AN IMPROVED SPEED INDICATOR
Year: 1873

page_text: LETTERS PATENT to Thomas Alfred Hearson, Assistant Engineer, in
H. M. Royal Navy, at present stationed at Devonport, in the County
of Devon, for the Invention of "AN IMPROVED SPEED INDICATOR.”
Sealed the 18th November 1873, and dated the 24th May 1873.
PROVISIONAL SPECIFICATION left by the said Thomas Alfred Hearson
at the Office of the Commissioners of Patents, with his Petition, on
the 24th May 1873.
I, THOMAS ALFRED HEARSON, Assistant Engincer, in H. M. Royal
6 Navy, at present stationed at Devonport, in the County of Devon, do
hereby declare the nature of the said Invention for "AN IMPROved Speed
INDICATOR," to be as follows, that is to say:-
-
This Invention relates to a strophometer or improved instrument
designed for indicating the speed of steam engines, in such a manner
that the pointer will not vibrate with the smaller and more frequent
variations of speed which last for only part of a revolution. The instru-
ment is however applicable for indicating the speed of any rotating
piece, and may, for example, be connected to a continuous screw log so
as to indicate the speed of a ship through the water.

page_text: The parts of the instrument are carried by a spindle fixed vertically on
a bracket or other convenient fixture, and motion is communicated from
the engine shaft or other part, the speed of which is to be indicated by a
cord or any convenient intermediate gearing to a pulley revolving on the
lower part of the spindle. Above the pulley there run loose on the
spindle two small fly wheels, the under faces of which are recessed; and
into the recess of the lower fly wheel there project up two or more studs
having chains connected to them, which chains fly out by the centrifugal
force against the inside of the rim of the fly wheel and act frictionally
thereon so as to make the fly wheel revolve. Similarly, chains from
studs on the lower fly wheel impart motion to the upper fly wheel.
With these driving arrangements the inertia of the fly wheels will
prevent them from being too easily affected by the changes of speed
which are not persistent, and if the small variations are not sufficiently
obliterated by the lower fly wheel they will be more completely so by
the upper one. Above the upper fly wheel there is on the spindle a
helical wire spring supporting a boss which is loose on the spindle, and
which is connected by two or more pairs of jointed links to the fly wheel.
These links carry balls on their middle joints, and the action of the
centrifugal force in moving these balls outwards causes the boss to be
more drawn down, and the spring to be more compressed the greater the
speed is. The movement of the boss is communicated by means of a
light wire and rack to a pinion on an arbor carrying a pointer which
sweeps over a marked dial carried by the spindle.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Alfred Hearson in the Great Seal Patent
Office on the 22nd November 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
ALFRED HEARSON, Assistant Engineer, in H. M. Royal Navy, at present
stationed at Devonport, in the County of Devon, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent bearing date the Twenty-fourth day of May, in the year
of our Lord One thousand eight hundred and seventy-three, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Thomas Alfred Hearson, Her special licence

page_text: that I, the said Thomas Alfred Hearson, my executors, administrators,
and assigns, or such others as I, the said Thomas Alfred Hearson, my
executors, administrators, and assigns, should at any time agree with
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "AN IMPROVED
SPEED INDICATOR," upon the condition (amongst others) that I, the said
Thomas Alfred Hearson, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Thomas Alfred Hearson, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement in writing, and on reference being had to
the accompanying Sheet of Drawings, that is to say :-
My said Invention relates to an improved instrument designed for
indicating the speed of steam engines in such a manner that the pointer
will not vibrate with the smaller and more frequent variations of speed
which generally last for only part of a revolution. The instrument
which I have named "strophometer is however applicable for indicating
the speed of any rotating piece, and may, for example, be connected to
a continuous screw log so as to indicate the speed of a ship through the
water.
And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append a Sheet of
explanatory Drawings to be herein-after referred to, and representing a
strophometer as made with my improvements. On these Drawings the
same reference numerals are used to mark the same or like parts wher-
ever they are repeated.
Figure 1 is a front elevation of the strophometer; and Fig. 2 is a
vertical section as at right angles to Fig. 1; Fig. 3 is a vertical
section as at right angles to Fig. 2 of a portion of the instrument;

page_text: Figure 4 is a horizontal section; and Figure 5 is a plan. The parts of
the instrument are carried by a steel spindle 1 which can be secured
firmly by a screw nut at the bottom to a bracket 2 fixed in any con-
venient part of the engine room, factory, or locality where the rotating
shaft or body is placed, the speed of which is to be indicated. On the
lower part of the spindle 1 a steel bushed pulley 3 revolves freely, a cord
or gut being led round it from the shaft or any suitable rotating part of
the machinery. Resting on the pulley 3 and running freely on the
spindle 1 there is a steel bushed fly wheel 4, a steel washer 5 with a
large bottom and small top being placed between so as to give a small 1
bearing surface for the fly wheel 4. The under face of the fly wheel 4 is
recessed, and into the recess 6 there project up from the pulley 3 two
studs 7, having each a chain 8 connected to it. The free ends of these
chains 8 fly out by the centrifugal force against the inside of the rim of
the fly wheel 4, and act frictionally thereon so as to make the fly wheel 1
rotate. In a similar manner chains 9 connected to studs 10 on the
upper side of the lower fly wheel 4 impart motion to another steel
bushed fly wheel 11 also running freely on the spindle 1, the bushics
being separated by a thin steel washer 12.
With the driving arrangements that have been described the inertia of a
the fly wheels 4, 11, will prevent them from being too casily affected by
the small changes of speed which are not persistent, and if the small
variations are not sufficiently obliterated by the lower fly wheel 4 they
will be more completely so by the upper one 11.
Surrounding the spindle 1 above the upper fly wheel 11 there is a
helical wire spring 13, the bottom of which is fastened to the boss of the
fly wheel whilst its upper end is attached to a boss 14 fitted so as to
move freely up and down and to revolve on the spindle 1. The boss 14
is also connected to the fly wheel 11 by two pairs of jointed links 15
which carry balls 16 on their middle joints. The action of the centri-
fugal force in moving these balls 16 outwards causes the boss 14 to be
more drawn downwards and the spring 13 to be the more compressed the
greater the speed is. The movement of the boss 14 is communicated to
a pointer 17 sweeping over a graduated dial 18 by means of a bent steel
wire 19 which nicely fits and slides in a groove formed for it in the
upper part of the spindle 1, and which clasps the top and bottom edges
of the boss 14. The wire 19 is jointed to a light rod 20 formed with
rack teeth at its upper end to engage with a pinion 21 on the arbor 22,

page_text: on which the pointer 17 is fixed. This arbor 22 and the dial 18 are
carried by a bracket 23 fixed on the upper end of the spindle 1. Cups
24, 25, 26, are provided for receiving oil for lubricating the various
working parts.
The amount of the frictional driving power of the chains 8, 0, which
will increase with the velocity and centrifugal force will be always a
little greater than the increasing resistance to rotation which the fly
wheels 4, 11, receive from the air. The constant driving friction of
cach fly wheel boss is made sufficient to overcome the constant resistance
of the friction of the spindle 1 by suitably proportioning the contact
surfaces. In this manner the upper fly wheel may be made to maintain
an almost uniform speed equal to the mean speed of the pulley 3.
The two fly wheels 4, 11, and the pulley 3 may be joined together by
a pin 27 as indicated by dotted lines in Figure 1, whereupon the upper
fly wheel will of course rotate exactly with the pulley 3, and the
fluctuations of speed will be indicated by the pointer 17, and may be
observed. It will be found that the mean position of the pointer will be
the same as that taken by it when the connecting pin 27 is removed.
By making trials in this way the proper length of the chains 8, 9, may
be determined with great accuracy. If the chains are too long the
pointer will oscillate more or less about its mean position, and if the
chains are too short the upper fly wheel will not when disconnected
quite attain the mean speed of the pulley 3 shown by the pointer when
the parts are connected by the pin 27.
°
The advantageous uses of the strophometer are numerous, and the
following applications may be instanced :-If a small propeller screw is
fitted outside and at a little distance from the side of a ship so as to turn
by the pressure of the water due to the onward movement of the ship,
and light gearing be led from it to a strophometer in the ship, the speed
of the ship will be continually indicated by the pointer 17, the dial being
graduated in a suitable manner whilst the numerous fluctuations of the
screw will be eliminated and the mean speed be shown. The instrument
is usefully applicable to locomotives for indicating the speed in miles per
hour; and in this casc as the fluctuations are small one of the fly wheels
may be dispensed with. The desirability of maintaining a uniform speed
in spinning and weaving machinery is well known, and the strophometer
affords a very convenient means for showing at any time how near an

page_text: approach to the required uniformity is realised. In such an application
the range of speed being comparatively small, either the pinion 21 should
be made smaller or the spring 13 should be made weaker in order that
the whole of the dial may be utilised.
In some cases it may be more convenient to substitute a toothed wheel
for the pulley or part 3, and to communicate the motion to the apparatus
through toothed gearing.
Having thus particularly described my said Invention, and the manner
of performing then same, I have to state that I do not restrict myself to
the precise details herein described or delineated, and that I do not claim 1
the applying of balls or weights arranged so as to be subject to centri-
fugal force for indicating speed, but that what I believe to be novel and
original and claim as the Invention secured to me by the herein-before
in part recited Letters Patent is,―
1. The combining together of parts to form an improved speed 1
indicator, substantially in the manner herein described and delineated.
2. The applying of the driving power to the fly wheel or fly wheels by
friction chains or equivalent parts acted on by the centrifugal force,
substantially as and for the purposes herein-before described.
In witness whereof, I, the said Thomas Alfred Hearson, have 2
hereunto set my hand and seal, this Twentieth day of November,
in the year of our Lord One thousand eight hundred and
seventy-three.