You are probably familiar with the term 'two-circuit brake' for both passenger cars and trucks. In the latter, there is also a two-line brake. But perhaps you have not heard of a two-circuit steering, the legislator prescribes for the vehicles shown in the video above. If the steering of the additional axle fails, the correct function must be ensured.

After all, the video above already indicates a double acting working cylinder for the additional steering axle. The steering linkage is also connected to a second, identical cylinder. Both are supplied with hydraulic pressure in separate systems, depending on the double acting control valve in the power steering.

A third pump can be installed which, however, is electrically and therefore independent of the engine. This works parallel to the one right in the picture above. It guarantees the servo function of the normal steering and the steering of the trailing axle if there is no engine run. A connection valve integrates it into the hydraulic circuit of the pump right. 10/16