View Full Version : Is my compressor sufficient?
Hi. I hope you folks aren't sick of compressor compatibility questions. I recently bought, at a price too good to pass up, a friend's Craftsman compressor. I'm sure it is fine for most air tools, but I'm also thinking of painting my truck myself. Here are the specs:
Model No. 919.167311
Single cylinder, oil-less
Max HP = 6
"Displacement" = 11.9 CFM (I'm not sure what this means.)
CFM @ 40 psi = 8.6
CFM @ 90 psi = 6.4
I've been told that the Devilbiss Finishline III HVLP gun would be a very decent gun to start out with, but it requires 12.5 cfm at 23 psi for 10 psi at the air cap. Would this not be a good choice? If not, is there another decent gun that'll work better with my compressor? Thanks.
05-19-2006, 12:31 AM
A bare bones minimum air compressor for any serious bodywork or any full paints is a 220 v, 60 gallon tank, 12cfm @ 90psi.
Could he perhaps paint one panel at a time? i know it would be risky as far as it all matching perfectly, and a pain in the rear. but could it be done with that compressor?
Thanks Phil. That's a short and direct answer.
Here's another novice's question, just so I can understand things a little better: For the sake of argument, what would be the consiquences of my trying to use the Finishline or a similar gun with my compressor? Would it not atomize correctly? Would I not shoot a full pattern. Or would it just not generate enough air in the long run to sustain a good paint pattern for very long?
My strategy was going to consist of painting the truck in stages--see attached pics as a handy guide :-)
1) Roof area (above the rain gutters) in white.
2) Right side (fender, door, Q-panel, roof side panels) in a satin-finish beige color, everything's in this color except the roof, FWIW.
3) Ditto for the left side.
4) The front clip (which I'd remove... easier to prep that way anyway).
6) Tailgate assy.
I should mention that this initial painting project would only do the outsides of these components. I'd be skipping the rockers, jams, inner doors, etc. I'm planning to deal with those areas later using a touch-up gun. I am only concerned with getting paint on the primed surfaces for now. I just figured doing it this way would be less taxing on my compressor and my nerves. Would this be possible in your opinion?
I should add that is an actual fourwheeler and I use it as such. I'm not expecting a showcar finish, especially with this being my first attempt. That's partly why I'm leaning toward satin/flatish finish with a single stage enamel.
Here's another idea... and forgive me if this sounds strange---I'm approaching this problem like a newborn child would and brainstorming a little. What if I were to paint my Scout in the stages described above using a touch-up gun, like a Devilbiss SRI? From what I read, their air demand is much lower than a standard HVLP gun, well within the capabilities of my compressor, yet their spray pattern can still be as big as 6 to 9 inches (depending on where you read). I know it's not how a decently equipped shop would ever do it, but could it be done? Does a TU gun lay on a proper thickness of paint? How much coverage would I get with a 4 or 8 oz. cup full of enamel?
Seems I'd be wanting a touch-up eventially anyway.
05-19-2006, 08:35 PM
Phil is right bare miniumum is a good 60 gallon compressor with a minimum of 10-14cfm@90psi for doing a full repaint. If you use the 30 gallon compressor you have it can be done in sections with a solid color. If your compressor puts out 8.6cfm@40psi I would go with the Astro LVLP gun that Len sells for $75. The Astro LVLP only takes 9.5cfm@25psi (versus Devilbiss Finishline 12cfm@25psi) so if you have 11.4cfm displacement compressor then at about 25psi you should have about 9.5cfm@25psi so in theory it would work.
When you use a smaller compressor such as yours if you were doing a full repaint all at one time even on a small car such as a Dodge neon your 30 gallon tank will run out of air less than half the way around the car and the compressor will be running wide open just trying to keep up with you which creates moisture (water) from the compressor overworking itself. This water translates into water in the paint even with the best water traps. When you start to run out of air the gun will not atomize the paint as well as it should which can result in heavy orange peel and a dry finish.
So if you use a gun like the Astro LVLP you could paint say the front clip all at once then the cab then the bed all in seperate spraying sessions. Just make sure to use a good water trap on the gun and one on the compressor also that can be drained. For the quality you are going for I would recommend a good single stage Urethane that is a solid color (so it will be easier to match when panel painting). Good Luck..........I've been there with the equipment you have and it can be done with some patience and good water traps.
05-19-2006, 10:53 PM
All good advice so far, but what is missing is prep work (the stuff you need to do before painting).
Unless the existing finish is in (near) perfect condition and you can get by with just scuffing, you'll have some sanding to do and trust me my friend if you think painting with a small compressor is going to be a hassle, wait to you try and operate a sander off it.
That is a true excersie in fustration, the sander kills off the air tank in 5 min's or so, then your waiting 10 min's or so for the tank to fill up before you can start again setting up a cycle that will take you a day to sand one panel.
Hence the spec's for a minimal compressor Phil V pointed out.
I'm a garage painter (novice) myself and started out the same way we all do with those big box store small tank compressors and quickly found out why they aren't good for full re-paints and bodywork.
Fortunately the place I was doing the work at had two Industrial Compressors to supply the plant with shop air so I could hook up to them for sanding and running tools. Come to think of it I did manage to get the car painted and cleared (Sharpe Platinum HVLP 7.5 CFM's at 40).
I have a SRI-W and run it off a 30 gallon tank compressor. I've only used it for parts painting so far and love it. I think my only beef with using it for a full re-paint job would be the size of the cup.
Thanks Steath and Greg (and Phil and AL). Sobering information. I guess a 'full power' gun like the FL3 is just not going to work for me. The SRI is available with an 8-oz. cup. Still a bit smaller than a full-size gun's, but twice the size of the cup specified on this site..... but maybe it has to be purchased extra. I don't know if that just means you could shoot half a Q-panel vs. only a quarter of a Q-panel though. If that's the case then big woop.
Anyone happen to know if 8 oz of paint would at least do one coat of paint on an SUV's rear Q-panel, or roof?
LVLP, huh? Is there a catch, meaning is there any disadvantage to using LVLP over LVHP with my particular goals in mind?
As I indicated (sort of), due to the type, condition, and intended use of the vehicle, I think I'm going to go with a low gloss paint of some kind. I got the inspiration from a line of paints called Hot Rod Flatz. It's made by TCP Global, which happens to be only six miles from my house. I talked to them about it and they say they can mix any factory color yielding that finish using PPG Enamel. And it's pretty inexpensive as paints go, from what I understand.
Last question for now: Would a urethane paint be better for working with and durability than acrylic enamel, for my application?
With the compressor you have, the SRI gun with the 8 oz cup will work fine.
The SRI has low air requirements. Since the gun comes with a 1mm tip the only
thing you will need to watch is the viscosity of the paint you are spraying.
On the paint side a urethane based paint is a better choice.
I believe you may run in to problems though if you need to operate a DA to do
some sanding. Also you may need to scuff and seal the existing surface so it
is uniform prior to painting. With the compressor you have there is little margin
for using larger guns such as might be used to apply regular high build primer
or epoxy primer.
Thanks X711. I'll have to ask the guys at TCP about which paints will work with an SRI gun.
I understand urethanes dry quicker than enamels, which is a plus. Can Urethane be done in a satin finish and still be very durable?
On sanding and priming, I don't know if you can tell from the tiny pics I attached earlier, but most of the priming and sanding is already done. I think I've done a pretty good job of it too and it was mostly done by hand. At least I've gotten a few compliments from friends on how it's looking so far. The truck had been repainted at some point, probably down in Tijuana, and the paint was looking downright frosty, all cracked and flaking in many places. I've made sure to at least sand down through the pale, oxidized surface of the finish. In most places it's down into the original finish, or even bare metal.
I've been using various sizes of Dura-blocks, plus a 1/3-sheet block to do the sanding, starting with 80-100-grit then finishing with 240 before priming. After I spray primer I block-sand again with 400-grit and feel the surface. It looks so much better than it did before, and it feels smooth and straight, which might be a better test, I dunno.
Funny though, it's taken me weeks to accomplish what you guys might do in a day, using the right tools and working more efficiently. But I guess that's why you guys get to charge the big bucks ;) The only power sander I currently have available is a Porter Cable finish sander, which I was using with 80-grit to try and take down the old paint a little. I found that muscle-powered wet sanding was working just as fast, and making a lot less noise. I was asking about DA sanders in another thread because it would be a nice tool to just have around. (I have another car direly in need of new paint.)
05-20-2006, 09:06 PM
The LVLP i mentioned is a Low Volume Low Pressure gun, but I guess the SRI would work but 8 oz of paint is going to be gone pretty quick, maybe enough to do 1 coat on an average front bumper cover. The 1.0mm tip seems to small to me for shooting Acrylic enamel but it might work if reduced enough. Urethane would be much more forgiving and dry's quicker, and I don't see why you could'nt get it in a satin, just seems it would be more durable with a gloss and easier to keep looking good.
I would personally try to find a good low CFM full size gun with at least a 20 oz cup so your not always stopping to mix paint and a gun with a larger tip like 1.3-1.5mm. Also how are you going to shoot your Primer/sealer? You will need a larger tip than 1.0mm to shoot primer.........Good Luck..........
Hi MrM, I saw your pics, and it looks to me like its nice work. Before you
spray though you might consider hitting those surfaces with a guide coat
to see if they are flat. You may have done that allready but taught I would mention it.
On the urethane paint, urethane is just the actual technology behind the paint.
I have not had a need for a satin finish so I am not sure if the finish you require
is available with urethane based paint. Im betting it is but you should check to
Stealth, I like your idea about using the Astro EVO gun. I have done some readings on this gun since you mentioned it. It's probably the most practical choice for my situation, and it is supposed to be a fine gun for the money. Plus it's a HECK of a lot cheaper than the STA.
On the paint itself I'll have to talk some more with TCP Global... and maybe get the opinion of an experienced customizer if I can find one. I prefer on this vehicle to try satin for a few reasons:
1) Because it's a fourwheeler and it is going to get the occasional scratches from brush and cactus. I'm thinking a non-glossy finish will make these less noticable.
2) The bodywork is pretty nice looking at a glance, but it isn't absolutely perfect. Low gloss is much more forgiving of my mistakes.
3) I'm not trying to make the truck look new. I'm taking inspiration from vehicles we all see occasionally; really old, but really well cared for if you know what I mean. Like a car or truck that's never been repainted, but it's been garaged most of the time for the last 40-odd years, in a color they just don't use anymore. I almost prefer that look over a glossy new paint job on some older vehicles.
I admit the satin idea a gamble using a beige. It might look really neat---to me anyway---or it could look kind of ugly. It's a bit of an experiment but I think it will turn out to my satisfaction. The color choice comes from the fact that the orig. factory color is a light gray. I kind of like the idea of repeating that, but in satin/semi-flat, of course it's just gonna look to all the world like primer. I love the color of "dune beige" Toyota Land Cruisers of the 1970s, and it isn't really too far off from my truck's original color really. International had a very similar color for their trucks in the 1960s called "malibu beige" that I might look into.
BY THE WAY, I resolved my sander issue. At a buddy's suggestion I went over to Home Depot and picked up a little 110v Ryobi random orbital sander for $35. Man, that little sucker kicks tail on 1/4-sheet finishing sander I tried using earlier. I don't know how it compares with a good DA sander driving by a monster compressor, but it sure does the job as far as I'm concerned.
05-23-2006, 12:05 AM
I see what your saying about a flat finish not leaving scratches and the rugged old sun faded but solid and rust free look. The satin finish like you said will not show waves in the bodywork like a high gloss would so it will be much more forgiving and accomplish the look you are looking for.
Good luck on your project, it looks solid in the pics you posted. Keep us posted on your progess.
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