<P> Representation of a Rzeppa joint </P> <P> It consists of two identical ball yokes which are positively located (usually) by four balls . The two joints are centered by means of a ball with a hole in the middle . Two balls in circular tracks transmit the torque while the other two preload the joint and ensure there is no backlash when the direction of loading changes . </P> <P> Its construction differs from that of the Rzeppa in that the balls are a tight fit between two halves of the coupling and that no cage is used . The center ball rotates on a pin inserted in the outer race and serves as a locking medium for the four other balls . When both shafts are in line, that is, at an angle of 180 degrees, the balls lie in a plane that is 90 degrees to the shafts . If the driving shaft remains in the original position, any movement of the driven shaft will cause the balls to move one half of the angular distance . For example, when the driven shaft moves through an angle of 20 degrees, the angle between the two shafts is reduced to 160 degrees . The balls will move 10 degrees in the same direction, and the angle between the driving shaft and the plane in which the balls lie will be reduced to 80 degrees . This action fulfills the requirement that the balls lie in the plane that bisects the angle of drive . This type of Weiss joint is known as the Bendix - Weiss joint . </P> <P> The most advanced plunging joint which works on the Weiss principle is the six - ball star joint of Kurt Enke . This type uses only three balls to transmit the torque, while the remaining three center and hold it together . The balls are preloaded and the joint is completely encapsulated . </P>

Difference between constant velocity joint and universal joint