Date: Thu, 13 Jun 1996 13:06:11 -0400
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Sglw@aol.com
Subject: Re: Westfalia Noise (Vehicle engineering little VW)
In my past life I was a development engineer at Ford of Europe in 1964-67. I
woorked in the NVH (Noise Vibration & Handling) department. And I had
theplease to have to fix the 69 Corsair that became known as the
Loncoln-Mercury Capri. this was the classic example of suck it a and see'
engineering. A car dictated by stylists and marketeers. The dynamics &
acoustics were not evaluated. As a reult:
1, the acoustic resonance between the rear window & the panel by the drivers
pedals was 100 Hz (Cycle per second)
2, the engine on its mounts vibrated at 100 Hz
3. the exhaust system vibrated at 100 Hz
4. The rear exhaust mount attached to the floot of the boot (trunk) this
panel vibrated at 100 Hz.
5. the secondary harmonic for a four cylinder enginr is 100 Hz at 3,000 RPm
6, 3000 RPM =60 mph
When you decelerated from 65 to 55 M{H the nose level in the rear seat was
over 96 DbB.
96 DbB is above the threhold of pain.
This was discovered when thay had made all the tooling and were about to roll
the first car off the production line, and some young egineeer who said 1
year earlier that they should spend 1 man-year of ananlysis to avoid this
problem. So I had much bucks and was told to fix it as I was one of the first
college grads to go to the motor industry.
Well there is a special acoustic blanket that is a combination of
potscrubbers(wire wool), cottton flocking and lead. this works wonders in
most cases and would fix anything in a vanagon. But it cannot change the
basic structural dynamics.
I had a good friend who worked at Rolls-Royce and they built the vehicle with
a set of mounts that were a combination of low pass filters (Pan Scrubbers)
and high pass filters (rubber engine mounts). This fixed the resonance
problems but may be not in the VW category.
The Capri had to have a major change in the tooling, Day 1 was delayed 6
mnths, and I left the motor industry for aerospace.
Get this wonder acoustic blanket.
Have fun. Sam 70 westy