90 



NA TURE 



[November 23, 1899 



during the lower portion of its circular path ; but unless special 

 devices are provided to enable them to draw the pedal upwards 

 throughout a much larger arc, they cannot make use of the 

 pulling muscles in a satisfactory manner. In order to do this 

 we have bent our pedal plates slightly forward, as shown on 

 Fig. 2, and we have prepared shoe plates of a form which 

 «nable them to hook into the back plate of the pedal. 



It will be seen that our pulling device differs essentially from 

 toe clips, which do not enable the upward pull being made 

 unless the toe is pointing downwards. We find that this 

 militates against good ankling action, and has a tendency to 

 induce cramp in the calf muscles ; on the contrary with our 

 pulling device, the calf muscles may be quite inert during the 

 <upwa^ stroke, the shank acting merely as a connecting rod in 

 tension. It will be seen that the pull stroke enables us to reduce 



Fig. 



Fig. 3. — Crompton patent pedal. 



tlie minimum pressure on the downward stroke, which is neces- 

 -sary to produce the average pressure F. Our experience of this 

 subject is that it takes a long time to teach these muscles, which 

 are seldom used except by running men, to take up their share 

 of the work of cycle propulsion, and those who begin to use 

 the pull stroke will find that, although it does greatly reduce 

 the pushing strain made by the upper thigh muscles in hill 

 climbing, yet that the thought and attention required to apply 

 it under ordinary conditions of riding is so considerable that 

 they do not persevere in practising it. It is our opinion that 

 it is well worth while for a rider to cultivate the pull stroke. 

 The pulling muscles are large and powerful, their elastic limit 

 as high, it is not easy to overstrain them, and the extra brain 



decreased, the force required to do this not coming from the 

 muscles which move his leg, but from the calf muscles, which 

 take a purchase, not against the saddle, as would be the case if 

 he did not use ankle action, but against the pedal itself, so that 

 the kinetic energy which is taken out of the leg in stopping its 

 descending weight is usefully employed in propelling the cycle, 

 and thus there is a great saving of energy by good ankle action. 

 If we take curve Fig. 4, the vertical Hnes of which represent 

 i velocity, the velocity downwards being represented by the 

 I vertical lines below the base line A B, and the velocities upward 

 by the vertical line above it ; if also we take the horizontal line 

 ! to represent time when travelling with 60 gear and 6-inch 

 cranks at 1071 miles an hour, M being 5, a complete revolution 

 is made in one second, and the upward and downward velocity 

 of the leg at any moment is shown by the curve. Now rate of 

 acceleration is change of velocity at a given time, and therefore 

 the acceleration at any point is represented by change of 

 velocity in a given time at that point. Suppose the acceleration 

 to remain the same throughout that time as it is at the point P, 

 the curve would describe a tangent to that curve at the point P 

 and the acceleration — that is, the change of velocity divided by 

 the time — would equal the tangent of the angle formed by the 

 tangent of the curve with the base line. 



You will notice that up to 90 degrees the tangent increases as 

 the angle increases, therefore the steeper the curve at any point 

 the greater is the acceleration at that point, and the greater the 

 acceleration the greater the rate at which kinetic energy has to 

 be taken out of the leg, and therefore the greater necessity for 

 ankling. If, however, when riding at the same speed we use 

 9-inch cranks with 90 gear M is still 5, but the curve takes the 

 form of the black line. You will see that the curve is obviously 

 of the same relative shape as the red curve, but it is drawn out 

 lengthways in the proportion of 6 to 9, and therefore the angles 

 which the curve makes with the base line at any point is less 

 than the angle which the red curve makes at a corresponding 

 point. The tangents of the angle of steepness vary as 6 to 9, 

 and the rate at which acceleration is reduced is also as 

 9 to 6, so that the necessity for careful ankling is in this case 

 reduced in the same proportion, in other words, for equal 



-Curve B shows vertical velocity of pedal of 6 inch crank, 60 gear ! 

 .. A ,, ,, „ 9 ,, „ 90 ,, J 



of 1071 miles per hour. 



waste that is required during the process of teaching these 

 muscles is soon found to be reduced, as by practice these 

 muscles automatically take up their share of the work. 



It has been said that increased crank length militates against 

 proper ankle action. The use of ankle action is not generally 

 understood. The moving portion of a man's leg has consider- 

 able weight, when it is at the top of the stroke it possesses 

 potential energy which is changed into kinetic energy as the leg 

 descends, when it gets at the bottom of the stroke it stops going 

 downwards and commences to rise, and the kinetic energy due to 

 the downward movement of the leg has to be given up. What 

 becomes of it? If the stopping of the leg is done by the same 

 muscles which lift the leg there is a considerable waste of power, 

 but if towards the lower end of the downward stroke the man 

 beg ins to flex his calf muscles the velocity of his leg is gradually 



efficiency long cranks do not require such careful ankling as 

 short ones ; although as more time is given in which to carry 

 out such ankling, it is easier for the average rider to acquire it to 

 a sufficient extent. 



It is unnecessary to deal at any length with the question of 

 saddle soreness. We cannot find that lengthened cranks have 

 made any notable difference in this respect. Those who were 

 liable to soreness with short cranks have not had this liability 

 increased, but rather decreased by the new system. The position 

 of the saddle has of course to be carefully attended to in riding 

 with the lengthened cranks. As to the bad steering, this is an 

 imaginary fault. We find that a well-designed machine will 

 steer just as well, hands off, with long cranks as with short ones. 

 It is true that the long cranks do introduce some extra strains 

 into the cycle. The cranks themselves have to be carefully 



NO. 1569, VOL. 61 J 



