idlers

An idler is a device or person that remains passive. In mechanical engineering, an idler is a passive wheel or roller that guides, tensions, or supports a belt, chain, or track. The term idlers is used for multiple such components. In everyday language, an idler may refer to a person who is idle or habitually inactive.

In belt and pulley systems, an idler pulley is a non-drive wheel that maintains belt tension and guides the belt along its path. Idlers can be fixed in place or mounted on adjustable frames to act as tensioners. In conveyor setups, several types of idlers are used, including return idlers (under the belt), carrying idlers that support the load, and impact or troughing idlers that shape the belt and absorb shock.

An idler gear or sprocket is used to redirect motion or adjust spacing between other gears or chains, without altering the overall gear ratio. Idlers help maintain proper meshing and center distance in gear trains and chain drives, and may serve to route cables or belts around obstacles in machinery.

People may be referred to as idlers when they do not work or engage in productive activity. In vehicles and machinery, idling describes the engine running at low speed without movement, or the period when the engine is running to maintain systems or readiness.