Sprocket

This article is about a gear or wheel with metal teeth. For the television comedy skit, see Sprockets (television).

16T type sprocket
Do: Sprocket diameter
Dp: Pitch diameter

A sprocket is a profiled wheel with metal teeth that meshes with a chain, track or other perforated or indented material. It is distinguished from a gear in that sprockets are never meshed together directly, and from a pulley by not usually having a flange at each side.

Sprockets are used in bicycles, motorcycles, cars, tanks, 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.

Cycles

In the case of bicycle chains by varying the diameter (and therefore, the tooth count) of the sprockets on each side of the chain, modifying the overall gear ratio of the chain drive is possible. This is the basis of Derailleur gears. A 10-speed bicycle, by providing two different-sized driving sprockets and five different-sized driven sprockets, allows up to ten different gear ratios. The resulting lower gear ratios make the bike easier to pedal up hills while the higher gear ratios make the bike faster to pedal on flat roads. In a similar way, manually changing the sprockets on a motorcycle can change the characteristics of acceleration and top speed by modifying the final drive gear ratio.

Tracked vehicles

A tank sprocket

In the case of vehicles with caterpillar tracks the engine-driven toothed-wheel transmitting motion to the tracks is known as the drive sprocket and may be positioned at the front or back of the vehicle, or in some cases, both.

Film and paper

Sprockets are used in the film transport mechanisms of movie projectors and movie cameras. In this case, the sprocket wheels engage film perforations in the film stock.

Sprocket feed was also used for punched tape and is used for paper feed to some computer printers.

See also

• Toothed belt