Practice Problem 2-1

Practice Problem 2-1

Given: A shaft with two gears, A and B, is driven by a motor. Gears A and B are acted upon by tangential forces F_A = 120 lb and F_B = 200 lb. The gear diameters are D_A = 6 in. and D_B =10 in., respectively.

Req'd: Determine the motor output torque T_M required to turn the shaft at a constant rate.

Sol'n: For the shaft to turn at a constant rate, the torques must be in equilibrium:

SM_z = 0 : T_A + T_M – T_M = 0

T_M = T_A + T_B

T_M = (F_A)(R_A) + (T_B)(R_B) = (120 lb)(3 in.) + (200 lb)(5 in.)

T_M = 1360 lb-in.

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Updated: 05/10/2009 DJD