RE: [CAD_CAM_EDM_DRO] Re: Al Extrusion Vibration Damping

FWIW, Bondo by itself is fairly lightweight, if weight is a goal. We
would mix it with clean sand to create artificial rock-climbing holds,
but eventually moved directly to a poly resin / sand mix since it was
cheaper in bulk. That is heavier too. The only trick is getting the
hardener mix right, and even that's not too critical. It's
applesauce-level pourable too.

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Fred Howe
Sent: Saturday, July 09, 2005 3:28 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Al Extrusion Vibration Damping

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Jim Colley" <jcolley@g...>
wrote:

> Just curious if anyone has any thoughts on how to increase the

vibration damping

> characteristics of aluminum framing products.
>

Several years ago, I worked on a project for a fellow who built $60,000
speaker systems. Naturally, acoustic damping was of high importance, so
he developed a mixture of material, the exact composition of which he
never revealed, but, the two main compoments were "Bondo" and gypsum.
The Bondo came from an auto parts store, and the gypsum came from
crushing up pieces of plasterboard (or so he claimed). I'm sure you
could find "raw" gypsum if you look for it.
Anyway, he mixed the gypsum into the Bondo base material, added hardener
and poured it onto wherever he wanted it. He claimed it was just about
as acoustically inert as any man-made castable product could be. I don't
know how he got it to be pourable, tho'.
I wouldn't use lead for anything, not even fishing sinkers. Nasty
stuff. Lead poisoning is pretty much permanent and causes a host of
related medical problems. Trying to heat it to melting could cause
irreparable damage to your aluminum framing. Pouring melted lead into an
aluminum frame could cause buckling and all sorts of internal changes to
the aluminum. If you can afford it, you could try some of the low temp
casting alloys,(i.e. cerro-lo, cerro-tru, etc) but that stuff is very
expensive. How about filling cavities with a non-resonent material, like
"great stuff" expanding foam filler. It's messy, but cleans up with
acetone, one of my least favorite chemicals.
It also comes in water-clean-up format (perhaps under another brand
name).






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