page_title: Idler-wheel
section_title: Idler gear
hierarchical_section_title: Idler-wheel / Idler gear
caption_attribution_description: English: Photograph of spur gears on a piece of farm equipment.
context_page_description: An idler-wheel is a wheel which serves only to transmit rotation from one shaft to another, in applications where it is undesirable to connect them directly. For example, connecting a motor to the platter of a phonograph, or the crankshaft-to-camshaft gear train of an automobile.
  Because it does no work itself, it is called an "idler".
context_section_description: 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.
caption: Gears in a machine. The middle, medium-sized gear is an idler gear.
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