Gears transmit motion and force in machines, with types like spur, bevel, worm and wormwheel, rack and pinion, meshed gears, and threaded bars, selected based on speed, direction, force, space ...

Gear ratios, which measure the input speed against the output speed, are a critical indicator of what type of gearbox is appropriate in a given application. Low gear ratios tend to transmit power more ...

This article was updated March 6, 2023. It was originally published Aug. 1, 2001. Gears—even plastic ones—need to be lubricated if engineers are going to coax the best performance out of them ...