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Quiet air compressors

videobobk

Well Known Member
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We have at least one new build project in a school classroom that does NOT have compressed air plumbed in. There is really no place to locate a compressor outside the room, so having a quiet compressor takes top priority, even if it is at the expense of some durability. The quietest one I can find advertised is the California Air Tools CAT 6310, at 60 Db. That is not much louder than a refrigerator. It is rated at 3.8 cfm, which will run about anything a group of kids will need to build and RV-12.

Have any of you actually bought and used this thing? I would like a report on one before I spring for it. They are less than $200 at HD and Lowe's. Thanks

Bob
 
I have a 3hp, 220v ingersol rand compressor. It has a 60 gallon tank and is very quiet, plus it doesn't need to run much with that big a tank. Northern Tool Supply, $800
 
Whatever you end up with, if it has a threaded intake port, you can find an intake muffler for air compressors at Grainger.

Belt driven and oiled compressors are quieter.
 
That's really impressive if they can get that quiet. I looked at CAT's web site and the 6310 is listed as "discontinued" but they have a replacement model.

I guessed it might be a rotary screw design but it turns out to be a double piston type. Really impressive if they can get a reciprocating unit that quiet.
 
or...

a bigger tank (or multiple tanks).

Many years ago, my dad told me about a work area in an electrical supply house that had a large air tank being fed by...wait for it...a re-purposed refrigerator compressor (as in, out of the back of a refrigerator). It quietly hummed in the background, & due to their minimal needs, they never ran out of air.

No clue how they avoided lube issues; perhaps it never spat out its oil while running.

Charlie
 
I bought a California Air Tools CAT-4610A for my hangar. It's amazingly quiet. I also grabbed an auxiliary 10 gallon tank to plumb in for extra capacity.

Unless you're sanding/buffing or using something that's continuously running, I think it'll be fine.
 
An option which is both quiet and affordable is an old 2-stage compressor.


The one in this photo is from a small automotive garage which went out of business a few years ago when the mechanic retired. I believe it cost $200-$250. It is large and quiet.

The flywheel acts as both the drive system - to two pistons - and the cooling fan which blows on a coil tube connecting the output of the first piston to the input of the second. (The pistons are located front-to-back.) I have the pressure switch set to run at 150 PSI and cut out at 180 PSI at the tank. A regulator is set to 100 PSI to the various tool drops. Depending on the locations, there can be additional water separators / filters, inline oilers, etc.

The original belt drive is quiet and dramatically reduces the RPMs of the pistons.

If this were still not quiet enough, it could easily be "boxed in" with HVAC insulation.

FYI: I listened to the video and - having compressors like the first two - I would estimate my two stage is as quiet or quieter then the California Air. Additionally, the old 2-stage compressors have a much gentler sound - more of a chuggah-chuggah-chuggah sound.
 
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Wow, thanks for the replies! A couple notes: absolutely can't box one in--fire codes. The "repurposed refrigerator compressor" really made me smile. Had one of those in an art studio back in the 80s. It was out of a '47 Ben Hur deep freeze, and ran at most four airbrushes. Really couldn't hear it, unless you paid attention. Used it for years with no maintenance.

Think I will have to give the CAT a try, and will plumb in a larger tank if I have to. Normally only using air drills and rivet pullers, fairly low volume devises. This is the first time we have had a dedicated classroom (not used for any other classes) but size and appearance will make a difference. We may be able to get one free, or at least at a good discount. We won't be starting until August (school year) but will fill you in on how it works out. It certainly sounds like a simple solution to the noise problem, and is portable. (I do have a two stage at home, but it is staying!)

Bob
 
What I found with mine

(Quincy two-stage) is that the highest noise level is not at the intake silencer but at the vent slots in the motor housing where its internal cooling fan puts out a fairly loud hiss. This was as measured by an iPhone noise-metering app at as close to uniform distances as I could eyeball. The motor cooling fan is 3 or 4 dB louder than anywhere else around the compressor.

Just a random data point :rolleyes:

-Stormy
 
The other reason I went with the California Air Tools compressor was I needed a low power compressor that wouldn't trip my hangar's 15 amp breaker. Airport Ops charges $$ to reset them.
 
Think I will have to give the CAT a try, and will plumb in a larger tank if I have to. Normally only using air drills and rivet pullers, fairly low volume devises. This is the first time we have had a dedicated classroom (not used for any other classes) but size and appearance will make a difference. We may be able to get one free, or at least at a good discount. We won't be starting until August (school year) but will fill you in on how it works out. It certainly sounds like a simple solution to the noise problem, and is portable. (I do have a two stage at home, but it is staying!)

I bought the quiet CAT. Mine is model 4610A which has two tanks with a total capacity a little less than the model you mention. Based upon the specs, it looks like it has the same motor/pump mechanism. Yours is portable with wheels, mine is portable with a handle. I have transported mine from home to hangar and back pretty easily.

It is pretty quiet but I would swear it's getting louder the older it gets. Not objectionably so, but perhaps indicative of wear? That said, it does the job and I would by another. It cannot keep an air drill or grinder running continuously or even for an extended period of time. They use too much air. When I'm running my grinder, I can easily outpace its ability to keep up and once the compressor starts, it'll never catch up unless I stop using the tool. For riveting with a gun or squeezer, it can keep up with no problem.

You mention adding more tank volume. I think this is a common tactic people use to increase working time before the compressor pump runs again. While that is the effect, once the compressor pump runs, it will run longer to fill the larger tank(s). The logical place to plumb another tank is via the tool outlets which I think on my model (similar on yours I'd guess) is on the tool side of the regulator. Most tanks are rated 120psi or more. On the tool side of the regulator, I doubt this thing would break 100psi after the regulator so you'd be giving up some capacity of your extra tank, not too mention then you might need another regulator to get down lower for tool use. That's a good chunk of air that your extra tank could hold but isn't. You could probably get at the plumbing on the compressor side of the regulator but at least on my unit, it's sort of tight -- doable, but it would require creative piping solutions.

You mention use in a classroom. I don't know what special demands that might place on the equipment. Perhaps multiple students using air tools at the same time? I don't think it would handle that well.

I think if you're looking for something that can keep an air drill running continuously, buying one that can compress a larger volume of air (more CFMs) would serve you better.
 
On rethinking this (thanks for all the help with that!) I believe you are right. I think I will still go with California Air Tools, but with two hp. I checked the volume on an air drill, and it is too much, especially when someone else may be using a puller. CAT seems to be the quietest of its type out there, and it doesn't use belts. Regardless of what type guard is in place, they can be a danger, especially in a room full of kids. The two hp unit is a little noisier, but still better than most. Will talk to Lowe's this week and see if they have a "scratch 'n dent" model. Lowe's has been very good to us. You might keep that in mind when shopping for tools...

I am going to post about the new project. Thrilled to get a chance in this school, the first where we were invited by a major manufacturer. Check it out.

Bob
 
We also bought a California Air Tools compressor to build our RV-10 and are very happy with it.
Much, much quieter than our other compressors from Bostitch (pancake) and Husky (20 gal., 175 psi).
 
Initial report on the California Air Tools 10020C, 2 hp 10 gal. compressor: We have had it for a couple of weeks, and it is doing the job. It is quiet, at least quiet enough to not be a problem, and you can't hear it at all out in the hall. We only have two hoses at present, but have used an air drill and rivet puller at the same time, and it doesn't run all that often, and then only for less than a minute. It is reasonably well made, although the wheels are pretty light duty. The line air pressure adjusts well. The fittings are a little tight, when putting in a hose fitting. The drain is too close to the floor. Since I got it for $202.50, plus $56 shipping on ebay, it is a tremendous deal for us. I would really like to have one in my workshop. Will it last? Stay tuned--we will use it pretty hard in the next year or so. At present, I recommend it over any small compressor I have ever used.

Bob
 
Initial report on the California Air Tools 10020C, 2 hp 10 gal. compressor: We have had it for a couple of weeks, and it is doing the job. It is quiet, at least quiet enough to not be a problem, and you can't hear it at all out in the hall. We only have two hoses at present, but have used an air drill and rivet puller at the same time, and it doesn't run all that often, and then only for less than a minute. It is reasonably well made, although the wheels are pretty light duty. The line air pressure adjusts well. The fittings are a little tight, when putting in a hose fitting. The drain is too close to the floor. Since I got it for $202.50, plus $56 shipping on ebay, it is a tremendous deal for us. I would really like to have one in my workshop. Will it last? Stay tuned--we will use it pretty hard in the next year or so. At present, I recommend it over any small compressor I have ever used.

Bob

Sorry to bring an old thread back to life, but I'm considering this compressor for my build. How's it holding up?
 
scuba tanks

A friend of mine built an entire RV-7 in with scuba tanks and a first stage regulator. It doesn't get any quieter than that. :)

Lenny
 
True.

I installed a Dayton squirrel cage fan for insurance, but found it to be overkill. A little planning and orientation can take advantage of the compressor's large pulley wheel with "fan blades".

Sound boxes do not need to be hermetically sealed. Judicious sound deadening (I used discarded carpet remnants) and the knowledge that sound doesn't like to "go around corners" works wonders.

FWIW
 
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