Torque-Twist Relationships  
scene 8 of 13
Diagram shows two vertical shafts A B marked 1 and C D marked 2 centered on the x and x prime axes respectively. A gear of 150 millimeter diameter is at A on shaft 1 at a height of 400 millimeters. A gear of 100 millimeter diameter is at C on shaft 2 at a height of 400 millimeters. Above the gear A a torque T is applied on shaft 1 in the counterclockwise direction.
The relationship between internal torque T in a shaft and its angle of twist φ is given by:

Therefore, the torque-twist relationships for shafts (1) and (2) can be expressed as: