Compressor size--advice needed

Hey guys,

I am about to order a compressor to use in restoring our 57 MGA. I've been getting some conflicting advice on the size needed for this job. I usually over-buy on stuff, but in this case that may become pretty expensive. From what I see out there, it's either a $300.00 1.5 hp/90psi/6CFM or the step up (or jump)to 3 hp/135psi/10CFM for $650-ish. Assuming I will sand, unbolt everything, use sheet metal nibbler, maybe even power up a sandblasting cabinet, what is the general consensus on need for this? Additionally, anyone know of a great deal going somewhere or best brand recommendation?

Thanks in advance for all help!
Geert

2-HP belt drive 2-cylinder compressor, 30 gallon horizontal air tank, fits under a work bench. Will draw 14 amps at 115-VAC or 7 amps a 230-VAC, can be wired either way. Largest compressor that can run on 115-VAC 20-amp circuit. Can produce 7.5 to 9.0 SCFM at 90 or 45 psi respectively. This will handle all small air tools and paint guns, about 50% trigger cycle for a circular sander, maybe 50% or 25% duty cycle for a sand blaster, depending on the blaster air requirements (more air = faster work).

If you think you need a larger compressor for air sanding work or for sand blasting, then consider 5-HP belt drive 2 or 3 cylinder 2-stage compressor sitting on on a 60 gallon vertical air tank. This can do about 15-SCFM at 150-175 psi, crams a hell of a lot of air into the tank, and can likely do 100% duty cycle for sand blasting (with a moderate size sand blasting unit).

I would recommend avoiding direct drive compressors as they run too fast, make LOTS OF NOISE, and are less efficient (but they are cheaper to buy).

Read half a dozen web pages starting here: http://mgaguru.com/mgtech/tools/ar101.htm
The "Good Deals" page is several years old, out of date, links probably don't work.

I like option three better. Look on Craigslist for a used 5hp two stage compressor .... Barring that, don't go with the 1.5 HP model, and be careful of unrealistic peak output claims - they are deceptive. Grinders and cutoff wheel tools take more cfm than what you're looking at to work well. Although I use an orbital air sander both at work and home, they are air hungry. I bought an electric 6" dual action sander that I've been really happy with , and it costs about one sixth as much to use it than to have the compressor running nearly constantly. I also bought an electric metal shear at Tractor Supply for about the same $ as air driven, and it takes a load off the compressor and is much quieter .

My vote goes for the upper end as well. Dont even bother trying to sand blast with the little guy. The bigger 2 stage one will run cooler and might allow you to operate with little or no water in the line as well, although if you are painting, you will want to add a water trap at the end of your line just as a precaution. I have yet to see a drop enter my low end trap, but my supply pipe is 1"dia and has built in slope back to drain legs.

You might consider looking for a good used one. I did that and bought a rebuild kit for it, but then never got around to putting it in. Runs so good, I am reluctant to mess with it.

Aw a question I can answer. I've been in the compressor business for 25 years. A few quick answers. First almost any 2 hp compressor will run tool although you'll need to watch the duty cycle, 50% means just that you can't run it continous. You'll never have much luck running a decent blast cabinent with anything short of a real 5hp. Easy way to tell if it's for real is you should have about 18 C.F.M. at the rated pressure, there's no secrets that the compressor people overate what the compressors will make and the tool guys are the same way rate their tools on the light side of air consumption. My sugestion if you're real serious and intend to keep doing this is get a name brand 5 HP (not develops) two stage compressor which is the smallest size I'd recomend for a bead cabinet. Other wise a two HP oil lubricated compressor will do just fine as long as you're not in a rush. Run it at 220 volt and you'll do fine. SOme of the name brands are IR, QUincy, Kellog, Curtis, sadly even these guys have entery level machines which means marginal. If you buy an older name brand machine parts and stuff are available> Bill

5hp minimum.
Ron

I have a 3.5 hp 45 gal unit that is just adequate for most jobs. Almost any compressor will run impact tools but when you go to air driven sanders and cutters that fall way short. Fortunately there are many electric tools that do as good a job with a lot less noise and dust. You can attach a vacuum to an electric dual action sander and other electric tools.
My unit works good with glass beads in a cabinet but is real weak in a driveway pressure blaster. I have not used it for big time painting but I have painted 8 cars with a smaller unit without a problem.. Without a problem except water in the line. For that I used 4 filter/traps and wound up with clean air, just don't overwork it. I used a box fan to help cool the compressor and that reduces condensation.
BUT,BUT as everyone else says buy a 5HP 60 gal tank unit if you can afford it and plan to do more than one cae.

I currently own 3 large compressors. A Quincy PLT15 and two PLT7.5 compressor. I use the big one in my 12 bay shop. The smaller ones are in 6 bay shops I rent to other businesses. Over the years I have owned compressors from 5 to 25 HP.
There are 2 kinds of compressors reciprocating and scroll. The scroll type is better and quieter but much more expensive. I am talking about Reciprocating type.
The best compressor to own is big and slow. The compressor RPM should be Under 1000 rpm. The pump should be pressure lubricated and have a low pressure cut off. It should have an automatic drain. Big slow compressors last forever and are quiet. Small fast compressors burn out quickly and make noises that are annoying as H%$#.
My PLT15 pump has a 10 HP motor turns at 676 RPM and puts out 37.2CFM @ 175PSI. The PLT7.5 with a 7.5 HP motor turns at 1025RPM puts out 22.5CFM @ 175PSI.
To get high out put from cheep compressors you just speed them up. Look good on paper but hate them in the shop. From Northern tool the 5HP Quincy runs at 1310 RPM 15.2 CFM @175psi. It will be louder than my big one but is better than the other ones they sell. Quincy's quality 5Hp runs at 942 rpm 17.2 CFM @ 175psi.
Spend money on the pump to get a better compressor. Bigger pump with a smaller motor is better than a small pump with a big motor.
The Ingersol Rand 5 hp compressor fron Northern has a 10,000 hour pump it will save you $300 compared to the "Cheep" Quincy with a 50,000 hour pump. When it comes to compressors you get what you pay for.
A Quincy PLT5 pump with the 3HP motor and a 80 gal vertical tank would make a great home compressor. Turns at only 583 RPM but still puts out 10.5CFM @ 175 PSI. AND it will do so quietly FOREVER. Price wise this would be just over $2000. Same compressor with a 5 HP would turn 942 RPM and put out 19.2 CFM @ 175 PSI.
For half that money you can get almost as much air 14.5 CFM @ 175 in a compressor that is rated to last 1/5 as long. And as a bonus it will probably annoy your wife and your neighbors each time it kicks on.
8 years ago the compressors below were $1700 and $3200.

Geert,

The Quincy I selected was Model# 2V41C60VC. It is a two-stage belt drive pump, single phase set up to plug into home electrical breaker panel. The Quincy and Ingersol seem to be about equal in quality and experience. I was about to pull the trigger on the IR when I took a good, long look at the specifications.

The Quincy rates their pump for 50,000 hours vs. Ingersol's 10,000. Probably because the unit operates at a much lower RPM. The Quincy warranty is two years vs. Ingersol's 12 months. The CFM rating on the Quincy is slightly higher 15.2 vs. 14.7 on the Ingersol. At the time of purchase, Northern Tools was running the Quincy unit on sale and it was just a little more than the 5 hp Ingersol. As an added bonus, the Quincy unit is American Made...may even be built at the plant in Bay Minette, Alabama. I like that. (tu) - David

David Shelly
Those are the 2 I compared and I think you made a good choice. One of the Better compressors marketed to homeowners. At just over $1000 it is as good as they get. Because of cost I may buy that one also. It is hard to justify almost double just to be a tool snob. I really like their Pressure Lubricated (PLT) pumps Splash lube works it just bothers me.

Guys--David, Randy, Gary, Bill, Barney, John, and Henry,

Thanks for all the advice given! It really helps having real life experience vs. mere stats on paper, especially seeing how spending the extra money to buy a two-stage compressor may be a time and heart/headache saver in the future. I know I would not have done that without serious recommendations and your first-hand knowledge. Wait a second...did I just thank you guys for costing me an extra $600-plus over my original upper limit?! Strange world this MGA thingy ;)

Thanks again,
Geert