Improvements in Bicycle Cranks.
Year: 1897

page_text: Date of Application, 3rd Feb., 1897
Complete Specification Left, 25th Oct., 1897-Accepted, 1st Jan., 1898
Improvements in Bicycle Cranks.
I, EDWARD REYNOLDS, of Clipston Rectory in the County of Northampton,
Clerk in Holy Orders, do hereby declare the nature of this invention to be as
follows:
-
I make the crank arm in two parts and connect them together by a joint pin as
is shown by the annexed sketch in which A and B are the two parts of the crank
arm, S the crank or gear spindle and P the pedal spindle, H the joint pin which
rotates with B.
By inclining the pedal end of the crank to the spindle end it is now easy to
shorten it at pleasure, and to adjust the arm to give a crank of any length between
the maximum and minimum. The minimum length depends on the relative
lengths of A and B.
By elaborating the simple pivot hinge some remarkable results are obtained.
By dishing or counter sinking A and making B thin enough in the plate to yield
a little when the hinge bolt is screwed up tight and consequently to act as a spring
or by inserting a spring washer between the head of the bolt H and B I get a joint
which will tighten under forward pedal pressure and slacken under back pedalling
pressure. So the rider need not stop to alter the length of his crank, all he has to
do is to back pedal hard for part of a stroke: the pivot bolt H unscrews a little in
the nut T, and B rotates about it to any position desired. Forward motion then
locks B to A in a new position. If the parts A and B be made of equal length
between the centres of the holes the pedal spindle comes into line with the bracket
spindle at the position of minimum length, and the rider can coast" without
taking his feet off the pedals, a great advantage for ladies.
The stress between the abutting parts of A and B, is always considerable. This
stress is maintained by restraining the tension nut T, from more than a very little
opportunity of unscrewing. This is done by back-nuts N properly adjusted on
the pivot bolt H.
This tension causes great friction at the hinge, and prevents B from turning
about the axis of H in the upcast, or in moderate back pedalling.
When the joint is of the pivot sort above described, there is nothing to hinder
complete rotation of B and H round the axis of H, except the grip of the hinge.
So the effect of continuous and severe back-pedalling (as when going down a steep
hill) is to cause B to continuously rotate about H. The result on the motion of
the machine is that of the ordinary back-pedalling and brake combined. So the
crank is virtually a brake as well as a crank.
If instead of a simple pivot hinge, a rule joint or a pivot joint with a double
stop be used, then the rotation of B is limited to a semi-circle or thereabout. The
tension nut in this case must be locked in a position affording the proper amount
of friction at the hinge, and not allowed to unscrew and screw up tight auto-
matically. B will then rotate (under sufficient pressure) backwards or forwards
through an angle of 180 degrees' or thereabout between the extreme positions of

page_text: maximum and minimum length. In this case it is very efficient at full length
or at the shortest, but not between.
66
Improvements in Bicycle Cranks."
I, EDWARD REYNOLDS, of Clipston Rectory, in the County of Northampton,
Clerk in Holy Orders, 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: —
The
I make the arm of the crank in two parts, and bolt them together by a joint
pin as is shown in the drawing annexed to the Provisional Specification.
joint pin H is parallel to the gear spindle of the machine and B abuts on the side
of A remote from the machine.
By varying the inclination of B to A, the effective length and throw of the
crank arm is also varied, and the relative inclination of the two parts can be
adjusted to give any effective length of crank arm intermediate between the maxi-
mum and minimum lengths. The maximum being when H is in the straight line
from S to P and between S and P; the minimum is when H, S and P are in line
and S intermediate.
By elaborating the simple pivot joint some remarkable results are obtained.
For instance, by interposing a spring washer between the tension nut T and the
abutting part of A, I get a joint that will tighten under propelling pressure of the
rider's foot and relax when he back pedals; so that he can alter the length of his
crank without dismounting. He need only back pedal hard to cause B to rotate
about the axis of H into any new position relative to A when forward action being
resumed locks 13 to A in a new position. In this case the screw thread on H will
be right-handed on one side of the machine and left-handed on the other.
For practical purposes three or four different crank lengths are sufficient. This
limited variety is obtained with great facility by attaching a ratchet wheel to B
by means of the pin H, to engage with a pawl carried by A, when the rider pedals
forward. By means of the ratchet and pawl, B is locked to A as long as forward
motion is maintained. But when the rider back pedals hard enough to overcome
the resistance of the joint, the pawl disengages, and B will revolve about the axis
of H into any other angular relation to A that may be desired. The teeth are so
arranged in the ratchet as to lock A and B in the most useful relative positions
for riding under more or less favourable conditions-say at the inclinations giving
full, half, or shortest effective lengths of crank, for uphill, level, or down gradient,
respectively.
Figures 1, 2 and 3 annexed to this specification show this arrangement of the
crank. Figure 1 is a back view. Figure 2 is a back view (with the nuts and
spring washer removed and the part A in another position). Figure 3 is a longi-
tudinal section.
In this case the part B of the crank has a ratchet wheel C fixed to it by means
of a pin H; and the part A carries a pawl which engages with the ratchet wheel C:
The pawl E is pressed outwards by a spring F.
The stress between the abutting parts of A and B is more or less severe and is
maintained by one or more back nuts properly adjusted on the pin H. In the
arrangements of the crank described it is this stress which prevents B from
turning about the axis of H during the ordinary upcast of the rider's foot, but

page_text: severe and continuous back pedalling (as when going down hill) overcomes the
resistance of the stress, which then gives rise to great friction between the abutting
parts of the joint. In this case A makes continuous revolutions about H, and
with B forms a kind of friction brake which keeps the machine under control.
Thus the crank is virtually a brake as well as a crank in the ordinary sense of
the word.
If a rule joint or a joint with a double stop be used so as to limit the rotation
of B to a semicircle or thereabout, between the extreme positions of maximum and
minimum length, the crank is then very efficient at full length or at the shorest
but will not afford any intermediate effective length, nor will it perform the
function of a friction brake.
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:-
1. A crank divided into two parts so that their relative positions can be varied
by turning one of them in one direction and secured by turning in the other
direction, substantially as described.
2. A crank divided into two parts connected by a stiff joint so that the
inclination of one part relative to that of the other can be varied by back pedalling
and secured in any one of several situations by forward pedalling, substantially
as described.
3. Cranks substantially as described and shown in the drawings.