Improvements in Cycle Gear.
Year: 1894

page_text: Date of Application, 15th Nov., 1894
Complete Specification Left, 15th Aug., 1895-Accepted, 15th Nov., 1895
Improvements in Cycle Gear.
DUNCAN KENNETH CAMPBELL RUSSELL 2 Albert Terrace, Edinburgh, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in cycle gear to reduce friction. Hitherto
there has been no arrangement of the radius of the crank chain wheel, crank
gear wheel, or connecting rod cranks, of equal size with the radius of the pedal
crank.
The current practice is to have the crank chain wheel, gear wheel, or connecting
rod crank, of less radius than the radius of the pedal crank.
My invention consists in having the radius of the crank chain wheel, crank gear
wheel, or connecting rod cranks at least equal to the radius of the pedal crank;
and, if desired, as much greater than the radius of the pedal crank as the
convenience of the legs of the rider will permit.of.
That is to say-If my pedal crank is 6 inches long, my crank chain wheel, or
crank gear wheel or connecting rod crank will have a 6 inch radius or 12 inches
diameter at the least, and a 16 inch or 18 inch diameter as the rider finds con-
venient. For the larger diameter the axle must be high enough to keep the wheel
clear of the ground and dirt.
The improvement in reducing friction, and so enabling the rider to travel quicker
and longer, and reducing tear and wear of the bearings can be demonstrated
mathematically as follows:-
In an ordinary cycle, if the pedal crank is 6 inches long, and the crank chain
wheel 3 inches radius or 6 inches diameter, and the rider weighs 2 ewt.; the thrust
on the pedal will be 2 cwt. and the corresponding pull on the chain will be 4 cwt.
minus the loss by friction which can be disregarded in the demonstration. Hence
the friction on the pedal crank axle will be 2 x 4 = 6 cwt. multiplied by the
coefficient of friction for certain revolutions per minute, and the friction on the
rear wheel will be the pull of the chain, namely 4 cwt. plus one sixteenth of 4 cwt.
of leverage, if the rear wheel is 24 inches diameter, equals 4 cwt. multiplied
by 4 times the first coefficient of friction, if the machine is geared 1 to 4. Let the
coefficient of friction for the crank axle be 05. Then the friction on the crank
axle equals 6 cwt. x .05 300 cwt. of friction; and on the rear wheel '05 × 4
= 2 × 4 cwt. = 850 of friction, or a total friction of 1.300 x 850 = 1.150 cwt.
Now let us take the improved crank chain wheel and gear wheel &c., at 8 inches
radius or 16 inches diameter with the same 6 inch pedal crank and 24 inch rear
wheel and geared 1 to 4 as before.
The thrust on the pedal is 2 cwt. as before the pull on the chain is as 8 inches
radius to 6 inches pedal radius, so is 2 cwt. to 14 cwt., the pull on the chain,
admitting of a lighter chain and frame and the total thrust 3 cwt. x '05 as
before 175 cwt. instead of 300 cwt. of friction as in the ordinary cycle.
-
And the friction on the rear wheel is '05 x 4 = 2 x (1 cwt. of chain pull,
plus 1 cwt. divided by 6) the leverage on the rear wheel of 24 inches = 2 ×
| (1 × 1 × ) = 350 cwt. of friction, instead of 850 cwt. and the total friction on
both wheels 175 x 350=525 cwt. of friction in the improved crank chain
wheel against a total of 1.150 cwt. in the ordinary cycle, or a saving of over 50 per
cent. in favour of the improvement of 16 inches diameter, or a saving of 625 cwt.
of friction proportionately greater for 18 inches diameter.
-

page_text: 1
This saving in friction of 625 cwt. in the case of the 16-inch wheel and 450 cwt.
as in the case of the 12-inch wheel as shewn in the demonstration, enables me to use
a lighter gear than ordinarily used, and consequently reduces the momentum of the
legs lost when racing, upon the low dead centre, or less effective arc of the crank,
which is very great when going fast, and rapidly tires the muscles when at their
extreme limit of effort, whereas when the stroke is slower there are fewer lost
momentums.
Any desired gear can be used with the large crank chain wheel, but a useful size
is a 13 inches crank chain wheel with a 6 inch crank and a rear wheel of inches
with a 24 inch road wheel making a 72 inch stroke, or with a 26 inch road wheel
making a 78 inch stroke.
This crank chain wheel is protected by the crank when leaning on a pavement-
with it the concussion on the balls is always the same as from the pedal thrust,
causing less and uniform wear of the balls and ball seat and axle, instead of at
present a pedal thrust concussion of 2 cwt. and a chain thrust of 5 cwt. in a machine
just measured. The chain likewise is only half the weight of the present chain,
having to carry 2 ewt. only, in the case of the 13 inch chain wheel and 6 inch
crank, instead of 5 cwt. and the wheel periphery also to carry 2 cwt. instead
of 5 cwt.
Racing machines can disregard the ordinary disadvantages of dirt on the road,
and so the 16 inch chain wheel has only a chain and periphery to carry 1 cwt. and
the rear wheel the same whether set at 1 to 3 or 1 to 4 or any intermediate gear,
but should carry 2 cwt. so as to be interchangeable with a 13 inch crank chain
wheel and the 18 inch wheel a still slighter chain and wheel periphery.
With the large racing wheel I prefer a steel band with punctures instead of the
chain, as both the strain and flexion are within its limits of tensile strength and
clasticity.
The larger wheels reduce the rapidity and amount of rotation of each link of the
chain upon its pin, and so reduce friction in exact proportion to the diameter of the
wheels, as a ship comes round a circle with a definite helm.
The excessive chain strain tells severely against the very small axle of the rear
wheel as it is supported by such small points or ares and so the less chain strain
admits of a smaller rear axle, and so lengthens the leverage to over-come
friction inch axle has one half the (friction) or resistance of a inch axle due
to leverage.
Dated this 14th day of November 1894.
I, DUNCAN KENNETH CAMPBELL RUSSELL, of 2 Albert Terrace, Edinburgh,
Civil 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 improvements in cycle gear to reduce friction. Hitherto
there has been no arrangement of the radius of the crank chain or gear wheel, or
connecting rod cranks of equal size with the radius of the pedal crank, or
approaching that limit defined by the least width of tread, the centre of weight on
the axle, longitudinally, and the projection of the chain thrust frame.
>
The current practice is to have the crank chain wheel, gear wheel, or connecting
rod crank of less radius than the radius of the pedal crank.

page_text: My invention consists in each and a combination of
following constructions, viz.―
an or any
First In having the radius of the crank chain wheel, crank gear wheel or
connecting rod cranks at least equal to the radius of the pedal crank: or, as large
and as near to that radius as attainable, limited by and compatible with the least
width of tread, the crank axle or centre of weight on the shortest longitudinal
axis, and the least or necessary projection of the chain thrust frame, the larger the
chain wheel the further back and so further out does it approach the back or
thrust frame, and as the large wheel is placed further out so does it in turn push
out the crank-to that extent does it increase the tread or distance apart of the
cranks; but as both cranks must be equidistant from the centre of the saddle to
prevent oscillation, hence a similar increment is added to the tread on the
opposite side; hence doubling the tread by the lateral movement of the chain
wheel.
Second: In having small axles, or small cone or ball race periphery.
The improvement in reducing friction and so enabling the rider to travel
quicker and longer, and in reducing tear and wear of the bearings can be
demonstrated mathematically as follows:-
In an ordinary cycle, if the pedal crank is six inches long, and the crank chain
wheel three inches radius or six inches diameter, and the rider weigbs two hundred-
weights, the thrust on the pedal will be two hundredweights, and the corre-
sponding pull on the chain will be four hundredweights, minus the loss by friction
Hence the friction on the
which can be disregarded in the demonstration.
pedal crank axle will be two plus four, equals six hundredweights, multiplied by
the co-efficient of friction for certain revolutions per minute, and the friction on
the rear wheel will be the pull of the chain, namely four hundred-weights, plus one
sixteenth of four hundredweights of leverage if the rear wheel is twenty-four
inches diameter, equals four and one-fourth hundredweights, multiplied by four
times the first co-efficient of friction, if the machine is geared one to four. Let the
co-efficient of friction for the crank axle be point cipher five-Then the friction
on the crank axle equals six hundred weights multiplied by point cipher five, equals
point three hundredweights of friction and on the rear wheel point cipher five
multiplied by four, equals point two, and multiplied by four and one-fourth hundred-
weights, equals point eight hundred and fifty hundredweights of friction: or a
total friction of point three hundred plus point eight hundred and fifty, equals one
point one hundred and fifty hundred weights.
Now, let us take the improved crank chain wheel and gear wheel, et cetera, at
eight inches radius, or sixteen inches diameter, with the same six inch pedal crank
and twenty-four inch rear wheel, and geared one to four as before :-
The thrust on the pedal is two hundredweights as before the pull on the chain
is as eight inches radius to six inches pedal radius, so is two hundredweights to one
and a half hundredweights: the pull on the chain admitting of a lighter chain
and frame, and the total thrust three and a half hundredweights multiplied by point
cipher five as before, equals point one hundred and seventy-five hundredweights,
instead of point three hundred hundredweights of friction as in the ordinary
cycle.
And the friction on the rear wheel is point cipher five multiplied by four, equals
point two, and multiplied by one and a half hundred weights of chain pull, plus one
and a half hundredweights divided by six, the leverage on the rear wheel of
twenty-four inches, equais point two, multiplied by one and a half plus one-fourth,
quals point three hundred and fifty hundredweights of friction, instead of point
eight hundred and fifty hundredweights, and the total friction on both wheels,
equals point one hundred and seventy-five, plus three hundred and fifty, equals
point five hundred and twenty five hundredweights of friction in the improved
crank chain wheel, against a total of oue point one hundred and fifty hundred-
weights in the ordinary cycle, or a saving of over fifty per cent. in favour of the
improvement of sixteen inches diameter, or a saving of point six hundred and

page_text: twenty-five hundredweights of friction, and proportionately greater for eighteen
inches diameter.
This saving in friction of point six hundred and twenty-five hundredweights in
the case of the sixteen inch wheel, and of point four hundred and fifty hundred-
weights as in the case of the twelve inch wheel as shewn in the demonstration,
enables me to use a higher gear than ordinarily used, and consequently reduces the
momentum of the legs lost when racing, upon the low dead centre, or less effective
arc of the crank, which is very great when going fast and rapidly tires the muscles
when at their extreme limit of effort: whereas when the stroke is slower there are
fewer lost momentums.
Any desired gear can be used with the large crank chain wheel, but a useful
size is a thirty-eight toothed chain wheel with a fourteen toothed rear wheel.
This crank chain wheel protected by the crank or pedal when leaning on a
pavement with it the concussion on the balls is always the same as from the pedal
thrust, causing less and uniform wear of the balls and ball seat, and axle, instead
of at present a pedal thrust concussion of two hundred weights, and a chain thrust
of five hundredweights, in a machine just measured. The chain likewise is only
half the weight of the present chain, having to carry two hundredweights only in
the case of an equal crank and wheel, instead of five hundred weights and the
wheel periphery also to carry two hundredweights, instead of five hundred-
weights.
With the large racing wheel I prefer to use a steel band with punctures instead
of the ordinary chain, the edges of the punctures being raised to present a rounded
surface to the teeth of the wheel.
The excessive chain strain tells severely against the very small axle of the rear
wheel, and the small balls which support it by such small points or ares, and so the
less chain strain admits of a smaller rear axle, and so lengthens the leverage to
overcome friction, and reduces the travel of the balls in each revolution,-one
fourth inch axle having one half the friction of a half inch axle due to leverage,
and one half the friction due to one half the travel, or one-fourth the combined
friction of leverage and travel.
In order to give effect to this mathematical fact of reduced friction from a small
axle, I employ a special bearing as shewn in Figure 1 of the accompanying
drawings.
Where the cone is reduced in the ball race from the usual to or nearly a
half, by making each cone and its corresponding half of the axle in one solid
piece, the adjustment of the said axle being made by a long socket joint in the
centre and so making the balls to roll on the axle.
Or as modifications I may employ the following arrangements which may be
cheaper to manufacture but not so efficient as that shewn in Figure 1. That is to
say 1 employ a solid bearing on one side only as in Figure 1, and on the other side
I may employ a screwed cone nutted outside the frame, or a plain cone fixed by
soldering or otherwise to the frame, and I may adjust the said bearings by means
of a small axle and a nut or nuts on the outside.
Or may employ cones fixed in both side frames and employ a tie rod passing
from side to side and provided with outside nuts for adjustment.
Figure 2 shews part of a chain wheel of forty-five teeth with the crank cast in
one piece along with it, the crank end being inside the wheel rim, which saves a
small amount of width of tread-as the cranks are placed equi-distant from the
centre the saving is doubled by a like amount on the other side. This is similar
to the old Scotch yarn winder.
In the accompanying drawings illustrating how my invention may be conveniently
carried into practice:
Figure 1 represents a simple bearing in which
A is the axle jointed in the centre by a long socket with an internal jam
nut K:

page_text: Figure represene
wheel.
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 I make no
claim to the construction of axle and bearing shown, except when the axle is small,
but what I claim is :-
1st. In cycle gear the employment of an enlarged chain wheel, of the radius of
the crank, such as can be used with advantage having due regard to a small tread,
substantially as herein before set forth and shown in the accompanying drawings.
2nd. In cycle gear the employment of a small axle jointed in the middle by
means of a ferrule and nuts, and the ends solid cones fixed into, or screwed and
nutted outside the frame substantially as hereinbefore set forth and shown in the
accompanying drawings.
3rd. In cycle gear the employment of a small axle constructed and arranged
substantially as set forth.
4th. In cycle gear the combination of an enlarged chain wheel and small axle
bearing substantially as herein before set forth and shown in the accompanying
drawings.
5th. In cycle gear the combination with a small axle or tie rod of one or more
detached and screwed or fixed cones substantially as hereinbefore set forth.
6th. In cycle gear the employment of a steel band with punctures, in lieu of a
chain, the punctures having raised and rounded edges substantially as hereinbefore
set forth.
7th. The general arrangement, construction and combination of the various parts
constituting my improvements in cycle gear, substantially as hereinbefore set forth
and shown in the accompanying drawings.
Dated this 7th dow of sunst 1805
JOHNSONS,
115 St. Vincent Street, Glasgow, Applicant's Agents.