Because of its gas compartment, the single-tube shock absorber is also often called gas pressure shock absorber. However, also in this case, the hydraulic liquid damps the vibrations and not the gas. It has a better cooling compared with the twin-tube shock absorber because of the missing, insulating, second tube. Moreover, it can also be installed in any position.The higher pressure, compared with the twin-tube damper, has advantages for the response behaviour of the disc valves in the piston, and also prevents possible foaming or aeration in the hydraulic oil.
The problem with the hydraulic damper, is that a compensation space for the penetration of the piston rod an must be found. In this case it is a dividing piston, which seals the lower portion of the chamber which has a gas pressure of 20-30 bar. The high gas pressure is also responsible, by the way, for the fact that the removed damper slowly extends if one lets go of it.
In the above diagram, one can see the different damping forces at tensile,- and at pressure strain. The oscillations are reduced - which the passengers hardly notice - during tensile strain. This is achieved through differing valves in the damper piston. 05/10