Subtopic: Measurement of force, stress, torque, speed, displacement and acceleration on machine elements – shafts, couplings, keys, bearings and knuckle joints
Question Statement:
Universal joints (Cardan joints) used in tractor PTO drive shafts create non-uniform output angular velocity when operated at an angle. To achieve constant velocity output:
Options:
(A) Two universal joints must be used with the intermediate yoke ears aligned in the same plane and equal joint angles
(B) The two joints must be oriented at $90^\circ$ phase offset
(C) Only single joints with rubber bushings should be used
(D) The drive shaft must be strictly hollow
Answer Key:
A
Step-by-Step Solution & Explanation
To cancel out cyclical speed fluctuations in a drive shaft, both universal joints must have equal operating angles ($\alpha_1 = \alpha_2$) and the inner yoke ears must lie strictly in the same plane.