Figure 5-5.Cross and roller universal jointdisassembled
Ball and Trunnion Universal Joint
The ball and trunnion universal joint is a T-shaped
shaft that is enclosed in the body of the joint (fig. 5-6).
The trunnion ends are each equipped with a ball,
mounted in needle bearings. and move freely in
grooves in the outer body of the joint, in effect,
creating a slip joint. Compensating springs at each end
of the drive shaft hold it in a centered position.
Variations in length is permitted by the longitudinal
movement of the balls in the body grooves. Angular
displacement is allowed by outward movement of the
balls on the trunnion pins. This type of universal joint
is recognized easily by the flexible dust boot that
Double-Cardan Universal Joint
The double-cardan universal joint uses two cross
and roller joints in tandem to form a single joint (fig.
5-7). The joints are linked through a centering yoke
that works in conjunction with a specially designed
spring-loaded centering ball. The components are
contained within the centering coupling yoke.
As the shafts rotate, the action of the centering ball
and yoke acts to maintain an equally divided drive
angle between the connected shafts, resulting in a
constant drive velocity.
CONSTANT VELOCITY (CV) JOINTS
The speed fluctuations caused by the conventional
universal joints do not cause much difficulty in the
rear-wheel drive shaft where they have to drive
through small angles only. In front-wheel drives, the
wheels are cramped up to 30 degrees in steering. For
this reason velocity fluctuations present a serious
problem. Conventional universal joints would cause
Figure 5-6.Ball and trunnion universal joint.