Planetary Gearboxes

A gearbox provides speed and torque conversions from a rotating power source to another device using gear ratios. The most common use is in motor vehicles, where the gearbox adapts the output of the internal combustion engines to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The gearbox reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Gearbox is also used on pedal bicycles, fixed machines, and anywhere else rotational speed and torque needs to be adapted. Often, a gearbox will have multiple gear ratios (or simply "gears"), with the ability to switch between them as speed varies. This switching may be done manually (by the operator), or automatically. Directional (forward and reverse) control may also be provided. Single-ratio gearbox also exist, which simply change the speed and torque (and sometimes direction) of motor output.