Idler-wheel

From Wikipedia, the free encyclopedia

An idler-wheel drive is a system used to transmit the rotation of the main shaft of a motor to another rotating device. For example the platter of a record-reproducing turntable or the crankshaft-to-camshaft gear train of an automobile.

An idler gear is a gear wheel that is inserted between two or more other gear wheels.

The purpose of an idler gear can be two-fold. Firstly, the idler gear will change the direction of rotation of the output shaft. Secondly, an idler gear can assist to reduce the size of the input/output gears whilst maintaining the spacing of the shafts.

An idler gear does not affect the gear ratio between the input and output shafts. Idler Gears

Note that in a sequence of gears chained together, the ratio depends only on the number of teeth on the first and last gear. The intermediate gears, regardless of their size, do not alter the overall gear ratio of the chain. But, of course, the addition of each intermediate gear reverses the direction of rotation of the final gear.

An intermediate gear which doesn't drive a shaft to perform any work is called an idler gear. Sometimes, a single idler gear is used to reverse the direction, in which case it may be referred to as a reverse idler. For instance, the typical automobile manual transmission engages reverse gear by means of inserting a reverse idler between two gears.

Idler gears can also transmit rotation among distant shafts in situations where it would be impractical to simply make the distant gears larger to bring them together. Not only do larger gears occupy more space, but the mass and rotational inertia (moment of inertia) of a gear is quadratic in the length of its radius. Instead of idler gears, of course, a toothed belt or chain can be used to transmit torque over distance.

This article does not cite any references or sources. (December 2007) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed.