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Sat Jul 12, 2003 5:56 pm

Our 50-year-old home shop has a built-in compressor of limited utility. It drops from 90 psi to about 55 psi after running a jitterbug (pad sander) for 40-50 seconds, then takes about 5 minutes of non-use to get back up to 90 psi. Works great with impact wrenches and to pump up tires, though, and it's pretty quiet when running. The tank is about 18" in diameter and 24" tall (20-30 gallon?); the motor and compressor are connected by a v-belt.

I also have a portable Coleman Powermate compressor (oilless), 4hp, 11 gallon, 120 psi (max), 7.0 cfm @ 90 psi. It keeps up pretty well with the siphon spray gun that came with it, but it's so noisy I can't stand to have it in the shop while it's running!

So . . . I'm thinking about replacement options - if possible, I'd like to keep the bigger tank I have and just replace the compressor (and the motor if I need a bigger one for a new compressor).

Questions:
1) What size of tank, hp of motor, psi of compressor, and cu.ft./min of the whole system are needed for HVLP painting and continuous use sanding?
2) What compressor types run quietly?

M D "Doc" Nugent
Renton, WA

Sat Jul 12, 2003 9:42 pm

look for a 50-60 gallon tank and at least 11 cfm@ 90 psi. a two stage compressor is much quieter than your single stage coleman. i installed my compressor in the former cold cellar in my basement at home, insulated the room, ran a fresh air inlet in from the outside wall,so it is as quiet as a ghost. then I ran copper hard line (3/4") through my basement and into my garage, with four outlets, with water traps, oil filters and regulators at each point. with all the additional line, i have probably added 10 gallons to my tank capacity, and i have air wherever i need it, inside or out, without having to drag hose all over the place.

Sun Jul 13, 2003 8:26 am

Something like this?
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=40946

Sounds like the 4hp motor off my Coleman would run it.

Also, could I plumb both of my tanks (the 11 gallon from the Coleman PLUS the 20-30 gallon shop tank) together to act as one bigger tank? Or would that be unsafe somehow?

Thanks for the help,
M D "Doc" Nugent

Sun Jul 13, 2003 9:19 am

You'd probably have to build a bigger mounting bed on top of your current compressor to mount that set-up, and you may find that 4 hp is a little light to get optimum performance. if the old shop tank is in good shape (no corrosion or dents, and is rated at greater than your compressor's max) then it is a good idea to connect them. You'll have greater capacity, which means your compressor will not have to run as often... but it will run longer when it does kick in.
here's a thought- instead of investing $350 in the pump alone, why not sell your current coleman set-up (if it is in good shape, it may be worth $100-150) and invest in a 6hp eagle, husky or c-h two-stage, with a 60 gallon tank? if memory serves, you can get one for right around $500, which will be more than ample for your needs.

Sun Jul 13, 2003 9:45 am

i should clarify- a two-stage compressor is best but don't overlook a high-volume single stage, either. do you have the capacity for 220v power? if not, then your options are a little more limited. the big factor is volume- if you are sandblasting, using HVLP paint guns, jitterbug sanders, you want LOTS of air.

Sun Jul 13, 2003 12:28 pm

This is getting way out of reach financially! And before I forget to answer the question, I only have 110v in the shop.

The Coleman works okay with both spraying and sanding, but I need hearing protection to work in the same room with it. I don't have a basement nearby - how else could I quiet it down?

Building an insulated "dog house" around it might help, but I'm afraid it also might lead to overheating. Is the sound coming right through the pump walls? Or is it coming from where the air goes into the pump (exiting air goes into the tank, so that shouldn't make noise)? If some sort of "intake muffler" would work, I have a spare turbo style muffler . . . .

MDN

Tue Jul 15, 2003 12:02 pm

If all you're running is a D.A. or "jitterbug" sander, I advise going electric. I have been restoring all makes and models of vehicles with one electric sander. It is a variable speed, DA, 110 volt, easy to hold, with waxing attachments Porter Cable brand beauty. It was worth every penny! Not too many pannies either, I paid about $120 for it, and they're even cheaper now. Standard 6inch disc makes a perfect match for any auto sandpaper. May save you the hastle of upgrading to a compressor that will run on 220, still run all of the time, fill your lines with unwanted water (unless you take the necessary and expensive precautions) and COST A LOT MORE! I do usse a compressor on a daily basis, in fact I own two, but I try not to devour the electricity by running air tools with a high draw on air.
Ryan
Bellingham, WA

Tue Jul 15, 2003 12:03 pm

I HONESTLY do not belieave that any 110 volt compressor can meet the demand for the air a DA requires for a sustained ruuning time.

Tue Jul 15, 2003 12:59 pm

My solution to the noise issue was to put it outside the garage, so your doghouse idea would work. Just build it w/ a good overhang. Then use some type of screen material for the top few inches of walls.

Tue Jul 29, 2003 2:12 pm

Doc,
I would say you would need a minimum of 14cfm to ensure pressure stabilty.
As regards the noise, most modern compressors are pretty quiet anyway.

Wed Jul 30, 2003 3:13 am

Sears has a not so quiet 32 gallon compressor for $250 i have one its not bad good for gettting them rust axel nuts off and other things too

Wed Jul 30, 2003 3:13 am

i think it has 120 psi ? good pressor