Shock Absorber Theory

[Turbobrick]

Twin tube vs MonoTube (from Bilstein website http://www.bilstein.com/products/basics.html)

 

Twin Tube

 

This principle of reducing the vibration through friction is still valid today.

 

Today's automobile must meet stringent requirements than its predecessors, the shock absorber has become an extremely important component in motor vehicles.

 

The twin tube shock absorber consists of two tubes. The inner tube is the pressure tube where the energy conversion occurs (kinetic energy converted through friction into thermal energy).

 

The outer tube, sometimes called the compensation chamber, contains the reserve chamber which fulfills an important role. Oil is displaced within the inner tube by movement of the piston rod. The displaced oil enters the reserve chamber through the back pressure valve. With the piston rod moving upwards, the oil is again sucked into the working chamber.

 

Monotube (Gas)

 

Such a compensation chamber is necessary on the Monotube type of shock absorber. The technology applied here has a number of considerable advantages. The expression "Gas Pressure" Shock Absorber often leads to the assumption that this shock absorber only contains gas. However the actual damping occurs within a column of oil. The dividing piston separates the oil chamber from the gas chamber.

 

The oil chamber contains a special hydraulic oil, and the gas chamber contains nitrogen, at a pressure of approx. 25 bar (approx. 350 psi)

 

Gas chamber function: enables the dividing piston to move further towards the gas chamber, thus reducing its size. When the piston rod is returned, the oil chamber becomes larger and the compressed gas cushion presses the dividing piston back into its start position. The high pressure in the gas chamber is transmitted by the dividing piston onto the column of oil and prevents the oil from foaming. Therefore optimum damping performance is achieved under all operating conditions.

Edited July 10, 2003 by Saaber