Page:The Cycle Industry (1921).djvu/77

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and proved unequal to the task of the double work. The modern motor cycle gear is now almost wholly of the countershaft type, and contained in a separate box or case like the change speed of most motor-cars. The Sturmey-Archer Co. and the B.S.A. Co. have specialized in these gears, but many other firms make their own.

Still another popular type of gear used by two firms in particular, Rudge-Whitworth, Ltd. and Zenith Motors, Ltd., is the expanding pulley type. In both instances a belt is used but in the Rudge-Whitworth case both front and rear pulleys expand and contract, and in the Zenith patent only the engine pulley expands and the slack of the belt is taken up by sliding the rear wheel from and to the engine as the call for a low or high-gear ratio is desired.

For a technical treatise on motor cycle gears, I would refer readers to handbooks published by the proprietors of The Modern Cycle, Iliffe & Sons, Ltd., 20 Tudor Street, London, E.C.4.