Big universal joints are primarily used in combination with cardan shafts. Transmitting substantial amounts of torque, there is for utility vehicles, considering
the same expense, at the
moment probably no alternative. However, they have also established themselves for a lot of connections (e.g., circuit, steering) for which a steady transmission of torque is not important.
How it works
Two forks are connected with each other through a journal cross via needle bearings. Diffraction angles up to 25° are possible. Universal joints themselves do not have a length offset. Nevertheless, it is possible by
putting a sliding piece in the shaft pipe. A larger diffraction angle causes the rotational movement to be transmitted differently. Because of this disadvantage universal joints are not used, e.g., as axle drive shafts to the
wheels particularly for front-wheel driven cars. Nevertheless, using a cardan shaft design, this can be compensated by a second, 90° twisted universal joint
with the same diffraction
angle. During the assembly of the sliding piece this must be respected.
With smaller universal joints, e.g., in the steering (figure) a maintenance-free sliding bearing on plastic basis is also possible. A duration-grease filling is sealed against influences from the outside. Heavy utility
vehicles must still be lubricated at this spot. (figure 2 completely on top). The sliding piece mostly has a stopper. One can screw in a lubricating nipple, however, should be careful with the grease amount. If this is too
big, axial forces on the gearbox develop and may cause damages.
Because universal joints transfer the rotary movement not steadily, they do not belong to the 'homo-kinetic' joints like the ball joints or
constant velocity joints. 09/08