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.

The shear stress magnitude in shaft (1) is:

τ1=T1c1J1=(43.768 lb-ft)(0.75 in./2)(12 in./ft)0.031063 in.4=6,340.455 psi=6,340 psi