ED STATES TMENT OF IMERCE

ICATION

national Bureau of Sta^

JUL 2 2 1970

A)

NBS TECHNICAL NOTE 536

r

c<\

DISCLOSURES ON:

U.S.

^RTMENT

OF

)MMERCE

National

Bureau

a

of

Standards

Viscous Damped Wind Vane

Nonskid Road or Runway

egrooved Pneumatic Tire With Removable Inserts

Device for Radially Positioning a Rotating Wheel

Method for Fabricating Precision Waveguide Sections

Distortion-Cancelling Loudspeaker System

Cryogenic Fluid Density Measurement System

Controlled-Atmosphere Weathering Device
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards ' was established by an act of Congress March 3. 1901. Today,

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divisions:Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molecular Physics—Radio Physics - —Radio Engineering - —Time and Frequency - —Astrophysics - —Cryogenics.

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BUREAU OF STANSAfcSS

to o

UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS

i . TECHNICAL NOTE 536

ISSUED JUNE 1970

Nat. Bur. Stand. (U.S.), Tech Note 536, 25 pages (June 1970)

CODEN: NBTNA

DISCLOSURES ON:

Viscous Damped Wind Vane

Nonskid Road or Runway

Regrooved Pneumatic Tire With Removable Inserts Device for Radially Positioning a Rotating Wheel

Method for Fabricating Precision Waveguide Sections

Distortion-Cancelling Loudspeaker System

Cryogenic Fluid Density Measurement System

Controlled-Atmosphere Weathering Device

Editors: David Robbins and Alvin J. Englert

Patent Advisor's Office National Bureau of Standards

Washington, D. C. 20234

jt!*« °" Cq.

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C., 20402

(Order by SD Catalog No. C 13.46:536). Price 35 cents
PREFACE

This NBS Technical Note is one of a continuing

series entitled "Disclosures on ...." This series consists

of short descriptions of recent developments from the

Department of Commerce primary operating units, departmental staff offices, and their contractors. It is

believed that these developments have important commercial

applications. Unless otherwise stated in the description

of a development, the property rights therein have been

retained by the United States as represented by the

Secretary of Commerce.

Previous NBS Technical Notes in this series are

NBS Technical Notes 237, 253, 263, 282, 287, 295, 437

and 440.

David Robbins

Patent Advisor

iL
CONTENTS

Title Author (s) Page

Viscous Damped Wind

Vane

Nonskid Road or

Runway

Regrooved Pneumatic

Tire with Removable

Inserts

Donald T. Aches on

Herman H. Crouser

F. Cecil Brenner

F. Cecil Brenner

Device for Radially Delmar J. Collenberger

Positioning a Rotating

Wheel

Method for Fabricating Delmar J. Collenberger

Precision Waveguide William J. Foote

Sections George R. Gieseke

Distortion-Cancelling G. Franklin Montgomery

Loudspeaker System

Cryogenic Fluid

Density Measurement

System

Control led-Atmosphere

Weathering Device

Wallace J. Alspach

Charles E. Miller

William F. Brucksch, Jr,

10

14

16

19

in
ABSTRACT

This Note describes and illustrates eight

developments that are believed to embody interesting

and unusual solutions to current problems in their fields

KEY WORDS

Accelerated weathering test; acoustic distortion,

cancelling; averaging wind vane; cryogen density,

measuring; distortion-cancelling loudspeakers; grooved

runway; hydroplaning skidding, prevention of; loudspeaker

system; photoactivated weathering test; radial

positioning, wheel on shaft; rubber- surfaced road; slush

cryogen density; tire groove insert; tire regrooving;

waveguide, precision fabrication; waveguide, adjustable

width; weathering test; wheel-shaft angle, shifting

during rotation; wind vane, damped.

IV
VISCOUS DAMPED WIND VANE

Donald T. Ache son

Herman H. Crouser

This instrument continuously displays average —rather

than instantaneous —wind direction. As shown in Fig. 1,

it includes a wind vane 10 secured to a vane shaft 12

that rotates in suitable bearings, not shown. The vane

shaft 12 has a crank arm 14 and a crank shaft 16. A

pulley 18 having a bearing 19 rotates on the crank

shaft 16. A coil spring 20 is looped about the pulley 18,

as shown in Fig. 2. The ends of spring 20 are connected

to pins 21 that are fastened to a circular plate 22. The

hub of plate 22 is fastened to an output shaft 24 that

rotates in bearings 26 mounted in a stationary housing 28.

The housing 28 has a ring-shaped well 27 that is filled

with a viscous silicone damping fluid 30. A damping

cylinder 32 formed integrally with the circular plate 22

dips into the damping fluid 30. The output shaft 24 drives

a remote wind direction indicator 34 through a connection,

e.g., electrical, represented by the dashed line 33. A

compass card 35 displays the compass directions.

In the operation of the instrument, the wind vane 10

rotates the vane shaft 12, and therefore cranks the

pulley 18, in accordance with the instantaneous wind

direction. The pulley 18 exerts a torque on the plate 22

through the spring 20. The plate 22 however is restrained by the damping force exerted on the damping

cylinder 32 by the viscous fluid 30 in the stationary

well 27. Therefore the plate 22, and the output shaft 24

and indicator 34 connected thereto, are constrained to

the average angular position of the wind vane 10. In

other words, the output shaft 24 and indicator 34

effectively do not respond to fluctuations in wind

direction that average to zero, but only to sustained

changes in wind direction.
VISCOUS DAMPED WIND VANE

Donald T. Acheson

Herman H. Crouser
Since the spring 20 is not fastened to the crank shaft 16

but rather is looped about the pulley 18 that rotates on

the crank shaft, the spring cannot be damaged by excessive rotation of the wind vane 10--the effect known

as wind vane breakaway.

The instrument can be stored or shipped without draining

the damping fluid 30. The fluid is retained in the

instrument by drawing the circular plate 22 down to the

stationary housing 28, thereby sealing the well 27. The

plate 22 has three holes 37, Fig. 2, through which

shipping screws such as shown in dashed lines at 38 in

Fig. 1, can be inserted to engage threaded holes 39 in

the housing 28. As the plate 22 moves down, the upper

bearing 26 compresses spring 40. When the shipping

screws 38 are subsequently removed to place the instrument in operation, the spring 40 returns the bearing 26

to its normal position and thereby lifts plate 22 and

unseals the well 27.
NONSKID ROAD OR RUNWAY

F. Cecil Brenner

Grooves are presently cut into concrete or asphalt roads

and airplane runways to prevent hydroplaning. The

grooves however induce "chevron cuts" in the tires. In

addition, groove -cutting resurfacing requires considerable

time and requires closing down the runway or road for

relatively long periods.

In the figure, a rubber mat 10 with parallel grooves 11

is bonded to a road or runway 12. The grooves are

positioned perpendicular to the direction of movement of

a vehicle on 12.

Mat 10 can absorb greater quantities of braking energy

than concrete or asphalt, and grooves 11 provide rapid

drainage of water to prevent hydroplaning and other forms

of skidding during rainy periods. The mat may be

removed and a new one installed rapidly with minimum

delay in returning the runway or road to use.
NONSKID RGAD OR RUNWAY

F. Cecil Brenner
REGROOVED PNEUMATIC TIRE WITH REMOVABLE INSERTS

F. Cecil Brenner

10
REGROOVED PNEUMATIC TIRE WITH REMOVABLE INSERTS

F. Cecil Brenner

Taxi and bus tires are presently manufactured with an

extra layer of rubber between the bottom of the molded

groove and the fabric carcass. When the groove depth

is worn to about 1/8 of an inch, new grooves are cut

into the tire with a hot knife. This process is costly

in terms of time and labor. In addition, sometimes the

regroover will cut too deeply and damage the fabric,

destroying the carcass.

Normally a tire is molded with a 1/2-inch groove depth,

with an additional 1/2 inch between the bottom of the

groove and the fabric carcass. In accordance with this

note, tire 10 in the figure is constructed with the same

amount of rubber but grooves 11 are molded to a full 7/8-

inch depth. After the tire is removed from the mold an

insert 12, approximately 1/2-inch thick, is placed in the

bottom of each groove. The inserts may be glued to the

main body 13 so that they will remain fixed in position.

When the tire has been worn to where the thread depth is

only 1/8 inch, the insert may be removed, producing a

new tire with a full-groove depth.

There are three advantages to this arrangement: the

original tread design is retained, the cost of regrooving

is greatly reduced, and there is no possibility of

damage to the fabric carcass 14.
DEVICE FOR RADIALLY POSITIONING A ROTATING WHEEL

Delmar J. Collenberger

8
DEVICE FOR RADIALLY POSITIONING A ROTATING WHEEL

Delmar J. Collenberger

This device may be used to vary the radial position of a

wheel relative to the shaft on which it is mounted, while

the wheel and shaft are in rotation.

Wheel 10 is slidably mounted on shaft 11, and pin 12 on

the wheel is positioned in slot 13 located in the shaft.

The inner races 16 and 17 of bearings 18 and 19,

respectively, are slidably mounted on the shaft 11 with

sufficient friction to rotate with 11. Inner race 17 is

spring loaded with spring 20 and fixed member 21. The

outer races 23 and 24 of the bearings are mounted in

support brackets 25 and 26, respectively. Bracket 25 is

fastened to a fixed member (not shown) with bolts 29,

while bracket 26 is slidably mounted on the fixed member

through bolts 31 and slots 32.

In a typical operation, the position of a reference mark

42 on wheel 10 is changed relative to a similar mark 43 on

shaft 11 while the shaft and wheel are rotating. To

accomplish this, screw 35 is loosened and pawl 36 now

allows teeth 37 and knob 38 to rotate. Knob 38 is rotated

clockwise so that 38 advances into bracket 25. The end

of the knob, which is positioned against the end of outer

race 23, moves bearing 18 and wheel 10 to the left in the

figure. As the wheel and bearing slide to the left,

bearing 19 moves in the same direction, compressing

spring 20 a'n additional amount. Again, as wheel 10 slides

longitudinally to the left on shaft 11, its pin 12 moves

along slot 13, changing the radial position of mark 42

relative to mark 43.
METHOD FOR FABRICATING PRECISION WAVEGUIDE SECTIONS

Delmar J. Collenberger

George R. Gieseke

William J. Foote

The usual techniques for fabricating precision waveguide

sections fail to achieve tolerances better than + 0.0002

inch, which limits the degree of accuracy that can be

attained in making microwave impedance measurements. The

present technique provides waveguide sections with

tolerances of + 0.00005 inch. The sections are an integral

part of some measurement systems in use at the National

Bureau of Standards.

As an example, in fabricating a WR90 waveguide, bars 12

and 13 (Fig. 1) are used as gauge blocks and are milled

to slightly less than 0.400 inch in the H dimension. The

bars are silver plated to slightly more than 0.400 inch,

ground to a roughness height of 5-6 microinches AA

(arithmetical average), and lapped to as near 0.400 inch

as possible. The maximum possible flatness is maintained

of all surfaces which form the internal walls of the

waveguide and care is exercised to maintain the squareness

of bars 12 and 13. Bars 10 and 11 are ground and lapped

on the surfaces that will form the internal walls of the

waveguide. The waveguide is preferably made of Invar

because of its very low thermal coefficient of expansion.

Clamping bolts (not shown) are positioned in holes 17 and

securely tightened. The holes pass through bars 10, 12,

and into bar 11. Eccentric shafts 18 are installed in

holes 19, as shown in Fig. 2, and bolts 20 are positioned

in holes 21 but are not tightened, as shown in Fig. 3.

At assembly, an appropriate airgauge spindle is inserted

into the waveguide and the eccentric shafts 18 are rotated

one at a time to move bar 13 toward or away from bar 12

as required to establish dimension W (0.900 inch.) After

W is adjusted within very small tolerances clamping

bolts 20 are securely tightened.

10
METHOD FOR FABRICATING PRECISION WAVEGUIDE SECTIONS

Delmar J. Collenberger

George R. Gieseke

William J. Foote

My. 3

SECTION Y-Y

11
METHOD FOR FABRICATING PRECISION WAVEGUIDE SECTIONS

Delmar J. Collenberger

George R. Gieseke

William J. Foote

12
When necessary, small adjustments to correct for "bell

mouthing" are accomplished as follows. With reference to

Fig. 4, slots 24 and 25 are cut into bars 12 and 13, and

holes 26 and 27 are drilled and tapped. Screws (not

shown) are inserted in the holes until they press against

the back walls of the related slots. When the screws are

tightened the structurally weakened areas at the bottom

of the slots act as hinges to reduce the magnitude of

dimension W. Correction of dimension H is accomplished

by permanently attaching a clamp across bars 10 and 11

at the end of the waveguide.

13
DISTORTION-CANCELLING LOUDSPEAKER SYSTEM

G. Franklin Montgomery

-3'

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14
DISTORTION-CANCELLING LOUDSPEAKER SYSTEM

G. Franklin Montgomery

In the system described here, a loudspeaker is used to

compensate for the nonlinear distortion in the sound

reproduced in another loudspeaker.

When signal E is applied to the input of amplifier 10,

the output of 10 drives electrodynamic loudspeaker 11.

Signal E1 is derived from a balanced bridge network 12

and is proportional to the voice coil velocity of loudspeaker 11. Signals E and E. are subtracted in the

input of amplifier 20 to form a correction signal

E = E - kE1

, which drives loudspeaker 21 through

amplifier 20. The gain of amplifier 20 is made adjustable to permit compensating for any difference in

acoustical efficiency between loudspeaker 21 and loudspeaker 11. The factor k is so chosen that for a small

signal E the correction signal E =0. Signal E then

becomes nonzero only when E becomes so large that

loudspeaker 11 begins to distort, and loudspeaker 21 produces an acoustic signal which cancels the distortion in

the acoustic output of loudspeaker 11.

15
CRYOGENIC FLUID DENSITY MEASUREMENT SYSTEM

Wallace J. Alspach

Charles E. Miller

This system may be used to measure the density of

cryogenic fluids including the liquid-solid mixtures

often referred to as slush cryogens.

For example, in the case of slush hydrogen, liquid

hydrogen is contained between the outer insulated tank 10

and the inner tank 11. Weigh tank 12, which includes a

flexible bottom member 13, and container 14 are positioned

in 11. The fluid in tank 12 is stirred by means of

stirrer 15, and calibrated masses 16 are suspended from

the flexible member.

The fluid, whose density is to be determined, is contained

in tank 12 and its volume is determined with liquid

sensor 17. The mass of the fluid, and the mass and

pressure of the ullage gas over the fluid, exert a force

on flexible member 13, causing it to be displaced from its

no load or null position. The displacement is sensed,

with masses 16 removed, by photoelectric displacement

sensor 19. The output of the sensor is applied to

pressure control device 20 which in turn operates valve 21

to allow helium gas to flow from source 22 through heat

exchanger 23 to container 14. The gas establishes an

opposing force against flexible member 13 in a direction

opposite to the displacing force. The magnitude of the

opposing force is automatically adjusted by the arrangement just described so that the flexible member is

returned to its null position.

16
CRYOGENIC FLUID DENSITY MEASUREMENT SYSTEM

Wallace J. Alspach

Charles E. Miller

HELIUM

GA5

SOURCE

17
The total force on flexible member 13 is due to the mass

of the fluid plus the mass of the ullage gas plus the

pressure of the ullage gas. If the mass of the ullage

gas is low by comparison to the mass of the fluid, as

would be the case when the fluid occupies nearly all the

volume of tank 12, then the force on the flexible member

is due to the mass of the fluid plus the pressure of the

ullage gas. The pressure of the ullage gas is eliminated

by differential pressure sensor 24 which is connected on

one side to the ullage gas pressure and on the other side

to the helium gas pressure. Thus, the output of the

sensor is directly related to the mass of the fluid, that

is to say, the differential pressure is proportional to

the mass of the fluid.

The differential pressure sensor 24 is calibrated as

follows:

1. With no fluid contained in weigh tank 12,

the pressures exerted on both sides of flexible

member 13 are made equal.

2. One of the calibrated masses 16 is

suspended from member 13, and the differential

pressure necessary to position 13 at its null

position is read on sensor 24 and noted.

3. Steps 1 and 2 are repeated with additional

mass 16 suspended from member 13.

4. A plot of differential pressure against

mass is made.

In a typical operation, the volume of the fluid in weigh

tank 12 is determined with liquid sensor 17 and the mass

with differential sensor 24. The density of the fluid

is then calculated from the relationship D M

V

18
CONTROLLED-ATMOSPHERE WEATHERING DEVICE

William F. Brucksch, Jr.*

This device performs accelerated weathering tests on

plastic films, elastomers, coatings, or fabrics. The

samples are mounted in closed, controlled-atmosphere

chambers that may be charged with photoactivators such

as sulfur dioxide, ozone, or oxides of nitrogen. The

chambers and an arc lamp are suspended in a refrigerated

water bath, whereby the samples are maintained at nearly

constant temperatures throughout exposure, and temperature

differences between dark-pigmented and light-pigmented

(or clear) samples are minimized.

As shown in Fig. 1, the refrigerated water bath consists

of an insulated container 10, a cooling coil 12, a refrigeration unit 14 for circulating a refrigerant through

the coil 12, and a stirrer 16 for stirring the water 18.

A xenon or mercury arc lamp 20 and its leads 22 are

enclosed in a glass tubular chamber 24 that is suspended

in the center of the bath. Surrounding the lamp 20 are

sample holders or chambers 26 containing the samples 28

to be tested. Each chamber 26 consists of a flattened

glass tube 30, a gas inlet tube 32 for introducing a

purge gas, and an elastomeric stopper 36 for admitting

the photoactivator, through a needle syringe (not shown).

The inlet and outlet tubes 32, 34 are connected to

elastomeric tubes 38, 40, which are clamped after the

purging operation and before the introduction of the

photoactivator.

In some cases it may be desirable to replace the

elastomeric tubes 38, 40 and their clamps with glass

stopcocks, and to isolate the elastomeric stoppers 36 from

the chambers 26 with glass stopcocks. The stopcocks

should be lubricated with a fluorinated elastomer grease.

The use of this glass apparatus gives more reproducible

results.

As shown in Fig. 2, the thin, flat samples 28 are mounted

near and parallel to the flattened walls of the glass

tubes 30. The tubes 30, only two of which are shown in

Fig. 1, are oriented so that the samples face the arc

lamp 20.

19
The capacity of the refrigeration unit 14 should be equal

to or slightly greater than the heat generated by the arc

lamp 20. If the two are balanced the temperature of the

bath will be constant. The refrigerated bath permits

the temperature of the sample to be controlled during the

test, whereby it is possible to differentiate between

reactions caused by light and those caused by heat. The

usual overheating of dark-pigmented stocks is minimized.

Also, it is possible to mount the samples closer to the

arc lamp and thereby shorten the exposure time.

* Former NBS Research Associate from

Manufacturing Chemists' Association, Inc.

20
CONTROLLED-ATMOSPHERE WEATHERING DEVICE

William F. Brucksch, Jr.

imimwKwvw^^^

IPicr. 1

21

* U. S. GOVERNMENT PRINTING OFFICE : 1970 431-988/1



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