An Improved Combination of Mechanism for Driving certain Bicycles and Tricycles.
Year: 1892

page_text: Date of Application, 17th Nov., 1892-Accepted, 28th Jan., 1893
COMPLETE SPECIFICATION.
An Improved Combination of Mechanism for Driving certain
Bicycles and Tricycles.
We FREDERIC BENNETT LANGTON and STEPHEN BENNETT LANGTON both
of 313 Coldharbour Lane Brixton in the County of Surrey Cycle Manufacturers 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 can only be applied to that class of bicycle and tricycle (commonly
called, in the case of bicycles, the "Safety" bicycle) in which a cogged wheel
(known in our trade as a gear wheel") secured upon the crank shaft drives a
smaller gear wheel secured upon the axis of the driving wheel (or driving wheel or
wheels in the case of tricycles) by means of an endless chain fitting the cogs upon
the peripheries of each of the gear wheels in the well known manner.
"
is
The advantage to the rider of what is called in our trade "narrow tread
well-known, and to effect it the distance between the crank axle bearings has been
narrowed, and as an additional, or as an alternative means various devices have
been employed for the purpose of connecting the gear wheel upon the crank shaft
to its adjacent crank so that they shall have but one
"boss or place of attachment
to the crank shaft instead of one each, and thus by economizing space in the
direction of the length of the crank shaft it can be shorter and the cranks with
their pedals (and consequently the feet of the rider) be brought closer together to
constitute a "narrow tread." We object to the means of obtaining narrow tread
by narrowing the space between the bearings of the crank shaft because the strain
and friction and wear upon these bearings is greater when they are nearer together
instead of as far apart as practicable and we therefore limit ourselves to the method
of economizing space between the feet of the rider by connecting together per-
manently or by originally making in one piece the gear wheel and its adjacent
crank, but always so that they shall have but one boss instead of one each.
An elliptic gear wheel is now in the course of coming into use (instead of the
circular one described) upon the crank shaft to drive the small circular gear wheel
upon the axis of the driving wheel of the machine. And it is found in practice
that this difference in the form of the two gear wheels upon the machine does not
involve such an amount of slackness in the endless chain as to constitute a serious
objection. The advantages obtained by this substitution of the elliptic form in the
larger gear wheel for the circular form are that by setting the pedal crank at or
about a right angle to the longest diameter of the adjacent gear wheel more speed
is obtained at the most useful part of the strokes of the feet and more power at the
less effective part of their strokes, which is when they are near to and are passing
the dead points.
The object of our invention is to combine in the same machine the advantages
of narrow tread, and an elliptic gear wheel as herein described so that they may
both be enjoyed by the same rider at the same time, which has not hitherto been
done.
To this end we fasten the elliptic gear wheel described to its adjacent crank
either by screws or by bolts and their nuts, or by rivets or by soldering or brazing
or by any well known equivalent means, or we stamp or cast the elliptic gear
wheel and pedal crank originally in one piece, but in all cases so that there shall be
but one boss or part for attachment to the crank shaft. The boss may belong to
the pedal crank or to the elliptic gear wheel.
In the accompanying drawing the elliptic gear wheel is brazed to the pedal

page_text: crank and the whole is shown as capable of attachment to the crank shaft by means
of a common key tightly driven in.
We make no claim to a circular gear wheel upon the crank shaft as any part of
our improved combination either when fastened upon the crank shaft separately or
when fastened to it in conjunction with a pedal crank, nor do we claim one part of
our improved combination when used alone, but
Having now described the nature of our invention and in the manner best known
to us of carrying it into effect we would have it understood that what we
claim is :-
The combination of the elliptic gear wheel with its adjacent pedal crank the
combination having but one boss for fixing it to the crank shaft.
Dated this 17th day of November 1892.
FREDERIC BENNETT LANGTON.
STEPHEN BENNETT LANGTON.