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History Suspension 7



The way that energy storage functions can be well explained by using a spring as an example. It takes in the energy when being compressed, then gives it out straight away by expanding again. Of course, depending on the type of spring, the amount of post-oscillations will vary. The multiple-layer leaf-spring, because of the friction between the leaves, will come to rest very quickly.

Those who have observed a car fitted with torsion bar springing and having no damper, will know, that even the slightest impulse is enough to render the car completely out of control. Whereby, those mentioned already, are two types of steel springs. In addition, there is also the coil-spring, at this point we'll emphasize for the last time, that of course, the coil-spring is only strained when under pressure.

Steel of course, together with elastic rubber, belongs in in the category of solid materials, quite the opposite to the gases. Liquids, because they are (almost completely) incompressible, are not suited for springing. When one speaks of a hydro-pneumatic suspension, what is actually meant is, a gas-suspension with height correction and damping by means of hydraulic oil. In the category steel-springs, the torsion bar has become very rare (an exception e.g., is the previous Mercedes M-Class), they only remain as stabilizers.

No, leaf springs have not become extinct in light vehicles, they have perhaps, been pushed into the area of reasonably priced systems (e.g., the VW-Caddy). In trucks, by the way, they are in competion to the much more expensive air-suspension.

These articles about the suspension, actually deal with the dynamics of vehicle movement, indeed, to keep things ordered, excluding the longitidinal dynamics. Apart from the movement around the three main axes, the oscillations, which belong to the vertical dynamics, must also be kept in check. Important: In a number of vehicles the center of gravity is found in varying places, the less the position is fixed, the more they can be loaded. The chassis designers can make their jobs simpler by going for a harder springing or damping.

The values given by e.g., a suspension test-bench, show that one can overdo things as well. The rear wheel shown here, has one bar more than the recommended pressure. It hopped around so much, that a sheet of paper could be passed, in steps of course, between the wheel and the vibrator-plate. The same phenomenon can be observed when the dampers are adjusted too hard. 03/17


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