March 20, 1884] 



NA TURE 



Machines of this class have many defects. The feeble 

 steering power, combined with their unsymmetrical 

 driving, render them altogether untrustworthy. If any 

 power is applied to the driver, which can only have its 

 share of the weight upon it, it slips on the ground ; if the 

 machine is quickly stopped, owing to the small weight on 

 the steering wheel, it is apt to swing round and upset ; 

 nevertheless, those who are content with pottering about 

 on our wood pavement and gravel roads find this class of 

 machine answer their purpose, and owing to their cheap- 

 ness and simplicity they do not care to get a better. 



The second arrangement of the model, in which riders 

 must have recognised the Coventry Rotary, is free from 

 most of the defects of the form just described ; there is 

 more weight on the driver, but not enough to prevent its 

 being made to slip round ; there are two steering wheels 

 a long way apart, with plenty of weight upon them, so 

 that the guiding power in this type of tricycle is all that 

 can be desired. 



Let me now return to the first arrangement, in which 

 two parallel wheels are opposite one another. If by any 

 possibility both wheels could be driven, and yet be free 

 to go at difterent speeds, then there being so large a 

 weight on the drivers they could not be made to slip ; 

 the driving being symmetrical, most of the twisting strain 

 would be taken off the steering wheel, and still the 

 machine would be capable of rolling round a curve with 

 perfect freedom. 



All the methods of solving the problem of double 

 driving come under two heads, one depending on the 

 action of a clutch and the other on differential or balance 

 gear. 



The clutch action being the simplest, I shall describe 

 that first. In going round a corner the inner wheel must 

 lag behind, or the outer wheel must run ahead of the 

 other ; as either wheel may be inner or outer according 

 to the direction of the curve, each must be able to lag 

 behind or each must be able to run ahead. If both were 

 able to lag behind, the machine could not be driven for- 

 ward, and it would be of little use ; if both were able to 

 run ahead, the machine could not be driven backwards — 

 a matter of small importance. There is on the table a 

 large working model, showing how a four-sided wheel is 

 free to revolve in a ring, but is instantly seized when 

 turned the other way, owing to a jambing action on one 

 or more of four rollers. The four-sided wheel then can 

 be employed to drive the ring one way but not the other. 

 One of these " clutches ' or " friction grips '' is pkced at 

 each end of the crank shaft in the '• Cheylesmore '' tri- 

 cycle, and a chain round the ring of each drives the 

 corresponding wheel. The machine named is a rear- 

 seerer; the clutch is also employed in some front- 

 steerers. 



The other method of double driving depends on the 

 use of the well-known gear of three bevel wheels or of 

 some equivalent mechanism. If the a.xle of the middle 

 of the three wheels ii turned round the common axle of 

 the other two, the applied force is divided between those 

 two wheels, yet the pair are free to move relatively. Let 

 then the chain drive a wheel carrying the middle bevel, 

 and let the side bevels be connected with the two drivers. 

 Whatever happens, the power of the rider will be equally 

 divided between them, \et the machine will be free to roll 

 round a curve. 



There are a great number of devices which are 

 exactly equivalent to this the simplest of all, which 

 is known as Starley's gear. There is on the table a 

 beautiful model of the gear used in the Sparkbrook 

 tricjcle, which has been lent me by the makers of that 

 machine, Bown's ditierenlial gear, and some others ; 

 but time will not allo.v me to describe them. There 

 is one gear, however, which presents many peculiarities, 

 which I have devised, and which may be of interest. 

 A large working model is on the table. Between the 



conical edges of two wheels which are connected to the 

 drivers lie a series of balls, outside which is a ring with 

 sloping recesses. If the ring be turned by a chain or 

 otherwise, the balls jamb in the recesses as the rollers do 

 in the clutch gear. Nevertheless they are free to turn 

 about a radial axis, and so allow the two driven cone 

 wheels independent motion. The bursting strain on the 

 ring and the side thrust on the cones acting on rolling 

 balls balance one another. With this gear the rider can 

 cause the balls to jamb one way or both ways, and so 

 have or avoid the " free pedal " as he pleases. 



In almost all good designs of front-steering tricycles 

 the power applied to the cranks is transmitted to a dif- 

 ferential gear by a chain. The crank and connecting 

 rod have also been used to transmit the power, but then 

 the clutch is necessary. 



There is, however, another type of tricycle, in which 

 the use of cranks is avoided, among which may be men- 

 tioned the " Omnicycle," the " Merlin," and that highly 

 ingenious machine, the rowing tricycle. On the table 

 there is the Omnicycle gear. In all these the power is 

 applied direct to the circumference of a wheel or sector, 

 and so dead po'nts are avoided, which is a point in their 

 favour when meeting with much resistance. On the other 

 hand, the sudden starting and stopping of the feet in the 

 two former machines and of the body in the latter make 

 this type utterly unsuitable for obtaining anything more 

 than a moderate speed. In the Omnicycle ingenious 

 expanding drums are employed, so that the power may 

 be applied with different degrees of leverage according to 

 circumstances. 



There remains one type of tricycle which, for rapid 

 running, surpasses many : I refer to what is known as 

 the Humber pattern. So excellent is this form in this 

 respect that the leading manufacturers have, by turning 

 out machines on the same lines, paid the original makers 

 a coaipliment which is not altogether appreciated. This 

 pattern departs less from the ordinary bicycle than any 

 other; it is one, in fact, in which, instead of one, there 

 are two great wheels, giving width to the machine, 

 between which the power is divided by the usual differ- 

 ential gear. 



Having spoken of the differential gear and the clutch, 

 I had better show the comparative advantages and disad- 

 vantages of the two methods of double driving. With 

 the differential gear the same force is always applied to 

 each wheel, so in turning a corner the outer one, which 

 travels furthest, has most work expended upon it (work = 

 force X distance). In this respect the differential gear is 

 superior. On the other hand, when one wheel meets 

 with much resistance from mud or stones, and the other 

 with hardly any, the latter has still half the strength of 

 the rider spent upon it, which is clearly a mistake. With 

 a clutch-driven machine running straight, the wheels take 

 such a share of the rider's power as is proportional to the 

 resistance they individually meet. When the machine is 

 describing a curve, that is generally, only the inner 

 wheel is driven, and the machine is for the time only a 

 single driver, with the driver on the wrong side. 



I must now describe some devices which are attracting 

 I much attention at the present time, the speed and power 

 gears. Let us suppose there are two machines with wheels 

 I of diflerent sizes, but in other respects alike. Then each 

 turn will take the larger wheeled machine further than 

 the smaller. In going up a hill the larger wheel will take 

 its machine up a greater height than the other in one 

 revolution, which involves more work and therefore more 

 strength. If on the large wheel the chain pulley w ere in- 

 creased in size, then for the same speed of the treadles it 

 would not turn so quickly, it would not take the machine 

 so far up the hill as before, it would in fact be equivalent 

 to a smaller wheel, so that less strength than before would 

 be necessary. This diminution of speed, though of great 

 advantage when climbing a hill, is the reverse on the 



