Why are CV Joints used on drive shafts rather than the old style hookes type ujs?
In a CV (or constant velocity) joint, the input and output ends of the joint rotate at the same speed at all times. In a conventional universal joint, even if the rotational speed of the input end is constant, the rotational speed of the output end will vary throughout each rotation. If you were to plot a graph of output speed as a function of input speed, the graph would be a sine wave, and its amplitude would be directly related to the angle of misalignment between the two shafts. In an application like an automotive drive shaft, there wouldn’t be very much variation between input speed and output speed, but any variation would certainly make the drive train less efficient.
