A multi-speed bicycle, by providing two or three different-sized driving sprockets and up to 11 (as of 2014) different-sized driven sprockets, allows up to 33 different gear ratios. In the case of bicycle chains, it is possible to modify the overall gear ratio of the chain drive by varying the diameter (and therefore, the tooth count) of the sprockets on each side of the chain. The earlier uses would now be seen as archaic. With time and common use of these devices, the overall wheel became known as a sprocket. The overall wheel was then termed a 'sprocket wheel'. The term 'sprocket' originally applied to the projection from the wheel that caught on the chain and provided the drive to it. It is distinguished from a gear in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have teeth and pulleys are smooth. The name 'sprocket' applies generally to any wheel upon which radial projections engage a chain passing over it. For other uses, see Sprocket (disambiguation).Ī sprocket or sprocket-wheel is a profiled wheel with teeth, or cogs, that mesh with a chain, track or other perforated or indented material. This article is about a gear or wheel with metal teeth. They can be run at high speed and some forms of chain are so constructed as to be noiseless even at high speed. Sprockets and chains are also used for power transmission from one shaft to another where slippage is not admissible, sprocket chains being used instead of belts or ropes and sprocket-wheels instead of pulleys. Some sprockets used with timing belts have flanges to keep the timing belt centered. Sprockets typically do not have a flange. Sprockets are of various designs, a maximum of efficiency being claimed for each by its originator. Early automobiles were also largely driven by sprocket and chain mechanism, a practice largely copied from bicycles. Perhaps the most common form of sprocket may be found in the bicycle, in which the pedal shaft carries a large sprocket-wheel, which drives a chain, which, in turn, drives a small sprocket on the axle of the rear wheel. Sprockets are used in bicycles, motorcycles, cars, tracked vehicles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear motion to a track, tape etc.

A sprocket or sprocket-wheel is a profiled wheel with teeth, or cogs, that mesh with a chain, track or other perforated or indented material.

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