Improvements in the Driving Gear of Velocipedes and other Pedo-motive Machines."
Year: 1897

page_text: Date of Application, 21st Oct., 1897-Accepted, 24th Dec., 1897
COMPLETE SPECIFICATION.
"Improvements in the Driving Gear of Velocipedes and other
Pedo-motive Machines."
I, CHARLES ALEXANDER HAMILTON, of 12 Artillery Street, Londonderry, 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 :-
This invention relates to the driving gear of velocipedes and other, pedo-motive
machines wherein compound cranks are used for the purpose of giving increased
leverage at the effective portion of each stroke, and it has for its object to improve
the construction and arrangement of the parts of such gearing.
And in order that my said invention may be properly understood I have hereunto
appended an explanatory sheet of drawings, whereon :-
Fig. 1 is a side view of the improved gear.
Fig. 2 is a vertical section of the gear.
Figs. 3 and 4 are detail views.
For the sake of illustration the gearing is shown as adapted for a bicycle.
On the drawings the same reference letters wherever repeated indicate the same
parts.
In carrying out my invention I fit at each side of the machine a hollow eccentric a
and these eccentrics are held rigidly in position by means of straps b, b¹. The straps,
as shown in the section at fig. 4, are secured at their upper ends to the lateral
pins d, d, of a collar c on the diagonal tube e of the frame by means of the nuts f, f¹.
As will be seen from fig. 4 the straps, for the purpose of being both strong and light,
are, by preference, made of a channel section. The two straps are, at their lower
ends, braced together by means of a cross stay and nuts.
Each eccentric is secured to its strap by means of lugs a² made in one with the
inner circumference of the eccentric. These lugs are bolted to the straps as shown.
The periphery of each eccentric is grooved or hollowed, as shown at fig. 2, and in
the groove balls are placed. Upon the balls a ring i revolves and this ring is
provided with an outwardly projecting slotted crank j. To the crank j the pedal is
fitted. k, fig. 1, indicates the pedal pin or spindle.
Z is the chain wheel; it is secured to, or made one with a three toed carrier m, the
sleeve m¹ of which is secured rigidly to the crank shaft n working in ball bearings as
usual in the bottom bracket o.
p is the driving crank which is provided at its end with a roller p¹ running on
balls p8 (see fig. 3) on a pin p² secured in the jaws p¹ of the crank. The roller p¹, as
the crank is revolved, is capable of travelling in the slot of the crank j.
The eccentric a is provided with an inward extension which constitutes a bearing
ring a¹ passing round the sleeve m¹. Balls q are fitted between the ring a¹ and the
revolving crank sleeve m¹.
On the opposite side of the machine from that shown at fig. 1 the arrangement is
the same with the exception that the chain wheel and its accessories are absent.
The ring a¹ of the eccentric in this case bears on balls carried by a sleeve or thimble
such as m¹ secured to the crank shaft.

page_text: As will be seen the chain wheel has or may have an inner ring to which the
three toed carrier m is secured.
My improved gear provides a simple and efficient arrangement whereby, at the
effective parts of each stroke of the pedals, an increased leverage is given.
With this invention machines can be fitted with a higher gear than usual and still
be driven with equal ease, or, in the case of a machine whose gear is not altered, they
can, by the application of my invention, be driven with greater ease than formerly.
The gear can be applied to tricycles and other pedo-motive machines.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
consider novel and desire to claim is:-
A compound crank gear for cycles and other pedo-motive machines constructed and
arranged substantially as herein before described with reference to the drawings
annexed.
Dated this 19th day of October 1897.
H. D. FITZPATRICK,
70 Wellington Street, Glasgow, Agent.