New or Improved Driving Mechanism for Bicycles or Velocipedes.
Year: 1898

page_text: COMPLETE SPECIFICATION.
A New or Improved Driving Mechanism for Bicycles or Velocipedes.
I, DE WITT WEBSTER SPENCE, of London Road, in the City of Guelph, County of
Wellington, and Province of Ontario, Dominion of Canada, Machinist, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
The object of this invention is an arrangement for driving bicycles in which
the dead points of one treadle do not coincide with those of the other.
I do not claim to entirely eliminate the dead points, but to so arrange them that
they will follow one another at such a distance that they are practically non-
existant.
It consists essentially of an arrangement by which the natural dead centre of
one treadle is carried forward till the dead centre of the other treadle has been
passed.
Reference being had to the accompanying sheet of drawings which shows the
mechanism as attached to a bicycle.
Rocking levers A A¹ and B B are fulcrumed at (o) in the ordinary crank hanger
bracket.
The front arms a a¹ of these rocking levers carry the pedals which are oscil-
lated by the feet in the usual manner.
The rear arms B B¹ project downwardly with a slightly rearward curve and are
provided with holes or stops for regulating the height of the primary connecting
rods C C¹.
These connecting rods C C¹ are pivotted near the lower end of swinging bars D D¹
which are suspended from a horizontal pin or axle E located on the lower bar of
the bicycle frame a short distance to the rear of the fulcrum (o) of the rocking
levers.
At the extreme lower end of the swinging bars D D¹ are pivotted the secondary
connecting rods F F¹, the other ends of which are attached to the crank arms G, G¹
of the front sprocket H.
The sprocket H, is in this instance placed well back on the frame and close to
the rear sprocket.
In the ordinary lever operated bicycle the dead points are exactly opposite and
very marked in the recurrence.
In my invention by jointing the connecting rods and connecting the hinged
joints by means of the swinging bar to a point in the rear of the fulcrum of the
rocking levers, the throw of the crank arms is increased so as to carry them well
over their respective natural dead points. The arrow shows the direction of rota-
tion of the sprocket wheel.
In the drawing the right foot has reached the end of its stroke and the end of
the secondary connecting rod F has reached its outer dead point (r).
This, however, has carried the end of the secondary connecting rod F", to an
exactly opposite point which as shown by the dotted outline on the drawing is
ED 077

page_text: considerably in advance of its inner natural dead point (z) and the other pedal has
already started on its downward course.
The same operation is repeated with each stroke of each foot.
It will thus be seen that each down stroke not only carries the opposite pedal
up but also starts it on its downward course easily and without shock.
This peculiar result is attained by the fact that each stroke of the pedal carries
the crank arm a little more than half way round with a positive motion, occasioned
and controlled by the double fulcruming of the connecting rod which is practically
driven from one centre and controlled by another a little in the rear.
Lengthening or reducing the swinging rods would increase or reduce the throw
of the crank arm on the sprocket thus carrying it more or less over its dead
centre as may be required.
By means of the holes or stops in the downwardly projecting rear arms B B¹
of the rocking levers, the forward ends of the primary connecting rods C C¹ can
be raised or lowered thus bringing them nearer to or further from the fulcrumed
centre () of the rocking levers, thus increasing or reducing the power and
lengthening or shortening the pedal stroke respectively and making the machine
high or low gear as may be desired.
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 claim is:-
The new or improved driving mechanism for bicycles or velocipedes consisting
of the rocking levers A. A carrying the pedals, suitably fulcrumed on the frame
of the bicycle, downwardly projecting arms B B provided with regulating holes
or stops on the said levers, primary connecting rods C C¹, the forward ends being
pivotted in one or other of the stops or holes, the rear ends being pivotted near the
ends of the swinging bars D D' which in turn are suspended from the horizontal
pin E, situate on the lower bar of the frame a little to the rear of the rocking
levers, the secondary connecting rods F F pivotted on the extreme end of the
swinging bars D D¹, the other end being attached to the cranks carrying the
sprocket wheel H, which drives the rear sprocket by means of a chain in the usual
manner, the whole combined and operating as hereinbefore described and illus-
trated in the drawings.
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1000