An epicyclic gear teach (also known as planetary gear) contains two gears mounted so that the centre of one gear revolves around the centre of the additional. A carrier links the centres of the two gears and rotates to carry one gear, called the earth gear or planet pinion, around the various other, called the sun gear or sunlight wheel. The earth and sun gears mesh so that their pitch circles roll without slip. A spot on the pitch Leaf Chain circle of the earth equipment traces an epicycloid curve. In this simplified case, sunlight equipment is set and the planetary gear(s) roll around sunlight gear.
An epicyclic gear train can be assembled therefore the planet gear rolls within the pitch circle of a set, outer gear band, or ring equipment, sometimes called an annular equipment. In this case, the curve traced by a spot on the pitch circle of the earth is a hypocycloid.
The mixture of epicycle gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train. In cases like this, the ring equipment is normally fixed and the sun gear is driven.
Epicyclic gears obtain name from their earliest app, that was the modelling of the motions of the planets in the heavens. Believing the planets, as everything in the heavens, to end up being perfect, they could only travel in ideal circles, but their motions as seen from Earth could not end up being reconciled with circular movement. At around 500 BC, the Greeks developed the idea of epicycles, of circles venturing on the circular orbits. With this theory Claudius Ptolemy in the Almagest in 148 AD could predict planetary orbital paths. The Antikythera System, circa 80 BC, had gearing which was able to approximate the moon’s elliptical path through the heavens, and also to correct for the nine-yr precession of that path. (The Greeks could have seen it much less elliptical, but instead as epicyclic motion.)