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View Full Version : What's a good vibration dampener? - Results



CCWKen
05-07-2004, 10:19 PM
First let me applogize for the delay. Out-of-town family members dropped in yesterday and threw the whole schedule off. (Is that fish I smell?) http://bbs.homeshopmachinist.net//biggrin.gif

This test was by no means scientific. I didn't use any special tools or test equipment. I played the violin in my younger days and played in a rock band in High School. I learned the songs by ear so that's the only test "equipment" that was used. I tried my best to keep the variables to a minimum--Variables that would affect the neutal evaluation of the media.

Some changes are to be noted. First the pipe size and second the nuts and bolts. The pipe used was 2" ID x 3/16 x 20" Long. The pipe lengths (4) were all within 1/16", or less, of each other. The pipe is ASTM-A53. These were going to be legs of a stand so each had a 3x4x3/16" flat plate welded to one end.

Second, I couldn't bring myself to dump/mix all the those nuts and bolts together. The thought of having to resort them overcame my desire for a scientific breakthrough. I did find a box (25lbs.) of mixed sheetmetal screws that I picked up at the salvage yard a while back. These are a mix of #8, 10 and 12 and range in length from 1" to 2 1/2".

One other change was the method of suspending the pipe. Originally, I was going to hang the pipe using nylon string. I decided instead to lay the pipe down on an 8' lengh of identical pipe. Each test piece was placed so that one end (plated end) contacted the cement floor and the other end on top of the perpendicular 8' pipe.

Setup:
Each piece of pipe was filled to within 4" of the top and left open. No sifting, shaking or packing was done. The media was allowed to just fall into the tube via a funnel. Care was taken to ensure a 4" gap at the top of each tube. (This is where the mix of cement ended up so the others were made to match.) I also added two more media types. One was 3/4" random fiber carpet padding and the other was rubber non-skid padding.

Test:
I used two different hammers to strike the pipe. One was a 12oz. ball pein and the other was a welding slag hammer (Spring handle). My best effort was used to strike each pipe with equal force. Basically, I allowed the hammer to fall onto the pipe. The only difference I noticed was the loudness of the strike. The tone remained the same. I also shiffted the location of the pieces after each test. I did this so that variations in it's location on the support pipe could be tested.

I struck the side of each pipe at three zones. The top (over the supporting pipe), midway and bottom. Little difference was noted on the bottom strikes. (The bottoms were in contact with the cement floor.) There were major differences between the upper and mid strikes. The upper strike seemed to provide the best comparison value.

I can't really rely on the test of the concrete filled pipe. As everyone noted, concrete shrinks and it did. I noticed cracking and separation around the inside wall of the pipe. Even with this condition, the cement faired well. At least better than some others.

Results:
I've listed the results from BEST to Not Best. Your mileage may vary.

1. Oil Dampened Sand - Mixed 1qt sand to 4ozs of 10-40 motor oil. This was "Patio Paver Sand", not play sand. This sand has particles from grains to 1/8".

2. Dry Sand - Same type of Sand above.

3. Concrete - Could have done better, maybe.

4. Dry All Purpose Gravel - Quikrete No. 1151, pea sized. Noticeable "ring".

5. Screws/Hardware - Overall tones were low but still had a slight "ring".

6. Rubber Non-Slip Pad - Rolled and inserted into pipe then allowed to uncoil to make contact with sides. Filled but not tight. Poor result.

7. 3/4" Random Fiber Carpet Pading - Rolled and inserted like the rubber pad. Almost NO change in the tone or ring of an empty pipe.

I'll be going with the oil dampened Paver Sand in my application. Take the results of this test with a grain of salt but my choice is based on MY tests.

wierdscience
05-07-2004, 10:54 PM
Ditch the oil for mercury http://bbs.homeshopmachinist.net//biggrin.gif

CCWKen
05-07-2004, 11:21 PM
Aside from the weight, how much would 48 fl.ozs. of mercury cost? http://bbs.homeshopmachinist.net//eek.gif

darryl
05-08-2004, 01:05 AM
Thanks for doing the tests and posting the results, CCW.

Evan
05-08-2004, 01:55 AM
Ken,

You can have the Hg for the cost of shipping... http://bbs.homeshopmachinist.net//eek.gif