The influence of the engine during excitation through unevenness and through the engine itself, namely through inertial forces, mass moments as well as moments from combustion pressures has well been discussed. A high damping of engine mountings in the region of the engine's natural frequency diminishes the engine vibrations, excited by unevenness, which driver and passenger feel in their extremities. These vibrations are called "motor shak e". On the other end a low damping within the engine mountings reduces the effect of engine excitation, if - as usual- their exciting frequencies are higher than the engine's natural frequencies. Both statements lead to the demand for a frequency depending damping. In the region of 15 and 25 hz a high, say hydraulic,damping will be necessary and in the region over 25 hz a small one, say material, damping. This frequency depending damping is achieved nowadays through so called hydro- mountings.
Abstract