# Vacuum Exhaust Muffler



## MAFoElffen (Jun 8, 2012)

Anyone with any thoughts on building a central vacuum style exhaust muffler?

Re: My shop vacs were not enough for dust control. I found what I thought was a central vacuum with a missing vacuum canister. The hose was there, which hooked up tp 2" pvc. What it turned out to be was an Old ServiceMaster commercial wet/dry vacuum (they use commercially for disaster recovery).

The airflow is monstrous. When I got the motor working, I had it atop a steel 35 gallon grease drum. A fraction of a second on and it tried to collapse the drum like a beer can.

Works great on the dust bin of my shop saw.

Problem: Running, it is louder than any piece of equipment in my shop. The airflow is much louder than the motor. Franky is sounds like a jet engine. Definite ear protection just turning on this vacuum.

I need to quiet it down. Mike said this vacuum was a service truck mounted vacuum. Unlike shop/vacs and central vacuums, it does not have an "exhaust port" where you can hook to a hose. It has many 1/2" holes drilled in the top of the motor housing with a hood above it acting as a defuser.

So... This is definitely "different" for me. Mike's idea is to somehow add chambers for the air to change directions. I guess I would have to replace to top hood and make a muffler to replace it? Something to be able to hook up an exhaust hose to vent outside? Thoughts?


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## friendly1too (Sep 25, 2004)

One way to handle this would be to station it outside the shop, even if you had to construct a weather-proof compartment for it.


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## MAFoElffen (Jun 8, 2012)

friendly1too said:


> One way to handle this would be to station it outside the shop, even if you had to construct a weather-proof compartment for it.


I looked at designs for enclosures... lining them with carpet, adding wooden baffles for the exhaust vent... For inside and possibly exterior.

Seems to me that that option would that up a lot of hose and space. Although that could be taken up via 2" pcv. That option is usually for a shop vac. And exterior here, we have high humidity and over 313 days a year of rain... and lots of those other days are still foggy or misty.

This commercial wet/dry vacuum is about the same dimensions and design as a central vacuum, enough capacity motor/fan for a 3000 sq/ft home. I have a welding tank clamp large enough to mount it out of the way on a wall. I have enough tools and equipment in my garage that I have to move stuff out into the driveway to work (and do that almost daily). ...So there is space concerns.

I figure if I take off the top cap/difuser, that I could replace with a section of 6 inch tubing. In that tubing, I could weld plates every 1 to 2 inches with holes staggered, so the exhaust doesn't have a straight exit, but not a restriction (baffles). Then at the end of that, cap it off and reduce to a 4" or 2" fitting. That way, if needed, it could be further ported to the outside.

Alternately, if I just did a 6" tube reducing it to 2", inline central vacuum exhaust mufflers (2") are only $14.

But I'm listening for any idea that might be easier or better.

Goal is that this vacuum would be for fines, with a dust separator before it. I generate over 5-10 gallons of sawdust a day. And one of the precautions Doctors tell me is "No dust."


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## DaninVan (Jan 1, 2012)

Hey Mike;
As you know, sound travels by conduction and by air movement. The baffling approach will help with the air movement aspect, but if you fix the unit to the wall, the vibrations will be picked up by the wall itself and it then becomes a membrane; something like a drumskin. If you do fasten it to anything you need to isolate it with sound dampening material. The drywall 'Z' bar approach would work.
The baffling works by interfering with the frquency of the vibrations. If the sound waves hit something resilient, like fibreglass insulation, the energy is dissipated. Add to that changing direction (90deg. corners) and the energy is quickly absorbed.
non-hard surfaces, ie springy, or extremely dense like lead, are the most effective.
Lead works by simply being too dense and yet malleable...not reflective of vibrations. Sheet lead is perfect for baffling. It used to be the material of choice for sound deadening.
Hope that adds to your ideas.


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## MAFoElffen (Jun 8, 2012)

DaninVan said:


> Hey Mike;
> As you know, sound travels by conduction and by air movement. The baffling approach will help with the air movement aspect, but if you fix the unit to the wall, the vibrations will be picked up by the wall itself and it then becomes a membrane; something like a drumskin. If you do fasten it to anything you need to isolate it with sound dampening material. The drywall 'Z' bar approach would work.
> The baffling works by interfering with the frquency of the vibrations. If the sound waves hit something resilient, like fibreglass insulation, the energy is dissipated. Add to that changing direction (90deg. corners) and the energy is quickly absorbed.
> non-hard surfaces, ie springy, or extremely dense like lead, are the most effective.
> ...


Thanks. I had not even thought of that... And since this was a "truck mount" vacuum, there is much vibration in this unit. Wow, something else to take into consideration. ::scratching head::


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## DaninVan (Jan 1, 2012)

Mike; if it's sitting on the floor, springs work well for sound isolation.


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## MAFoElffen (Jun 8, 2012)

I'm wondering just how much is resonating from/through that steel 35 gallon drum(?). There is over an inch of dense foam between the vacuum unit and the drum. I guess I should post a photo...


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## DaninVan (Jan 1, 2012)

Good point!! The drum drum....


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## MAFoElffen (Jun 8, 2012)

DaninVan said:


> Good point!! The drum drum....


Got your PM... Maybe a water heater blanket or maybe glue on some carpet to dampen it(?).. will see how much the muffler quiets it down. I wish this forum took sound files as attachments. At least to gauge a before and after. (Not planning on a decibel meter that I would use once.)

Pic 1 - the vacuum converted to a shop vac.

Pic 2 - the data plate. which is pretty much unless as there's no info available for it.

Pic 3- the top cover without the diffuser. Shows that there is a 4 1/2 hole for the exhaust and 1/2" holes for the motor vent. (I was wrong, I thought all was 1/2" holes.)

Pic 4 - the motor. Exhaust out the top of the motor. vent holes in the side.


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## MAFoElffen (Jun 8, 2012)

I guess I could also spray the barrel with undercoating... Thinking of trying this first.

Looking at that 4 1/2 inch exhaust hole, I'm thinking a 4" PVC Closet Flange, 4" PVC pipe, couplings, Plexiglass baffles, Transition to a 4" to 2" bushing, 2" PVC pipe, 2" 90's, 2" rubber coupling.

I'm thinking the closet flange would be about the right size to bolt to that cover (with a rubber gasket) without covering those vent holes.

This was free. Someone dumped it in a horse pasture where my horses are. What I'm afraid of is that the motor is old school commercial -- truck mounted -- before anyone thought about high noise or cared about it. I can muffle the exhaust noise. I can dampen the drum. The motor.. well a new motor of the type and rating is $400-$600, which would be updated and quieter. I don't have the money to do that, especially just based on db levels. With the old, the only thing I can think of is to put it into an enclosure... but would take more room, which I'm pressed for.

If it is still too loud, I guess I will have to sacrifice that extra space.

Edit-- All good ideas so far. Looks like I need to get parts. All the materials I had planned to use for for this, won't work.


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## MAFoElffen (Jun 8, 2012)

Remember this is still new territory for me.

Some questions for planning:

What would be more effective, baffle openings straight across (180 degrees) from each other or at 90 degrees? Like I said, I've never built a muffler before.

In the baffles, how big should I make the opennings? I currently have a 2" feed hose. The hose that was there with it when I reclaimed was 2". The intake under the motor is 4 1/2" bell with about a 4" ball in a cage (wet/dry). The exhaust is 4 1/2". I have no idea what it was rated for. Since truck mounted, it could have been a 4" hose going from the truck to a manifold with 2" feeds. My worry, is that if I cut it down to 2 inch on the exhaust, that I'm going to restrict the airflow.

What would dampen sound more, undercoating or a truck bed liner such as like rino-liner? Both are available in spray cans. I'm thinking that bed liner is more durable, but undercoating , being more pliable and not smooth might be more dampening? But again, I have no #$%^&* idea on that.

On the restriction side... Just thoughts. If I go from 4 1/2 inch to 6" tubing, add baffles, go back to 4"... I don't know yet, just thinking. If I tested with a closet flange and slipped in and taped a 4" to 2" bushing, that "might" show me if it is being restricted... But it has so much airflow that I might not really be able to tell. I guess if I didn't bolt that down and tried to hold that to the exhaust...

I have it working, but I don't want to burn it up doing something wrong, you know?


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## MAFoElffen (Jun 8, 2012)

I really flunk out on this one.

I looked at fittings at HD while I was wasting time for an appointment's time. When I got home from my appointment., I decided I needed to use the vacuum, so I put it back together without the diffuser.

Now I feel stupid and bewildered. I turned it on and expected the exhaust to come out the top of the motor. Wrong. That is the intake for the motor. The holes around the motor... then the 1/2" holes on top the top housing, are the exhaust ports.

So the only way I can make a muffler is to either remake the whole top housing or to make a baffle vented enclosure to put the whole thing into. Arrgh. Now I have my answers. Not the ones I was looking for, but answers none the less. Housing it outside in the driveway is looking attractive at this point.


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## TRBaker (Jul 5, 2012)

Mike, I've got to say that I like your maple burl problem a lot better than this one.


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## MAFoElffen (Jun 8, 2012)

TRBaker said:


> Mike, I've got to say that I like your maple burl problem a lot better than this one.


Me too. 

I figure now... It's not as much a priority now. Best I can figure is the top housing houses the exhaust between it and the motor housing. The dense foam strips act as a separator between the exhaust and motor intake.

3 options- 
1. Make a top housing from sheet and put in a 2" tube into the side as an exhaust port. Plasma cutter, weld...
2. Tape a piece of 2" tube to the old housing. Cover it all with wax paper. The old as a mold- fiberglass over it.
3. Build an enclosure.

Either would then be the new housing, separating the exhaust and intake... and making an exhaust port in a manageable size. Like I researched first, a 2" inline muffler is only $14. The materials I looked at today would have come up to around $30. At 2"ID, I can easily run an exhaust line from that outside if needed.

But yes. This has really turned into a pain.


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