transmission is very important for delivering adequate power and

http://en.wikipedia.org/wiki/Gear_ratio

Torque ratio[edit source | editbeta]

A gear train can be analyzed using the principle of virtual work to show that its torque ratio, which is the ratio of its output torque to its input torque, is equal to the gear ratio, or speed ratio, of the gear train.

This means that the input torque T_A applied to the input gear G_A and the output torque T_B" on the output gear G_B are related by the ratio

where R is the gear ratio of the gear train.

The torque ratio of a gear train is also known as its mechanical advantage, thus