Ross J Fox wrote:
> I've decided to redo the interior of my 75 TR6. All panels, seats and
> carpeting have been removed and happily there is little rust. My question
> regards the use of sound deadening materials. Does anyone have
> experience with materials besides the standard underfelt? Moss describes
> a "sound deadening underfelt" which is precut and self adhesive. This
> sounds ideal. What about Dynamat -- the thin but heavy wieght foil which
> sticks to the metal surfaces. Is this better. What about using it in
> combination with underfelt? Do these materials really help?
>
> My second question has to do with the door window track tie-rod. In my
> car it fits very loosely about the window tracks in both doors and appears
> to serve no pupose, or at least not function properly. I'm apt to remove
> it to stop the rattle. What is it's function and proper fit? Any harm in
> simply disgarding it?
>
> Ross
> '75 TR6
Ross, The two sound absorbing materials you describe are not alike. The "sound
deadening underfelt" is a thick pad made from recycled material. The purpose
of this felt is to absorb airborne noise such as exhaust shell noise, gear
train noise and other high frequency (above 400 Hz) sound. This material is
also a good thermal insulator. The second material you describe as "Dynamat
sounds to me to be a combination what I call "mastic" (a thick
rubberlike/tarlike material) which conforms to the contours of the metal shell
it is connected to (like a floorpan) and a lead or aluminum barrier. This
material is useful in damping an acoustically active body panel. Vibrations
from the engine, transmission, driveline or tires can excite the natural
frequencies of flat panels and make them "acoustically active" (similar to a
drum). I suggest that you only use this stuff if you know you have a panel
which is "acoustically active" and you can hide it under something like a
carpet. Typically you this stuff will only work on low frequency (<600 Hz)
problems.
One other detail to make you TR6 a little quieter, is to ensure that any hole
in the dash panel (firewall) be plugged, filled or sealed. This includes
Tunnel covers and gear shift lever boots. These are paths for high frequency
noise to enter the passenger compartment.
WTR the rattle issue, I don't know much about the architecture of the door
window track in a TR6 and cannot offer any suggestions other that perhaps
place a piece of foam weather-strip around the rattling part to isolate it.
--
Patrick Barber
74 Spitfire 1500 (Organ donor)
70 Spitfire MkIII
Allen Park, MI
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