FIGURE 7. BALL-AND-TRUNNION UNIVERSAL JOINT.
In another type of universal joint (ball-and-trunnion type), the universal joint itself
contains a feature that eliminates the need for a slip joint. Notice the cutaway view of a
ball-and-trunnion type universal joint. In this type of joint, a trunnion pin is pressed
through a hole in the end of the propeller shaft. The pin is fitted with balls which ride in
grooves in the flanged body. The balls are assembled on bearings so they rotate with
little friction. Compensating springs at each end of the propeller shaft hold the shaft in a
centered position. Changes in drive-line length are permitted by the endwise movement
of the balls in the body grooves. Changes in the angle between shafts are made possible
by inward and outward movement of the balls on the trunnion pin. The ball-and-
trunnion universal joint is easily recognized by the flexible dust boot that covers the
propeller shaft end.