People’s proud invention of gears was preceded by mindless evolution: The tiny points on the legs of juvenile planthopper insects move like intermeshing cogs. Those cogs in young Issus coleoptratus ...

Backlash, a clearance between mating gear teeth, is built into speed reducers to let the gears mesh without binding and to provide space for a film of lubricating oil between the teeth. This prevents ...

Gears are compact, motion-control components that determine a driven machine's speed, torque, and direction of rotation. To turn smoothly, they require lubrication — oil — which forms a film between ...