT 315712; Accession 221209; 

Boston Model No. 2-1081; 2 hp at 400 r.p.m.; 

size of unit 20" X 45"X 34"). Boiler and steam 

engine are integrated into a compact selfcontained unit. Designed to operate automatically without need of supervision, it served 

successfully as a prime mover in a variety of 

workshops and small factories. Apart from the 

shaft governor on the steam engine and the 

obligatory safety valve, it has automatic control systems for the supply of feedwater and 

fuel oil. The water level in the boiler is 

measured by a pivoted float in the chamber 

near the center of the machine (Figure 80). 

The float is connected by linkages to a valve 

in the waterline to the feed pump. When it 

FIGURE 81.—Shipman "Automatic Steam Engine," detail view of steam pressure control system. (Photo 

CLG.) 

rises it will reduce the feedwater supply, and 

vice versa. The steam pressure is regulated 

by varying the rate of fuel input (Figure 81). 

The steam header at the top of the boiler 

is directly connected to a spring-loaded diaphragm which actuates a valve in the fuel-oil 

line. In normal operation this valve is open, 

and kerosene flows freely to the two burners. 

If the steam pressure rises, the fuel flow is 

throttled until the steam pressure sinks. When 

fuel resumes flowing again, proper ignition is 

assured by pilot flames. Both systems can be 

regarded as simplified examples of equivalent 

but more refined systems in use on larger 

steam boilers. 
CHAPTER 6 

Pressure Regulators 

A great variety of feedback devices are used 

to maintain constant pressure in distribution 

lines of steam, gas, air, or water. The Museum's 

collections contain several early pressure 

regulators and reducing valves. The oldest of 

these is a patent model (Figures 82 and 83) 

of Charles E. Lloyd dating from 1854 (U.S. 

Patent 11128 of 20 June 1854) describing a 

combined gas meter and regulator (NMHT 

FIGURE 82.—Patent model of gas meter with pressure 

regulator by C. C. Lloyd, 1854. (NMHT 309279. Smithsonian photo 616-G.) 

FIGURE 83.—Schematic diagram of Lloyd's pressure 

regulator. Reprinted from U.S. Patent No. 11128 of 

June 20, 1854, Patent Specifications, fig. 2. 

309279; Accession 89797; brass and tin, 

7i/2"X 10i/2"X 13"). As a gas meter, the device 

is of conventional design. It employs a large 

paddle wheel rotating in proportion to the 

volume of gas consumed where the count of 

revolutions provides the basis for billing. Like 

other gas meters of that period, it is partly 

filled with water; thus the bearings of the 

paddle wheel are sealed, to prevent gas leaks, 

and lubricated at the same time. The patented 

invention combines two features. Apart from 

shutting off the gas (to avoid dangerous leaks) 

when the water level is too low, it maintains 

a constant gas pressure in the line of the consumer. This removes an important source of 

uncertainty from the billing procedure, for 

the meter registers only volume without rec73 
74 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 84.—Patent model of steam pressure regulator 

by George H. Corliss, 1869. (NMHT 309236. Photo 

CLG.) 

ognizing that the value of gas increases with 

its pressure. The device for sensing pressure 

(Figure 83) is similar to an arrangement used 

on pressure regulators for steam boilers, for 

example by Boulton Sc Watt in 1803.68 It consists of a float swimming in a vertical pipe, 

the lower end of the pipe is submerged, while 

the upper end is vented to atmosphere. 

Since the water level in the gas meter outside 

of this cylinder is exposed to the gas, the level 

in the pipe will rise with increasing gas pressure. The float, in turn, is linked to a double 

cone valve in the gas intake line, which is of 

such shape that it will seal both in its high 

and in its low position, opening the line at 

positions between the extremes. Consequently, 

the flow of gas will be shut off both when the 

float rises too high due to excessive pressure, 

and when it sinks too low due to the absence 

of water. 

An 1869 patent model of a steam pressure 

regulator (Figures 84 and 85) is the work of 

George H. Corliss (U.S. Patent 85566 of 5 

January 1869; NMHT 309236; Accession 

89797; wood model with brass valve parts; 

8i/2" diam., 3i/2" high).69 This regulator was 

intended to serve as a reducing valve in steamheating plants. It consists basically of a flat, 

circular chamber with elastic sides that will 

bulge outward under internal pressure. Placed 

in the center of one wall is a valve the cone 

of which is connected to the opposite wall in 

such fashion that the valve will close at the 

expansion of the chamber, and open at its 

contraction. The chamber is connected with 

the steam line to be regulated, while the upstream side of the valve is facing the highpressure steam supply. When the controlled 

steam pressure falls below the desired value, 

the elastic chamber contracts, opening the 

valve and admitting steam until the desired 

pressure is restored. 

A more advanced stage of development is 

displayed in the gas pressure regulator of A. 

Kipp and H. Murphy, represented by a patent 

model (Figure 86) for the U.S. Patent 224190 

of 3 February 1880 (NMHT 308713; Accession 

68. Dickinson and Jenkins, James Watt and Steam 

Engine, p. 239, pis. 40, 90. 

69. Taylor, Catalogue of Mechanical Collections, 

p. 75. 

•^ss^2SZ2mm^m^^zms22zmsMz^^^L 

FIGURE 85.—Cross-section drawing of Corliss's pressure regulator. Reprinted from U.S. Patent 

No. 85566 of Jan. 5, 1869, Patent Specifications. 
NUMBER 12 75 

FIGURE 86.—Patent model of gas pressure regulator by 

A. Kipp and H. Murphy, 1880. (NMHT 308713. Photo 

CLG.) 

89797; two-dimensional schematic model, 

wood, 8i/c>"Xl2"). In contrast to Corliss's design, the functions of measuring and regulating are here fully separated. Mounted above 

a conventional double-seat poppet valve is a 

flat, circular chamber containing a diaphragm 

attached to the valve stem. Th e space below 

the diaphragm is connected with the downstream side of the valve, that is, the pressure 

to be controlled, while the upper side is 

vented. Th e weight of the valve stem is balanced by a counterweight arranged on a lever 

above the unit. Th e regulator works similarly 

to that of Corliss. If the controlled pressure is 

at the desired value, the force on the diaphragm will be great enough to close the 

valve; if the pressure sinks, the valve will be 

opened, admitting the required quantity of 

gas. 

A somewhat exotic variation on this basic 

theme is the regulator on a water-driven air 

ejector used to maintain the vacuum in the 

return line of a steam-heating system (Figure 

87) . Th e device dates from about 1910 and 

was built by the Hancock Inspirator Co. exFIGURE 87.—Hancock-Cryer vacuum regulator used in 

steam heating, about 1910. (NMHT 315438. Photo 

CLG.) 
76 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

clusively for the T. B. Cryer Company, 

Newark, N. J. (NMHT 315438; Accession 

216348; unmarked and severely corroded, cast 

iron, 8"X10"X16"). The regulator is 

mounted on a conventional air ejector energized by water. A set of circular spring-loaded 

bellows connected to the vacuum line expands 

or contracts according to the measure of the 

vacuum. By suitable linkages this motion is 

transmitted to a valve that apparently controls 

the water supply to the ejector. 

A number of contemporary reducing valves, 

found in the Museum in various functions and 

places, have not been cataloged. Generally, 

these perform like the Kipp-Murphy regulator. 
CHAPTER 7 

Temperature Control 

The first known temperature regulator 

was invented about 1620 by Cornelis Drebbel 

(1572-1633), a Dutch engineer in the service 

of King James I of Britain. To maintain constant temperatures in chemical furnaces and 

in incubators (Figure 88), he connected a 

thermoscope with a damper so that it would, 

at excessive temperatures, reduce the oxygen 

supply to the fire.70 During the following 

centuries the invention evolved gradually. 

Bimetallic rods came into use as temperaturesensing elements in the late eighteenth century; in 1830 Andrew Ure introduced the term 

"thermostat." At the end of the nineteenth 

century, thermostats were found in numerous 

industrial applications.71 The collections of the 

National Museum of History and Technology 

hold only a few examples of thermostats that 

can be called historic. 

Starting at the end of the last century, the 

Honeywell Heating Specialities Co. had 

developed a system of automatic temperature 

control for home central-heating plants. The 

Museum has a set of the main components 

of such a system (Figure 89), dating from the 

early 1920s. The system was very versatile; it 

could be adapted to most furnaces regardless 

of whether they burned coal, oil, or gas; and 

whether the heating medium was air, water, 

or steam. The present system was probably 

employed on a coal-burning hot-water plant. 

It consists of three devices: a room thermo70. F. M. Gibbs, "The Furnaces and Thermometers 

of Cornelis Drebbel," Annals of Science 6(1948):32-43. 

71. A. R. J. Ramsey, "The Thermostat or Heat 

Governor: An Outline of its History," Transactions of 

the Newcomen Society 25 (1945-47):53-72. 

FIGURE 88.—Cornelis Drebbel's chicken incubator with 

temperature regulation, about 1620. Reprinted with 

permission of the Cambridge University Library from 

MS 2206, part 5, fol. 218. 

stat (NMHT 316657), a spring regulator 

motor (NMHT 316656), and an "Aquastat" 

(NMHT 316658; Accession 226965 for all 

three). The system operates electrically on the 

power of a 12-volt dry-cell battery. The room 

thermostat ("Honeywell Model 4. Plain Pattern") consists of a spiral-shaped bimetal 

strip which tends to straighten with rising 

temperature, and whose outer tip is free to 

move between two closely spaced electrical contact points. Depending on the ambient temperature, this free tip touches one of the two 

contacts, closing a circuit to turn on the 

77 
78 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 89.—Honeywell home temperature control system, about 1920. From left to right: 

"Aquastat"; spring motor for actuating damper; room thermostat. (NMHT 316658, 316656, 

316657. Photo CLG.) 

furnace when more heat is required, or turning off the furnace when the temperature is 

too high. The desired temperature can be 

adjusted from 50° to 90° F along a calibrated 

scale by changing the starting position of the 

bimetal strip. 

The spring motor (NMHT 316656), marked 

"Arco Temperature Regulator but identical 

with a unit marketed by Honeywell, converts 

electrical signals from the thermostat into an 

action affecting the fire in the furnace. The 

signals energize a solenoid which releases a 

spring motor, opening or closing both the 

fresh air and the flue dampers of the furnace. 

Since the dampers cannot be held in any intermediate positions, the system provides merely 

on-off control. The motor is driven by a powerful spring which has to be rewound every 

one to two weeks. A pointer indicates the 

state of unwinding of the spring. 

The third unit of the system, a Honeywell 

Style B Aquastat (NMHT 316658), is in 

essence also a bimetallic thermostat. Installed 

in the line of hot water leaving the furnace, 

it is wired to override the command from the 

room thermostat whenever the water temperature exceeds a certain maximum value. 

Another important field of application for 

thermostats is in the temperature control of 

furnaces and ovens. A representative of this 

group is an electric vacuum oven (Type 

Weber, sold by the Arthur H. Thomas Co.) 

of about 1930 (NMHT 326619; Accession 

261654; serial no. IBS 26396; overall size 

16"X15"X30"). The thermostat is mounted 

on the top of the oven; its principle of operation is similar to that of the Honeywell room 

thermostat, except that it acts upon electrical 

heating elements. The desired temperature can 

be set at values between 20° and 150° F. 

The thermostat is marked "Type VAC; Serial 

No. 3573; Volts 115 DC; Amps 8; U.S. 

Patent No. 1594481, Aug. 3, 1926."

 72 

72. Arthur H. Thomas Company, Laboratory Apparatus and Reagents, 1931 edition (Philadelphia, 

1931), p. 608. 
CHAPTER 8 

Feedback Control on Textile Machinery 

In the collection of the Museum's Division 

of Textiles we found four machines employing feedback. Three of these are let-off mechanisms for power looms, the fourth is a 

regulator for cotton drawing frames. 

After the introduction of the power loom 

the problem of inventing satisfactory takeup and let-off motions received the attention of a great many inventors. The purpose 

of a let-off mechanism is this: on power looms, 

the warp is commonly drawn through the 

machine at constant speed. For a product of 

high quality, it is important that the tension 

of the fabric is constant during the process 

of weaving, which is made difficult because 

the diameter of the yarn beam, on which 

the unwoven yarn is coiled, diminishes as the 

yarn is "let off." Of the countless patented 

mechanisms for letting off yarn in such a way 

that constant tension is maintained while the 

speed of rotation of the yarn beam changes, 

only a few employ the principle of feedback. 

On these, the tension is measured directly 

by a spring-loaded roller pressing against the 

warp: the distance by which the warp is 

deflected from its normal course by the roller 

is assumed to be inversely proportional to 

the tension. The yarn beam's speed of rotation is then automatically adjusted according 

to this measurement. At high tension the 

speed is increased, at low tension, reduced. 

The take-up motion is, as the term implies, 

FICURE 90.—Patent model of let-off mechanism for 

power looms by Richard Walker, 1867. (NMHT 

T-11412. Smithsonian photo 71296.) 

FIGURE 91.—Patent model of let-off mechanism for 

power looms by George Richardson, 1867. (NMHT 

T-11411. Smithsonian photo 71298.) 

79 
80 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

:-rr "-'-.'_ 

•'!•: v - ,;•**•- *//$%% 

FIGURE 92.—Draper "Model A Northrop" power loom, 1895, equipped with "Bartlett" let-off 

mechanism (not visible). (NMHT T-8571. Smithsonian photo 71299.) 

the opposite of the let-off motion; the machinery employed is very similar in both cases. 

The oldest of our let-off mechanisms for 

power looms is a patent model (Figure 90) 

by Richard Walker of Milford, Massachusetts, 

for the U.S. Patent 62168 on 19 February 

1867 (NMHT T-11412; Accession 89797; 

mostly wood, 6i/2"X7i/2"X5") . The rotation 

of the yarn beam is here controlled by an 

escapement-like mechanism employing a double ratchet, powered by the oscillatory motion 

of the lay sword of the loom. A tensionsensing bar pressing against the warp 

determines whether the lay sword during its 

work stroke will actually engage the escapement. In the case of low tension the mechanical train will be interrupted, arresting 

the escapement until the tension in the warp 

has risen back to the desired level. 

In the patent model (Figure 91) by George 

Richardson of Lowell, Massachusetts (U.S. 

Patent 64147 of 23 April 1867), the same 

purpose is achieved quite differently (NMHT 

T-11411; Accession 89797; cast iron and 

wood, 11"X9"X9"). Here the yarn beam is 

retarded by a simple brake. The sensing beam 

pressing against the warp will release this 

brake whenever the tension exceeds the 

proper level. 

A third let-off mechanism is represented 

not by a patent model but by a full-scale 

power loom used in actual production (Figure 92) . The feature that made the "Northrop Loom" of the Draper Company in 
NUMBER 12 

81 

FIGURE 93.—The "Bartlett" let-off mechanism as used on NMHT T-8571. Reprinted from The 

Draper Co., Labor Saving Looms, 2nd edition (Hopedale, Massachusetts, 1905), p. 93. 

Hopedale, Massachusetts, famous is the automatic shuttle-bobbin changer. In our Museum this loom is represented by a "Model 

A" unit built in 1895, the year the invention was introduced (NMHT T-8571; Accession 160340). The let-off mechanism on 

this loom (Figure 93) is of an older, established design, known as the "Bartlett LetOff," invented by D. W. Snell and S. S. 

Bartlett (U.S. Patent 16405; 13 January 

1857). In principle it resembles the let-off 

motion of R. Walker (Figure 90). The yarn 
82 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FICURE 94.—Patent model of regulator for drawingframes by Samuel J. Whitton, 1869. (NMHT T-11421. 

Smithsonian photo 71297.) 

beam, through appropriate gearing, is rotated 

by a ratchet drive powered by the continuously oscillating lay sword. The length of 

stroke of the ratchet motion, however, is 

variable; it is controlled by the tensionsensing device which is—as before—a springloaded beam pressing against the warp. If 

the tension is high, the stroke of the ratchet 

is shortened, and vice versa.73 

73. George Draper, "Let-Off Motion for Looms," 

Proceedings, New England Cotton Manufacturers' Association 8 (1870):22-27; The Draper Company, Textile 

Texts for Cotton Manufacturers (Hopedale, Massachusetts, 1901); The Draper Company, Labor-Saving 

Looms, 2nd edition (Hopedale, Massachusetts, 1905), 

pp. 94-96, 151-152. 

A very different kind of feedback device 

is the patent model of a regulator for drawing 

frames (Figure 94) invented in 1869 by 

Samuel J. Whitton (U.S. Patent 86719 of 

9 February 1869; NMHT T-11421; Accession 89797; an exceptionally well-made model of cast iron and steel; size 9"X6i/2"X 12"). 

In cotton spinning, generally, the actual 

process of spinning is preceded by that of 

"drawing." The cotton sliver, a fluffy strand 

of cotton, untwisted yet and therefore of 

little tensile strength, passes consecutively 

through two sets of friction rollers, of which 

the second one advances at a higher speed 

than the first, so that the sliver becomes 

longer and thinner. The purpose of the present invention is to regulate the thickness of 

the resulting sliver. The thickness is measured by a trumpet-shaped funnel located between the two sets of friction rollers. The 

funnel is mounted at the end of a pivoted 

lever held in position by a counterweight. 

On its way through the process, the sliver 

is fed through the funnel; if it is thin, it 

will pass without disturbing the funnel; if 

it is thick, it will push the funnel back by 

a distance depending on the thickness of the 

sliver. While the first set of friction rollers 

rotates at constant speed, the second one is 

driven through a variable-speed transmission 

(consisting of two parallel, opposite cone 

drums connected by an endless belt which 

can be shifted sideways), of which the ratio 

is controlled by the thickness-sensing device. 

The second pair of friction rollers, then, will 

be accelerated with increasing thickness. It 

will draw the cotton sliver more strongly 

lengthwise, thus making it thinner. If the 

cotton sliver becomes too thin, the process 

is reversed. 
CHAPTER 9 

Feedback Control on Land Vehicles 

Railway Technology 

In the Museum's collections of land vehicles, the search for feedback devices has 

proved more fruitful among the automobiles 

than in the railroad technology. Apart from 

FIGURE 95.—Westinghouse air pressure regulator for 

pneumatic braking system; installed on Southern Railway Locomotive No. 1401, 1926. (NMHT 320000. 

Photo CLG.) 

safety valves, which, as stated earlier, are not 

to be cataloged because of their simplicity 

as well as overabundance, the only feedback 

device discovered in railroad equipment is 

a Westinghouse air-pump regulator ("Type 

AD. Single Top") which is part of the pneumatic brake system on the large passenger 

locomotive of 1926 (NMHT 320000; Accession 196330; Southern Railway Locomotive 

No. 1401; built by the American Locomotive 

Co., Richmond, construction no. 66888) . The 

pressure regulator (Figure 95) consists of a 

spring-loaded diaphragm mounted on a 

throttle valve in the steam line on the left 

side of the engine, above the middle drive 

wheel, directly to the right of the compressor. 

It maintains a constant supply pressure for 

the air-brake system by manipulating the 

steam flow rate to the steam-driven air compressor feeding the system. 

Steam Automobiles 

On automobiles, in contrast, feedback devices appear in great diversity, ranging from 

the various controls on the boilers of early 

steam cars, through speed governors, thermostats, pressure regulators, and voltage regulators, to power steering. Many of these 

devices were adopted from other fields. Some 

early steam automobiles, for example, employed automatic controls resembling those 

on previous stationary steam engines. The 

steam pressure regulator of the "Locomobile" 

steam automobile of 1900 (NMHT 309639; 

Accession 106490; "Style 2" of the Locomobile Company of America, Bridgeport, 

83 
84 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 96.—Steam pressure regulator on "Locomobile" steam automobile, 1900. Upward view 

under the right side of the car, in front of right rear wheel. (NMHT 309639. Photo CLG.) 

w c 

FIGURE 97.—"Locomobile" steam automobile. Side elevation drawing of steam boiler and pressure 

regulator (T). Reprinted from W. Worby Beaumont, Motor Vehicles and Motors (Westminster, 

1900), p. 461. 
NUMBER 12 85 

FIGURE 98.—Steam pressure regulator of White steam automobile, 1902; view under the left seat 

showing the diaphragm throttling valve (center). (NMHT 309497. Photo CLG.) 

FIGURE 99.—White steam automobile: water supply circuit and steam pressure control system. 

Pressure sensing diaphragm (H); throttle valve 

(K); steam connection (L); water supply (B-J); 

water line to boiler (G). Reprinted from Paul N. 

Hasluck (ed.), The Automobile, 2nd edition (London, 1903), p. 573. 
86 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Conn.; serial no. 2795)74 operates on the 

same principle as that on the older "Shipman Automatic" steam engine, described 

above (Figure 81). It is located (Figures 96 

and 97) in front of the boiler, under the 

right passenger seat, and consists of a springloaded diaphragm actuating a throttle valve 

in the fuel line to the burner. The diaphragm 

is exposed to boiler pressure. In case of rising 

pressure it will reduce the rate of combustion, and vice versa. Not regulated automatically, however, is the supply of feedwater. 

Instead, a sight glass is provided, by means 

of which the driver monitors the boiler level 

in order to make the necessary adjustments 

manually.75 The vehicle's name, "Locomobile," incidentally, is misleading: the cars 

design is identical with that of the better 

known "Stanley Steamer"; the car was renamed after the Stanley brothers' original 

firm changed hands in 1899. 

Similar, but somewhat more refined, are 

the controls (Figures 98-101) on the White 

steam automobile of 1902 (NMHT 309497; 

Accession 101849; built by the White Sewing 

Machine Company of Cleveland; serial no. 

260) .

76

 Here both the pressure and the exit 

temperature of the steam are regulated automatically. The pressure regulator consists of 

a diaphragm throttle valve (located under 

the left seat, Figure 98) similar to that of the 

Locomobile, except that it adjusts the flow 

rate of feedwater instead of fuel (Figure 99). 

The water level of the boiler, therefore, no 

longer requires the driver's attention. In a 

second feedback loop, a constant temperature 

of the steam is maintained by a thermostat 

(Figure 100). It consists of a bimetal temperature-sensing element / immersed in the 

slightly superheated steam at the boiler exit, 

which actuates a needle valve (below K) in 

the fuel line to the burners. This valve will 

be closed with rising, and opened with falling, steam temperatures. The thermostat is 

74. S. H. Oliver and D. H. Berkebile, The Smithsonian Collection of Automobiles and Motorcycles 

(Washington, D.C, 1968), pp. 49-51. 

75. William Worby Beaumont, Motor Vehicles and 

Motors (Westminster, 1900), pp. 462^163. 

76. Oliver and Berkebile, Smithsonian Collection of 

Automobiles, pp. 61-63. 

found underneath the car, slightly in front 

of the right rear wheel (Figure 101). Since 

both the steam pressure and the flow rate of 

the fuel are regulated automatically, the 

driver controls the vehicle's speed by adjusting the flow rate of steam to the cylinders.77 

Speed Governors on Trucks and 

Tractors 

Another class of control devices adopted 

from an older technology were the speed 

governors. They had no purpose of course 

on passenger cars, where the driver cherishes 

the power of determining the speed himself. 

On trucks and tractors, however, they served 

an important function. In the era of cobblestone roads, solid rubber tires, and stiff 

springs, the only way to protect the vehicle 

from continuous exposure to the most severe 

shocks was to drastically limit its speed. 

Speed governors disappeared gradually during the 1920s, when trucks began to be 

equipped with pneumatic tires. The arrangement of such governors was usually simple. 

They were geared to the engine and manipulated the throttle valve in the gas intake 

pipe. Sometimes an adjustment was provided 

for changing speeds. Truck governors were 

usually set and sealed at the factory for top 

speeds between 10 and 20 miles per hour, 

depending on the size of the vehicle. 

Our Museum has two tractors and two 

trucks with such speed control. The "Waterloo Boy" tractor of 1918 (first tractor marketed by the John Deere Co., Model N; 

NMHT 67A2; Accession 270864) is equipped 

with a simple centrifugal governor mounted 

conspicuously on top of the engine block and 

acting on the throttle. The governor is spring 

loaded; the controlled speed can be varied 

manually from the driver's seat by changing 

the initial compression of the spring. Similarly 

equipped is the Avery Bulldog Tractor of 

1919 (NMHT 58A6; Accession 222860). 

Here the governor is arranged less visibly 

under the hood, between radiator and engine 

77. Paul N. Hasluck (ed.), The Automobile, 2nd 

edition (London, 1903), pp. 72-74, 569-572. 
NUMBER 12 87 

FIGURE 100.—White steam automobile: fuel connections, gasoline burner and thermostat (J-K). 

Reprinted from Paul N. Hasluck (ed.), The Automobile, 2nd edition (London, 1903), p. 572. 

FIGURE 101.—White steam automobile: view under the car in front of right rear wheel, showing 

bottom of boiler and parts of the thermostat (center). (Photo CLG.) 

block. The Autocar Heavy Duty engine of 

1921, a 28.9-hp, four-cylinder gasoline engine 

was used to drive the heavy Model 26 Autocar trucks (NMHT 307254, engine only; 

Accession 68520; cutaway for display purposes) . It is equipped with a hydraulic 

governor manufactured by the Pharo Mfg. 

Co., Detroit, Michigan (patented 17 April 

1917). The governor consists of a centrifugal 

pump impeller in a closed oil-filled capsule 

bounded on one side by a movable springloaded baffle. The pump impeller is geared 

to the engine. With rising speed it displaces 

the baffle which actuates a throttle valve in 

the gas intake line. An adjusting screw for 

the spring tension—i.e., the desired speed— 

is factory sealed. Even the Mack "Bulldog" 

truck of 1930 still carries a governor (NMHT 

322560; Accession 251010; model "AC," 7 

tons, 156" wheelbase).78 The conventional 

78. Oliver and Berkebile, Smithsonian Collection of 

Automobiles, p. 150. 
88 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

centrifugal governor, located at the front of 

the engine block directly to the upper left of 

the starter crank, is totally enclosed against 

tampering. It was set for a top speed of 18 

miles per hour. 

Automobile Thermostats 

It was early recognized to be advantageous 

if the cooling water surrounding the cylinders 

could be kept at a constant optimum temperature despite changes in vehicle speed, 

load, and ambient air temperature. On many 

early cars this was done manually by the 

driver who watched a cooling water thermometer and accordingly adjusted by dampers 

the airflow through the radiator. Several 

thermostatic arrangements were proposed to 

perform this function automatically. The advantage advertised for such systems was a 

substantial saving in fuel. One of the first 

mass-produced automobiles to employ this 

innovation was the eight-cylinder Cadillac, 

introduced in 1915, and equipped with cooling water thermostats in 1917. The Museum 

has the chassis of a later model of this car, 

a "Model 61" of 1923 (NMHT 308218; Accession 71005) .

79

 The thermostat employed 

here works on the same principle as many 

designs of today (Figure 102). It consists 

simply of a cylindrical capsule with accordion-shaped walls, partly filled with a special 

liquid chosen for a boiling point coinciding 

with the desired water temperature. The capsule actuates a throttle valve in the cooling 

water circuit. When the water temperature 

is below the desired value, the capsule contracts, restricting the circulation of cooling 

water until the temperature rises to the proper level. At higher temperatures the capsule 

expands, freeing the water passage, thus increasing the cooling action. The 1923 Cadillac has separate cooling circuits for the two 

halves of its V-8 engine. The thermostats 

are installed on each side in front of the respective water pumps, located between the 

radiator and the bottom of the engine block.80 

Radiator 

From Carburetor 

Water Jacket 

79. Ibid., pp. 143-145. 

80. American Technical Society, Automobile Engineering, 6 vols. (Chicago, 1921), 1:439-440. 

EnlorqedView 

Showing 

Thermostat 

FIGURE 102.—Cooling water thermostat as installed in 

1923 "Model 61" Cadillac. Reprinted, with permission, 

from The American Technical Society, Automobile 

Engineering, 6 vols. (Chicago, 1921), vol. 1, p. 293. 

For many years an alternate type of cooling 

water thermostat was in use. The thermostat 

proper similarly consisted of a liquid-filled 

capsule submerged in the hot water return 

line from the engine. Instead of manipulating 

the cooling water flow, however, it controlled 

the flow of cooling air by adjusting a row 

of shutters in front of the radiator. Upon 

falling water temperature the shutters would 

close, restricting the flow of cooling air, until 

the water temperature had returned to the 

proper level. Our Museum has no specimens 

of automobiles equipped with this type of 

temperature control, but an adequate substitute is perhaps the Packard "Winterfront" 

from the 1920s. This is a detachable radiator 

grille with thermostatically controlled shutters (Figure 103) designed to be clamped 

in front of automobile radiators during the 

cold season (NMHT 329286; Accession 

281784; marked "PACKARD MOTOR CAR 

CO. WINTERFRONT" and "PINES AUTOMATIC WINTERFRONT PATENTED 

OCT. 20, 1914; APRIL 11, 1916; JUNE 8, 

1920; OCT. 11, 1921. MADE IN U.S.A. 

OTHER PATENTS PENDING"). The 

liquid-filled bellows, located at the top center, 

is mechanically linked to move the shutters. 

Because the capsule is not in direct contact 

with the water, it had to be clamped tightly 
NUMBER 12 89 

FIGURE 103.—Packard "Winterfront," 1920s: view from front and back. The shutters are operated 

by a thermostat (top center) which senses the radiator temperature through metal contact. 

(NMHT 329286. Smithsonian photos 71537, back, and 71538, front.) 

against the radiator to sense the cooling water 

temperature by heat conduction. 

Thermostatic shutters eventually went out 

of use, leaving the field to thermostats directly installed in the cooling water circuit. 

A more recent witness to this, in our collections, is the 14-ton Bantam Army truck of 

1940, an experimental forerunner of the 

"Jeep" (NMHT 312822; Accession 167398). 

The thermostat, similar to that on the 1923 

Cadillac, is installed in the water outlet elbow 

of the cooling water circuit.81 

Float-Feed Carburetors 

Virtually all contemporary automobile carburetors employ, in many different forms, 

a simple and ancient feedback device, the 

float valve: a float connected with a needle 

valve in the fuel line, with the function of 

maintaining a constant level of gasoline in 

the supply chamber of the carburetor. The 

first float-feed carburetor was invented in 

1893 by Wilhelm Maybach, Daimler's collaborator, who was doubtless unaware that 

a similar float valve had been employed in 

the water clock of Ktesibios of Alexandria 

in the third century B.C.82 

It is neither possible nor worthwhile to 

list here all float-feed carburetors in the Museum's collections; instead we mention as a 

single representative that of A. L. Dyke of 

1900 (Figure 104), reportedly the first American-made float-feed carburetor publicly marketed (NMHT 308479; Accession 87038; 

marked "A. O. DYKE MNFG'R.") ,

83

 It consists mainly of the float chamber (marked) 

and the mixing chamber (showing the air 

intake opening). The lever arrangement 

above is the external part of the throttle 

valve by which the engine speed is controlled. 

The gasoline enters the float chamber at the 

top; after flowing through the needle valve, 

it is sprayed into an upward stream of air. 

Then the combustible mixture passes through 

81. War Department Technical Manual, TM9-803: 

1/4-Ton 4x4 Truck (Washington, D.C, 1944), pp. 105, 

143. 

82. Beaumont, Motor Vehicles and Motors, p. 71. 

83. Taylor, Catalogue of Mechanical Collections, 

p. 169. 
90 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 104.—A. L. Dyke float-feed carburetor, 1900. 

(NMHT 308479. Smithsonian photo 18494-C.) 

line was not, as today, pumped to the engine 

directly by a gasoline pump; instead a positive air pressure was maintained in the gasoline tank by an engine-driven air pump, 

which forced the gasoline into the supply 

line to the carburetor. Installed in the line 

from the air pump to the gasoline tank was 

a relief valve set to open at some pressure 

above normal. Systems of this type are found 

on the 1912 Simplex automobile (NMHT 

309549; Accession 104418) and on the "Model 

61" Cadillac (NMHT 308218; mentioned before) ,

84

 The Cadillac also employs a similar 

system for regulating the pressure of the 

engine lubricating oil. The oil is pumped 

into a main header from where it is conducted to the bearings of the crankshaft, 

etc. Connected to the header is an overflow 

valve or "pressure regulator" which at excessive pressures will open up a bypass line. 

the mixing chamber and the throttle, before 

it is drawn into the intake manifold of the 

engine. 

Many carburetors, incidentally, are 

equipped with automatic adjustments for 

such variables as engine speed, manifold or 

outside temperature, etc., which are occasionally described as "governors" or "thermostatic." These arrangements do not maintain 

an equilibrium between a controlled variable 

and a reference variable by acting on their 

difference, instead they simply make an adjustment in a fixed relationship with some 

independent variable. Because such devices 

do not employ feedback they are not considered here. 

Pressure Control by Relief Valves 

Some cars employ pressure regulators that 

can be classified as feedback systems with 

similar justification as the safety valves of 

steam boilers. In such systems the supply 

pressure of a medium is maintained by an 

unregulated pump, while protection against 

excessive pressures is furnished by a relief 

valve. Examples of this are early gasoline 

supply systems. On early motorcars the gasoVoltage and Current Regulation 

When motorcars were equipped with storage batteries charged by electric generators, 

the following problem arose: the current output of a generator is proportional to its 

generator's speed of rotation, which on automobiles fluctuates widely, while a storage 

battery will be damaged if it is charged at 

a rate exceeding a certain limit. To protect 

the battery, a variety of systems limiting the 

generator output have been invented. (These 

are not to be confused with cutoff relays 

which interrupt the circuit when the generated voltage sinks below the battery voltage.) 

Two among these stand out: The method 

of "field distortion regulation," or "thirdbrush regulation," consists of arranging the 

internal circuitry of the generator so that the 

output vs. speed curve becomes horizontal 

for excessive speeds. This removes the cause 

of danger without resorting to feedback control. In the second method some outputsensing device is mechanically linked to a 

switch, which breaks the battery circuit at 

excessive charging rates. Most commonly such 

84. Oliver and Berkebile, Smithsonian Collection of 

Automobiles, pp. 102-106, 143-145. 
NUMBER 12 91 

devices are designed as vibrators, consisting 

of a steel reed oscillating between two contacts, attracted to one by a spring, and to 

the other by the electromagnetic field of a 

coil in the battery circuit. When at excessive 

charging rates the electromagnetic force overcomes the spring force, the reed shortcircuits 

the battery, leaving only a small part of the 

total current to pass through the battery. 

Depending on whether the coil is connected 

in series or shunt, the controlled variable 

is current or voltage, voltage regulators being 

the more common. Since the control action 

is based here on a comparison between a 

desired value (spring force) and the actual 

value (force of coil) of a variable, voltage of 

current regulators of this type must be classified as feedback systems, if only of a level 

similar to pressure control by relief valve. 

Regulators such as these are found, of 

course, only on automobiles with storage 

batteries, i.e., cars with electric self-starters. 

Earlier motorcars, started by hand crank and 

employing magneto ignition, had no application for such regulators. 

T h e subject of generator regulation has 

been exhaustively treated in the automotive 

literature. Th e following list will only identify 

the systems employed on the automobiles in 

the Museum's collection, citing literature 

where detailed information can be found.85 

1. 1912 Simplex "Type 50" speedster 

(NMH T 309549; Accession 104418; serial 

no. 778): equipped with electric generator and starter motor, both of system 

"Bijur," factory identification labels illegible; later addition, probably early 

1920s. Th e generator employs thirdbrush regulation. 8 8 

2. 1912 Pierce-Arrow "Type 6-36" runabout 

(NMH T 326222, Accession 255546; serial 

no. 32813) : Pierce-Arrow double-igni85. Paul M. Stone, Electricity and its Application to 

Automotive Vehicles (New York, 1924), pp. 354-384; 

A. L. Dyke, Automobile and Gasoline Engine Encyclopedia, 12th edition (St. Louis, no date [approx. 1920]), 

passim; furthermore, all following automobiles are 

described in Oliver and Berkebile, Smithsonian Collection of Automobiles. 

86. Stone, Electricity and Motor Vehicles, pp. 561— 

577. 

tion system (magneto and battery system) ; with vibrator-type regulator, 

located in "Autocoil" box on dashboard.87 

3. 1913 Ford "Model T " automobile 

(NMH T 311052; Accession 120103; serial 

no. 211098): equipped with WardLeonard electric generator and starter 

motor, both subsequently added. Th e 

vibrator-type regulator on the generator 

is marked "Ward-Leonard Automatic Dynamo Controller Type CC-315 No. 

10669."

 88 

4. 1917 White bus on H/2-ton "Model TBC" 

truck chassis (NMH T 326151; Accession 

257078): Bosch high-tension magnetoignition system, to which was subsequently added a North East Electric Co. 

combination starter-generator (Model 

GA, Type 3992, serial no. 1773609, 12 

volts), employing third-brush regulation.89 

5. 1918 Oldsmobile "Model 37" touring car 

(NMH T 323569; Accession 241983; serial 

no. 153041): Delco 6-volt battery system 

with third-brush regulation.90 

6. 1920 American-LaFrance fire truck 

(NMH T 323518; Accession 250762): 

Eisemann dual magneto and battery system with vibrator-type regulator.91 

7. 1923 Cadillac "Model 61 " chassis 

(NMH T 308218; Accession 71005) : 

Delco battery ignition system where the 

generator also serves as starter motor; 

third-brush regulation combined with a 

thermostatic regulator sensing excessive 

charging currents through temperature 

increases on the generator.92 

8. 1924 Franklin "Model 10-C" sedan 

(NMH T 321454; Accession 244503) : 

Atwater-Kent electrical system with a generator (replacement) by Owen-Dyneto 

Corporation (Type CG 697, serial no. 

648799) using third-brush regulation.93 

87. A. L. Dyke, Automobile Encyclopedia, 12th 

edition, p. 278. 

88. Stone, Electricity and Motor Vehicles, pp. 815— 

817. 

89. Ibid., pp. 701-717. 

90. Ibid., pp. 617-621. 

91. Ibid., pp. 258-261. 

92. Ibid., pp. 630-638. 

93. Ibid., pp. 640-643, 658-668. 
92 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 105.—Power steering unit and high-pressure oil pump by F. W. Davis, 1926. (NMHT 

314522. Smithsonian photo 71540.) 

9. 1940 Bantam 14-ton Army truck (NMHT 

312822; Accession 167398) : vibrator-type 

voltage regulator marked "Autolite Full 

Voltage Regulator—Current Control; 

model VRP 4006-G, serial no. 8V17212, 

6-volt, max. amps. 25." 

Power Steering 

Items of special historical interest are the 

original steering unit and hydraulic pump 

(Figure 105) of the power steering system 

invented by Francis Wright Davis of Waltham, Massachusetts (NMHT 314522; Accession 202515). The devices were built in 

1925 and installed in the inventor's PierceArrow roadster. In October 1926 Davis drove 

this car to Detroit, where he demonstrated 

his invention to a number of automobile manufacturers. Their first reaction was enthusiastic, and some agreements were reached 

to introduce power steering on one of Detroit's larger cars. But a long series of obstacles, among them the depression and World 

War II, delayed until 1951 the moment when 

power steering actually became a huge success 

in mass-produced passenger cars. Davis's system of power steering was protected by numerous American and foreign patents. The 

basic one among these, U.S. Patent 1790620 

of 27 January 1931 (application filed on 14 

April 1926), describes the original system in 

great detail. Apart from the main element, 

the steering unit, the system consists of an 

oil pump driven by the engine, a bypass 

pressure regulator, and an oil supply tank. 

The steering unit outwardly resembles a conventional manual steering column and, like 

it, it converts the rotation of the steering 

wheel into a rotation of the Pitman arm 

shaft which determines the directional angle 

of the front wheels. The internal arrangement of the steering unit is extremely complex. Its principle of operation is the same 

as that of a hydraulic servomotor, which has 

been described before in connection with 

hydraulic governors. Several special features 

are added to this: for example, the power 

steering unit is designed so that it will also 

work as a conventional manual steering column in the case of failure of the hydraulic 

power system. Special springs are arranged 

in such a way as to simulate for the driver 

the "feel" of the road; provisions are made 

to avoid internal damage when the front 

wheels are fully turned to one side while 

the driver continues to turn the steering 

wheel.94 

The history of Francis W. Davis's invention of power steering is the subject of a 

recent book.95 

94. Francis W. Davis, "Power Steering for Automotive Vehicles," Transactions of the Society of Automotive Engineers 53 (1945):239-256. 

95. Houston Branch and Wendell Smith, The Unreasonable American (Washington, D.C, 1968). 
CHAPTE R 10 

Feedback Control on Watercraft 

Servo Steering Devices 

Turning the rudder of a big ship requires 

tremendous force. Friction and inertia alone 

are considerable, but on a moving ship they 

are small compared to the hydrodynamic 

forces that resist any deflection of the rudder 

from the direction of travel. Traditionally, 

when the rudder had to be moved by muscle 

power, the necessary force had to be provided 

by employing a sufficiently large number of 

men (using four men was not uncommon), 

and by a high-gear ratio. Steering by this 

method was neither precise nor responsive. 

Early in the nineteenth century, when ships 

grew in size as well as in speed, the need to improve the maneuverability provided a strong 

motive to search for a source of auxiliary 

power. 

The earliest steam steering gear is believed 

to have been invented in 1849 by the American Frederick E. Sickels, also known for his 

invention of a variable cutoff valve gear for 

steam engines in 1841. His steering engine 

was patented in 1853 (U.S. Patent 9713 of 

10 May 1853) and again, for essentially the 

FIGURE 106.—Patent model of Frederick E. Sickels' steam steering gear, 1853. (NMHT 252595. 

Smithsonian photo 70468.) 

'i:', 
94 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 107.—Prototype of Frederick E. Sickels' steam steering gear, 1850s. (NMHT 180024. 

Smithsonian photo 14488.) 

same design, in 1860 (U.S. Patent 29200 of 

7 July 1860). The Museum has both patent 

models (Figure 106) (NMHT 252595 and 

252596; Accession 49064), as well as, and 

more importantly, the original full-scale prototype of this invention (Figure 107), an item 

with a remarkable history (NMHT 180024; 

Accession 20574) . After being first exhibited 

in 1853 at the Crystal Palace in New York, 

this steering gear was later installed on the 

steamer Augusta which operated in the intricate coastal waters of the southern Atlantic 

seaboard. After two years of successful service, 

the steering engine was removed from the 

Augusta to be demonstrated on several other 

ships, and then to be sent to London, where 

in 1862 it received a medal at the World's 

Fair. It was once more shown in 1876 at 

the Centennial Exhibit of Philadelphia. Sickels' steering gear reportedly worked well; although it received a good deal of praise, and 

apparently inspired other inventions, it had 

no commercial success. 

Its principle of operation is simple. The 

apparatus consists of a two-cylinder steam 

engine arranged in V-formation at an angle 

of 90°, with valve gear controlled by a common eccentric, and working on a common 

crankshaft geared to the rudder. The eccentric, however, is not fixed on the crankshaft; 

instead, a hand crank is attached to it, operated by the steersman. As the action of the 

valve gear, and consequently the motion of 

the steam engine, depends on the position 

of the eccentric, the steering engine will follow, turn by turn, the rotation of the hand 
FIGURE 108.—Experimental model no. 1 of servo steering engine, by Herbert Wadsworth, 1870s. 

(NMHT 310474. Smithsonian photo 70245.) 

FIGURE 109.—Experimental model no. 2 of servo steering engine, by Herbert Wadsworth, 1870s. 

(NMHT 310475. Smithsonian photo 70242.) 

FIGURE 110.—Experimental model no. 3 of servo steering engine, by Herbert Wadsworth, 1870s. (NMHT 

310476. Smithsonian photo 70247.) 
96 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 111.—The patented design of Herbert Wadsworth's servo steering engine. Reprinted from 

U. S. Patent No. 203224 of April 30, 1878, Patent Specifications, fig. 1. 

crank. This is, of course, not a feedback system, but instead a typical example of openloop control, reported here only for the 

historic importance of the invention. 

Another steering engine also without feedback is represented by a patent model by 

John Gates (NMH T 308559; Accession 

89797; U.S. Patent 208231, 24 September 

1878). Here two hydraulic cylinders moving 

the rudder are simply controlled by a hand 

valve. 

Genuine feedback steering systems were invented in 1866 by J. McFarlane Gray, whose 

steering engine served successfully on the 

Great Eastern, and by the French engineer 

Joseph Farcot, who in 1872 published the 

first book on servomotors, relating experiences over the ten previous years.96

 Our Museum has three operational models of servo 

steering engines (Figures 108-110) similar to 

those of Farcot, which date probably from 

the late 1870s (NMH T 310474, 310475, 

310476; Accession 119413). They belonged to 

Herbert Wadsworth of Geneseo, and later 

Avon, New York, who on 30 April 1878 received U.S. Patent 203224 on a hydraulic 

steering engine (Figure 111). Th e models 

represent three different versions of the patented invention, but they were apparently 

not patent models. All three are typical examples of hydraulic servomotors, operating 

on the same principle as the servo-powered 

hydraulic governors described earlier. Each 

one consists of a pilot valve, manipulated by 

96. H. G. Conway, "Some Notes on the Origins of 

Mechanical Servo Mechanisms," Transactions of the 

Newcomen Society 29(1953-55):57-64. 

the operator, determining the side of the 

power piston to which the high-pressure fluid 

is admitted. Th e power piston acts upon the 

tiller, which in return is connected with the 

pilot valve by means of a feedback linkage, 

stopping the flow of power fluid when the 

tiller holds the desired position. Th e three 

units differ only in details of construction. 

T h e first two consist of single horizontal 

power cylinders, the first one using a rotary 

pilot valve, the second a flat slide valve. On 

the third model two vertical oscillating cylinders work upon a common crankshaft, set 

at a phase angle of 90°. A rotary pilot valve 

is located between the cylinders; the position 

of the crankshaft is "fed back" to the pilot 

by means of a worm gear drive, of which 

one part is missing. 

Feedback Control in Torpedoes 

T H E WHITEHEAD AND THE BLISS-LEAVITT 

TORPEDO.—Since the American Revolutionary War, the term "torpedo" has been applied 

to a variety of underwater weapons, but in 

the modern meaning of the word, the torpedo 

is distinctly the invention of the British engineer Robert Whitehead who developed it 

in the late 1860s at Fiume, then an Adriatic 

base of the Austrian Navy. Whitehead's original torpedo was remarkably mature; it has 

served as a model for practically all subsequent designs, and its influence is recognizable even in the torpedoes of today. It 

also had immediate success in the commercial 

sense. By selling torpedoes to all navies, 

Whitehead's establishment soon acquired a 
NUMBER 12 97 

u u 

FIGURE 112.—Cross-section of the rear portion of a Whitehead Mark I torpedo, showing the 

depth-control system. Reprinted from U. S. Bureau of Ordnance, The Whitehead Torpedo, 

2 vols. (Washington, 1901), vol. 2, pi. 3. 

monopoly position that lasted for several 

decades.97 

Toward the end of the century some of 

the major naval powers began to manufacture 

Whitehead torpedoes under license. The 

American manufacturing rights for the Whitehead torpedo were purchased by the Brooklyn 

firm of Bliss 8c Williams, later E. W. Bliss 

& Co. One of the first torpedoes produced 

there, a unit with the serial number 30, built 

in 1892, is in the collections of our Museum 

(NMHT 31114; Accession 66742; type 

"Whitehead 3.55mX45cm Mark I"; 11'8" 

long, 17.7" diameter, speed 30 m.p.h., range 

800 yards). Although considerably more refined in detail, this torpedo reflects quite 

faithfully the original Whitehead design. Motive power is derived from compressed air 

contained in a tank in the center section, 

taking up approximately half of the torpedo's 

volume. A pressure regulator—in the form of 

a conventional reducing valve—reduces this 

high-pressure air to the lower working pressure of the engine, a radial three-cylinder 

reciprocating engine which drives two coaxial 

propellers rotating in opposite directions 

(Figure 112). The working pressure of the 

engine can be adjusted from outside, a higher 

working pressure resulting in higher speed 

97. For a general survey of the history of the torpedo, see Peter Bethell, "The Development of the 

Torpedo," Engineering (London), 159 (1945):403-405, 

442-443; 160 (1945) :4-5, 41-43, 301-303, 341-344, 365-

367, 529-531; 161 (1946):73-74, 121-122, 169-170, 242-

244. 

but shorter range, and vice versa. The warhead is located in front of the air tank, while 

the rear section holds the engine and various 

control mechanisms. 

The most important control device is an 

ingenious depth-control system, a device that 

was jealously kept secret for many years so 

that it acquired a reputation as Whitehead's 

"Secret." This system (Figure 113) employs 

two separate sensing elements: one is the 

spring-loaded hydrostatic piston d which expresses the depth of the torpedo's travel— 

sensed through the hydrostatic pressure—in 

terms of the compression of a spring. The 

desired depth can be adjusted easily from 

the outside by changing the initial compression of this spring. The other sensing element 

is pendulum V swinging in the fore-and-aft 

plane, sensing deviations from the horizontal 

in the torpedo's orientation. Both the hydrostatic piston and the pendulum act together 

through common linkages upon the single 

rod / which, in the original design, was connected directly to the horizontal rudder. As 

early as 1876, however, the pneumatic servomotor F (Figure 114) was added to this 

arrangement. The control rod now moves 

only the servo's pilot valve, while the horizontal rudder is tilted by the power cylinder 

using air at engine working pressure. Apart 

from the pressure-reducing valve, the depthcontrol mechanism, and the servomotor, 

which all use feedback, this torpedo employs a number of open-loop control devices. 

A starting gear, for example, turns on the 
98 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 113.—Whitehead Mark I torpedo: the depth-control system. Reprinted from U. S. Bureau 

of Ordnance, The Whitehead Torpedo, 2 vols. (Washington, 1901), vol. 2, pi. 7. 
NUMBER 12 99 

,~r—I " <, 

FIGURE 114.—Whitehead Mark I torpedo: pneumatic servomotor powering the depth rudders. 

Reprinted from United States Bureau of Ordnance, The Whitehead Torpedo, 2 vols. (Washington, 1901), vol. 2. pi. 14. 

motor when the torpedo leaves the discharge 

tube; a distance gear—in practice runs— 

turns off the motor after a predetermined 

distance; and a sinking gear scuttles the torpedo after an unsuccessful war shot. 

As on all earlier models of the Whitehead 

torpedo, the vertical rudder of our 1892 unit 

was set experimentally in one fixed position 

for a straight run. Toward the end of the 

century, various schemes based on gyroscopes 

were introduced to keep torpedoes on a 

straight course. Probably the best known design was that of Ludwig Obry, adopted by 

the Whitehead establishment in 1895, and 

only a year later by the United States Navy. 

Its basic element is a "free gyroscope," a gyrowheel with three degrees of freedom, spinning 

on an axis parallel to that of the torpedo, 

supported in frictionless bearings by a horizontal inner gimbal and a vertical outer 

gimbal, so that the direction of the spin 

axis will remain fixed in space regardless of 

the direction of the torpedo. If the torpedo 

deviates from the desired direction, this is 

indicated by an angular displacement of the 

outer gimbal with respect to the frame of 

the torpedo. This relative motion is employed 

for corrective action; the outer gimbal is 

directly linked to the pilot valve of a pneumatic servomotor which in turn positions the 

vertical rudder, so that any deviation from 

course leads directly to a steering correction. 

T h e gyroscope receives its rotation (initially 

2400 r.p.m.) from a wound-up spring released at the moment of launching. 9 8 

A torpedo equipped with an Obry gyroscope, in the collections of our Museum, is 

the Bliss-Leavitt 20'1"X21 " torpedo built in 

1912 by the aforementioned Brooklyn firm 

(NMH T 31115; Accession 66742; serial no. 

2169; cutaway). Apart from the gyroscopic 

steering gear, this unit is distinguished from 

the basic Whitehead design only by a more 

powerful propulsive system employing turbines powered by heated air. 

T H E HOWELL TORPEDO.—In addition to the 

"Whitehead," the United States Navy used 

an American-designed torpedo that, although 

smaller in size, was in some regards superior. 

This torpedo, developed approximately between 1870 and 1884 by Comdr. John Adams 

Howell, was powered by the kinetic energy 

98. U. S. Bureau of Ordnance, The Whitehead Torpedo, 2 vols. (Washington, D.C, 1901). 
100 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 115.—Howell Mark I torpedo, 1890s: the flywheel in which the torpedo's propulsive 

energy is stored can be clearly seen in the center. (NMHT 53774. Smithsonian photo 71766.) 

of a heavy flywheel which was spun up to 

high speed (about 10,000 r.p.m.) before the 

launching. Th e Howell torpedo, consequently, could run without leaving the widely 

visible telltale wake characteristic of airdriven torpedoes, and furthermore it derived 

from the gyroscopic properties of the flywheel a degree of directional stability far 

superior to that of a Whitehead torpedo without Obry gear. Th e Museum has two identical 

specimens of this torpedo ("14.2 inches, Mark 

I") ; one was built in 1890 by the Hotchkiss 

Ordnance Company (NMH T 31113; Accession 66742; serial no. 47), the other is a 

cutaway demonstration model (Figure 115), 

presumably also dating from the 1890s, of 

which further particulars are unknown 

(NMH T 53774; Accession 190105). Th e 

Howell torpedo was undoubtedly inspired by 

the Whitehead design, but its distinctive propulsion system led to several important differences. 

Its immersion regulator, like Whitehead's, 

combines the action of a hydrostatic piston 

with that of a pendulum swinging in the 

fore-and-aft plane, both together controlling 

the horizontal rudder. Instead of a pneumatic 

servo, it uses an "impulse mechanism," a 

mechanical servo system that positions the 

horizontal rudder according to the output 

signal of the immersion regulator powered 

by energy from the flywheel. 

More remarkable is the control system responsible for holding the torpedo on a 

straight course. Th e heavy flywheel, rotating 

at high speed on a horizontal axis perpendicular to that of the torpedo, is mounted 

rigidly in the middle of the torpedo. Because 

it is a gyroscope with constrained axis, it 

will respond with a motion of precession to 

all forces displacing its axis. Specifically, the 

gyroscope will react on horizontal forces deflecting the torpedo from its course by rolling 

the torpedo around its lengthwise axis. Th e 

angle of roll, then, serves as a measure of 

deviation from course; it is sensed by a second 

pendulum, swinging in an athwartships 

plane, which acts, again through a mechanical 

servomechanism, upon the vertical rudder, so 

as to return the torpedo into its proper 

course. 

One further control device deserves mentioning, although it does not contain feedback. Th e flywheel is geared directly to the 

two propellers rotating in opposite directions 

on parallel shafts. Th e pitch of these propellers is changed automatically to compensate for the slowing down of the flywheel 

during the run. Th e adjustment is carried 

out according to a rigid program contained in 

a contoured cam which begins to run off a 

certain interval after the launching. 9 9 

OTHER TORPEDOES IN THE MUSEUM'S COLLECTION.—Four other torpedoes can only be 

listed briefly because descriptive material is 

not accessible. 

99. Naval Torpedo Station, Bureau of Ordnance, 

The Howell Torpedo: U.S. Navy-14.2"-Mark I: General Description, (n.p., 1896); Bruce McCandless, "The 

Howell Automobile Torpedo," Proceedings, U.S. Naval 

Institute 92.10 (October 1966): 174-176. 
NUMBER 12 101 

1. German torpedo of World Wa r I, 5.5 

m X 500 mm (NMH T 31155; Accession 

66742; 18' long, 19" diameter). 

2. Japanese torpedo of World Wa r II, Type 

91, Model 5 (NMH T 58762-N; Accession 236599; 17' long, 18" diameter; 

cutaway). 

3. Japanese torpedo of World War II, Type 

95, Model 2 (NMH T 58763-N; Accession 236599; 21' long, 18" diameter; 

cutaway). 

4. United States Navy torpedo, contemporary, Mark 37 (NMH T 58761-N; Accession 236599; 21' long, 21 " diameter; 

cutaway). 

Gyroscopic Compasses 

As phenomena in theoretical mechanics, 

the properties of the gyroscope were first 

made known to a wider audience in 1852 by 

the French physicist Le^on Foucault. Foucault 

described two features. Th e first is the phenomenon that the axis of a spinning wheel 

suspended with three degrees of freedom is 

fixed in space. In this he recognized an alternative to his famous pendulum as a method 

of demonstrating the rotation of the earth. 

T h e proposed method consisted simply in 

observing under sufficiently large optical magnification the rotation of the gyro axis 

relative to a reference frame fixed on the 

earth's surface. From this phenomenon 

(which allows us to see the earth turn) he 

derived the term gyroscope. Th e second property involves a gyroscope with two degrees of 

freedom. If a weight was suspended from the 

inner gimbal so as to maintain the spin axis 

in a horizontal plane, the combined effect 

of gravity and of the earth's rotation would 

cause the gyroscope to precess until it aligned 

itself with the meridian, pointing to the geographic North Pole. Foucault lacked a gyroscope that could rotate at very high speed 

for a long enough period, therefore, he was 

not able to demonstrate this latter feature. 

During the following half century a number 

of unsuccessful attempts were made to employ 

this effect in the construction of a compass, 

by such men as G. TrouvC", G. M. Hopkins, 

E. Dubois, Sir William Thomson, Van den 

Bos, and Werner Siemens. Th e first practical 

instrument was that of H. Anschtitz-Kampfe 

which, after successful tests on shipboard in 

1908, was soon widely used in navigation.100 

Elmer A. Sperry (1860-1930), from 1909 

to 1911, developed a gyrocompass that was 

a marked improvement over the Anschiitz 

design. On 11 June 1911 he applied for two 

patents to cover this invention, which were 

finally granted as U.S. Patents 1255480 on 

5 February 1918 and 1279471 on 17 September 

1918. Like those of his predecessors, Sperry's 

compass was based on the meridian-seeking 

properties of Foucault's two-degree-offreedom gyro; his most important improvement was to employ the principle of feedback to make the directional indication of 

the sensitive element more powerful.101 

T h e operation of the Sperry gyrocompass 

is very complex. Th e following brief sketch 

cannot do more than point out its chief 

characteristics. Functionally, the instrument 

consists of two parts, the sensitive element 

and the follow-up system. Th e sensitive element is an enclosed gyrowheel driven at high 

speed by an electric motor. It is suspended 

with two degrees of freedom, the third being 

constrained by a pendulum to hold the spin 

axis in a horizontal plane. This pendulum 

(termed by Sperry "the bail"), in combination with the gyroscope's rotation around the 

earth's axis, causes the wheel to precess until 

its axis lies in the plane of the meridian, 

pointing to the poles. 

T h e meridian-seeking motion of the sensitive element, however, is not powerful 

enough to drive with accuracy the various 

indicating devices of the compass. Th e orientation of the sensitive element, therefore, 

is the input for a servo device that adds 

power to the directional signal. Th e sensitive element is free to rotate around the 

vertical axis within the fixed case of the com100. Boris V. Bulgakov, Applied Theory of Gyroscopes, 2nd edition, trans. J. J. Schorr-Kon (Washington, D.C, 1960), pp. 87-90. 

101. Thomas P. Hughes, Elmer Sperry: Inventor and 

Engineer (Baltimore, 1971). 
102 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 116.—Elmer Sperry's first experimental gyrocompass, 1910. (NMHT 309636. Smithsonian photo 

71965.) 

pass. Between the sensitive element and the 

case, on the same vertical axis, rotates a ringshaped frame, the "phantom element," driven 

by a reversible electric motor. This motor is 

connected to two electrical contacts, one 

positive, one negative, separated by a neutral 

zone over which slides a trolley attached to 

the sensitive element. When the sensitive 

element begins to turn relative to the compass 

case, the trolley will move from the neutral 

zone to one of the contacts, switching on 

the motor so that the phantom will follow 

the sensitive element until the trolley reaching the neutral zone breaks contact. Consequently, the motor-driven phantom will 

duplicate closely all motions of the sensitive 

element, but with a great increase in power. 

The compass indication is displayed not only 

on a compass card directly connected to the 

phantom; it is also transmitted from the 

master compass to a number of repeater compasses at various locations on the ship. 

Three Sperry gyrocompasses are in the collections of our Museum. The oldest is Elmer 

Sperry's first experimental model (Figure 

116), built in 1910, tested in spring 1911 on 

the steamer Princess Anne (Old Dominion 

Line) and on the destroyer Drayton of the 

United States Navy. Then it was installed 

on the battleship Delaware, where in August 

1911 it performed faultlessly under battle 

conditions. Consequently, the United States 

Navy placed their first order for several Sperry 

compasses (NMHT 309636; Accession 

106664; rotor diameter about 14"; the system 

is assembled on a wooden structure 30"X30" 

X36"). 

The gyrocompass Mark 1—Model 2—No. 

109 built in December 1912 was the ninth 

unit ordered by the Navy. Installed on the 

battleship Wyoming, it served as a master 

for five repeater compasses. As a modification 

to the original design, it contains a "floating 

ballistic," a small additional gyroscope stabilizing the connection between the bail and 

the sensitive element (NMHT 313403; Accession 667424; 19" diameter, 3'8" high). 

The Sperry compass Mark 2-Model 9-No. 

350 (Figure 117) is designed especially for 

submarine service, dating probably from 

World War I. After serving on United States 

Navy submarines for a number of years, it 

was installed on submarine Nautilus with 

which in 1931 the Wilkins-Ellsworth expedition approached the North Pole below the 

ice cap. For this purpose the compass had 

been converted into a free gyro, because conventional gyrocompasses lose their meridianseeking properties in the vicinity of the poles. 

Subsequently, the compass served on the 

mothership of Admiral R. E. Byrd's Antarctic 

expeditions of the early thirties (NMHT 

39596-N; Accession 245666). 

The Sperry Gyropilot 

Perhaps the most spectacular invention of 

Elmer Sperry's is the gyropilot, where he 

combined the gyrocompass with the servosteering system of the ship into an automatic 

steering system capable of replacing the helmsman altogether. Sperry began to work on 

this invention soon after the gyrocompass 

had proved successful. The application for 

his basic patent was filed on 13 November 
NUMBER 12 103 

FIGURE 117.—Sperry "Mark 2-Model 9" gyrocompass, 

special design for submarine service, World War I; 

in the 1930s, this compass took part both in North 

Pole and Antarctic expeditions. (NMHT 39596-N. 

Photo by Sperry-Rand.) 

1914 (granted as U.S. Patent 1360694 on 30 

November 1920). The war, however, interrupted this work. After tests in 1922 on three 

experimental gyropilots, the first ten production models were built in 1923 (serial nos. 

101-110). The unit 105 (Figure 118) of this 

series, installed 17 December 1923 on the 

tanker Pennsylvania Sun of the Sun Oil Co., 

is now in our Museum's collections (NMHT 

309634; Accession 103045: marked "Sperry 

Gyroscope Co., New York. Gyro Pilot Mark 

II, Model 0, Volts 110, Serial No. 105"). It 

is a duplicate of the gyropilot (serial no. 109) 

that, also in 1923, was the first to automatically steer a ship (RSMS Laconia) around 

FIGURE 118.—Sperry gyropilot, 1923, shown in its 

former location at the Arts and Industries Building. 

(NMHT 309634. Smithsonian photo 43506-B.) 

the earth. Under the designation "SingleUnit Gyro-Pilot" this model was manufactured essentially unchanged for many years. 

In contrast to the later "Two-Unit" and 

"Triple-Unit" devices, it was designed to be 

added when a separate servo-steering machine 

was already installed on the ship. 

Apart from the servo-steering system, the 

principle of which has been described, the 

gyropilot comprises two feedback loops. 

The input to the outer, main loop is the desired course, defined as a certain compass bearing, and represented by the angular position of 

a hand wheel. This signal is compared with 

the actual heading of the ship, indicated by 

a repeater compass, by means of a differential 

gear serving as a mechanical comparator. The 

resulting error signal—the ship's deviation 

from the desired course—serves as the input 

for a second, internal, feedback loop that will 

manipulate the steering wheel. This subordinate feedback loop resembles the electric 

servo system on the gyrocompass. Its input, 

the deviation from course, is represented by 

the angle of rotation of a drum carrying 

positive and negative electrical contact strips 

separated by an insulating zone. A trolley 

sliding over this drum is wired to a reversible 
104 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

D.C. motor. When the system is in equilibrium, the trolley is in contact with the insulating strip; in the event of an error signal 

the trolley will make contact with one of 

the conducting strips, energizing the motor 

so that the steering wheel will be turned in 

the appropriate direction. The support platform of the trolley, which can also rotate, 

is connected with the steering wheel by means 

of a special feedback gear train so that the 

trolley will follow the insulating strip as the 

steering wheel is turned. The internal feedback system, as a result, provides proportional 

control: the angle by which the steering wheel 

is turned is proportional to the deviation 

from the desired course. 

The output of the gyropilot, the angular 

position of the steering wheel, is received as 

a command by the servo-steering system and 

converted into a proportional angular position of the rudder. The main feedback loop 

of the system is then closed by the motion of 

the ship itself. The gyropilot, after comparing 

the desired direction with the ship's actual 

heading, turns the steering wheel and 

through it the rudder. The changed heading 

of the ship, sensed by the gyrocompass, is 

then promptly transmitted to the gyropilot 

which accordingly modifies its output.102 

102. Sperry Gyroscope Company, The Gyro-Compass 

and Gyro-Pilot: Their Operating Principles, Construction and Uses, Publication No. 17-1610 (Brooklyn, 

New York, no date [about 1933]), pp. 25-34. 
Feedback in Electrical Technology 

The Regulation of Electric Arc Lamps 

The possibility of employing electric arcs 

for lighting was recognized early in the nineteenth century. During a public lecture at the 

Royal Institution in 1809, Sir Humphry Davy 

used a voltaic battery of 2000 elements to 

produce a 3-inch arc between two carbon 

electrodes. From this physical experiment to 

the development of a practical system of 

lighting, three obstacles had to be overcome: 

improving the material of electrodes; finding 

more economical ways of generating electric 

current; and regulating the distance between 

electrodes in such a manner as to produce light 

of constant intensity. In the context of this 

catalog, the first problem concerns us not at 

all, the second indirectly, but the third directly. 

The control problem had these implications: (1) An arc of constant intensity can 

be maintained only if the gap between the 

electrodes is kept constant; the tips of the 

electrodes, however, are slowly consumed in 

operation at an irregular rate. (2) In order 

to relight an arc lamp after power has been 

turned off, the carbons first have to be 

brought into direct contact before they can 

be drawn apart to produce an arc. (3) 

Economy requires that more than one lamp 

can be put into the same circuit. The con103. The scope of this catalog did not permit inclusion of the electronic devices in the Museum's collection which incorporate feedback in a variety of 

ways. This seemed to be all the more justifiable as 

such devices, "black boxes" from the outside and 

highly complex in their functioning, are generally 

much less approachable to the Museum visitor than 

the other objects described here. 

trol system of the individual lamp, therefore, must function without introducing 

instability into the overall system.104 

EARLY ARC LAMPS.—The problem of automatically controlling the arc length was first 

solved around 1848 simultaneously by W. 

Edward Staite of London and by Leon 

Foucault, the French physicist.105 

Foucault perfected his lamp in collaboration with his instrument maker Jules 

Duboscq (1817-1886),106 under whose name 

it then was sold with considerable success. 

A Duboscq lamp (Figure 119) is the oldest 

arc lamp in our collection (NMHT 315717; 

Accession 217544; inscribed "J. Duboscq a 

Paris, Appareil Brevete" S.G.D.G. No. 393"; 

10i/2"X5i4"X22i/2"). It is a relatively late version of Duboscq's design, dating probably 

from the late 1860s. Its system of regulation 

is characteristic for that of most early arc 

lamps. An electromagnet is employed both 

to sense the magnitude of the gap between 

the electrodes and to manipulate the electrodes to keep this gap constant. The current 

flowing through the arc decreases with the 

arc length. The pull of the electromagnet, 

however, is directly proportional to the current going through it. Being wired in series 

with the carbon electrodes, the electromagnet 

therefore exerts a force upon a spring-loaded 

104. Francis B. Crocker, Electric Lighting, 2 vols. 

(New York, 1896 and 1901), vol. 2, ch. 15. 

105. W. James King, "The Development of Electrical 

Technology in the 19th Century," Contributions from 

the Museum of History and Technology, USNM 

Bulletin 228 (1962):334-344. 

106. Dictionnaire de Biographie Frangaise, under 

"Duboscq, Jules." 

105 
106 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 119.—Foucault arc lamp built by Jules 

Duboscq, 1860s. (NMHT 315717. Smithsonian photo 

45391-A.) 

armature that is inversely proportional to the 

gap, reaching a maximum when the electrodes touch each other. This force is used 

in most systems to regulate the length of 

arc, although the mechanical details vary 

widely. In the Foucault-Duboscq system the 

electrodes are positioned by a spring-powered 

clockwork that is reversible and therefore 

capable of moving the electrodes toward, as 

well as away from, each other. The direction 

of motion of this clockwork is determined 

by the electromagnet. If its pull upon the 

armature is stronger than the resistance of 

the spring, then the clockwork will be set 

in motion to separate the electrodes, and 

vice versa. Reportedly the Duboscq lamp performed well when carefully maintained but 

was highly susceptible to damage because of 

its complexity.107 

In the same class belongs the Siemens-von 

Hefner Alteneck lamp (Figure 120) from 

the early 1870s (NMHT 319279; Accession 

23501; marked "Siemens Brothers, London 

No. 177", 4"X4"X24"). As before, the electromagnet is wired in series with the arc. 

The method of manipulating the electrodes 

is different. The motion in one direction, 

toward each other, is caused simply by gravity. 

The electromagnet begins to act only when 

the electrodes are too close. Arranged as an 

oscillator, similar to that of an electric doorbell, it drives the electrodes apart by means 

of a ratchet mechanism and stops as soon 

as the arc current has come down to its 

equilibrium level.108 

Based on the same principle of regulation 

is the arc lamp of Matthias Day, represented 

by a patent model for U.S. Patent 147827 of 

24 February 1874 (NMHT 251223; Accession 

48865; nonoperational mock-up; 4" diameter 

X 12" high) . Here the fine adjustment of arc 

length is accomplished by a solenoid, wired 

in series, which directly positions the lower 

electrode. Also wired in series is an electromagnet which acts as an electric clutch. 

Whenever, due to carbon consumption, the 

arc has grown too long, the clutch disengages, 

permitting gravity to bring the electrodes 

closer together. 

All these early arc lamps, where the regulating electromagnet is wired in series with 

107. A. Merling, Die elehtrische Beleuchtung 

(Braunschweig, 1882), pp. 248-252; E. Alglave and J. 

Boulard, The Electric Light, trans. T. O. Sloane (New 

York, 1884), pp. 61-63. 

108. Merling, Die elektrische Beleuchtung, pp. 311-

313; James Dredge (editor), Electric Illumination (London, 1882), 1:405-406. 
NUMBER 12 107 

the arc, have one predominant shortcoming: 

only one such lamp can be used in a given 

circuit. If, for example, two lamps were arranged in series, not only would current fluctuations due to control action in the first 

lamp upset the stability of the other, a breakdown of one lamp would interrupt the circuit 

altogether. In the laboratory this drawback could be tolerated but not in a system 

of street lighting. 

SYSTEMS OF ARC LIGHTING.—For more 

than half a century after Sir Humphry Davy's 

arc-light demonstration, arc lamps depended 

on electricity generated in chemical batteries. 

Their use was limited therefore to special 

events such as gala performances of opera 

or to the physics laboratory. In the mid-1870s, 

with the arrival of the self-excited generator, 

this state of affairs changed abruptly. The 

lighting of streets and public buildings offered 

the first opportunity for employing the newly 

found cheap electricity on a larger scale. Almost simultaneously, a number of technically 

sound systems of arc lighting made their 

appearance. In America among the earliest 

were those of Wallace-Farmer, Brush, Thomson-Houston, and Weston, of which, at least 

at the beginning, the Brush system emerged 

as the most successful.109 

Generally each of these systems was distinctive not only in the design of its arc 

lamps but also in its other main components, 

chiefly the generator. In the present context, 

we will discuss only the regulation of the 

arc lamps. Other instances of feedback control in the overall system will be treated later 

such as the current regulation of the generators. 

The Brush System: The first system of electric lighting to attain commercial success was 

that of the Brush Electric Co. of Cleveland, 

Ohio. In our collections the oldest related 

item is a patent model (Figures 121 and 122) 

by Charles F. Brush (U.S. Patent 203411 of 

7 May 1878; NMHT 252649; Accession 

49064; 5" diameter, 12" high). It is a simple 

FIGURE 120.—Siemens-von Hefner Alteneck arc lamp, 

about 1870. (NMHT 319279. Smithsonian photo 

71878.) 

109. Harold C. Passer, The Electrical Manufacturers, 

1875-1900: A Study in Competition, Entrepreneur ship, 

Technical Change, and Economic Growth (Cambridge, 

Massachusetts, 1953), pp. 11-71. 
108 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 121.—Patent model of arc lamp by Charles F. 

Brush, 1878. (NMHT 252649. Smithsonian photo 

44552-E.) 

FIGURE 122.—Cross-section of Brush arc lamp NMHT 

252649. Reprinted from U. S. Patent No. 203411 of 

May 7, 1878, Patent Specifications, fig. 1. 
NUMBER 12 109 

arc lamp in which the regulating solenoid 

is wired in series with the arc so that only 

one lamp can be used per circuit. Th e system 

of regulation is this: while the lower electrode 

is fixed, the upper one is attached to a metal 

rod that is free to slide downward under the 

effect of gravity but is suspended by the 

solenoid through a friction clutch. This friction clutch, the patented feature, was to become a standard component of Brush arc 

lamps. It consists simply of a flat washer 

fitting loosely over the suspended rod. When 

its axis is aligned with that of the rod, it 

will slide freely; if, however, it is tilted, it 

will firmly seize the rod. Th e core of the 

solenoid, when energized, will lift up one 

side of the washer; by thus engaging the 

friction clutch, it will pull the supporting 

rod upward. If the solenoid is not energized, 

the washer will settle flatly on a supporting 

ring, permitting the rod to slide downward 

until it meets the lower electrode. Closing 

the circuit and reestablishing the arc will 

reenergize the solenoid, which will pull the 

supporting rod upward until its magnetic 

force, with decreasing arc current, will return to a level where it just balances the 

weight of the upper electrode and its supporting rod.110 

Production models of Brush arc lamps embodying this patent are two identical table 

lamps (Figure 123), probably for laboratory 

purposes, of the 1880s (NMH T 181554; Accession 32407; serial no. 13013; and NMH T 

325989; Accession 256489; serial no. 13014; 

size 4"X8"X28"). They are wired in the 

fashion of the Foucault lamp where only 

one lamp can be used in a given circuit. 

Our next patent model (Figure 124) of 

a Brush arc lamp (U.S. Patent 212183 of 

11 February 1879) offers a solution to this 

problem (NMH T 251232; Accession 48865; 

6" diameter, 12" high). In the use of the 

customary friction clutch, this lamp is mechanically equivalent to the preceding one. 

T h e difference is only electrical. Th e new 

110. Paget Higgs, The Electric Light in its Practical 

Applications (London, 1879), pp. 35-37; John W. 

Urquhart, Electric Light, its Production and Use, 3rd 

edition (London, 1890), pp. 335-342. 

FIGURE 123.—Brush arc lamp, 1880s. (NMHT 181554. 

Smithsonian photo 44552-B.) 
110 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 124.—Patent model of arc lamp employing 

differential circuit, by Charles F. Brush, 1879. (NMHT 

251232. Smithsonian photo 44552-F.) 

"differential" circuit permits any desired 

number of such lamps to be connected in 

series. The solenoid consists of two separate 

coils. The main coil is wired, as before, in 

series with the arc. The other one, the shunt 

coil, is connected parallel to the whole lamp; 

it has roughly the same number of turns but 

a much higher resistance and is wound in 

the opposite direction to the first, so that the 

FIGURE 125.—Patent model of double-arc lamp by 

Charles F. Brush, 1879. (NMHT 251230. Smithsonian 

photo 44552-A.) 

magnetic force induced by it will counteract 

that of the main coil. While the main coil, 

when energized, draws the electrodes apart, 

the shunt coil—acting in the same direction 

as gravity—brings them together. In normal 

operation only a small fraction of the total 

current will flow through the shunt coil. 

When the main circuit, however, is interrupted, the shunt coil will (1) act as a bypass 

to the arc, thus assuring the continuity of 

operation of other lamps in the same line; 
NUMBER 12 111 

and (2) draw together the electrodes in 

order to relight the arc.111 

The Brush system achieved its first triumph 

in 1878 with the installation of twenty arc 

lamps in the Wanamaker department store 

in Philadelphia. For the lamps used here, 

C. F. Brush took out another patent (U.S. 

Patent 219208 of 2 September 1879). The 

patent model accompanying this application, 

a full-scale production model (Figure 125), 

is in our collection (NMHT 251230; Accession 48865; serial no. 345; 24"X47" high). 

This lamp combines various previously patented features—the friction clutch, the differential circuit, and the cutoff relay (a 

magnetic switch bypassing the lamp when 

the arc is broken) -—-with a new dual-arc arrangement: the lamp was equipped with two 

sets of electrodes working alternately to 

lengthen the operating period. 

Two actual street lamps in our collection 

are very similar to this lamp. The older one, 

a single-arc lamp, is unmarked (NMHT 

327945; Accession 271855; 18i/2"X33" high), 

but its regulator is of the same design as 

the previous lamp. The other one is a dualarc lamp marked "Brush E. Co. Standard; 

No. A/31/20667, 9.6 amperes. Patented by 

C. F. Brush: Feb. 11, 1879; Sept. 2, 1879; 

Nov. 16, 1880; Feb. 10, 1885. T. E. Adams 

Patent May 27, 1888; other patents pending." 

(NMHT 327946; Accession 271855; 8"X46" 

high). 

Several other patent models of arc lights 

by C. F. Brush in the Museum's collection 

do not contain feedback. 

The Wallace-Farmer System: The lighting 

system of William Wallace and Moses G. 

Farmer, one of America's earliest, used the 

traditional method of regulation. The solenoid is wired in series with the arc; the 

upper electrode approaches the lower one 

by gravity, but in order to spring (start) the 

arc it is lifted upward slightly by the solenoid 

through a friction clutch similar to that of 

C. F. Brush. The Wallace-Farmer arc lamps 

are distinguished only by the unusual form 

of their carbons, which are shaped not as 

pencils but instead as plates of considerable 

width. For a given life span such carbons 

require far less adjustment. This shape of 

carbon electrode was patented by William 

Wallace in 1877 (U.S. Patent 198436 of 18 

December 1877. The actual patent model, 

without any control device, is in our Museum 

111. Crocker, Electric Lighting, 11:339. 

FIGURE 126.—Wallace arc lamp, 1880s. (NMHT 201365. 

Smithsonian photo 71887.) 
112 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

under NMHT 251235). Our Museum has 

two such early Wallace-Farmer arc lamps, 

dating probably from the early 1880s (1. 

NMHT 201365; Accession 35164; marked 

"Wallace's Patent, Dec. 18, 1877"; 7"Xl6i/ 2 " 

high [Figure 126]. 2. NMHT 201363; Accession 35164; serial no. 117; marked "Wallace Electric Lamp, Patented Dec. 18, 1877. 

Manufactured by Wallace & Sons, Ansonia, 

Conn. USA"; 15i/2" wide, 14" high).112 

Of Moses G. Farmer, Wallace's collaborator, the Museum has two experimental arclamp regulators dating probably from the 

1880s. (1. NMHT 181973; Accession 34583; 

double magnet, clockwork, etc., on wooden 

base 12"X12". 2. NMHT 181974; Accession 

34583; wooden box, 6i/2"X9i/2"X9"). 

The Thomson-Houston System: Elihu 

Thomson and Edwin J. Houston, two high 

school science teachers from Philadelphia, devised a system of arc lighting that appeared 

on the market in 1879. The ThomsonHouston Company, formed to promote their 

inventions, proved enormously successful. 

The company purchased the Brush Electric 

Co. in 1889, and in 1892 it became one of 

the parent firms of the present General Electric Company.113 

Our Museum has the patent model (Figure 

127) for the first arc-lamp patent by E. Thomson and E. J. Houston (U.S. Patent 220508 

of 14 October 1879; NMHT 251233; Accession 48865; 7"XH " high). Its main distinction from the arc lamps encountered so far 

is the circuit used. C. F. Brush had solved 

the problem of how to connect a larger number of arc lamps in series by wiring each 

lamp with the "differential circuit" described 

earlier. The Thomson-Houston lamps instead 

used the "shunt circuit," on which the lamp 

patent of 1879 (Figure 128) is based.114 Each 

circuit has a shunt line bypassing the arc. In 

the "differential" circuit the main line and 

the shunt line each contain a solenoid, wound 

in opposite directions, acting against each 

112. Dredge, Electric Illumination, 1:410-413. 

113. Passer, Electric Manufacturers, pp. 21-31. 

114. For a discussion of the "shunt" circuit versus 

the "differential" circuit, see Crocker, Electric Lighting, 11:338-340. 

FIGURE 127.—Patent model of arc lamp by E. Thomson 

and E. J. Houston, 1879. (NMHT 251233. Smithsonian 

photo 71886.) 

other. In the "shunt" circuit the electromagnet controlling the arc gap is in the shunt 

line alone. If the current bypassing the arc 

becomes too powerful due to an excessive 

arc gap, this electromagnet is energized and 

releases an escapement permitting the upper 

electrode to move downward under the effect 

of gravity. A second electromagnet, wired in 

series with the main circuit, when energized 

pulls the electrodes apart against the force of 

a spring. Its purpose is only to establish an 

arc after the current has been turned on at 

start-up. The advantages claimed for the 

"shunt circuit" are that the regulation is 

unaffected by sudden variations in arc resistance, and that the mechanism is essentially 

independent of current strength. Lamps designed according to this patent were first installed at a Philadelphia bakery in 1879. 

Subsequent Thomson-Houston, and later 

Thomson-Rice, arc lamps differed considerably in mechanical aspects but retained the 

"shunt circuit." Representative for this later 

stage of development is a Thomson-Rice 

double arc lamp (Figure 129) of the late 
NUMBER 12 113 

E. THOMSON & E. J. HOUSTON. 

Regulator for Electric-Lamp. 

No. 220,508. Patented Oct. 14, 1879. 

FIG.I . 

F\ G.2 . 

WITNESSES . 

A

 K INVENTORS 

FIGURE 128.—Patent specification drawing for Thomson-Houston arc lamp NMHT 251233. Reprinted from U. S. Patent No. 220508 of Oct. 14, 1879. 
114 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FICURE 129.—Thomson-Rice double-arc lamp, late 

1880s. (NMHT 219016. Smithsonian photo 71885.) 

FIGURE 130.—Patent model of arc lamp by Charles J. 

Van Depoele, 1880. (NMHT 252652. Smithsonian 

photo 71877.) 
NUMBER 12 115 

FIGURES 131-134.—Patent models of arc lamp regulating mechanisms by Charles J. Van Depoele, 

1882-1884: 

131. (NMHT 308597. Smithsonian photo 71880.) 132. (NMHT 251222. Smithsonian photo 71881.) 

133. (NMHT 251227. Smithsonian photo 71875.) 134. (NMHT 308598. Smithsonian photo 71876.) 
116 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 135.—Patent model of arc lamp by Edward Weston, 1881. (NMHT 252660. Smithsonian 

photo 71884.) 
NUMBER 12 117 

FIGURE 136.—Patent model of arc lamp by N. S. Keith, 

1882. (NMHT 251225. Smithsonian photo 29680.) 

1880s (NMHT 219016; Accession 40913; 

"Class M," No. 92737; 8"X52" high).115 

MISCELLANEOUS ARC LAMP REGULATORS.— 

The Museum's collection contains a considerable number of other automatically regulated 

arc lamps. They are mostly patent models 

from the 1880s, when for a brief period arc 

115. Ibid., pp. 349-351. 

light was the predominant form of electric 

light. These are listed without detailed 

explanation: 

NMHT 252655; Accession 49064: patent 

model by Hiram S. Maxim (later Sir 

Hiram) for U.S. Patent 208252 of 24 September 1878. Full-scale arc lamp, now incomplete; base 7i/2" diameter, 27" high. 

NMHT 252656; Accession 49064: patent 

model by Hiram S. Maxim for U.S. Patent 

230953 of 10 August 1880. A small, simple 

wooden mock-up of an arc-lamp regulator; 

9"X7"X7". 

NMHT 252652; Accession 49064: patent 

model (Figure 130) by Charles J. Van 

Depoele for U.S. Patent 227078 of 27 April 

1880. A small but apparently operational 

model of a simple arc lamp, 2"X3i4"X 

1434". 

NMHT 308597; Accession 89797: patent 

model by Charles J. Van Depoele for U.S. 

Patent 261260 of 18 February 1882 (Figure 

131). Regulating mechanism only; full 

scale; 6" diameter, 12y2" high. 

NMHT 251222; Accession 48865: patent 

model by Charles J. Van Depoele for U.S. 

Patent 291553 of 8 January 1884 (Figure 

132). Regulating mechanism only; full 

scale; 6" diameter, 8" high. 

NMHT 251227; Accession 48865: patent 

model by Charles J. Van Depoele for U.S. 

Patent 291651 of 8 January 1884 (Figure 

133). Regulating mechanism only; full 

scale; 614" diameter, Hi/2" high. 

NMHT 308598; Accession 89797: patent 

model by Charles J. Van Depoele for U.S. 

Patent 294165 of 26 February 1884 (Figure 

134). Regulating mechanism only; full 

scale; 6" diameter, 614" high. 

NMHT 252660; Accession 49064: patent 

model by Edward Weston for U.S. Patent 

240210 of 12 April 1881 (Figure 135). One 

of twelve arc-lamp regulator patents that 

Weston took between 1880 and 1882. Fullscale operational arc lamp; 15i/2"X6i/2" 

X21". 

NMHT 251225; Accession 48865: patent 

model by N. S. Keith for U.S. Patent 

255795 of 4 April 1882 (Figure 136); full-
118 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 137.—Sperry high-intensity arc lamp, about 1918. (NMHT 309633. Smithsonian photo 

60975-A.) 

scale lamp, probably mass produced; 14" 

X5i/2"X30". 

NMHT 251236; Accession 48865: patent 

model by Barton B. Ward for U.S. Patent 

444472 of 13 January 1891 and 484479 of 

18 October 1892. Full-scale lamp, probably 

taken from mass production; 8i/2"X4"X 

18" 

NMHT 219017; Accession 40913: AdamsBagnall Arc Lamp, late 1890s. Marked 

"The A.B.E. Co. Clev'd, O. Pat'd. Oct. 22, 

95. No. B-7983." Production model, cutaway; 10" diameter X 27" high.116 

116. This lamp is shown on Figure 286, Crocker, 

Electric Lighting, 11:352. 
NUMBER 12 119 

NMH T 309633; Accession 103045: Sperry 

high-intensity arc lamp (Figure 137), built 

about 1918. Marked "Sperry Gyroscope Co. 

New York. 150 Ampere-Search-Light Lamp. 

Mark 36-1 Mod. 1. Ser. No. 7 Insp'r— 

Patent Applied For.' Th e lamp was developed in 1916 as a military searchlight. 

This unit is a duplicate of one used in 

1924 by A. A. Michelson for his speedof-light measurements on Mt. Wilson. Th e 

accuracy required from the control system 

for positioning the electrodes is unusually 

high, because the arc crater must always 

be in the focus of the reflector. Th e position of the arc is sensed by a thermostat 

pointed toward the focus. If the arc is not 

located correctly, the thermostat will sense 

a decrease in temperature and in response 

cause the repositioning of the electrodes. 

Size: 37"X 10"x31i/ 2 ". 1 1 7 

117. Hughes, Elmer Sperry. 

Feedback Control on Electric Machines 

CONSTANT CURRENT REGULATION IN ARCLIGHTING SYSTEMS.—Early systems of electric 

lighting, where a large number of arc lamps 

were powered by a common steam-driven 

DC generator, generally employed the series 

circuit. Experience had shown that individual 

arc lamps performed best at a potential drop 

of 40 to 50 volts and at a current between 

6 and 10 amperes. Th e series circuit provided 

the best way of accommodating such operating requirements to the performance characteristics of the self-excited series generators 

then available. For example, a typical generator producing an electromotive force of 

2000 volts at 10 amperes was then capable 

of supplying 40 arc lamps with current. Arc 

lamps, in general, proved to be highly sensitive to fluctuations in current. Particularly 

undesirable were rises in the line current 

occurring when some of the lamps in the 

FIGURE 138.—Thomson-Houston current regulator, 1880. (NMHT 181725. Smithsonian photo 

71888.) 
120 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

circuit, accidentally or purposely, went totally out of operation. To attain tolerably 

steady arc light, it became necessary to provide some form of automatic control that 

could maintain a constant current in spite 

of all disturbances. 

The most successful current control system 

was that of Thomson-Houston, and it was 

largely upon this system that the early competitive advantage of that company was 

based. In our Museum it is represented by 

an early arrangement from 1880 (Figures 

138-139) and two sets (one incomplete) 

of the maturer design of the late 1880s (Figures 140-142). In order to understand the 

functioning of this system, it is best to study 

the later version first.118 

As Figure 142 shows, the system consists 

of three main parts: the generator with 

movable commutator brushes; the electromagnet RA; and the wall-mounted controller 

ST. The bottom of Figure 142 shows the 

DC generator with armature and field wired 

in series, equipped with two pairs of commutator brushes that can be rotated toward 

each other by a few degrees. When the distance between the positive and the negative 

brushes is thus reduced, the output electromotive force of the generator will decrease. 

The two pairs of brushes are connected by 

a lever so that they can be shifted simultaneously by a common linkage. This linkage 

is moved by the armature of the electromagnet R, whose pole is shaped paraboloidally 

to increase its operating range. Armature and 

magnet are connected by the dashpot, which 

has the function of arresting the armature 

whenever the electromagnet is deenergized. 

The current to the electromagnet R, in turn, 

is controlled by the solenoid S whose two 

coils are wired in series with the main circuit. 

Normally the electromagnet is not energized. But whenever the line current becomes 

strong enough that the solenoid will attract 

its armature against the opposing spring 

force, the contact T will be closed, con118. Silvanus P. Thompson, Dynamo-Electric Machinery, 4th edition (London, 1892), pp. 464-474; 

Crocker, Electric Lighting, 1:333-335. 

necting the electromagnet into the main circuit. The magnet then will pull its armature 

upward and, by moving the commutator 

brushes closer, it will reduce the generator 

output, until the solenoid breaks contact at 

T. The resistance r merely serves to prevent 

sparks at T. It will be noticed that this 

system can only take corrective action against 

excessive currents. The system is laid out 

for a maximum number of arc lamps; disturbances that would increase this load, that 

is, decreasing the current, are unlikely. 

A system exactly like the one just described, 

and dating probably from the late 1880s, is 

installed (Figure 140) on the ThomsonHouston DC generator, serial number 3634 

(NMHT 328424; Accession 272928). Attached to it is part of the regulator (corresponding to ,R in Figure 142) inscribed 

"C12 3448," and carrying the following nameplate: "Automatic Regulator No. (blank) ; 

Patented Jan. 20, '80; Mar. 1, '81; Dec. 26, 

'82; Feb. 6, '83. Manufactured by Thomson 

Houston Electric Co., Lynn, Mass. U.S.A." 

The remaining part of this system (ST in Figure 142) is the wall-mounted controller (Figure 141) containing the solenoid (NMHT 

328068; Accession 270107; marked "3284"; 

nameplate same as on previous regulator; in 

wooden box, 12"X5"X17"). Another Thomson-Houston current regulator, of the same 

type as the last, is incomplete. It consists of 

the electromagnet of the regulating system 

(NMHT 320573; Accession 241557; inscribed 

"E2 3549"; nameplate same as on previous 

regulators) mounted on a DC generator 

(NMHT 181720; Accession 33185; the commutator is defective). The wall-mounted box 

containing the solenoid that would complete 

the system is missing. 

These two examples of the mature Thomson-Houston current regulator, where the 

control device is divided into two separate 

units, are contrasted by an early model of 

the regulator (Figure 138) dating from 1880 

(NMHT 181725; Accession 33185). This 

earlier device works according to the same 

principle as the later design, but it combines 

all functions in a single compact unit, as 

described in E. Thomson's and E. J. Houston's 
NUMBER 12 121 

Patent 223659 of 20 January 1880 (Figure 

139). The regulator was probably connected 

with a Thomson-Houston generator of 1879, 

also in the Museum's collection (NMHT 

181727). 

The Wood regulator used on the Grammetype generators built by the Fort Wayne 

Electric Company is somewhat similiar to 

the Thomson-Houston current control system. The Museum has a specimen of this 

r iG 

FIG.a. 

FIG - 3 

WITNESSES. INVENTORS. 

FIGURE 139.—Various arrangements of current regulators, proposed by E. Thomson and E. J. 

Houston. The system of Figure 2 represents the current regulator of NMHT 181725. Reprinted 

from U. S. Patent No. 223659 of Jan. 20, 1880, Patent Specifications. 
FIGURE 140.—Thomson-Houston D.C. generator with current regulator, late 1880s. (NMHT 

328424. Smithsonian photo 74617.) 

FIGURE 141.—Thomson-Houston wall-mounted current 

regulator. (NMHT 328068. Smithsonian photo 71879.) 

FIGURE 142.—Circuit diagram of the Thomson-Houston 

current control system, as represented by NMHT 

328424 and 328068. Reprinted from Silvanus P. 

Thompson, Dynamo-Electric Machinery, 4th ed. (London, 1892), fig. 315. 

MJ&^^X&M} 
NUMBER 12 123 

FIGURE 143.—G.E. constant current transformer, about 

1905. (NMHT 326554. Smithsonian photo 74615.) 

design identified by its nameplate as a "Wood 

Dynamo Electric Machine No. 5; Pat'd May, 

1882; Jun e 19, 1889; July 9, 1889; Dec. 31, 

1889; Jan. 28, 1890; Feb. 11, 1890. Other 

Patents Applied For. No. 366" (NMH T 

322247; Accession 205734). As in the Thomson-Houston system, an electromechanical 

regulator is used to shift the commutator 

brushes; the system differs in that the field 

consists of two exciting circuits wound differentially in opposite directions. Th e main 

circuit of these is connected in the usual 

fashion to a pair of fixed commutator brushes. 

T h e second one, however, is a demagnetizing 

circuit connected between one of the main 

brushes and a movable pilot brush manipulated by the regulator. As the current increases, the pilot brush moves away from 

the main brush, increasing the current passing through the demagnetizing circuit, and 

thus reducing the current output. 1 1 9 

At the end of the century, when alternating 

current was introduced into arc lighting, the 

basic series circuit was retained, and therefore it remained just as essential as before 

to keep the current in the line constant. Although a number of current regulators were 

proposed similar to those used on direct current, the constant current transformer soon 

was generally accepted for this task. In principle the regulating action of this transformer 

makes use of two phenomena: First, the primary and secondary coils of a transformer, 

if both carry current, repel each other with 

a force proportional to the currents. Second, 

the current induced in the secondary coil 

decreases with growing distance from the 

primary coil. A typical constant current 

transformer then is arranged as follows: Th e 

primary coil is attached horizontally to the 

lower part of the core. Th e secondary coil 

is suspended directly above it, balanced by 

counterweights, free to slide up or down 

along the core of the transformer. When 

the secondary current increases, the rise in 

electromagnetic repulsion will force the secondary coil to move up and away from the 

primary, thus reducing the secondary current 

and closing the feedback loop. Th e desired 

secondary current is determined by the weight 

of the counterpoises. In our Museum this 

transformer class is represented by a unit 

(Figure 143) built about 1905 by the General 

Electric Company (NMH T 326554; Accession 

260953; Type RB-Form A-No. 502808; Primary 2200 volts, 60 cycles. Secondary 5.5 

ampere, output at Unity Power Factor 8 

kW).m> 

SPEED CONTROL OF MOTORS.—Our collection has only one example of an electric 

motor in which the speed is controlled by a 

feedback device. Th e direct-current motor 

(Figure 144) marked "Max Kohl & Co., 

Chemnitz," dating from about 1900, was made 

for use in college physics laboratories by a 

well-known German supply house for laboratory equipment (NMH T 327873; Accession 

119. Thompson, Dynamo-Electric Machinery, pp. 

476, 774-776; Crocker, Electric Lighting, 1:335-336. 

120. Crocker, Electric Lighting, 11:171-174; Jesse 

Berthold Gibbs, Transformer Principles and Practice 

(New York, 1937), pp. 131-138. 
124 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 144.—Constant-speed D.C. motor by Max Kohl & Co., about 1900. (NMHT 327873. 

Smithsonian photo 71883.) 

271855; 10"X7i/2"X15i/2"). The speed is 

sensed in the traditional way by a centrifugal 

governor (of Pickering type) mounted on 

the motor axis. Corrective action is taken by 

varying a resistance which is connected in 

series with the two field coils and the armature of the motor. The mechanism employed 

is this: on the side of the motor, standing 

freely, is a row of vertical straight resistance 

wires, all arranged next to each other and 

connected in series. The top of each wire 

carries an uninsulated spur with the end 

bent vertically downward, staggered in length. 

The governor output arm actuates a long 

lever with a counterweight on one end and 

a mercury trough at the other. This trough 

is suspended directly below the row of spurs, 

moving upward with decreasing speed. As 

more and more spurs are submerged in the 

mercury, a corresponding portion of the resistance is shortcircuited, with the effect of 

increasing the torque of the motor. 
CHAPTE R 12 

Electronic Computers 

Analog Computers for Process Control 

Analysis 

In the 1920s and 30s, a great deal of progress was made in the theoretical analysis of 

feedback control systems. One result was the 

discovery that many control processes, although occurring in totally different physical 

media, such as mechanical, thermal, hydraulic, or electrical processes, could be described 

mathematically by the same differential equations. If differences of coefficients were taken 

into account by adjustments of scale, such 

systems were dynamically equivalent. This 

meant that a control problem, given in a 

physical medium where experimentation was 

difficult, could be simulated and solved by 

analogy in a more manageable medium such 

as hydraulics or electricity. 

George A. Philbrick (1913- ) of Cambridge, Massachusetts, one of the pioneers 

in the field of analog computation, began to 

develop his electronic analyzer for control 

problems in 1936. The unit in our Museum 

(NMHT 327546; Accession 282961; 20"X18" 

X39") represents an early stage of his work 

(1938-40), but it incorporates all the basic 

features of modern analog computers (Figure 145). It is essentially the same as a device 

for which Philbrick received the U.S. Patent 

2503213 on 4 April 1950 (application filed 

on 21 December 1946). 

The analog computer represents the complete feedback loop, process as well as controller. The simulated system consists of a 

pneumatic three-response controller (proportional, derivative, integral) employed to 

• e 9 

FIGURE 145.—Philbrick electronic analog computer for 

feedback control system analysis. (NMHT 327546. 

Smithsonian photo 61757-A.) 

125 
126 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

maintain a constant level in a tank containing a liquid. In addition, the process includes 

three resistance-capacitance elements, to represent time constants, connected in series 

ahead of the tank. This hydraulic system, of 

course, can also easily be translated into the 

terms of a mechanical, thermal, or pneumatic process, as found in actual practice. 

The controlled variable in the hydraulic 

process, the liquid level, is represented electrically by a voltage, and the flow of liquid 

into this tank by a current. The controller 

is simulated by a combination of several vacuum tube amplifiers. 

The control problem to be solved is to 

adjust the parameters of the controller for 

optimum behavior of the controlled variable 

in the event of uncontrollable outside disturbances. This is done empirically: the 

operator introduces disturbances, watches the 

controlled variable by means of an oscilloscope, and adjusts the controller parameters, 

until the system responds to disturbances in 

the manner of a strongly attenuated sine 

wave. An obvious problem is that the electronic system responds far more rapidly than 

a nonelectric process. This is solved by introducing the disturbances repeatedly in rapid 

succession, at the same frequency as that of 

the horizontal sweep of the oscilloscope beam. 

The sine curve on the screen thus appears 

stationary. 

Analog computers such as this one have 

come to play an important part in modern 

engineering, as an instrument in solving 

actual problems, and as an incomparable 

educational tool. 

Digital Process Control Computer 

In a sense every conventional feedback controller is an analog computer. A threeresponse controller (proportional, integral, 

derivative) , for example, as the most general 

type, is programmed to solve the equation 

output = KYe + kx fe dt + k2-^-) 

(where e = desired variable — controlled variable) , while the other controller types solve 

simplified versions of this equation. Complicated chemical processes, however, comprise a great number of such feedback loops 

controlling variables like pressure, temperature, level, and flow rate, which are all interrelated by definite laws depending on the 

process. Special digital computers have therefore been developed that not only replace 

in a single unit all the conventional controllers used before, but are capable also of 

optimizing the performance of the overall 

system by coordinating the individual control 

loops in a unified manner. 

The Ramo-Wooldridge RW-300 reportedly was the first digital computer ever used 

on closed-loop process control (put into 

operation on 13 March 1959 on a Texaco 

refinery at Port Arthur, Texas). The unit 

in the Museum, serial number A8, is an exact 

duplicate of this computer. (Accession L 

282964; size of the computer proper: 56"X 

29"X36": input-output cabinet: 24"X24"X 

83"). It was employed to control an ammonia 

process at the Luling, Louisiana, plant of 

the Monsanto Co. Since the computer functions in a digital language, while the measuring instruments and control devices of the 

process communicate in analog signals, a separate input-output unit serves as interpreter 

between the process and the computer. In 

contrast to analog controllers, the digital computer operates not continuously but intermittently. It samples all process variables 

at regular intervals, calculates on this basis 

the required control signals, and, if necessary, 

causes corrective action. The sampling intervals, chosen according to the needs of the process, range in length between a few seconds 

and several minutes.121 

121. "Computer Runs Refinery Unit in Texas," 

Business Week (4 April 1959); A. L. Giusto, R. E. 

Otto, T. J. Williams, "Digital Computer Control," 

Control Engineering (June 1962). 
Location Guide 

The following list gives the location of the cataloged specimens roughly at the 

beginning of 1970. Changes occur, of course, continuously. The locations listed 

here, unless marked otherwise, are to be found in the National Museum of 

History and Technology. The Initials S.H. refer to the Silver Hill storage 

facility in Suitland, Maryland. Open exhibits are in italics. Exhibits identified by asterisk are in preparation and not yet opened to the public. 

NMHT No. Specimen Location 

58 A6 Avery "Bulldog" tractor 

58 A9 Frick "Eclipse" portable steam engine 

60 A74 Hart-Parr tractor 

62 A10 J. I. Case portable steam engine 

67 A2 J. Deere "Waterloo Boy" tractor 

T-8571 Draper "Northrop" loom 

T-11411 G. Richardson, let-off mechanism (pat. model) 

T-11412 R. Walker, let-off mechanism (pat. model) 

T-11421 S. J. Whitton, drawing-frame regulator (pat. model) 

31113-N Howell torpedo 

31114-N Whitehead torpedo 

31115-N Bliss-Leavitt torpedo 

31155-N German torpedo 

39596-N Sperry gyrocompass 

53774-N Howell torpedo 

58761-N MK 37 (USA) torpedo 

58762-N Japanese torpedo 

58763-N Japanese torpedo 

1015 Bell & Tainter graphophone 

180024 F.E. Sickels steering engine 

180029 J. Stevens safety valve 

181554 C.F. Brush arc lamp 

181725 Thomson-Houston current regulator 

181973 M.G. Farmer, arc lamp regulator 

181974 M.G. Farmer, arc lamp regulator 

201363 W. Wallace arc lamp 

201365 Wallace-Farmer arc lamp 

202871 Edison phonograph 

219016 Thomson-Rice arc lamp 

219017 Adams-Bagnall arc lamp 

251222 CJ. Van Depoele arc regulator (pat. model) 

251223 M. Day, arc lamp (pat. model) 

251225 N.S. Keith, arc lamp (pat. model) 

251227 CJ. Van Depoele, arc regulator (pat. model) 

251230 C.F. Bush, arc lamp (pat. model) 

251232 C.F. Brush, arc lamp (pat. model) 

S.H. Bldg. 17 

S.H. Bldg. 17 

Hall of Agriculture 

Hall of Agriculture 

Hall of Agriculture 

Hall of Textiles* 

4509 

4509 

4509 

S.H. Bldg. 15 

S.H. Bldg. 15 

S.H. Bldg. 15 

S.H. Bldg. 15 

S.H. Bldg. 15 

Hall of Armed Forces* 

S.H. Bldg. 15 

S.H. Bldg. 15 

S.H. Bldg. 15 

Hall of Light Machinery 

S.H. Bldg. 17 

Hall of Railroads 

5001 

Hall of Electricity* 

5001 

5001 

5001 

Hall of Electricity* 

Hall of Light Machinery 

5001 

5001 

5001 

5001 

5001 

5001 

Hall of Electricity* 

5001 

127 
128 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

NMHT No. Specimen Location 

251233 Thomson-Houston arc lamp 

251236 B.B. Ward, arc lamp (pat. model) 

251287 Stearns & Hodgson governor (pat. model) 

251288 H.A. Luttgens, governor (pat. model) 

251289 C.T. Porter, governor (pat. model) 

251290 D.A. Woodbury, governor (pat. model) 

252595 F.E. Sickels, steering engine (pat. model) 

252596 F.E. Sickels, steering engine (pat. model) 

252616 T.A. Edison, printing telegraph (pat. model) 

252617 T.A. Edison, multiplex telegraph (pat. model) 

252649 C.F. Brush, arc lamp (pat. model) 

252652 CJ. Van Depoele, arc regulator (pat. model) 

252655 H.S. Maxim, arc lamp (pat. model) 

252656 H.S. Maxim, arc lamp (pat. model) 

252660 E. Weston, arc lamp (pat. model) 

253757 Berliner-Clark gramophone 

261315 centrifugal pendulum 

307254 Autocar gasoline engine 

308218 1923 Cadillac chassis 

308479 A.L. Dyke carburetor 

308559 J. Gates, steering apparatus (pat. model) 

308597 CJ. Van Depoele, arc regulator (pat. model) 

308598 CJ. Van Depoele, arc regulator (pat. model) 

308646 G.H. Corliss, steam engine (pat. model) 

308667 Kelley & Lamb, governor (pat. model) 

308678 A.J. Peavey, governor (pat. model) 

308700 Thompson & Hunt, governor (pat. model) 

308713 Kipp & Murphy, pressure regulator (pat. model) 

308715 G.H. Corliss, governor (pat. model) 

309236 G.H. Corliss, pressure regulator (pat. model) 

309242 J. Reid, governor (pat. model) 

309243 J.G. Bodemer, governor (pat. model) 

309244 Judson & Cogswell, governor (pat. model) 

309279 CC. Lloyd, gas regulator (pat. model) 

309497 1902 White steam automobile 

309549 1912 Simplex automobile 

309556 Schleicher-Schumm "Silent Otto" engine 

309639 1900 Locomobile steam car 

309633 Sperry arc lamp 

309634 Sperry Gyropilot 

309636 Sperry Gyrocompass 

309637 Hornsby-Akroyd oil engine 

309817 Corliss cut-off governor 

309818 Corliss throttle governor 

309820 Corliss steam engine, model 

309881 G.E. steam turbine (1927) 

309924 Westinghouse "Junior Automatic" steam engine 

310241 "U.S. Military Dept." steam engine 

310289 Pickering governor (1880s) 

310290 Pickering governor (1931) 

310371 Atkinson "Cycle" gas engine 

310474 Wadsworth steering engine, model 

310475 Wadsworth steering engine, model 

310476 Wadsworth steering engine, model 

311017 Bosch fuel injection pump 

311052 Ford Model T automobile 

311875 Parsons steam turbine 

311902 Otto gas engine 

Hall of Electricity* 

5001 

Hall of Power 

Hall of Power 

Hall of Power 

Hall of Power 

5006 

5006 

5001 

5001 

5001 

5001 

5001 

5001 

5001 

Hall of Light Machinery 

5400 

Hall of Automobiles 

S.H. Bldg. 19 

5006 

5006 

5001 

5001 

Hall of Power 

Hall of Power 

5400 

Hall of Power 

5400 

5400 

5400 

5400 

Hall of Power 

5400 

CB-069 

Hall of Automobiles 

Hall of Automobiles 

S.H. Bldg. 17 

Hall of Automobiles 

5001 

S.H. Bldg. 17 

Hall of Marine Transportation* 

Hall of Power 

5400 

5400 

CB-069 

Hall of Power 

S.H. Bldg. 17 

S.H. Bldg. 17 

Hall of Power 

5400 

Hall of Power 

5006 

5006 

5006 

5400 

Hall of Automobiles 

Hall of Power 

Hall of Power 
NUMBE

R 12 129 

NMHT No. Specimen Location 

311991 Reynolds-Corliss steam engine, model 

312822 Bantam Army Jeep 

312825 Bosch fuel injection pump 

313403 Sperry Gyrocompass 

313703 Brayton oil engine 

314511 Hendey steam engine 

314522 Davis automobile power steering 

314658 Otto & Langen gas engine 

314791 Harlan & Hollingsworth steam engine 

314818 Corliss-Naylor steam engine 

314820 Terry steam turbine 

314822 Baldwin steam engine 

314843 De Laval steam turbine 

314888 Abbot chronograph governor 

314945 M.A.N. Diesel engine 

314989 graphophone 

315042 Lenoir gas engine 

315111 Olds gasoline engine 

315243 chronograph 

315438 Cryer vacuum regulator 

315708 Allis-Chalmers hydraulic servo governor 

315709 Allis-Chalmers governor 

315712 Shipman steam engine 

315717 Foucault-Duboscq arc lamp 

315858 Woodward type-L.R. governor 

315891 Porter-Allen steam engine 

315896 Woodward type3 governor 

315897 Woodward type-UG8 governor 

316013 Greene steam engine, model 

316096 Telescope clockwork 

316139 Bancks steam engine, model 

316276 chronograph (German) 

316578 Atlas-Imperial Diesel engine 

316656 Arco damper motor 

316657 Honeywell thermostat 

316658 Honeywell aquastat 

316726 "American" Diesel engine 

316806 Aermotor gasoline engine 

318011 Rodney Hunt governor 

318170 Otis elevator engine 

318460 Judson governor 

319024 Buick gasoline engine 

319243 Frick refrigerator compressor 

319279 Siemens arc lamp 

319405 Holloway steam engine 

319407 Mietz & Weiss oil engine 

319477 Skinner "Unaflow" steam engine 

319765 Siemens & Halske printing telegraph 

320000 Southern Railway Locomotive 

320023 I.R.T. steam engine generator, model 

320136 Lombard typeF governor 

320331 Woodward typeD governor 

320573 Thomson-Houston D.C. generator 

321454 1924 Franklin automobile 

321888 W. Yates, governor (pat. model) 

322000 Parsons steam turbine 

322247 Gramme-Wood D.C. generator 

322259 steam engine, model (Johns Hopkins U.) 

CB-069 

S.H. Bldg. 19 

Hall of Power 

S.H. Bldg. 15 

Hall of Power 

Hall of Power 

5006 

Hall of Power 

Hall of Power 

Hall of Power 

Hall of Power 

Hall of Power 

Hall of Power 

5120 

Hall of Power 

Hall of Light Machinery 

Hall of Power 

S.H. Bldg. 17 

Hall of Astronomy 

5400 

S.H. Bldg. 17 

S.H. Bldg. 17 

Hall of Power 

5001 

CB-069 

Hall of Power 

Hall of Power 

Hall of Power 

Hall of Power 

5120 

Hall of Power 

5120 

Hall of Power 

5400 

5400 

5400 

Hall of Power 

S.H. Bldg. 17 

CB-069 

S.H. Bldg. 17 

5019 

Hall of Power 

Hall of Power 

5001 

Hall of Power 

S.H. Bldg. 17 

Hall of Power 

5001 

Hall of Railroads 

Hall of Power 

CB-069 

S.H. Bldg. 17 

Hall of Electricity* 

Hall of Automobiles 

5400 

Hall of Power 

CB-069 

Hall of Power 
130 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

NMHT No. Specimen Location 

322282 telescope clockwork, G. Boulitte 

322455 chronograph 

322556 Westinghouse compound steam engine 

322557 Ball steam engine 

322560 Mack model AC truck 

323494 James Watt steam engine, model 

323495 "Silent Otto" gas engine 

323518 American-La France fire truck 

323569 1918 Oldsmobile automobile 

323697 Otto gas engine 

323716 Holloway steam engine, model 

324000 Hermany-Leavitt steam engine, model 

325525 Waters governor 

325611 T. Silver, governor (pat. model) 

325612 H.N. Throop, governor (pat. model) 

325613 G.H. Miller, governor (pat. model) 

325614 T.S. La France, governor (pat. model) 

325615 J. Knowlson, governor (pat. model) 

325664 Harrisburg steam engine, model 

325904 White & Middleton gasoline engine 

325905 Baxter steam engine and boiler 

325908 steam engine, model (Jerrehian) 

325989 Brush arc lamp 

326151 1917 White bus 

326222 1912 Pierce-Arrow automobile 

326536 Jarecki "Erie" compressor governor 

326554 G.E. constant current transformer 

326619 Weber-Thomas vacuum oven 

326987 Wiechert seismograph 

327546 Philbrick electronic analog computer 

327675 Corliss steam engine, model 

327711 telescope clockwork (Princeton) 

327873 D.C. motor with speed regulation 

327945 street arc lamp 

327946 Brush street arc lamp 

327954 Siemens & Halske printing telegraph 

328068 Thomson-Houston current regulator 

328394 Lorimer gasoline engine 

328424 Thomson-Houston D.C. generator 

328660 Linde-Wolf refrigeration compressor 

328723 Willans compound steam engine 

328889 chronograph governor 

329211 Corliss steam engine, model 

329286 Packard winterfront 

329758 Gardner governor 

329792 "Domestic" gasoline engine 

330028 Marquette governor 

330029 Woodward type-SI governor 

loan Bunker-Ramo digital process control computer 

5120 

5120 

Hall of Power 

S.H. Bldg. 17 

Hall of Automobiles 

Hall of Power 

Hall of Power 

S.H. Bldg. 17 

S.H. Bldg. 19 

S.H. Bldg. 17 

Hall of Power 

Hall of Power 

5400 

5400 

5400 

5400 

5400 

5400 

5400 

S.H. Bldg. 17 

CB-069 

Hall of Power 

5001 

Hall of Automobiles 

Hall of Automobiles 

CB-069 

CB-069 

5120 

Hall of Physics 

Hall of Mathematics 

Hall of Power 

CB-069 

5001 

CB-069 

CB-069 

CB-069 

5001 

S.H. Bldg. 17 

Hall of Electricity* 

American Brewery, Baltimore, Md. 

S.H. Bldg. 17 

5120 

5400 

Hall of Automobiles 

5400 

Hall of Power 

5400 

5400 

Hall of Mathematics 
Index 

Abbott, C. G., clockwork by, 66 

Adams-Bagnall arc lamp, 118 

"Aermotor" gasoline engine, 54 

Airy, George Biddell, 64 

Albion Mill, 4 

Allen, John F., positive cutoff gear by, 14 

Allis-Chalmers Co., hydraulic servo regulator by, 16 

American Bosch fuel injector, 60 

American Diesel Engine Co., 56 

analog computer for process control analysis, 125-126 

arc lamps, regulation of, 105-119 

"astatic" governors, 6 

Atkinson "Cycle" gas engine, 55 

Atlas-Imperial marine Diesel engine, 60 

Autocar Heavy Duty engine, 87 

automatic cutoff control, general, 7-13 

detachable, or drop-off, 8, 14 

positive, 8, 14, 17, 33 

Avery Bulldog Tractor, 86 

Baldwin, Mathias W., steam engine by, 6 

Ball, Frank H., 35, 37 

Bartlett let-off mechanism, 81 

Baxter combination steam engine, 30 

Bell & Tainter graphophone, 68 

Berliner Gramophone, 68 

Bliss, E. W., & Co., 97, 99 

Bodemer, Johann Georg, water turbine governor by, 26 

Boesch model steam engine, 35 

Bosch fuel injection pumps, 60-61 

Boulitte, G., clockwork built by, 65 

Boulton, Matthew, 4 

Boulton & Watt, 4, 6, 74 

Brayton oil engine, 55 

Brush, Charles F., 107 

Brush Electric Light Co., 14 

lighting system of, 107-111 

Buckeye Engine Company, 34 

Buick gasoline engine, 49 

carburetors, float-feed, 89-90 

Case, J. I., portable steam engine by, 28 

centrifugal governor, 4-69, 86-88, 123-124 

invention of, 4 

centrifugal pendulum, 3 

chronographs, 64-65 

Clark, Alfred C, 68 

clockwork for telescopes, 64—65 

closed loop control, see feedback control 

Cogswell, William A., 27 

Columbia Phonograph Co., 68 

compass, gyroscopic, 101-102 

"compensating" governor, 42-43 

compressor governor, 32 

computers, electronic, 125-126 

analog, 125-126 

digital, 126 

Corliss, George Henry, 8, 9, 10, 11, 24, 74 

Cryer, T. B., Co., 76 

current regulation, 10-92, 118-123 

Custer, Jacob D., 33 

Davis, Francis Wright, 92 

Day, Matthias, 106 

Deere, John, Co., 86 

de Laval, Gustav, 48 

depth-control system for torpedoes (immersion regulator), 97, 100 

derivative response, governor with proportional plus, 

19, 33 

Diesel engine, speed regulation of, 56 

"differential" circuit for arc lamps, 110-112 

digital process control computer, 126 

"Domestic" gasoline engine, 53 

drawing-frame for cotton, 82 

Drebbel, Cornelis, 3, 77 

Duboscq, Jules, 105, 106 

Dyke, A. L., float-feed carburetor by, 89 

Edison, Thomas A., 68, 69 

Edison's phonograph, 68 

electronic devices, feedback in, 105 fn 

Elektrosignal G.m.b.H., 65 

Farmer, Moses G., Ill, 112 

Fauth & Co., chronograph by, 65 

Fecker, John W., 23-inch refractor built by, 65 

feedback control, definition, 1-2 

feedback devices, origins, 2-3 

feedback on servomotors, 42, 44 

float valve level regulator, 2-3, 70-72, 89-90 

Foucault, Leon, 101, 105, 106 

Frick "Eclipse" portable steam engine, 30 

friction governors, 64-69 

fuel injection pumps, 56-61 

Gardner Governor Company, 30, 31 

gas meter, 73 

Gasmotoren-Fabrik Deutz, 50 

Gates, John, 96 

General Electric Company, constant current transformer, 123 

Curtis steam turbine, 49 

Gibbs, Charles E., 39 

LSI 
132 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Greene, Noble T., model of steam engine, 11, 13 

"gusf'-governing, 47-48 

gyropilot, 102-104 

gyroscopes in torpedoes, 99-100 

gyroscopic compasses, 101-102 

gyroscopic governor, 26 

Hancock Inspirator Co., 75 

Harlan & Hollingsworth steam engine, 7 

Harrisburg Foundry and Machine Co., 34 

Hart-Parr agricultural tractor, 53 

Hendey, Henry J., rotary steam engine by, 28 

Heron of Alexandria, 2 

high-speed steam engine, 13-15 

"hit-and-miss" governing, 50, 53-54 

Holloway, Thomas, steam engine by, 6 

Honeywell Heating Specialties Co., 77-78 

Hornsby-Akroyd hot-bulb oil engine, 55 

Howell, John Adams, 99 

Howell torpedo, 99-100 

Hughes-type printing telegraph, 69 

Hunt, Nathan, shaft governor by, 34 

Hunt, Rodney, waterwheel governor by, 39, 42 

hydraulic governors, 21-24, 87 

immersion regulator, 97, 100 

inertia governor, 19, 34—38 

integral response, control with, 17, 20, 42, 62, 63 

"isochronous" governors, 6, 62 

Jarecki Manufacturing Co., compressor governor by, 32 

Jerrehian toy steam engine, 28 

Judson, Junius, 27, 28 

Keith, N. S., 117 

Kelley, Oliver A., and Estus Lamb, steam engine governor by, 20 

Kipp, A., and H. Murphy, pressure regulator by, 74 

Knowlson, John, steam engine governor by, 25 

Ktesibios of Alexandria, water clock of, 2 

LaFrance, T. S., steam engine governor by, 21 

"Lap" engine, 4, 5 

Leavitt, Erasmus D., steam pumping engine by, 16 

Lenoir gas engine, 49 

let-off mechanisms for power looms, 79-81 

Lloyd, Charles E., 73 

"Locomobile" steam automobile, 83-86 

Lombard Governor Co., 44 

looms, power, 79-81 

Lorimer gasoline engine "Sturdy Scott," 49 

Luttgens, H. A., governor by, 16 

Mack "Bulldog" truck, 87 

M.A.N. Diesel engine, 56 

Marquette Metal Products Co., 62 

Mason Regulator Co., 24 

Maxim, Hiram S., 117 

Maybach, Wilhelm, 89 

Mietz & Weiss hot-bulb oil engine, 55 

Miller, S. H., steam engine governor by, 20 

"Nautilus," submarine, 102 

Naylor, Jacob, steam engine by, 10, 11, 12 

Northrop loom, 80-81 

Obry, Ludwig, 99 

Olds gasoline engine, 54 

Otto gas engine, 50, 53 

Packard "Winterfront," 88 

Papin, Denis, safety valve of, 3, 70 

Parsons, Charles A., 45—47 

patent models of governors, 16-27 

Peavey, Andrew J., hydraulic vane governor by, 21 

Pharo Manufacturing Co., governor by, 87 

Philbrick, George A., 125 

phonographs, 66-69 

Pickering, Thomas R., spring governor by, 28-31 

Pierce Governor Co., 50 

Porter, Charles T., "loaded" governor by, 13-16 

Porter-Allen high speed steam engine, 14, 15, 16 

power steering, automobile, 92 

pressure regulator, 70, 72, 73-76, 83, 86, 90, 97 

proportional control, 4, 6, 17, 43, 50, 55 

proportional offset, 6 

railway technology, feedback control in, 83 

Ramo-Wooldridge computer, 126 

Reid, Joseph, gyroscopic governor by, 26 

Rennie, John, 4 

Reynolds-Corliss engine, model of, 11 

Richardson, George, 80 

safety valve, 3, 70, 72 

Schleicher, Schumm & Co., 53 

Scholfield, N., governor by, 39 

servo governors, mechanical, 39 

servomotor, hydraulic, 16, 43, 92 

servomotor, pneumatic, 97, 99 

servo steering, ships, 93-96 

shaft governor, 33-38, 54, 68, 72 

Shipman "Automatic" steam engine, 34, 70-72 

"shunt" circuit for arc lamps, 112 

Sickels, Frederick E., 8, 11, 93 

Siemens-von Hefner Alteneck arc lamp, 106 

Siemens & Halke telegraph, 69 

"Silent Otto" gas engine, 50 

Silver, Thomas, marine steam engine governor by, 18 

Skinner "Universal Unafiow" steam engine, 38 

speed control of electric motors, 123-124 

speed governors on trucks and tractors, 86-88 

Sperry, Elmer A., 101-104 

Sperry high-intensity arc lamp, 119 

Spindler & Hoyer, Gottingen, 65 

steam automobiles, 83-86 

steam boilers, automatic control of, 70-72 

steam steering gear, 93-96 

Stearns, G. S., and W. Hodgson, governor by, 17-18 
NUMBER 12 133 

Stevens, John, 70 

Sulzer Brothers, Winterthur, Switzerland, steam engine by, 15 

telegraphs, 69 

telescope regulators, 64-65 

temperature regulation, 3, 77-78, 86, 88-89 

Terry steam turbine, 49 

textile machinery, feedback control on, 79-82 

thermostat, see temperature regulation 

Thompson-Hunt shaft governor, 34 

Thomson-Houston current control system, 120-121 

Thomson-Houston electric lighting system, 112 

Thomson-Rice double arc lamp, 112 

Throop, H. N., marine steam engine governor by, 

19,33 

Thurston, Benjamin Francis, 11, 13 

torpedoes, feedback control in, 96-101 

transformer, constant current, 123 

Troughton & Simms, equatorial telescope, 64 

Ure, Andrew, 3, 77 

vacuum regulator, 76 

Van Depoele, Charles J., 117 

voltage regulation, 90-92 

Wadsworth, Herbert, 96 

Walker, Richard, 80 

Wallace, William, 111 

Wallace-Farmer electric lighting system, 111-112 

Wamsutta Mills, New Bedford, Mass., 8 

Ward, Barton B., 118 

"Waterloo Boy" tractor, 86 

Waters, Charles, steam engine governor by, 30 

waterwheel governors, 39 

Watt, James, 3, 4-6 

Weber, electric vacuum oven, 78 

Westinghouse, Henry Herman, 35 

Westinghouse air pressure regulator, 83 

Westinghouse "Automatic" compound steam engine, 35 

Westinghouse "Junior Automatic" engine, 35 

Weston, Edward, 117 

White steam automobile, 86 

White & Middleton gasoline engine, 53 

Whitehead, Robert, 96-99 

Whitton, Samuel J., 82 

Wiechert, seismograph, 65 

Willans central-piston compound, engine, 33 

Wood regulator on Gramme-type generator, 121-123 

Woodbury, Daniel A., 33 

Woodward, Amos, 40 

Woodward, Elmer E., 40-42 

Woodward Governor Co., 44-45, 61-63 

Yates, William, steam engine governor by, 24 

-Cr U S. GOVERNMENT PRINTING OFFICE: 1971 O 406-928