In the truck one must look at the gear changing and the activity of the clutch as a combined occurence. There are more possibilities than is the case with the motor car. Not only that a vehicle can be delivered with, or
without a clutch pedal, but also with a pedal that can be folded out of the way. The gearshifting can be eight speeds in the double H pattern, in a simple, single H pattern, or as a sort of joystick with plus- and minus
The gear changing in trucks has always been supported by compressed air. Previously, when one, e.g., shifted from 4th into 5th gear, the group was automatically changed. Nowadays however, a slight amount of
support is given with every gear change. The above figure shows the complete controlling unit for the activity of the selector rods. The large lever on the left is for the rod connection with the gearshift, the small black
one on the right, for the Bowden cables. In spite of the direct control, an error in the shifting operation is prevented by the RPM supervision of the engine. One can of course, also assign the gear changing completely to
a sort of automatic.
More complicated than in the motor car, is the automatic controlling of the clutch. Nonetheless, the driver can still make the choice in especially difficult situations. It then works as usual with hydraulic activity which is
supported by compressed air. 06/10