IMPROVEMENTS IN ROTATION DYNAMOMETERS
Year: 1878

page_text: LETTERS PATENT to Alexander Melville Clark, of Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS
IN ROTATION DYNAMOMETERS." A communication from abroad by François
Jules Morin and le Baron Raymond Seillière, both of Paris, France.
Sealed the 23rd May 1879, and dated the 13th December 1878.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 13th December 1878.
tr
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middlesex,
Patent Agent. IMPROVEMENTS IN ROTATION DYNAMOMETERS." [A communication
from abroad by François Jules Morin and le Baron Raymond Seilllière, both of Paris,
France.]
This Invention relates to improvements in what are known as rotation dynamo-
meters. Dynamometers of this kind are but little used, as they are costly and
cumbersome, and their indications cannot be observed while the machine is running,
as the entire mechanism revolves with it. Moreover, in many cases a special
arrangement of belt is required to drive it, owing to the size of the pulley which
encloses the mechanism.
The improved dynamometer of this Invention is of much more simple and much
less expensive construction; it may be made to give at same time both visible indi-
cations and a graphical register of the results which it denotes, and it may be
inspected at a glance while at work. The instrument is composed of two distinct
parts, the one movable for receiving and transmitting the forec, and the other fixed,
indicating its value. The movable part consists of a disc which is keyed on the
machine shaft, and has mounted on one of its faces a pair of spring balances placed

page_text: symmetrically at either side of the shaft and parallel to a diameter of the disc. The
cases of the balances are attached to fixed studs on the disc, and the rods of the
pistons by which the springs are compressed are connected to a common crosshead
or bar beneath the shaft, from the middle of which crosshead a stem projects per-
pendicularly to it.
This stem slides in a guide, and its extremity is bent at a right angle and passes
through a radial slot in the disc, along which it moves to an extent equal to that of
the pointers of the spring balances. To the middle of the crosshead is also attached
the end of a steel band or chain, which passes first in a radial direction coincident
with that of the stem and slot above mentioned to and around a pulley mounted
upon the disc near its circumference. If the machine be set in motion by putting
on the steel band in a direction perpendicular to that in which it first passes from
the crosshead, the spring balances will first indicate the value of the force exerted,
and the machine will be put in motion. The end of the steel band is attached to an
arm projecting from the face of the pulley upon which the driving band from the
motor runs, and the steel band and spring balances are thus the intermediary
through which the power is transmitted from the motor to the apparatus which it
drives. The instrument thus furnishes all the necessary data for estimating the
dynamometric result, which is done by multiplying the indications of the spring
balances by the circumference of the circle described by a point on the periphery of
the pulley (round which the steel band passes) farthest from the centre of the disc,
and by multiplying the product by the number of revolutions; thus if the balances
indicate 6 kilogrammes and the point of contact of the steel band be about 16 centi-
metres from the centre, i.e., if it describes a circle one meter in circumference at
every revolution, and makes 600 revolutions per minute, the result will be 6 kilo-
grammes x 1 meter per revolution (i.e., 6 kilogrammneters) × 10 revolutions per
second =
60 kilogrammeters per second.
The results are indicated upon the stationary part of the apparatus, for which
purpose the disc before mentioned is furnished on the opposite side to the spring
balances with a central boss having an angular groove around it, and upon this boss
in the said groove rides a steel plate having an opening of angular form at the
upper part through which the boss passes, and terminating below the shaft in a
pendant arm which hangs in a vertical line passing through the centre of the shaft.
This pendant arm is furnished with a slide which works thereon with slight friction,
and carries an index that travels over a scale marked on the arın. This slide is
furnished with two abutments, the one above the other, separated by a small interval
corresponding to the diameter of the bent end of the stem, which, as above men-
tioned, passes through a radial slot in the disc, and passes between the two abutments
at each revolution it makes with the disc.
The lower abutment is rectilinear and horizontal, and consequently perpendicular
to the direction of motion of the slide, and when struck by the bent end of the said
stem it (as well as the slide to which it is affixed) is moved until it is tangential to
the circle described by such bent end, the index carried by the slide thus indicating
the maximum force exerted in a given time. The other abutment on the slide has
a convex surface of smaller radius than the nearest distance the slide can approach
to the centre of motion of the disc, so that when the bent end of the said stem
strikes said convex surface it will move the slide towards the centre of the disc;
this second abutment alone would indicate the minimum force exerted during a
given time. By leaving only the necessary interval between these two abutments
for the bent end of the arm to pass between them, and fixing them on the same
slide, the index of the latter will indicate upon the scale of the pendant arm the
force acting on the spring balances, to whose scales the said scale exactly corresponds.
By combining a pencil with the slide the indications may be recorded upon a
paper strip made to unwind across the pendant arm.
The same results may also be obtained by other means acting on the same prin-
ciple. One such consists in a pinion carried by the revolving disc, and mounted

page_text: upon an axis at right angles to that of the shaft, and gearing with a rack forming a
substitute for the bent stem before mentioned; a second rack at right angles to the
first also gears with the pinion, and moves parallel with the machine shaft, this
second rack being furnished at its extremity with a disc of suitable diameter, and in
contact with the said shaft.
The periphery of this disc would terminate in an acute angle, and form a circular
index for reading off, in connection with a fixed scale, the pressure upon the spring
balances. A tell tale or counter may also be attached either to the bottom or top of
the pendant arm or plate before mentioned, which would be acted on by a stud or
wiper, for indicating the number of revolutions.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
13th June 1879.
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN ROTATION DYNAMOMETERS." A communication
from abroad by François Jules Morin and le Baron Raymond Seillière, both of
Paris, France.
This Invention relates to improvements in what are known as rotation dyna-
mometers. Dynamometers of this kind are but little used, as they are costly and
cumbersome, and their indications cannot be observed while running, as the entire
mechanism revolves. Moreover, in many cases a special arrangement is required to
drive them, owing to the size of the pulley which encloses the mechanism.
The improved dynamometer of this Invention is of much more simple and much
less expensive construction; it may be made at will to give at the same time both
visible indications and a graphical register of the results which it denotes, and its
indications are as legible at a glance while it is at work as those of a clock.
In order that the Invention may be more readily understood I have illustrated it
in the annexed Drawings, and will proceed to describe it more fully with reference
thereto.
Figure 1 is an elevation partly in section of the entire apparatus constituting
dynamometer; Figure 2 is a transverse section on line 1-2, Figure 1; and Figure 3
is a top plan of Figure 2.
The instrument is composed of two distinct parts, the one for receiving and
transmitting the force to be measured, and the other for indicating its value.
The first part consists of a cast iron plate A, which is keyed on the dynamometer
shaft C, and has mounted on one of its faces a pair of spring balances placed sym-
metrically at either side of the shaft C, and parallel to a diameter of the shaft.
Each spring balance consists of the spiral spring r contained in a cylindrical case B
fixed to the plate A, the spring being confined between the bottom of the case and
a head b' formed on the end of a rod b, which passes down through the spiral spring
and projects through the bottom of the case. Both rods b are connected to the ends
of a cross head D, to the middle of which a rack e is fixed perpendicularly to said
cross head to actuate the second part of the instrument. A pulley E loose on shaft
C is connected with the cross head D by a steel band or chain passing round a
small pulley mounted upon the plate A, such steel band or chain being attached by
one end to the circumference of the pulley E, and by its other end to the cross
head D. Instead of this connection from the pulley E to the cross head D it may
be preferable to fix a second rack d to the said cross head, and substitute for the
small pulley above mentioned a pinion P mounted to revolve on a stud fixed to the
plate A, with which pinion P the rack d is made to gear, the said pinion being made
of sufficient length to gear also with a toothed segment on the inside of the rim of
the pulley E, upon which runs the driving belt from the motor shaft. On power
being applied to pulley E the force exerted will be transmitted through the steel
band or the rack d and pinion P to the springs 7, which will be compressed to an
extent corresponding to the tractive force applied through the driving belt and to
the resistance opposed by the machine or apparatus to be driven, to which the
power is transmitted by a belt running on a pulley F keyed on shaft C. The com-
pression of the spring balances will thus indicate the intensity or value of the force
exerted
The instrument thus furnishes all the necessary data for estimating the dynamo-
metric result, which is done by multiplying the indications of the spring balances B
by the circumference of the pulley E, and this product by the number of revolutions
observed with a counter; thus if the balances indicate 6 kilogrammes and the cir-
cumference of pulley E is 1 metre and makes 600 revolutions per minute, the result

page_text: will be 6 kilogrammes x 1 metre per revolution (i.e., 6 kilogrammetres) × 10 revo-
lutions per second 60 kilogrammetres per second.
=
I will now describe the second part of the instrument, by which the indications
are rendered visible at all times whilst the dynamometer is rotating. The rack e
connected to the upper side of the crosshead D gears with a toothed sector S
mounted in a plane coincident with the axis of shaft C, and pivotted at & between
two arms cast or fixed on the plate A. The said sector gears in turn with a rack T
fitted to slide in a longitudinal groove in shaft C, and having attached to it a rod t
passing axially through the said shaft. The rod t terminates in a flat head t
bevelled to an acute angle at its circumference to serve as an index to indicate on a
fixed and suitably graduated scale g the movements resulting from the variations
in the pressure upon the spring balances. Although this index t' rotates with the
shaft C, its position relatively to the fixed scale g is none the less visible, as being
circular and concentric with the axis of shaft C its rotation is hardly perceptible, and
in no way affects the reading off of its position on the scale.
By combining an inking roller with the index t¹, which then becomes a marker,
and substituting for the fixed scale g a scale marked paper strip I, travelling at a
rate proportionate to the angular speed of the apparatus, a graphical register of the
results is furnished by which the visible indications may be checked.
G is a loose pulley upon which the belt is shifted when it is desired to stop the
machine driven.
The sector S is weighted at 8¹ in order to compensate for the effects of centrifugal
force upon cross bar D and rack d. The two masses being diametrically oppo-
site one another, tend to move in opposite directions, but are prevented by the rack
gear, whereby this movement is neutralized, and errors which would result there-
from are prevented.
Having thus described the nature of the said Invention, and the manner of per-
forming the same, I would have it understood that what I claim as the Invention to
be protected by the herein before in part recited Letters Patent is,―
First. A rotation dynamometer in which the power is transmitted to its shaft
through spring balances and measured by their compression, and in which the
amount of this compression is by an index shown on a non-rotary scale or tape,
and may be read off at a glance during the rotation of the dynamometer, substan-
tially as specified.
Second. The combination of mechanism constituting the improved rotation
dynamo-meter, arranged and operating substantially as shown and described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twelfth day of June, in the year of our Lord One
thousand eight hundred and seventy nine.
A. M. CLARK. (L.S.)