An epicyclic gear teach (also referred to as planetary gear) contains two gears mounted to ensure that the centre of one equipment revolves around the centre of the other. A carrier connects the centres of the two gears and rotates to transport one gear, Stainless Steel Chain called the earth gear or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gears mesh so that their pitch circles roll without slide. A point on the pitch circle of the planet equipment traces an epicycloid curve. In this simplified case, sunlight gear is set and the planetary equipment(s) roll around the sun gear.

An epicyclic gear teach can be assembled so the planet equipment rolls within the pitch circle of a fixed, outer gear ring, or ring gear, sometimes called an annular gear. In this instance, the curve traced by a spot on the pitch circle of the planet is a hypocycloid.

The mixture of epicycle gear trains with a planet engaging both a sun gear and a ring gear is named a planetary gear train.[1][2] In cases like this, the ring equipment is usually fixed and the sun gear is driven.

Epicyclic gears obtain name from their earliest program, that was the modelling of the movements of the planets in the heavens. Believing the planets, as everything in the heavens, to be perfect, they could just travel in ideal circles, but their motions as viewed from Earth cannot end up being reconciled with circular movement. At around 500 BC, the Greeks created the idea of epicycles, of circles traveling on the circular orbits. With this theory Claudius Ptolemy in the Almagest in 148 AD was able to predict planetary orbital paths. The Antikythera Mechanism, circa 80 BC, got gearing which was able to approximate the moon’s elliptical path through the heavens, and even to improve for the nine-year precession of that path.[3] (The Greeks would have seen it not as elliptical, but rather as epicyclic motion.)