Improvements in the Propulsion of Bicycles, Tricycles, Motor Carriages, and like Vehicles.
Year: 1896

page_text: Date of Application, 23rd Sept., 1896-Accepted, 6th Mar., 1897
COMPLETE SPECIFICATION.
Improvements in the Propulsion of Bicycles, Tricycles, Motor
Carriages, and like Vehicles.
I, EDGAR ARTHUR ASHCROFT, of "Maycroft "Newcommen Street, Newcastle in
the Colony of New South Wales, Metallurgist, do hereby declare the nature of my
invention and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
The object of this invention is to facilitate the propulsion of bicycles, tricycles, motor
carriages and like vehicles propelled either by pedal or motive power.
It is well known that in the case of the machines referred to, especially in hilly or
uneven country, it is highly desirable to be able to adjust the gearing of the machine
in such a manner that while maintaining the motion of the pedals or motor shaft at as
nearly as possible the same speed, greater or less purchase may be provided at the
wheel axle or shaft so that greater power may be obtained for surmounting hills or
traversing rough and irregular roads and greater speed conveniently maintained on
smooth and level roads. It is also very desirable that the adjustment should be
accomplished as often as necessary without arresting the motion of the machine and
without the rider alighting.
The principle of my invention is the employment of the varying torque of the
sbafts resulting from the increasing or decreasing resistance encountered in the
propulsion of the machine to automatically adjust the purchase which is applied to
the wheel axle.
the.
The means I prefer for accomplishing this are diagramatically illustrated in Figure 1
in which A and B are two pulleys fitted with any suitable mechanism by which the
diameter of the one is diminished and the diameter of the other is increased in propor-
tion to the torque upon the driving shaft and wheel axle. The solid lines in the
drawing indicate the normal proportions of the two pulleys. Here the driven pulley
makes a greater number of revolutions than the driving pulley. When any increase
in resistance occurs the additional torque upon the shafts is made to move
mechanism preferably against the action of a suitably connected spring, with the
result that the diameter of the one pulley is lessened and the diameter of the other
increased in proportion. This effect is shown in two stages. In the first stage
which is indicated by the ordinary dotted lines the pulleys being now of the same
diameter, the wheel axle will make the same number of revolutions as the driving
shaft and a greater purchase will be secured. A still further adjustment of the
relative size of the pulleys will result upon further increase of torque. This final
stage is shewn by the long and short dotted lines.
I have indicated several methods by which the desired object may be attained
but it will be obvious that there are many other mechanisms which may be
employed to accomplish the same result without departing from the principle of the
invention.
In the drawings Figure 2 represents two pulleys C and D each formed of a spiral
spring of suitable strength and form. The internal end of each spring is fastened to
its driving shaft and axle respectively while the external end slides upon the outer
coil as the pulley expands and contracts.
The spring C in its normal state is uncoiled and the spring D coiled up as shewn
and both springs are of such size and strength that when severe strain is put upon
them such as in climbing a hill D is uncoiled by the torque upon the wheel axle and

page_text: Cis coiled up by the torque upon the driving shaft (the belt being of fixed length).
By making the spring D slightly weaker than C any slackening of the belt is
avoided.
The outer periphery of the spring or pulley is flat, grooved, or of other section
or form to suit any description of belt or chain which may be preferred.
This will apply to all the constructions illustrated herein.
Figure 3 illustrates my invention adapted to ordinary expanding pulleys. In
this case the disc E carrying the radially moving segments is loose upon the
driving shaft. The disc F carrying the screw which moves the segments inwards
or outwards is keyed to the driving shaft. One end of the spring G is secured
to the driving shaft and the other end is connected to the disc E..
The pulley upon the wheel axle is identical in construction except that the spring
connecting the loose disc to the shaft and the operation of the screws are reversed
in action so that under torque the pulley is expanded while the pulley upon the
driving shaft is decreased.
The action of this will be, that upon severe strain being put upon the driving
shaft the spring G is wound up causing the disc E to rotate against the disc F the
segments being thereby drawn inwards and the circumference of the pulley reduced
whilst the torque upon the wheel axle by winding up the spring causes the driven
pulley to expand.
Figures 4, 5 and 6 illustrate another method of applying my invention. Figure 4
is a plan, Figure 5 a side view and Figure 6 a vertical section. In this case the.
driving shaft and the wheel axle are each provided with two pulleys connected by
two separate bands or chains. Both the pulleys on the wheel axle are keyed thereto.
The two pulleys H. J on the driving shaft are engaged alternatively by clutch
mechanism according to whether the torque is lessened or increased. The pulleys
are mounted on a sleeve K which has a spiral slot fitting over a pin on the driving
shaft. On the ends of this sleeve are clutches L and M. The pulleys are prevented
from end movement on the shaft by suitable collars N N. The sleeve is connected
to the axle by a spring P at each end.
Under normal conditions the springs P. P. are unwound and the clutch L engages
the pulley H. As increased resistance is met with the torque upon the driving
shaft winds up the springs and the sleeve is moved along the shaft and the clutch M
engages the wheel J."
Figures 7 and 8 illustrate another modification. In this case a single pulley R
is used on the driving shaft and a double pulley S on the wheel axle. The pulley R
upon the driving shaft is connected thereto by a spiral spring W. The pulley is
provided with an internal spiral groove which engages a key on the driving shaft
so that upon extra resistance being met with the torque winds up the spring and
rotates the pulley upon the shaft and it is drawn along. By this means it is brought
in line with the larger portion of the double pulley upon the wheel axle. In order
to allow the band or chain to pass from the one to the other part of the double
pulley a suitable lead off X is provided as shown in the drawings. In this case
the bolt or chain will under normal conditions be slack and this slackness is taken
up by means of a jockey pulley.
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. Automatically adjusting the purchase between the driving shaft and the wheel
axle of a bicycle, tricycle, motor carriage or like vehicle by means of mechanism
operated by the varying torque upon the shafts resulting from varying resistance
encountered in propulsion, substantially as and for the purposes described.
2. In bicycles, tricycles, motor carriages and like vehicles the employment of
suitable means and mechanism whereby the varying torque of the shafts, resulting
from the varying resistance encountered in propulsion, is caused to vary the relative
size or position of the pulleys on the pedal and wheel shafts and so to automatically

page_text: adjust the purchase between the driving shaft and the wheel axle, substantially as
described.
3. In bicycles, tricycles, motor carriages and like vehicles the employment of springs
acting against suitable mechanism whereby the varying torque upon the shafts
resulting from the varying resistance encountered in propulsion is caused to auto-
matically adjust the purchase between the driving shaft and the wheel axle substantially
as and for the purposes described.
Dated this 23rd day of September 1896.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.