Assignment

The springs have the job of absorbing road-impacts and of bringing the unsprung masses (wheels, brake discs etc.) back into their initial position as quickly as possible. They brace themselves against the sprung masses (bodywork, engine etc.), which is where oscillations develop and which should be, for safety sake, reduced as quickly as possible, causing as little loss of comfort for the passengers as possible. Oscillation dampers are found, among other places, also on the steering, on trailer drawbars and in utility vehicle cabs.

Mostly, and fortunately, defective dampers are changed, before they have completely stopped working. Mechanics und hydraulics, in contrast to electronics, simply slowly lose their efectivity. a car with complete damper collapse just goes on see-sawing endlessly. Each new bump in the road increases the movement making intentional steering impossible. The oscillations are not only vertical, but often sway the bodywork in a certain direction. All one can do, is to steer in the direction of the swaying, regardless of whether kerbs, guardrails or trees are in the way. One only has the choice between overturning and crashing. At higher speeds, it only gets worse ...

Function

The first oscillation dampers in the motor car construction function on the principle of the multi-disc clutch. For a long time now, only 'hydraulic telescopic dampers' are installed. This means that they are extendable and that oil takes over the damping function - also in the so-called gas pressure dampers.

When compressing or rebounding, a piston is moved back and forth in a cylinder filled with hydraulic oil. The oil must work its way from one side of the piston to the other, thereby converting kinetic energy into heat. this occurs primarily around the lamellar valves in the damper piston. The hardness of the damper is dependent on their resistance. They are thus adjusted, that the flow is more difficult for the oil when rebounding than it is when compressing. In the rebound-damping, the dampers are, as a rule, generally laid out harder than for the compression damping. If here the highest amount of energy is reduced, the passengers are less aware of uneveness in the roads. The damping can be variably laid out through grooves the the cylinder walls, softer in the normal condition and harder when compressed. Defective dampers are ascertained on a test bench. All other methods are only suitable for the recognition of completely worn out dampers.

We have become accustomed to the long service life of oscillation dampers. Just how difficult the job of sealing is for the piston-rods, can be seen by the fact that, in journeys in the desert, the dampers are sealed with outer protective rubber tubing (bellows). Sand on the piston-rod would ruin the seals in a very short time.

Important

The usual description of 'shock absorber' would be more suitable for the spring suspension. Based on its effect, it is an oscillation damper. It is usually used between two masses which are resiliently connected to each other. 07/11