A report on the 1924 Motor Cycle Show reads, in part:
The J.D. motor cycle which is exhibited on this stand is particularly interesting, in that it is friction driven. An endless chain connects the engine flywheel sprocket to a larger one, adjustably mounted on a bracket brazed to the chain stay of the machine. This driven sprocket is built up with a friction roller and runs on a double row of roller bearings. Special frictional material conveys the drive to a U-shaped rim attached to the rear wheel.
The friction roller is attached to a swinging arm and so mounted on the chain stay that the whole can be swung into and out of action by means of a lever on the handle bar. When engaged, contact is maintained by means of the springs acting on an extension lever of the drive arm, but the ingenious feature of the transmission is that the swing arm carrying the friction roller is so mounted on the chain stay that the stronger the pull exerted on the driving chain by the engine, the greater is the pressure applied to the friction roller. Two machines running under electric power demonstrate this transmission.
The engine is a two-stroke, of 116 c.c.
Bowden Wire, Ltd., Victoria Road, Willesden Junction, London, N.W. 10.
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