re:Re: Active damping

The Philly resins site has a very interesting idea. A single large square
tube contains 4 smaller square tubes. They are separated by flexible epoxy,
which is a moderately good damping material. The neutral axes of the small
tubes is different than that of the outer larger tube, so there is
differential motion when the outer tube flexes.
They claim a peak Q of about 10, compared with several hundred for other
materials undamped.

A big plus for this system is that all of the damping is internal to the
tube, so nasty environmental stuff won't get to it.

I wonder how well it would work with a liquid in there rather than a solid,
perhaps mud.

Sand filled panels have been used in loudspeaker cabinets for many decades,
by Wharfdale (?).

FYI the Newport tables have a Q < 1.

Elliot Burke

>Message: 24
> Date: Fri, 19 Jan 2001 00:02:16 -0500
> From: "Les Watts" <leswatts@...>
>Subject: Re: Active damping

> Les,
>
> Exactly what brand or kind of concrete would that be? Where would one

find

> some? I have some 3" square 1/4" wall tubing that is resonating as part of

a

> column on a small mill. I'd like to try the polymer concrete.
>
> Peter
> THRD, Inc.

>Try this:
>http://www.phillyresins.com/v2.htm

>Note that several steel square tubes are placed inside a larger
>steel tube and the space in between is filled with a damping polymer
>compound. That material is therefore almost ideally
>situated as a constrained layer damper. If you just filled the whole thing
>mass would go up but not damping.

>It would work with round tubes too.

HighTide Instruments