Re: ATM Truss tube vibrations - cloth jackets

["Kenneth Hunter" <kb7h@onemain.com>]

Anything that is "PACKED" into the tube will not dampen the vibrations completely, it will simply change the frequency. You need to have relative motion between the tube and the dampening material so that the energy is absorbed and transferred into some other form of energy... In this case heat. If the tube is packed with water, vermiculite or any other material, it will transmit the energy from one side of the tube to the other side of the tube with some losses depending on the density of the packing, This still allows the tube to vibrate. 

If you were to cut and fill the tube with styrofoam "peanut" packaging material, the light pieces of styrofoam will simply go for a ride when the tube vibrates. You need enough stationary MASS to absorb and cancel the vibrational MASS.

Ughhh... Wish I could explain it better.

Ken Hunter

-----Original Message-----
From: "Dan Robinson" <danrob@efn.org>
Date: Mon, 20 Aug 2001 10:04:03 -0700
To:  <atm@shore.net>
Subject: Re: ATM Truss tube vibrations - cloth jackets


> 
> ----------
> > From: Peter D. Brooks <pdbrooks@pacbell.net>
> > To: Leftfieldstar@aol.com
> > Cc: lifedata@vol.com; atm@shore.net
> > Subject: Re: ATM Truss tube vibrations - cloth jackets
> > Date: Friday, August 17, 2001 7:38 PM
> > 
> > Leftfieldstar@aol.com wrote:
> > > 
> > >  Beans would work fine. Excellent at decoupling and dampening. So
> is mixed
> > > aggregate and sand. If only they could be light in weight.
> > 
> > Don't know how easy it would be to get any more, but the styrofoam
> pellets used
> > in the old 'bean bag' chairs are light.  I'd experiment, but my bb
> chair is
> > deep in some landfill....
> 
> I'm new here, and very much a novice, but mechanical things are my
> specialty. The rope method sounds good, but I would have gone first
> with packing "peanuts", pieces of styrofoam or maybe foam rubber, or
> maybe a mixture."Pearlite", volcanic glass, sounds like corners would
> wear off and it would get loose. How about "Vermiculite" (expanded
> mica crystals?), that stays soft, from gardening stores? But also I
> thought it would be good to have a relatively rigid component at the
> center. Maybe any of the above packed around a smaller diameter PVC
> pipe. Or how about large diameter soda straws packed in fairly tight,
> some cut to different lengths so you don't have nodes?
> 
> Dan Robinson
> Eugene, OR
> 
> 

-- 

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