An epicyclic or planetary gear system consists of one or more planet gears that revolve around a central sun gear. The planet gears are mounted on a carrier that can also rotate relative to the sun gear. An outer ring gear meshes with the planet gears. Epicyclic gearing allows for large gear ratios in a small space through the planetary motion of gears revolving and rotating simultaneously. Applications include marine gearboxes, electric screwdrivers, lathe back gears, hoists, pulley blocks, wristwatches, bicycle transmissions, and automobile transmissions.