Improvements in and relating to Bicycles.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in and relating to Bicycles.
I, ALEXANDER DUNCAN, Balgedie Manse, County of Kinross, Scotland, Engineer,
do hereby declare the nature of this invention to be as follows:-
An improved driving gear for bicycles, consisting of a toothed pinion fast on
the crank axle, another toothed pinion fast on the back wheel of the bicycle, and
an intermediate pinion, between, and in gear with, these others. This intermediate
pinion to be composed of two circular plates of hard steel, having an equal number
of radial slots cut in each, and fastened together, on a common axis with the slots
abreast, and at such a distance as to retain between each pair of slots a hardened
steel ball, free to roll radially, but with a minimum of side-play in the slots.
The tooth spaces in the other pinions each of which consists of one circular plate
of hard steel, are to be cut so as to allow the balls in the intermediate pinion to
enter and pass along each radially, with a minimum of side play.
These pinions are to be fitted together so that the extreme ones pass between the
plates forming the intermediate one, and the balls roll successively between the
edges of the slots, and the teeth of the extreme pinions, thus forming a frictionless
gear.
To allow of this gear being entirely contained between the back stays of the
bicycle, the bottom or crank bracket may be made in two parts and the first, or
driving pinion, keyed on the crank axle between them.
The axle on which the intermediate pinion revolves can be attached on the
outside to a lug on the lower back stay, and on the inside, to the ends of two
stays dropped from the upper back stay, and the seat post, respectively.
It will be necessary to duplicate the bottom stay from the steering head to the
crank bracket, and the seat post or diagonal must also consist of two separate
tubes, one to each crank bracket. These tubes may be fastened together at their
upper extremities by one or more bridges, having a hole bored through each to
allow the seat pillar to pass down between these tubes.
An extra stay to be attached from the lower end of the seat pillar to the end of
the seat pin which is to be fastened to this stay and also to the seat pillar by
hinged joints.
The lower ends of this stay and of the seat pillar to be attached to each other
and to the diagonals by a clip and bolt so that the height and also the inclination
of the saddle may be altered to suit various riders.
Dated this 18th day of April 1898.
ALEXANDER DUNCAN.
Applicant.

page_text: Improvements in and relating to Bicycles.
I, ALEXANDER DUNCAN, of Balgedie Manse, County of Kinross, Scotland,
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:--
An improved driving gear for bicycles consisting of a toothed wheel fast on 5
the crank axle, another, fast on the back wheel hub, and an intermediate one be-
tween, and gearing with these other two. This intermediate wheel is to be com-
posed of two circular plates of hardened steel, each having the same number of
radial slots equally spaced, and similarly placed at equal distances from the centres,
cut in each.
These plates are to be fastened together parallel to each other, and on the axis,
with the slots abreast, and at such a distance as to retain in each pair of slots a
hardened steel ball free to roll radially along the slots, but with a minimum of
play in other directions.
The spaces between the teeth on the other two wheels, which must each con-
sist of a plate of hardened steel, are to be cut so as allow the balls in the inter-
mediate wheel to pass between the teeth with a minimum of play circumferentially.
These wheels are to be fitted together so that the edges of the extreme ones
pass between the plates forming the middle one, and so that each ball as it comes in
contact with either of the extreme wheels, rolls between a tooth on that wheel
and the edges of the slots retaining it in the intermediate wheel, thus forming a
gear from which all but rolling friction is eliminated.
If the plates of the intermediate wheel be made so thick that the balls do not
project through them, grooves may be substituted for slots in those plates.
I do not limit the use of this ball gearing to the three wheel gear described
above, but may apply it to any driving gear containing toothed wheels.
The space between the plates of the intermediate wheel, may be filled by a disc or
ring of wood or, of metal encircled by a band of leather or other soft material, of
such a diameter as to limit the inward travel of the balls and thus deaden the
noise caused by their striking the ends of the slots or grooves.
The first and third pinions, being composed of thin steel plates, can be made
fast in position by being bolted or rivetted to the faces of discs or collars,. screwed
or keyed on to the crank shaft or back wheel hub respectively. In bicycles driven
by the three wheel gear above dscribed, to allow of a back stay being fitted in one
piece and in a straight line between the crank bracket and the back wheel centre
on the gear side, I make the crank bracket in two separate parts, one on each side,
and place the first driving pinion on the crank axle between these two parts. The
seat post or diagonal stay of the bicycle must then be forked at its lower end so
as to join both crank brackets and, similarly, the bottom stay from the crank
brackets to the steering head must for the same reason be also forked.
The intermediate pinion can then be hung from a lug brazed or otherwise
attached to the lower back stay, on the outside, and, on the inside, from the ends
of two stays dropped from the upper back stay and from the seat post respectively.
The accompanying drawing illustrates my invention as applied to a three pinion
gear:-
Figure 1 is a elevation of a bicycle driven by such a gear and shown inclined to
the plane of projection, so as to exhibit the forked seat post G and bottom stay K.
Fig. 2 is a view on a larger scale of the intermediate pinion, half in cross sec-

page_text: tion, half in side elevation. The relative positions of the other pinions are also
indicated on either side.
Fig. 3 shows to the same scale the shape and position of the ball holding slots,
and Fig. 4 is a cross section through a pair of these slots showing the ball in
position.
In these views A, B, and C, are the first, intermediate, and third pinions re-
spectively; in Figs. 2 and 4, B, is also used to distinguish the two hard steel plates
forming the middle pinion. D, D, are the slots in those plates and E, E the balls
retained in the slots D, D. F is the wood packing between the plates B, B.
L and M are stays dropped from the upper back stay and seat post respectively,
and supporting on the inside the intermediate wheel B. N, N, are bolts tying
the plates B, B together to prevent them being sprung apart by the driving pres-
sure on the balls. These bolts are preferably placed at equal intervals on as
large a circle as possible. P, P', are the bolts securing the plates B, B, to their
hub S. R is the lower back stay supporting through a lug affixed to it, the wheel B,
on the outside. The broken lines T indicate the shape and position of the
collar, keyed on the crank shaft, to whose face the first pinion A is rivetted; and
similarly denotes the disc screwed on the back wheel hub to which the third
pinion C is fastened.
Having now described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what is
claim is:-
1st A pinion formed of two plates of hardened steel, with radial slots or
grooves cut in each, and fastened together so as to hold in each pair of slots or
grooves, a ball free to roll lengthwise along the slots or grooves but with a mini-
mum of side play in other directions.
2nd; The placing of the first pinion in a bicycle driving gear formed of three
pinions in series, between two separate crank brackets, and inside the back stays.
3th The hanging the intermediate pinion in such a gear, from a lug brazed
on, or otherwise attached to, the lower back stay of the bicycle, on the one side,
and on the other, the inside, to the ends of two stays dropped from the upper back
stay, and from the seat post respectively.
Dated this 16th day of January 1899.