Apparatus for Indicating and Recording Variations in the Angular Velocity of Rotating Bodies.
Year: 1896

page_text: Date of Application, 18th Apr., 1896
Complete Specification Left, 18th Jan., 1897-Accepted, 13th Mar., 1897
PROVISIONAL SPECIFICATION.
Apparatus for Indicating and Recording Variations in the Angular
Velocity of Rotating Bodies.
1, JOHN SMITH RAWORTH, of 46 Christchurch Road, Streatham Hill, in the
County of London, Engineer, do hereby declare the nature of this invention to be
as follows:-
My invention has reference to apparatus designed to show by means of a
diagram, the amount by which a revolving body such as a shaft or wheel, deviates
in any revolution, or part or parts thereof, from constant angular velocity.
The apparatus comprises a shaft driven by the shaft or wheel to be indicated and
on which is fixed an arm that drives a fly wheel mounted loose on said shaft.
Motion is communicated to the fly wheel from the arm through light springs, which
whilst having sufficient strength to overcome the air friction of the wheel, are still
light enough to allow freedom of motion, within limits governed by stops, between
the arm and the fly wheel, so that whilst the fly wheel revolves with a constant
angular velocity, the arm, when revolving with a varying angular velocity, will not
remain in a fixed position in relation to any given radius line on the wheel.
For the purpose of rendering these variations visible by means of a diagram, a
marker such as a pencil or a metallic marker, is fixed on the face of the fly wheel
for the purpose of describing a datum circle on a sheet of paper or card and
another pencil is fixed on the end of a lever carried by the wheel and connected
with the arm on the shaft in such manner that motions of the arm in relation to the
fly-wheel will cause the pencil carried by the lever to vary its radial distance from
the centre of the wheel and thus to draw a line, which, by its varying distance from
the true circle, will indicate the effect of the varying speed of the shaft or other
rotary body from which the apparatus is driven.
The paper or card on which the diagram is to be drawn, is fixed on a hinged or
sliding board so arranged that it may be easily brought by hand into a position
parallel to the plane of revolution of the pencil-points and so that the two pencils
may just touch the paper.
Dated this 18th day of April 1896.
Apparatus for Indicating and Recording Variations in the Angular
Velocity of Rotating Bodies.
I, JOHN SMITH RAWORTH, of 46 Christchurch Road, Streatham Hill, in the
County of London, Engineer, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
My invention has reference to apparatus designed to show by means of a

page_text: diagram, the amount by which a revolving body such as a shaft or wheel, deviates
in any revolution, or part or parts thereof, from constant angular velocity.
The apparatus comprises a shaft driven by the shaft or wheel to be indicated and
on which is fixed an arm that drives a fly wheel mounted loose on said shaft.
Motion is communicated to the fly wheel from the arm through light springs,
which, whilst having sufficient strength to overcome the air friction of the wheel,
are still light enough to allow freedom of motion, within limits governed by stops,
between the arm and the fly wheel, so that whilst the fly wheel revolves with
a constant angular velocity, the arm, when revolving with a varying angular
velocity, will not remain in a fixed position in relation to any given radius line on
the wheel.
In order to render these variations visible by means of a diagram, a marker, such
as a pencil or a metallic marker, is fixed on the face of the fly wheel for the purpose
of describing a datum circle on a sheet of paper or card, and another pencil is
fixed on the end of a lever carried by the wheel, and connected with the arm on
the shaft in such manner that motions of the arm in relation to the fly-wheel will
cause the pencil carried by the lever to vary its radial distance from the centre of
the wheel, and thus to draw a line, which, by its varying distance from the true
circle, will indicate the effect of the varying speed of the shaft or other rotary body
from which the apparatus is driven.
The paper or card on which the diagram is to be drawn, is fixed on a hinged or
sliding board so arranged that it may be easily brought, ly hand, into a position
parallel to the plane of revolution of the pencil points, and so that the two pencils
may just touch the paper.
Referring to the accompanying illustrative drawings,
Fig. is a side elevation of an apparatus constructed according to my
invention.
Fig. 2 shows the apparatus in end elevation as seen when looking in the direction
of the arrow represented in Fig. 1.
A is the base plate and B a standard carrying a bearing in which is mounted to
rotate freely a shaft C whereon is fixed a disc or flange D whereby the shaft C can
be coupled to a revolving body to be indicated and whereby the shaft C will then
be rotated. E is an arın fixed or the shaft C. F is a fly wheel free to rotate upon
the shaft C. G G are light springs, each of which is secured at one of its ends to
the arm E and at its other end to the fly wheel F. H H are stops carried by the
fly wheel. J is a pencil or marker carried by a spring arm J fixed to the fly
wheel and provided with an adjusting screw J. This pencil or marker is for the
purpose of describing a datum circle upon the paper or card on which the diagram
is to be drawn. K is a lever whose lower end is made flexible, is provided with an
adjusting screw K' and is adapted to carry a pencil L. This lever is pivoted
at K to the fly wheel F and is by a link M connected to the arm E. N is a board
adapted to carry the card or paper as at O. In the example the board N is
secured to a support P, able to be turned about a hinge pin Q and provided with a
handle P and with a set screw adjustable so as to determine the position of the
card or paper in relation to the pencils.
An obvious modification and in some respects an improvement of the construction
can be made by attaching the pencils to the arm E instead of to the fly wheel F.
Let it be assumed that my apparatus is coupled to the crank shaft of an engine,
for obtaining an automatic graphic representation of the velocity of such shaft
throughout a revolution, then when the engine moves, the arm E puts the fly
wheel F into motion. Until the inertia of the fly wheel is overcome the arm
remains in contact with the stops, but when this is overcome the fly wheel will, of
course, go on travelling at the mean speed of the shaft, and the arm E will take a
central position under the influence of the springs. Now, if any divergence from
uniformity in the rate of rotation of the crank shaft occurs it will be seen that the
inertia of the fly wheel comes into play, and it lags behind, or is momentarily
ahead of, the crank. When a card on the hinged board shown is lightly pressed

page_text: against the pencils two rings are made, one a circle, and one an imperfect circle
depending on the departure from uniformity of the rotation speed, and the departure
from circularity shows in what part of the engine fly wheel greater or less weight
would be of advantage, and it shows to one who can interpret the graphic indications
where improvements may be made in the engine as to balance and as to steam
admission, etc. By means of this instrument the exact cause and extent of
irregularity in the turning of an engine can be ascertained in a few minutes.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In an apparatus for indicating and recording variations in the angular velocity
of rotating bcdies, an arm or device that carries a marker or pencil and is so
connected to a part of the apparatus rotating at a uniform speed and to another
part of the apparatus rotating with the body being indicated that the radial distance
of the point of the said pencil or marker from the axis of a datum circle is caused
to vary in direct proportion to the extent of departure from uniformity of rotation
of the body being indicated.
2. In an apparatus for indicating and recording variations in the angular velocity
of rotating bodies, the combination of an arm adapted to be driven by the revolving
body to be indicated, a fly wheel mounted freely on a shaft so as to receive motion
through springs from the said arm, and stops to limit relative motion between the
fly wheel and the arm, the fly wheel and the arm each carrying a pencil or marker,
and the arrangement being such that whilst the fly wheel revolves with a constant
angular velocity, the arm, when revolving with a varying angular velocity, will
cause the movable pencil to alter its radial distance from the centre of the
fly wheel.
3. The combination of parts as described for producing a diagram which by its-
radial departure from a datum circle shall indicate the amount of deviation
of a rotating shaft or. body from constant angular velocity.
4. My improved apparatus substantially as described and illustrated for the-
purpose specified.