mechanicalfarm-blog - Tumblr blog

[mechanicalfarm-blog]

A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the rear wheel. Shaft drives were introduced over a century ago but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleur. If roller bearing could be accurately and cheaply made by machinery, it is possible that bearing of this description might supplant, to a great extent.

The pinion drive shaft system eliminates eight points of chain sliding friction and replaces it with just two points of higher-efficiency bearing rolling friction. Shaft-driven bikes have a roller and pinion where a conventional bike would have its chainring. Pinion meshes with the roller bearing provided at the rear side of the shaft. The roller and pinion allow the axis of the drive torque from the pedals to be turned through 90degrees. The driveshaft then has another roller bearing near the rear wheel hub which meshes with a pinion on the hub where the rear sprocket would be on a conventional bike, canceling out the first drive torque change of axis.

An automotive drive shaft transmits power from the engine to the differential gear of a rear-wheel drive vehicle. The driveshaft is usually manufactured in two pieces to increase the fundamental bending natural frequency because the bending natural frequency of a shaft is inversely proportional to the square of beam length and proportional to the square root of the specific modulus which increases the total weight of an automotive vehicle and decreases fuel efficiency.