

| Subject: | Re: On I4 Engine Vibration |
| From: | Frank Grunthaner |
| Date: | Mon, 30 Sep 2002 11:02:58 EDT |
In a message dated 9/30/02 5:22:45 AM, jweis@WHY.BOTHER.COM writes: << Unless you also intend to alter the laws of physics, wouldn't vibration always be a function of the mount, even with a more efficient mount? Just a better dampening unit and less vibration transferred to the chassis. >> Of course, bad syntax! You are definitely correct. Its always a function of the coupling media. That said, for a similar mass of material, the active mount handles narrow band sources better than do passive ones. Its impressive to see the heating of a properly designed isolator when coupled to a significant vibrational power source. The dampening is achieved by converting that vibrational displacement energy into heat in the working fluid. For wide band sources (vibration from a few Hz to 10 kHz for example) the passive isolation is often superior. By the way, there are some very good discussions of isolation technology on the web (see for example www.lord.com) as well as the technical papers posted to Alistairs's site. You will find that VW's passive isolation is a very interesting approach. Clearly state of the art for the time. As Alistair and others have posted in times past (very subtle archive reference) there are new energy dissipating materials (eg. sorbothane) that are far more effective than the original rubber at isolation. New carrier bushings made from these materials could prove very effective. Frank Grunthaner
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