1884.] on Bicycles and Tricycles in Theory and in Practice. 21 



four-sided wheel, tlieu, can be employed to drive the ring one way 

 but not the other. One of these " clutches " or " friction grips " 

 is placed at each end of the crank-shaft in the " Cheylesmore " tricycle, 

 and a chain round the ring of each drives the corresponding wheel. 

 The machine named is a rear steerer. 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 bevil wheels, or of some equivalent mechanism. 

 If the axle of the middle of the three wheels is 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 bevil and let the side bevils 

 be connected with the two drivers ; whatever happens, the power of the 

 rider will be equally divided between them, yet 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 

 tricycle which has been lent me by the makers of that machine, Bown's 

 differential gear, and some others ; but time will not allow 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 is 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 another set of 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. 



Having spoken of the differential gear and the clutch, I had better 

 show the comparative advantages and disadvantages 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 exjDended upon it (work = force 

 X distance). In this respect the differential gear is superior. On 

 the other hand, when one wheel meets wdth 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. 



In almost all good designs of front-steering tricycles, the power 



