Diagram shows two shafts marked 1 and 2 of length 36 inches and 96 inches respectively. They are connected by two gears at B which has 24 teeth on the shaft 1 and at C which has 72 teeth on the shaft 2. The shaft 1 is connected to a motor at A. The shaft 2 has a gear at D on which a torque T subscript D is applied.

From a free-body diagram that cuts through shaft (2) and includes gear D, the following equilibrium equation shows T2 to have a positive internal torque:

Mx'=TD-T2=0   T2=TD=+131.303 lb-ft

The presence of gears B and C will cause shaft (1) to rotate opposite to the direction of shaft (2). The sign of the torque in shaft (2) is positive. Therefore, the sign of T1 must be negative:

T1=-43.768 lb-ft