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CCWKen
05-04-2004, 10:29 PM
I'm putting the final touches on a combination planishing hammer and english wheel frame. The frame is made from square and rectangular tubing. The problem is that it "rings like a bell".

Before I button up the frame, I want to fill it with something. Maybe sand? Lead shot is out. That's toooooooo heavy. The space to be filled will be about .6 cubic feet (1024 cubic inches).

I need something that won't explode or burn when I weld up the caps.

Joel
05-04-2004, 11:16 PM
How about oil sorb/kitty litter? Should work well, and be lighter then sand. If you do use sand, make sure it is dry. I was thinking about “Great Stuff" but I don't know if it is flammable after it dries. I have some I can test if you like.

wierdscience
05-04-2004, 11:46 PM
Sand,kitty litter,how bout steel shot?

CCWKen
05-04-2004, 11:46 PM
Yea, I've tried that "foam in a can" stuff on another project. It didn't work. It cures with too much air in it. It needs to be very dense.

The kitty litter idea might be worth a try. I'll try that tomorrow on a small piece mock up. I wonder if concrete would work?

Edit:
Hummmmmm. I was just thinking. Kitty litter would have to packed in tight. Otherwise, there would be lots of air pockets around fairly light material. That may not work.

Steel shot? Seems like that would add a "ringer" to the bell. (And about 250lbs.)

I'll try a test with sand and concrete.

[This message has been edited by CCWKen (edited 05-05-2004).]

John Garner
05-05-2004, 12:08 AM
CCWKen --

No first-hand experience with sand fillings myself, but a former coworker claimed that oil-dampened coarse sand works well to damp the ringing of a hollow-member weldment. The same guy was not satisfied with concrete filling; he said that the concrete didn't bond to the steel well enough and pulled away while curing.

I don't know what, if any, surface preparation he did before pouring in the concrete, but concrete does bond to clean steel so I suspect that he may well have cut some corners on the cleaning.

Even with good cleaning, though, it might be worthwhile to consider using one of the slightly-expansive concrete materials such as "anchoring cement" or "machine grout".

John

NAMPeters
05-05-2004, 12:21 AM
First you need hydraulic cement, it expands on curing.

To dampen something you need friction and dead mass, nothing light and fluffy. Varying the stiffness will change the natural frequency of the structure, the stiffer the higher the frequency.

How about some pictures to see what your weldment looks like?

------------------
Neil Peters

CCWKen
05-05-2004, 01:05 AM
Neil - I wish I had a digital camera. http://bbs.homeshopmachinist.net//frown.gif
I've been taking film pictures of the build but finishing the roll and waiting on the pictures is a PITA.

The main structure looks like a capital "I". The vertical beam is 4x4x3/16" and 39" long. The top and bottom bars are 2x3x3/16" and 60" long, centered on the vertical. The 4x4 was notched at the top and bottom so that the horizontals would fit full length "through" the vertical and flush on top and bottom.

On the top horizontal, I have a spead "M" shape bridge. This is made from 1x1/4 flat. The center of the M is centered over the vertical. The lower horizontal bridge is constructed the same way in a spread "W" form. There's a vertical stringer from the apex of the M and W legs to the horizontals.

The plan is to also add gussets on the inside corners. The form is VERY stiff and has a high pitched ring if struck.

There will be other parts added for the hammer and e-wheel mechanics but the main shape is all that will be filled. There will be a dampener under the hammer anvil too.

CCWKen
05-05-2004, 01:07 AM
Got the mail. Thanks Joel.

Joel
05-05-2004, 01:14 AM
I am not sure about the acoustics involved in an enclosed tube, but sound insulation relies on the decay of energy by repeated impacts. I wouldn’t think that the air pockets would necessarily be bad. You could try it loose or lightly tamped, and then pack it to see if there is a significant difference.

I am surprised that the concrete didn’t work better. Concrete shrinks when it is cured, so I am unsure that a spotless tube would change things very much. Anchoring cement might just be the answer. It sure would be easy to work with, just pour it in. It’s not particularly cheap though. Floor leveling compound is similar, but IIRC, it shrinks as well. Concrete without any water wouldn’t shrink, but your getting back to mostly sand. Any powder might work, like plaster, gypsum, or even flour? I wonder how well foam pipe insulation would work (melting aside), maybe neatly zip tie it on the outside?
I guess you sparked my curiosity, I hope you’ll post your results.

Doc Nickel
05-05-2004, 02:35 AM
Don't use Cement or grout. Among other things, you'd have to leave the ends uncapped for several weeks in a warm, dry shop for most of the moisture to migrate out.

Sand is fine. You want something somewhat loose (IE, it can shift a bit to absorb the vibration motion) and reasonably dense.

Don't use beach sand due to the salt. Commercial landscaping sand is fine, just be sure it's dry before sealing it up. If you're not sure, spread the sand out on tarps or Visqueen on the floor of your garage for a night or two, then collect it up and dump it right in.

Doc.

Forrest Addy
05-05-2004, 04:38 AM
Use gravel, old chain, or junk nuts and bolts but don't fill the spaces up. Dense is better. The media has to have freedom to jostle and rattle. Several trays of loose stuff in a single layer is far more effective than a loose pack.

You only need damping at the ends of an "C" shaped structure. This catches the first and third order of resonance and the feet in contact with the floor will deal with the second and fourth. Generally there's so much intrinic damping there's little problem with third and higher orders unless there's direct excitement.

Don't use oil or grease thinking the viscous damping will help. It's effect is mostly as a coupling medium unless fluid shear han be evoked somehow. There's too much chance for a leak unless the sturcture is seal welded.

SGW
05-05-2004, 08:43 AM
I'd do hydraulic cement, as per NAMPeters.

Paul Gauthier
05-05-2004, 10:25 AM
I would go with the sand first, if it dosen't work you can remove it and try something else, not so with concrete. With cat litter I think that over time vibrations would break it down into dust, it is just lumps of clay. Anything liquid or semi-liquid would just be messy to remove if it didn't work.


------------------
Paul G.

Evan
05-05-2004, 10:48 AM
You might experiment with oil based modeling clay. It stays pliable for decades and should dampen pretty well, won't rattle either. It won't leak but I wouldn't get it too close to the welding bits. Weld one end, make up a bunch of clay balls and drop them in.

Ian B
05-05-2004, 01:40 PM
Ear plugs?

darryl
05-05-2004, 02:26 PM
I wonder now, if hydraulic cement expands on curing, that should stiffen the structure by virtue of being incompressible, as well as by pre-stressing the tubing. I think that would actually improve the machine slightly, even if resonance was still there. For the volume you'd be using, the weight increase wouldn't be problematic. You could always wrap a layer of bituminous felt around sections of the tubing to control resonances. You don't need to cover all surfaces, as any section that has damping will control resonances throughout the structure.

ibewgypsie
05-05-2004, 07:43 PM
I didn't put anything in mine..

ONE note: On my english wheel frame, I put a 2x2 socket on the bottom, I mounted my tubing bender on a piece of 2x2 tubing, mounted my brake on, mounted my hydraulic press on, mounted press for harley fenders and of course light planishing hammer.

I am working on a attachment for my shaper.. NOW that will be a power hammer..

My english wheel frame is a good stable platform that rarely got used as a english wheel. I wish I had not recently put them stinking rollers on it thou.. Much better on the floor solid.

I got dimensions on mine off the net.. it is made from 2x4 tubing with 1x2 braces.

Top forged wheel came from www.grainger.com (http://www.grainger.com) for 143$.. bottom have to be cut on lathe by hand.. so far.. Soon thou.. Roller bearings come from Harbor freight as mini-bike bearings.. 5/8 arbor.. Press into anvil wheels.
MY bottom set of rollers must have caught someone's eye, they no longer are here... I've only had one or two in my shop I don't trust completely.
I have lower anvil patterns I can post if anyone needs them.
English wheeling is really great till you roll up on your thumb and pinch the blood out. then it ain't too fun..

These sell pretty good on ebay, but not at the $2500 everyone asks.

David..

CCWKen
05-05-2004, 10:04 PM
I set up some tests using some cutoffs I have. I filled one with concrete and that should be set up by tomorrow. I'm using 2x3/16 x 15" pieces of pipe for the test. I drilled a through-hole at the top of each so I can hang them in free air for the ring test. I'll do the tests tomorrow but here's what I'll be using--Mostly because this is what I have on hand. I don't have any test equipment so I'll be playing this one by ear.

1. Dry Play Sand
2. Dry Gravel (pea size)
3. A mix of 1/4, 5/16 and 3/8" x 1" nuts and bolts
4. Concrete

I'll take the best one of these four and compare it to an oil-wet play sand trial (I only have four tubes to test with). I should have the results by this time tomorrow.

CCWKen
05-05-2004, 10:28 PM
David - Did you put swivel casters on the e-wheel side? http://bbs.homeshopmachinist.net//biggrin.gif
Mine will have fixed casters on the e-wheel side and swiveling on the hammer side. You can take a lot of movement out of the wheels by using chocks. I make chocks for almost all my stuff on cansters.

Take two short pieces of angle iron and place them V down (A); one on each side of the wheel. Take a piece of flat and stand it up on edge against the sides of the two A's. Clamp together, remove and weld.

They'll look like this from the side: A-A
On the wheel(s), they look like this: AOA

Makes for a pretty solid wheel, If your bearings are good.

See.... Another reason not to throw out cutoffs.

PolskiFran
05-05-2004, 11:20 PM
A few year ago at a machinery show I picked up a machinery mount sample. It was a square pad made of 3/4" thick felt. Something like this put inside the tube, like a plug, at intervals might be able to lessen the ringing.

Frank

CompositeEngr
05-06-2004, 03:33 AM
how about:
cap the ends, then drill. Run a length of threaded rod through with a nut on either end to add a compressive stress on the frame.

Would have the added advantage of being able to tune it for the pitch you like http://bbs.homeshopmachinist.net//smile.gif

Peter S
05-06-2004, 07:01 AM
CCWKen,
How about adding oil-soaked sand to your list of trials?
This is something I have seen used, would be interested to see if it makes it worse/better/neutral.

Forrest Addy
05-06-2004, 09:42 AM
Ken your tests will determine whether your damping system will work on a wind chime. I predict there will be little difference among them.

You won't be testing the effectiveness of the damping method as applied to a "C" shaped fabricated structure having a much lower resonance and a strong recurring exitation.

Radmachine
05-06-2004, 09:51 AM
The Chinese army uses oil soaked cotton waste in their submachinegun silencers. Won't be fireproof, but could be used to fill most of the tube. Put a wood or cardboard washer on top of the stuff, and then put in something fireproof so you can weld the end.

Techtchr
05-06-2004, 06:35 PM
My background with musical instruments tells me that a hollow column of air will resonate the sound created by a vibrating object such as your planishing hammer. If you stop the air vibration you will damp the sound. If you want something light which is fairly fire proof, why not fill the hollow tubes with fiber glass insulation, weld the caps shut then when you are done paint the machine with something like plastidip or a ruberized coating.

Brake drums are kept from vibrating by stretching a lead weighted rubber band around them as they are turning. In other words, I thing yu can solve the problem from the outside too.
Just a thought
Matt

ibewgypsie
05-06-2004, 09:15 PM
CCW..

No swivels on the front side, one post on the beam side. The rollers under the wheel are fixed.

Pretty busy here.. installing XP.. geeze.. Seen the reboot screen about a hundred times.


David

winchman
05-07-2004, 03:20 AM
It probably wouldn't be too hard to seal-weld the tube frame and install a fitting so you could apply shop air pressure. Pressurizing the frame would likely change both the acoustics and the vibration response. It would be easily adjustable, inexpensive, and wouldn't add much weight.

You could also install some plugs to allow filling the frame with oil if the pressurization didn't work well enough.

One other thing you could try is running a brace from the top of the frame to the ceiling or wall after it is secured in place on the shop floor.

Roger

pgmrdan
05-07-2004, 08:19 AM
Automobile undercoating material is for soundproofing. They spray the stuff with a wand.

Do you think that would do it? Can you get to the inside with a wand?

[This message has been edited by pgmrdan (edited 05-07-2004).]

jfsmith
05-07-2004, 08:47 AM
As that I am a blacksmith, I use sand to dampen the ring from my anvils. It's simple I build a box and filled it with play sand. No ring or noise.

Jerry

ibewgypsie
05-07-2004, 04:23 PM
I welded mine to the frame on my building.

Now the whole building vibrates. Mass dampens vibrations.

David