An Improved Variable Throw Crank for Cycles.
Year: 1896

page_text: Date of Application, 22nd May, 1896-Accepted, 27th June, 1896
COMPLETE SPECIFICATION.
An Improved Variable Throw Crank for Cycles.
HERBERT LUZERNE TODD, Electrician 44 Upper Tollington Road, Holloway N.
London and FREDERICK WILLIAM MCCLELLAN, Clerk, Lincoln House, Asteys
Row, Canonbury, N. London 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:-
This invention consists of a mechanical appliance to cycles that will auto-
matically increase the power without changing the sweep of the foot in pedaling,
and at the same time apply the power upon that portion of the revolution of the
crank where most required. To accomplish this propose to firmly attache to the
frame of the cycle two circular plates or disks so constructed that each are alike
and placed one on each side of the machine. These disks are to be in diameter
less than the outside diameter the pedal is to make in turning the crank, and a
groove or race is to be placed, cut or cast in the same, deep enough and wide
enough to allow of a strong wheel to run, the said wheel being firmly attached to
the crank in any manner that will insure its being held to the crank while it rolls
round in the race. This race is to be near the edge of the disk, in fact, as close
to the edge as the strength of the material from which it is made will allow.
Between the centre of the disk and the inner edge of the race is to be a hole for
carrying the crank-axle, preferably at or midway between the centre of the disk
and the race. That portion of the disk within the race is to be less in thickness
than the outer rim. The crank-axle is to be of one piece and made in such
manner that each end is supplied with a screw thread or tapped with a screw
thread for firm attachment to a part of the crank to be hereafter described, as
well as to carry the wheel for working the chain or cord used for propulsion.
The part to be attached to the crank-axle is to be constructed as follows, one piece
of which is to have a bottom and two sides and attached to the bottom a
cylindrical piece of a size to fit the hole in the disk for the crank-axle. The total
length of this first piece to be no more than twice the length from the centre of
the crank-axle to the outer edge of the race and when placed in position and
securely fastened to the crank-axle it will appear like an oblong box without ends
or a top or lid and can easily be turned upon the surface of the disk without
touching the inner face of the outer edge of the race, a lid is to be fitted to this
piece and so fastened as to be easily removed and for such purpose screws could
be used, although for all practical purposes the top could be permanently fastened
or cast with its parent part to form one piece. The object of this particular part
is to receive the lever bar and should be perfectly smooth upon the inner surface
of the box formation, the lever bar is to be provided with smooth sides that enter
the box shaped piece and fit it neatly, as well as carry the wheel which runs in
the race.
The two disks are to be fastened to the frame of the cycle by bolts,
tubes provided with screw threads for screws put through holes in the disk or in
any manner that will properly hold them to the frame. In attaching the disk to
the frame they should be placed in such position that a line drawn through from
the centre of the crank-axle to the centre of the disk should be at an angle of
about 45° with the ground, this will allow of the rider having the most power of
the thrust of the foot upon the pedal at the longest length of the lever and when
the crank has turned half way round the lever will be at its shortest point, for, in
turning the lever by the pedal the wheel attached to the lever in turning in the race

page_text: gradually pushes the lever into the box shaped piece attached to the crank-axle
until it reaches the opposite or lower side of the disk and then commences to
elongate itself on the upward turn of the pedal, and where the length of the lever
from the centre of the crank-pin to the pedal is say 9 inches on the long side and
3 inches on the short side and the sweep of the pedal is a one foot circle an
increase of power amounting to one half results, or a greatly increased speed
could be obtained with the same power: To more fully describe this invention
reference is made to the accompanying drawings in which like letters represent
similar parts:
Fig. 1. is a side elevation showing the crank in its longest-length.
Fig. 2. is a side elevation showing the crank in its shortest length.
Fig. 3. is a cross section, showing connections.
A. is the disk. B. the race. C. the lever bar. D. the wheel in the race and
fastened to the lever bar. E. the box shaped piece. F the crank-axle. G. the
bolts to fasten the disks to the frame H. I. the chain wheel. K. dotted line
showing sweep of pedal.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
-claim is.
1. In a crank for cycles the combination of two circular disks with a race at
their outer edge, a wheel to revolve in the said race the said wheel attached to
the crank lever, the box shaped piece to receive the lever bar, and slots in the
circular disks for the reception of screws, or bolts to fasten the disks to the frame
substantially as described.
2. In a cycle crank the combination of a lever bar that is automatically moved
into a box shaped piece by a wheel attached to the lever bar, said wheel to run
in a race attached to a disk and the disks fastened to the frame as and for the
purpose set forth.
Dated this Twenty-second day of May 1896.
HERBERT LUZERNE TODD.
F. W. MCCLELLAN.