Design, Construction and Testing of a Vibration Isolation Module

A conceptual design for a Vibration Isolation Module VIM is described and analyzed. The VIM was designed to attenuate significantly vibrations over a frequency range from 110 cps to higher frequencies likely to be encountered. A prototype VIM was constructed and tested. It involved the use of a multiple piston arrangement in which the stagnation pressure at the fore end of the VIM was converted to a force which matched the drag of the towed body. In this way it was possible to preserve a low modulus while avoiding a high elongation, since the main towing effort was balanced in such a way that the damping mechanism carried only the fluctuation and not the active force. During tests, the VIM did not attenuate in the frequency range for which it was designed below 5 cycles per second. The primary cause of the failure to meet design requirements was the high level of the frictional forces. Detrimental hydrodynamic forces were also encountered.