compressor – need suggestions

You'd be amazed what you can paint a car with. I've done it with an antique AC compressor with a 1/4HP motor mounted on a 40 Gal tank. Actually, it was a Suburban I painted. AND I painted it with a gun that only had a 16oz material cup. Just lots and lots of long beer breaks letting the compressor catch up.

I now have a 110V 5HP portable on a 30 GAL tank. Only thing I ever painted with it was a golf cart (still with the 16oz touch up gun). It certainally had no problem keeping up.

I suspect that unless you are using a gun or material that requires a lot of pressure or volume - the compressor you mentioned will keep up just fine.

 

I believe with lacquers it is important to keep a "wet edge" although I can't remember why. Modern finishes (enamels and such) are much more forgiving.

95% of your results will be set before you ever put the finish in the gun. SAND SAND SAND. Prime, Wet sand, Prime, Wet sand.

Make sure the gun is in motion before you pull the trigger, and that it is still in motion after trigger is released to reduce sags (of course you can't lay it down real thick either - especially with metalic flakes where the flakes will sag even if the paint doesn't).

Get too close, or too high pressure = Orange Peel. Too far away - finish is rough and dulled.

The best way to develop the proper technique is to practice on the wife's car.

 

Sno, check out the HVLP guns and see what they are rated for. Then go looking for compressors and see if they exceed what the gun requires.

I bought my compressor first from CDN Tire (based on price and the ratings seemed pretty good). It's a Mastercraft 58-7922-8 with a 4 gallon tank, 7.3 SCFM @ 40 PSIG and 4.6 SCFM @ 90 PSIG. Higher CFM at the higher PSI would be great to have (good for those small sand blasters to work well).

My HVLP gun came from a Princess Auto sale. It's a Powerfist model, has a 21oz paint tank and wants 7 to 9 CFM @ 20 to 50 PSI.

This was my first spary job, it seemed to work okay painting my tank and fender. The compressor ran most of the time while spraying. I put a fan at the compressor to keep air moving over it for cooling purposes.

 

What's your budget?

I was a compressor mechanic for over a decade. Worked on everything from 1/3 hp single cylinder machines up to 300hp twin screw industrial units and 10,000 rpm oil-less Atlas Copco instrument air compressors, dryers, blowers, vacuum pumps, refrigerated dryers etc..

My first suggestion is to avoid oilless compressors. They are loud, cheap and don't last. I would also avoid Porter Cable compressors, especially the JetStream, as they have proven troublesome. I once saw 4 come though the shop in one month, all with burnt up motors. Porter Cable do make decent power tools, unfortunately, their compressors are not among them.

They may not be sexy, but the best units are the heavy, twin cylinder, belt driven oil lubricated compressors. Since it is likely that you will not be going to any industrial compressor suppliers, in which case I would suggest buying a small Champion or Quincy (the best there is), I would recommend either a twin cylinder Campbell Hausfeld, or a twin cylinder Coleman Sanborn unit, both available from Canadian Tire. Husky compressors are re-badged Campbell Hausfelds, as are some Ridgid's. I refer to the cast-iron pumps, as most aluminum pumps (excepting Champions) are not very well built, but use the metal for its casting and cooling properties

Please note, my recommendation of the Campbell Hausfeld twin, oil lubed unit does not imply any further recommendation of CH products, most of which is throwaway junk. Same goes for Coleman. Can Tire used to sell some nice twin cylinder IR units awhile ago, but I don't see them anymore. I guess they were a bit pricey. Probably why they don't sell Milwaukee tools there anymore either. They are really selling a lot of crap there nowadays. They used to be a half decent store once, now it's all Chinese crap, some of which is the same stuff you can get at Princess Auto. (For the Americans on this site, Princess Auto is a lot like Harbour Freight, but it has a lot of other stuff geared towards farmer's and tradesmen, like welding equipment, large fans, stuff to build trailers etc. They also carry a lot of stuff bought up from other companies liquidating stock, and bankruptcies and the like, so you never know what you'll find when you go there. It's an addictive shopping experience. Sometimes they have weirdo stuff like military generators that run at 400Hz and stuff If you are near the border, you might finds something worth getting shipped to you, they have a weekly flyer at their website http://www.princessauto.com).

DeWalt compressors are good units, as they are the old Emglo's. I think some of them use the CH twin cylinder pump as well.

If you must, you can get small compressors from Princess Auto for dirt cheap. Longevity is questionable, as is workmanship. I do know that PA does not stock many parts. We had a guy come through our shop once with a PA compressor that he tipped over and broke the flywheel on. It was going to take 8 weeks for them to get him a new one. I guess the old Buick engine blocks had not yet been melted down in China. Anyhow, it is useful to remember a few things:

Ratings on air tools are usually base on a 25% duty cycle, so actual air consumption under heavy loads can be up to four times greater than advertised. Also, it is physically impossible to draw 5hp worth of electricity out of a 110V outlet, and very difficult to do out of a 220V home service. It works out to something like 40amps @ 110V, which, if you can manage it, will certainly put you on a first name basis with the local fire captain. Also consider that compressor can draw up to 10 times the rated amp draw on start up, so if you need air far from the compressor, lengthen the hose, not the power cord, indeed, avoid using ANY extension cords with an air compressor, as they are one of the highest current drawing machines there is on startup and need as much voltage as they can get.

Disregard any output ratings at 40psi. You will rarely, if ever do anything at that low of a pressure, except possibly HVLP spraying, in which case it might be relevant. Rule of thumb is 4cfm per ACTUAL hp @ 100psi. So, by reverse logic, you can take the CFM output @ 100 psi and divide by 4 and you will be able to roughly calculate what the actual HP output of a compressor is. There is a lot of wild exaggeration on power outputs in this end of the compressor market, with companies using some pretty dubious methods to measure HP. Some use Peak Power, which is basically how much power the motor can develop with a locked rotor and someone holding the breaker on with his thumb. Others use the amp draw at startup Watts = Volts X Amps, 1 hp = 746 watts etc. Others use the "potential energy equivalent" available from a tank of air @ 100 psi etc.., none of which have any bearing whatsoever on real world conditions. Campbell Hausfeld was actually successfully sued a few years ago for inflating (pardon the pun) the HP ratings of their machines and were forced to give customers who had bought their products a $50 voucher towards the purchase of a new CH unit. They are far from being the only ones, but I guess they were the biggest target.

Anyhow, happy shopping. I sold a nice unit a few months ago that I had built up from a good motor/pump from one machine, and a good tank from another. Never did get to use it, and I had nowhere to keep it, so out it went. It was one of the sad ironies of being a compressor mechanic. Everything you fixed got sold, and every time you went out to fix something, you never had any air for your own tools because the compressor wasn't running! I did manage to snag a beautiful old 2hp Webster compressor from a fire hall for my brother in law. Built in 1961. It was big and heavy, nicely built, quiet and smooth. Webster was based in London, Ontario, and made some great old stuff in their day.


Decent Machine at Can Tire



Although if it IS running up to 150 psi, the first thing I'd do with it is open the pressure switch and turn it back to 125. Single stage compressors lose a lot of their efficiency at higher pressures and make a lot of heat if worked had.