Hydraulic Systems 4
At the moment we are dealing more with static processes. They appear, as soon as there is a prevailing balance, which is then dealt with by the hydrostatic field. A fitting example of this field can be shown by a 450-
ton excavator, which is swivel-mounted on a gigantic axial bearing. Oil is pressed in between the surfaces of the two bearing parts, so that only fluid-friction takes place and the excavator can be rotated by manpower
without any other assistance.
We now carry on with the hydrostatic pressure. We further assume an ideal installation without large flow-losses, heat- or sealing problems. Our oil viscosity has been sensibly selected for the job at hand and
there are no air-pockets present either. The pump produces enough pressure and that, together with the force that is to be generated, is what we want to observe.
We have now arrived at the physical basics. E.g., that pressure spreads out evenly in all directions. One group, in which the meaning of pressure is particulary important, is the underwater divers. The deeper they
go down, the higher the pressure becomes because the amount of water above them increases. Expeditions on the sea-bed are only possible when using especially pressure-resistant capsules.
Thus, the force pressing down on an area of one square meter, depends solely on the height of the water level above it. It would, for example, make no difference whether a cylinder shaped volume with a height of
10.000 meters, or the entire ocean in the shape of a funnel were pressing downwards, the compressive force at the base would always be the same.
The fact that pressure and cross-sectional area form an important connection, can be seen in the two pictures above. The fact that the force F2, seen in the first picture can be increased by a smaller
diameter, can be observed in any comparison between the piston in a master brake-cylinder and the disc-brake.
A suitable example for picture 2, would be the hydraulic jack. By means of a relatively long leverage, more and more hydraulic oil is pumped into the space on the right, the different diameters provide an increase
in the force, which is proportional to their cross-section ratios, this makes it possible to raise, using only your own strength, e.g., a truck weighing 10 tons or more. 05/12