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).