1.      If the axis of the shafts over which the gears are mounted are moving relative to a fixed axis , the gear train is called the epicyclic gear train.

2.      Problems in epicyclic gear trains.

Differentials: 

·        Used in the rear axle of an automobile.

·        To enable the rear wheels to revolve at different speeds when negotiating a curve.

·        To enable the rear wheels to revolve at the same speeds when going straight.

Problem:1