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Sound Deadening Material For Vibration Control

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#1 TCW

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Posted 28 January 2014 - 09:12 PM

I am contemplating lining the pier of my Cave 12.5 inch mount with automotive sound deadening material to absorb vibrations. Has anyone tried this and if so how did it work? :confused:

#2 Bomber Bob

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Posted 28 January 2014 - 09:36 PM

Never tried it. But, for my old Jaeger's 5' steel pier, I cut a length of white PVC pipe, glued foam pipe wrap to it, and pushed that up the pier. It greatly reduced vibration.

#3 amicus sidera

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Posted 29 January 2014 - 12:56 AM

That PVC pipe/ foam trick sounds like a winner; it would certainly tend to break up any natural resonance.

#4 bremms

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Posted 29 January 2014 - 03:29 PM

Fill it with concrete. Sorry, I couldn't resist. You wanted to be able to lift it?? PVC/ foam trick is a GREAT low cost solution.

#5 TCW

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Posted 29 January 2014 - 06:22 PM

My pier is over 6" in diameter so I don't think the pvc/foam idea will work although I might be able to fill it with expanding foam.

#6 Bomber Bob

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Posted 29 January 2014 - 06:29 PM

"I might be able to fill it with expanding foam"

I initially consider fine sand, but the pier & mount were heavy enough already! Spray-in foam? That's probably an even better solution - maybe it would help prevent rust, too.

#7 TCW

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Posted 29 January 2014 - 06:33 PM

This is a portable mount so I need to keep it on a diet.

#8 Bomber Bob

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Posted 29 January 2014 - 06:41 PM

Lightweight polyester quilt batting is another option.

#9 Lane

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Posted 29 January 2014 - 10:00 PM

I lined a pier with dynamat extreme and it did not work nearly as well as I thought it would. I think the problem is that this material is designed primarily to kill long wave low level vibrations coming into the car from the road and tires, so you hear your audio system better. It also prevents rattles in the car panels from the subwoofer. So it works great in my car, but I don't think it does much to kill short wave vibrations and I believe those are the kind of waves that are the main problem with telescope mounts.

#10 PowellAstro

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Posted 29 January 2014 - 10:06 PM

You could get the inside of the pier coated with Rhino Liner. This will kill the vibrations. We use this in our shop and it does a great job when it Is used at about 3/16" thick.

#11 Joe Cepleur

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Posted 30 January 2014 - 01:10 PM

I lined a pier with dynamat extreme and it did not work nearly as well as I thought it would. I think the problem is that this material is designed primarily to kill long wave low level vibrations coming into the car from the road and tires, so you hear your audio system better. It also prevents rattles in the car panels from the subwoofer. So it works great in my car, but I don't think it does much to kill short wave vibrations and I believe those are the kind of waves that are the main problem with telescope mounts.


+1

Your car dampens the big, honking, violent vibrations of 3,000 pounds hitting a bump at highway speeds. At the scope, the trouble is the fast, little, gentle, but annoying vibrations of your nose tapping the eyepiece.

#12 TCW

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Posted 30 January 2014 - 01:34 PM

Nothing like real world experience. Thanks!

#13 ngc2289

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Posted 30 January 2014 - 04:06 PM

I use "GREAT STUFF" foam to fill voids in my mount center column. Works pretty good at dampening vibrations.

#14 amicus sidera

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Posted 30 January 2014 - 04:31 PM

Foam that hardens in the pedestal functions differently from a PVC pipe with closed-cell foam wrapped around it. The former works by reducing the modulus of elasticity, basically making the column stiffer; the latter dampens vibrations by means of its elasticity, e.g., the compression/rebound properties of the foam. Either will work, dependent upon the application, although "ringing", i.e., relatively long-duration vibrations of low amplitude, can occur with hard foam.

#15 wfj

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Posted 30 January 2014 - 06:38 PM

Right Fred.

Stiffness damps vibration, usually higher frequency vibration by means of "scattering" its energy through multiple paths that statistically are destructive in interference. The paths come from geometrically diverse fibers or foam bubble contacts, the less elastic the better.

The "roll off" of this frequency is due to the size of the column. For low frequency in a column to be damped, it must be absorbed in the axial direction of the acoustic wave by a damping force. An example would be a column of a viscous substance (like oil which is heavy). In this case, the energy is in effect "refracted" in place by the substance.

#16 Joe Cepleur

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Posted 30 January 2014 - 06:44 PM

In cold weather, some foams stiffen, likely reducing the desired dampening. Memory foam, for example, would be a terrible choice.






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