Home SCIENCE Understanding PLANETARY GEAR Set & How It Works

Understanding PLANETARY GEAR Set & How It Works

The planetary gear set, also known as the epicyclic gear train, is one of the most important and interesting inventions in engineering.

source/image: Learn Engineering

They are great speed variation mechanisms, and are often used in automobiles as a vital part of automatic transmissions. We will explore the secrets of the planetary gear set in this video. Watch the video by: Learn Engineering

The most basic form of planetary gearing involves three sets of gears with different degrees of freedom. Planet gears rotate around axes that revolve around a sun gear, which spins in place.


A ring gear binds the planets on the outside and is completely fixed. As a fact, the planetary Gear Set is much better than the standard gears and pinion reducers. The speed of the planetary gear depends upon its mode of application.