<P> 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 . </P> <P> An idler - wheel may be used as part of a friction drive mechanism, as in a phonograph, or as a belt tensioner in a belt drive system . </P> <P> 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 . </P> <P> An idler gear does not affect the gear ratio between the input and output shafts . 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 . </P>

Where can a simple gear with idler be used