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Hydraulic Systems 3


In the field of utility vehicles, hydraulics have already been established for decades, think of the tippers and multitude of tail-gate-lifters, not to mention those which have a special function. In the field of motor cars, the hydraulic power-steering is well known and in certain upper-class models, also the power-braking system. For a long time the hydraulic suspension was only found in the Citroen. At the moment (2004), hydraulic systems are celebrating a boom, particularly as far as convertibles are concerned, to operate the folding roof.

The above shown equipment is not sufficient to be used in a convertible with a retractable hard-top, possiby not even for the hydraulic operation of a canvas roof. In this case, a cylinder on each side would be necessary. This by the way, is exactly what makes hydraulic systems so attractive, they can apply great force just where it's needed. Because this force is generated from a central point, the respective, relatively lightweight and space-saving components can be installed exactly where they are needed. The more components of this type there are and the higher the forces, the more sense it makes to use hydraulic- instead of electrical systems. One important aspect, compared with the electrical operation, is the more gentle intervention and the simple force-limitation, e.g., through a pressure relief valve.


The above shown equipment consists, in the first place, of a supply unit above and a ram-cylinder below it. This has a connection on each side of the cylinder. Pressure coming in from the (red) hose causes the piston to be driven out, from the (blue) one, the piston is retracted again. The two pressure hoses, which are only about 8 mm thick, must be connected to the supply unit according to their colour markings. The suppl unit consists of a container carrying up to half a liter of hydraulic fluid, the electric/hydraulic control in the middle and the electric pump on the right. Accordingly, the control unit can then distribute the pressure by means of small valves, to the correct line(s), or open the line(s) to allow the flow-back to the container to take place. 05/12