Gear-train is any combination of gear wheels by which motion is transmitted from one shaft to another shaft. In epicyclic gear-trains, the axes of shafts on which the gears are mounted may move relative to a fixed axis.
To measure epicyclic gear ratio between input shaft and output shaft
To measure epicyclic gear ratio between input shaft and holding drum
To measure input torque, holding torque and output torque
It consists of two types of epicyclic gear-trains