Date:         Mon, 30 Sep 2002 11:02:58 EDT
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Re: On I4 Engine Vibration
Comments: To: jweis@WHY.BOTHER.COM
Content-Type: text/plain; charset="US-ASCII"

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