Variable motion control devices and methods of use. The devices and methods relate to providing an output, such as a rotational shaft output, transmitted from a rotational shaft input, with the output varying based on a control input. The devices and methods are used, for example, to provide a variable output for use with a compressor, power take off, or transmission or differential application. To provide the variable output, the devices and methods include use of mechanical component systems, such as spur gear planetary systems, ring gear planetary systems, bevel gear arrangements, or combinations of such features. The control input is implemented, for example, by arrangements of bindably meshed gears, tension between pulleys joined by belts or similar arrangements of sprockets and chains, use of magnetic clutches, hydraulic or pneumatic controls, or braking devices.