Epicyclic gearing

Epicyclic gearing (also called orbital gearing) is a type of gear system that uses a series of gears or ‘wheels’ to transfer motion between two different sized shafts. The first wheel is attached to a larger 'sun' wheel (the main wheel), while smaller gears (the 'planet' wheels) are placed on axles around the outside of the sun wheel. The planet wheels have small teeth around the inner edge which mesh with the larger teeth of the sun wheel. This allows power to be transferred from the high-speed outer planet wheel to the slow-speed inner sun wheel, and vice versa. This is especially useful when you need to transfer motion between two shafts that are not the same size, since epicyclic gearing can convert speed or torque from one shaft to another.