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Posted by: BeatNavy Dec 26 2019, 02:18 PM

This may have been covered before, but I did not find it answered explicitly:

What size air compressor is good enough for doing a decent quality paint job on our cars and otherwise work with air tools? I don't have one now, but I am thinking of making the plunge and trying to paint my car at some point. I don't think I would really do anything bigger than a 914.

Here's a more specific question: is a 60 gallon, 3HP, 11.5 CFM at 40 psi; 10.2 CFM at 90 psi good for this? There's one on CL not far from me that could be a decent deal and serve as my post-Christmas gift to myself.

Posted by: TJB/914 Dec 26 2019, 02:45 PM

Rob,
Good question. I am looking to upgrade my failing 1.5-hp air compressor and wondering what electrical service plug is required. I think a 3-hp motor might needs a 220 hookup?
Tom

Posted by: BeatNavy Dec 26 2019, 02:54 PM

Hi Tom,

Yup, definitely a 220/240 connection. Fortunately I have one of those available.

rc

Posted by: tygaboy Dec 26 2019, 03:09 PM

I did a ton of research and (budget and space available), I'd do a minimum of 5-hp, 2-stage, 60 gallon, 80 is even better.
There are often good deals on these things on Craigslist.

Also, you don't necessarily need to shy away from a used 3-phase setup I successfully ran a 3-phase, 5-hp on single phase 220 by using a solid state phase converter.

Yes, this means I was only getting 3.5 hp, and it was likely to wear out the motor more quickly. But I had no issues.

I happily confess that I recently upgraded (downgraded?) to a single phase 5 hp motor, just because I wanted to simplify all the wiring and in the end, it's "better".

My $.02. Hope it helps.

Posted by: Chris914n6 Dec 26 2019, 03:18 PM

I have an older Craftsman 30gal 110v roll around that works just fine for car wrenching. I have to let it catch up using a saw/cutter/sand blaster but it's not a big deal. Haven't tried to paint a car with it but I think it would with a little patience, HVLP isn't that air intensive.

At some point I'll have to replace it so I'm looking at a 60gal like this https://www.lowes.com/pd/Kobalt-60-Gallon-Two-Stage-Electric-Vertical-Air-Compressor/1000542193

Posted by: jd74914 Dec 26 2019, 03:31 PM

Mine is has very similar specs (it's 3.75 hp and 11.2 cfm @ 90 psi) and has worked really well for just about everything. I painted my car with it in fact and didn't have any issues. Compressor was more ready than me.

Note: I don't have a sandblaster so I'm not sure about that pairing (haven't looked at air consumption). But it does fine with the HVLP gun and basically all air tools.

Posted by: Superhawk996 Dec 26 2019, 03:52 PM

It's like buying a boat. Whatever you buy, soon you'll be looking at the next size up.

I have 3 HP 60 gallon vertical Ingersoll compresor with similar specs and it is more than enough for anyting but extended duration sandblasting.

I painted my first car with 1.5HP 20 or 30 gallon tank affair. Spraying paint doesn't take much air. Die grinders and other tools not so much!

If you want to sandblast effectively 5HP dual stage 80 gallon tank or more but now we are taling $2k for an air compressor.

Also be aware that even cast iron piston compressors do wear out (but can be rebuilt). CL used not necessarily bad but if you can't verify it before you buy it, beware, and price accordingly.

Posted by: 914Sixer Dec 26 2019, 04:24 PM

More hp is better. 3 is good 5 is better. 60 gal is plenty good with 5 hp.

Posted by: Superhawk996 Dec 26 2019, 04:33 PM

40 HP VW is better


https://www.youtube.com/watch?v=v6qtHxp_ZGg


I've seen this done too by simply running the VW on 3 cylinders of GAS, and using the 4th to pump air.

Posted by: BeatNavy Dec 26 2019, 05:00 PM

That's really cool. I've got a spare Ghia lying around...

Seriously, thanks for all the feedback so far. It's great info. I'm not planning on sandblasting -- just trying to do a decent paint job at some point and working with air tools. I realize more HP is better -- but it's also more expensive, and a slippery slope

Posted by: Mark Henry Dec 26 2019, 05:15 PM

Doing heavy work, blasting, big paint jobs, entry level shop, etc 220v, 5hp, 80 gal, minimum. My compressor is 7.5/120 gal.
Smaller use I'd still get as big as I could afford.

Posted by: mepstein Dec 26 2019, 05:41 PM

We have a commercial screw compressor at the shop. No air issues.


Attached image(s)

Posted by: IronHillRestorations Dec 26 2019, 06:11 PM

The issue for painting is clean, dry air so be sure to get a good quality filtration set up. I have three moisture traps and a coalescing stage with dessicant.

Posted by: Costa05 Dec 26 2019, 06:40 PM

I am running a 3.7 hp Dewalt 60 gal from Tractor Supply. $550 on sale Veterans day ad. Great entry level and affordable. Handles paint just fine. Air tools fine too. The only one that struggles a bit is the 3" cutting wheel I use to cut my sheet metal. I just back off if it needs catching up in pressure. Needs 20 amp 240v circuit.

Posted by: jcd914 Dec 26 2019, 07:36 PM

I rented a trailer mounted commercial gas powered compressor and jack hammer to dig up an in-ground lift at the first shop I worked in. The compressor was a Ford V8 with 1 bank of cylinders running off a carb and the other bank was the air compressor.

Jim

Posted by: 76-914 Dec 26 2019, 08:06 PM

Thats the one I have Chris. It keeps up with any tool I connect to it. I caught mine on sale for about $450, IIRC. That was about 8-9 years ago.

Posted by: jmitro Dec 26 2019, 08:20 PM

I painted two cars with a 60 gal/ 3.7HP compressor, 11.7 CFM at 90 psi. so yes yours will work fine. anything requiring higher pressure and more sustained use (like my home soda blasting unit) will quickly make it run continuously

Posted by: 914forme Dec 26 2019, 09:17 PM

I used to paint with compressors, and since went to an HVLP Turbine system.

With Mark, if you can find a screw compressor buy it if it is in your price range and performs to specification, you will also need a tank, but you can find 60-80 gal tanks on Craigslist that include none working compressors. Or just tie several 20 gallon units together. If you have loft space the screw units can be lifted up there, and then the tanks installed.

You will also need a great dryer system, I pulled one out of a dental office, it is one the AC units that cools the air and dehumidifies it. My system is bone dry. And I still prefer to shot with the HVLP Turbine system.

I have a 5hp 60 gallon 2 stage unit, it runs most of my stuff well, I need a bit more for the blast cabinet.

Of course if you have the coin, https://www.eastwood.com/eastwood-elite-qst-30-60-scroll-air-compressor.html?SRCCODE=PLA00010&gclid=EAIaIQobChMIjOfQtO7U5gIVCNbACh2IEQLoEAQYASABEgKq-PD_BwE

Posted by: BeatNavy Dec 27 2019, 05:40 AM

That Eastwood scroll compressor looks pretty sweet, but at $1799 probably outside my price range for post Christmas self-gifts

I guess I also have to decide if it's better to go higher and get brand new vs. a good condition one at roughly half price (e.g., new for ~$600 vs. used but good at $300 or below). That DeWalt one looks solid as well.

Posted by: mb911 Dec 27 2019, 06:45 AM

What about dbs? I may need a quiet one ..

Posted by: roblav1 Dec 27 2019, 07:45 AM

My old 110V portable Sears unit I bought in 1988 crapped out (piston slap) last summer. I needed 110V and portable given my current shop conditions (big extension cord running to the shop / garage). So I bought this:

IR Garage Mate Small Portable Reciprocating Air Compressor 2 hp

It has almost the same CFM as the old Sears unit, but the larger tank helps. It's also very quiet. Runs paint sprayers and the usual air tools just fine.

Posted by: enikolayev Dec 27 2019, 09:18 AM

https://www.youtube.com/watch?v=cfjSm_ieRkE

Air compressor ratings explained. Essentially need a compressor with 4x the CFM rating for the tool you want to run.

Posted by: bbrock Dec 27 2019, 09:42 AM

Great advice on size. I will add that I would avoid an "oil-free" air compressor. When I started my build, I bought a barely used 60 gallon, 6 HP Devilbiss Pro Air II with killer cfm specs. I didn't know anything about oil-free compressors. Right off the bat, the thing seemed to have slow recovery times so I rebuilt the pistons. That didn't change much. Nevertheless, that unit got me through all the cutting, grinding, spraying primer, and even sandblasting the entire car, but I spent a LOT of time waiting for the compressor to catch up. Despite trying to be careful to keep it to a 50% duty cycle, recovering times got worse and a second piston rebuild was completed (About $50 per cylinder for parts). Finally, the compressor literally blew up, sending a shattered piston top into the head. Huge waste of money.

I now run a 60 gal. 5HP 2-stage compressor and and am MUCH happier with it. As others have said, it is more than enough for lower consumption tools and paint sprayers. It is adequate for blasting, but requires waiting for it to catch up to keep the duty cycle reasonable.

I think for most DIY occasional use guys, the 60 gal. 5HP 2-stage is about the sweet spot. You can do a lot with a smaller compressor, but you can also nurse this size through occasional more demanding tasks that smaller units couldn't handle. For example, when I have a lot of cabinet blasting to do, I try to set up one or two other projects that don't require air to switch off to while the compressor is catching up and getting a rest.

Posted by: tvdinnerbythepool Dec 27 2019, 10:26 AM

I think what you mention in the original post will work well.

One of my jobs is in guitar manufacturing and we run an Ingersoll compressor about 15hrs a day for Paint mostly. Some sanding and occasionally sandblasting car parts for me.

The name of the game is CFM. You can have a big ass tank and a high PSI rating, but if it can't continue to produce that PSI rating, you're toast. We learned that the hard way!

Posted by: rhodyguy Dec 27 2019, 10:55 AM

Continuous duty cycle.

Posted by: jd74914 Dec 27 2019, 01:24 PM

Wonder how quite that scroll compressor is? All of the larger one's I've seen are pretty loud.

My lab has a nice screw compressor (similar to what Mark pictured-just older). Thing puts out ~350 cfm @ 100 psig (25hp motor) and has a refrigerating dryer and a 500 gallon tank.

That said...I wouldn't recommend anyone buying a used screw compressor unless you're really committed to maintenance and understanding it or have a large checkbook. There isn't much technical documentation online and as such troubleshooting the electro-mechanical controls is not for the faint of heart or really anyone not intimately familiar with industrial systems. Part prices are crazy too.

Posted by: IronHillRestorations Dec 27 2019, 06:05 PM

The Eastwood scroll looks interesting to me, but the reviews are either good or bad. I'm going back and forth on whether to move mine or get a new one, whenever I can move.

I've got a 5hp two stage Champion with an 80 gallon tank that I got new in 1995, and it still works great, but it's noisy as a locomotive. I don't have any neighbors at the old shop, but the new one I will, so I'm exploring options, which is why I got excited about the Eastwood scroll, but it's pretty much 100% MIC which kind of scares me. My old Champion had a 5 year warranty

Posted by: mb911 Dec 27 2019, 06:44 PM

Perry,

Same here. Looking at a California compressor.. They seem well liked.

Posted by: maf914 Dec 28 2019, 07:54 AM

I am curious what sort of filter/separator is needed to provide clean air for painting, when the compressor is not oil-free.

I am familiar with small scale hobby type systems using an oil free compressor. Even with these, an oil/water filter/separator is important for clean air.

Posted by: mb911 Dec 28 2019, 08:16 AM

From a sound stand point I am going to look at sound absorption panels 1st..

Posted by: Mark Henry Dec 28 2019, 08:48 AM

there are all kinds of DIY water trap vids on YT like this one.


https://www.youtube.com/watch?v=KzBNscMrQMs