Sprocket


Sprocket
16 tooth sprocket. Do = Sprocket diameter. Dp = Pitch diameter
A sprocket and roller chain

A sprocket[1] or sprocket-wheel[2] is a profiled wheel with teeth, cogs,[3] or even sprockets[4] that mesh with a chain, track or other perforated or indented material.[5][6] The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over 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.

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. Perhaps the commonest form of sprocket is 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. Early automobiles were also largely driven by sprocket and chain mechanism, a practice largely copied from bicycles.

Sprockets are of various designs, a maximum of efficiency being claimed for each by its originator. Sprockets typically do not have a flange. Some sprockets used with timing belts have flanges to keep 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 can be run at high speed and some forms of chain are so constructed as to be noiseless even at high speed.

Contents

Transportation

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. 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

Tread drive sprocket of the Leclerc main battle tank (2006).

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. There may also be a third sprocket, elevated, driving the track.

Film and paper

Moving picture mechanism from 1914. The sprocket wheels a, b, and c engage and transport the film. a and b move with uniform velocity and c indexes each frame of the film into place for projection.

Sprockets are used in the film transport mechanisms of movie projectors and movie cameras.[7] 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.

External links

See also

References

  1. ^ "Sprocket - Definition". Merriam-Webster. http://www.merriam-webster.com/dictionary/sprocket. Retrieved 2011-11-14. "sprocket, n. 1: a toothed wheel whose teeth engage the links of a chain" 
  2. ^ Oxford English Dictionary (2nd ed.). Oxford University Press. 1989. "sprocket, n. 2. b. ellipt. A sprocket-wheel, esp. that of a cycle; and (Cinematogr.), one that propels film by engaging with perforations along its edge." 
  3. ^ Oxford English Dictionary (2nd ed.). Oxford University Press. 1989. "cog, n. 1. a. One of a series of teeth or similar projections on the circumference of a wheel, or the side of a bar, etc., which, by engaging with corresponding projections on another wheel, etc., transmit or receive motion." 
  4. ^ Oxford English Dictionary (2nd ed.). Oxford University Press. 1989. "sprocket, n. 2. a. A projection (either forked or simple) from the rim of a wheel, engaging with the links of a chain." 
  5. ^ The Encyclopedia Americana: a library of universal knowledge, sprocket. pg 460
  6. ^ Elements of machine design By Oscar Adolph Leutwiler
  7. ^ Motion picture handbook By Frank Herbert Richardson

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Look at other dictionaries:

  • Sprocket — Sprock et (spr[o^]k [e^]t), n. [Etymology uncertain.] (Mach.) (a) A tooth or projection, as on the periphery of a wheel, shaped so as to engage with a chain. (b) A sprocket wheel. [Webster 1913 Suppl.] …   The Collaborative International Dictionary of English

  • sprocket — ► NOUN 1) each of several projections on the rim of a wheel that engage with the links of a chain or with holes in film, tape, or paper. 2) (also sprocket wheel) a wheel with projections of this kind. ORIGIN originally denoting a triangular piece …   English terms dictionary

  • sprocket — [spräk′it] n. [Early ModE < ?] 1. any of a number of teeth or points, as on the rim of a wheel, arranged to fit into the links of a chain 2. a wheel fitted with sprockets on its outer rim, used in a chain drive: in full sprocket wheel …   English World dictionary

  • sprocket — 1530s, originally a carpenters word for a piece of timber used in framing, of unknown origin. The meaning projection from the rim of a wheel that engages the links of a chain is first recorded 1750 …   Etymology dictionary

  • sprocket — A disc with teeth on its circumference for driving a chain, a general term that applies both to chainrings and to freewheel cogs. See camshaft drive sprocket camshaft sprocket crankshaft sprocket driven sprocket drive sprocket …   Dictionary of automotive terms

  • sprocket — sprock|et [ˈsprɔkıt US ˈspra: ] n 1.) also sprocket wheel a wheel with ↑teeth (=parts along the edge) that fit into and turn a bicycle chain, a photographic film with holes etc 2.) one of the teeth on a sprocket wheel …   Dictionary of contemporary English

  • sprocket — UK [ˈsprɒkɪt] / US [ˈsprɑkɪt] noun [countable] Word forms sprocket : singular sprocket plural sprockets one of several parts on the outside of a wheel that fit into the holes in something such as a chain or a piece of film and pull or turn it… …   English dictionary

  • sprocket — /sprok it/, n. 1. Mach. a. Also called chainwheel, sprocket wheel. a toothed wheel engaging with a conveyor or power chain. b. one tooth of such a wheel. 2. Carpentry. a wedge shaped piece of wood extending a sloping roof over the eaves with a… …   Universalium

  • sprocket — [[t]sprɒ̱kɪt[/t]] sprockets N COUNT A sprocket is a wheel with teeth around the outer edge that fit into the holes in a chain or a length of film or tape in order to move it round …   English dictionary

  • sprocket — sprock·et || sprÉ‘kɪt / sprÉ’k n. wheel with teeth or cogs to engage the links of a chain, sprocket wheel; tooth of a wheel which engages the links of a chain …   English contemporary dictionary