Ian
Notorious member
Celotex makes it, its a 4x8x1/2" or so fiberboard sheet impregnated with asphalt. Used as a backer for stucco and targer backers at many gun ranges.
Machining rubber anti-vibration mounts
- Thread starter KeithB
- Start date
Celotex makes it, its a 4x8x1/2" or so fiberboard sheet impregnated with asphalt. Used as a backer for stucco and targer backers at many gun ranges.
F
freebullet
Guest
I've used hole punches on hydraulic press to make similar. Mine were only 3/8-1/2" thick though. Nice idea on the hole saw.
KeithB
Resident Half Fast Machinist
After thinking over what Ian pointed out about isolation I decided to rework my design a little. I bought a piece of 2-1/2" wide x 1/2" thick neoprene rubber sheet and some 1/2" ID x 7/8" OD neoprene hose and a tube of glue. Also bought a holesaw set. I plan to cut out some 2" diameter washers from the sheet and drill a hole in the center big enough to feed a short piece of tubing through it and glue it in place. I'll take a carbide bur and open up the hole in the compressor foot so the tube can fit down inside it. This should prevent any metal to metal contact betweent the compressor, stud, and floor.
Ian
Notorious member
Mo'betta. Only other thing I would suggest is drilling the hole in the top aluminum plate of the bottom insulator to a bit over your hose OD and instead of gluing it, make the hose long enough to slide down the anchor stud through the top plate. Doing that will ensure the hole in the top Al plate doesn't contact the stud and defeat all your other work.
Working with close tolerances, masonty bits, and heavy machinery is a bit fiddly as you well know, so give yourself plenty of tolerance.
Assuming you have a way to lift the compressor and set it straight down on the studs, my approach would be drill the top plates for the hose and maybe a little more into the pad, slip the pads over the installed studs, cut enough hose to go from the bottom of your larger hole to the bottom of the hose piece as shown in your 2nd design, slip the pieces over the studs and make sure they go down through your pad's top plate and bottom out on the rubber, then set the compressor in place, slip the top pieces of hose over the studs making sure they fill the space between the bottom hose and top metal washer, install the rubber washer, steel washer, and self-locking nut. No glue necessary and making the hose in two parts and installing them in stages will ensure the plate is isolated and nothing slips down the shaft after the glue gives up the ghost. I hope that made sense, I can make a sketch and photograph it if you like.
Working with close tolerances, masonty bits, and heavy machinery is a bit fiddly as you well know, so give yourself plenty of tolerance.
Assuming you have a way to lift the compressor and set it straight down on the studs, my approach would be drill the top plates for the hose and maybe a little more into the pad, slip the pads over the installed studs, cut enough hose to go from the bottom of your larger hole to the bottom of the hose piece as shown in your 2nd design, slip the pieces over the studs and make sure they go down through your pad's top plate and bottom out on the rubber, then set the compressor in place, slip the top pieces of hose over the studs making sure they fill the space between the bottom hose and top metal washer, install the rubber washer, steel washer, and self-locking nut. No glue necessary and making the hose in two parts and installing them in stages will ensure the plate is isolated and nothing slips down the shaft after the glue gives up the ghost. I hope that made sense, I can make a sketch and photograph it if you like.
KeithB
Resident Half Fast Machinist
Finished up mounts today after redesigning to incorporate some very good suggestions from Ian. Here is drawing of final design, and several photos of the final products. One side of the rubber pads came pre-glued with paper peeloffs so that was used to stick on one aluminum plate. I used double sided carpet tape to stick the other plate to the opposite side. A contact cement recommended by the vendor of the rubber hose and the material used for the rubber washers was used to glue the hose segments inside each mount and inside each washer.
The washers were made from a strip of 1/2" x 2-1/2" neoprene. I used a 7/8" hole saw to cut a series of holes in the center of the strip. Then I made a guide by turning down a piece of 7/8" diameter scrap to 1/4" and anchoring that in the hole saw arbor in place of the normal 1/4" drill bit. This let me use a 2-1/8" hole saw to cut a perfectly centered OD around the existing center hole.
With this design there is absolutely no hard surface contact between the compressor and the floor.
The washers were made from a strip of 1/2" x 2-1/2" neoprene. I used a 7/8" hole saw to cut a series of holes in the center of the strip. Then I made a guide by turning down a piece of 7/8" diameter scrap to 1/4" and anchoring that in the hole saw arbor in place of the normal 1/4" drill bit. This let me use a 2-1/8" hole saw to cut a perfectly centered OD around the existing center hole.
With this design there is absolutely no hard surface contact between the compressor and the floor.
Victor Wowk has some excellent books on machine vibration for those looking towards the more analytical study. I have a first edition around here somewhere.
Further,and can't think of the "principle" or theory named after the guy who came up with,"A" way( certainly not the "only") of lowering the noise frequency on intake runners. It's used on sportbike's,to mention one place,intakes to help not only modify the "growl" but to an equal effect,changes tuning on the factory setup. Roundabout way to say you can significantly lower an air compressor sound with a simple modification to the intake runner. Google is your friend. I learned about years ago on bike tuning.
Further,and can't think of the "principle" or theory named after the guy who came up with,"A" way( certainly not the "only") of lowering the noise frequency on intake runners. It's used on sportbike's,to mention one place,intakes to help not only modify the "growl" but to an equal effect,changes tuning on the factory setup. Roundabout way to say you can significantly lower an air compressor sound with a simple modification to the intake runner. Google is your friend. I learned about years ago on bike tuning.
smokeywolf
Well-Known Member
I once designed and fabricated mounts or rather pads for a machine (a telecine), to isolate the machine from the vibrations and harmonics in the building in which the machine was housed.
5" x 5" x 1" aluminum with 4" x 4" x 3/4" pocket milled in it. Cut 3/4" thick Sorbothane sheet to just under 4" square pieces, punched 1/2" hole thru and placed in milled aluminum pockets. Those were the "pads". Feet for the machine had 3-3/4" square x 1/4 thick aluminum plates with 1/2" dia. pin protruding to index into hole in Sorbothane.
5" x 5" x 1" aluminum with 4" x 4" x 3/4" pocket milled in it. Cut 3/4" thick Sorbothane sheet to just under 4" square pieces, punched 1/2" hole thru and placed in milled aluminum pockets. Those were the "pads". Feet for the machine had 3-3/4" square x 1/4 thick aluminum plates with 1/2" dia. pin protruding to index into hole in Sorbothane.
Last edited:
Ian
Notorious member
Looks good, Keith, no chance of grounding out on the studs now. Air compressors can drive you nuts indoors, your efforts are for good reason. The rotary screw units don't have the percussive thump of a recip, but Tomme is right they are screamers and very difficult to quiet due to the high frequency sound.
I have an upright, 3 hp twin-cylinder oil-less Craptsman (spelling correct) unit that hasn't given me but a little trouble over the years but it is LOUD. Had to build a corner closet to put in and insulate it with asphalt sheathing and sheet rock to make the noise tolerable. It operates at high RPM and has a high drone somewhere around 850Hz which is a tough frequency to control in a rectangular room that just so happens to have a standing wave near that frequency. For isolation and mobility (pull it out of the closet to do maintenance/repair), I mounted it on some old hospital gourney casters which have a really thick rubber tire.
I have an upright, 3 hp twin-cylinder oil-less Craptsman (spelling correct) unit that hasn't given me but a little trouble over the years but it is LOUD. Had to build a corner closet to put in and insulate it with asphalt sheathing and sheet rock to make the noise tolerable. It operates at high RPM and has a high drone somewhere around 850Hz which is a tough frequency to control in a rectangular room that just so happens to have a standing wave near that frequency. For isolation and mobility (pull it out of the closet to do maintenance/repair), I mounted it on some old hospital gourney casters which have a really thick rubber tire.
KeithB
Resident Half Fast Machinist
Both of our compressors are V twins mounted on 60 gallon upright tanks. One is a single stage, the other is a lower flow higher pressure two stage unit. The former runs quieter, the latter has a distinctive pop pop pop when running. We plan to put an insulated freestanding enclosure around each one. We are also going to dampen the vibrations of the belt guards, they are both wire grates that vibrate and rattle especially at the connections.
Once we are up and running I plan to invite the students in one of my full time colleague’s Vibrations class to come to shop with their sound meters and do a study.
Once we are up and running I plan to invite the students in one of my full time colleague’s Vibrations class to come to shop with their sound meters and do a study.
Home | Advanced Antivibration Components
AAC carries cylindrical, base, square mounts for damping and reducing vibration and shock protection.
www.vibrationmounts.com
Tomme boy
Well-Known Member
Make sure to have a drain access. Easiest is just a ball valve somewhere on the outside of the cabinet if you are enclosing it. I will second the dynomat. We sold a cheaper version that was 1/2 the price of actual dynomat when I was at the paint store. It was adhesive backed so it was very easy to install.