Page:The Cycle Industry (1921).djvu/80

66 Particularly does this apply when free wheeling, because if the cranks be allowed to assume a horizontal position, one at 3 o'clock and the other at 9 o'clock, the rider can stand on the pedals and allow his knees to form the joint of a spring, the muscles of the calves and thighs being the springs. A skilled rider invariably adopts this position when free wheeling on rough roads and also instinctively falls into it when pedalling forward, with either a fixed or free wheel; with the former he slackens speed and bears his weight on the rising pedals, so raising his weight out of the saddle; with the latter he allows the machine to over run the cranks, by free wheeling momentarily, and at the same time raising his weight on the stationary pedals.

Motor-cycle Springing. The motor-cycle springing mechanism is a far bigger and more complicated proposition than that of a bicycle. Practically every motor bicycle has a spring front fork, although at one time only rigid forks were obtainable. Increase of speed and deterioration of road surfaces made spring forks a necessity, and no motor-cyclist would buy a machine now without one.

Lately there has been a tendency to spring both wheels of a motor bicycle, the generally accepted design being some form of leaf spring, which permits the rise and fall of the wheel against the action of the spring without throwing the wheel spindle out of its correct position in relation to the transmission.

The drawbacks to any form of springing are the rapid wear of the hinges or joints by which the wheel is connected to the springs and the springs to the rigid portion of the frame, and the bouncing effect that is set up by the uncontrolled movement of the springs.

Springs are also fitted to some designs of side-car wheels as well as to the body of the side-car.