sprocket wheel

A sprocket[1] or sprocket-wheel[2] is a profiled wheel with the teeth, or cogs,[3][4] that mesh with a chain, monitor or other perforated or indented material.[5][6] The name ‘sprocket’ applies generally to any wheel upon which radial projections engage a chain moving over it. It is distinguished from a gear in that sprockets should never be meshed together directly, and differs from a pulley for the reason that sprockets have teeth and pulleys are smooth.

Sprockets are used in bicycles, motorcycles, cars, tracked automobiles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or even to impart linear motion to a monitor, tape etc. Perhaps the most common form of sprocket could be within the bicycle, where 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. Early automobiles had been also largely powered by sprocket and chain system, a practice mainly copied from bicycles.

Sprockets are of various designs, no more than efficiency being claimed for each by its originator. Sprockets typically do not have a flange. Some sprockets used in mixture with timing belts have flanges to keep carefully the timing belt centered. 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. They could be run at high speed and some forms of chain are so built as to be noiseless also at high speed.