Air Compressor Idea for Paintwork

[SpidersWeb]

Ok, 1.5HP compressor, got it new for $100 on sale.
3HP compressor, $800. The extra price is purely because its actually useful at 3HP.

Anyway, when painting my car the air compressor only kept up for about 30 seconds, then the pressure would drop below 50psi, and the paint would not atomise properly and it all went to hell. The compressor is capable of flowing my air gun at 30psi. I want 50-60. So surely two of these compressors would be capable, and much cheaper, for a quick car paint.

Now I did put some thought in to this, thinking about how the regulator reads pressure, what happens when the secondary tank is full etc, anyway looks to me like its doable. Basically the two air regulators are set at 120psi, but because there are two pumps producing airflow, the regulators will open when each compressor is combining 60psi. So the tank would charge at 120psi, giving a good bit of headroom to work with. If that makes sense?

If you guys could look, have a think, and let me know what you think?

It'd save me a crapload of money, since I wont use them for bugger all else.



Green circles are regulators. The tank I can get off trademe, rated to 125psi, $50, with regulator.

[SpidersWeb]

And I dont see it hurting the compressors, even if one has charge flowed in reverse (if thats possible), it will just fill the tank. Both those compressors would be identical, and shutdown when their internal tanks hit 125psi.

This would also give me 55L of air tank combined.

EDIT: Quick correction, $50 tank has guage not regulator, but Im sure I can buy a regulator for a reasonable price.

[hcca]

Plenty of people do this - I don't even think you need a tank - just the two cheapo compressors hooked up will work.

Are you trying to spray with a gun pressure of 50-60psi? That's far too much for most guns. I use about 35psi.

[SpidersWeb]

Hey hcca,

glad to hear that about other people already do it :) thanks for that

Im using a basic high pressure gun, not a HVLP gun (which most people use). They flow about the same amount of air, but one operates at 50-60psi, the other at 30-40. I know HVLP guns are a lot better, but I bought the gun before I found that out. Gun works great though, just compressor flows less than the gun uses :(

But still, need more air flow.

Think I might get one of those gravity feed HVLP guns. Painting the roof and bonnet with the suction feed was a pain in the ass. Didn't do too bad though, no bubbles, no cracks, no paint flaking off, just "gloss black" became matt black with a textured finish :(

[hcca]

Gravity guns are nicer to use - can use lower pressure so less orange peel off the gun... saves time sanding! Also gravity guns are easier to spray horizontal surfaces with (and don't leak out the sides like some suction guns do).

I have a 13CFM renegade compressor.. it's great, but with hose/regulator/water trap etc it was about $800.

[Chryzla]

Grav gun :)


i just muck around with the painting on my car, second attempt at a car. who cares, its only a sigma :P

[Junkers]

Wow where did you get a compressor for $100?

[SpidersWeb]

Supercheap

A 1.5hp compressor is really almost useless, so they're cheap as. Was on special at the time, normally 139 I think. With a SuperCheap auto High Pressure gun at full blast it was able to hold 30psi, I needed 60 for the gun, we would do the adjustments, get it going mint, then 15 seconds later it would be crap again as the pressure changed. With a HVLP gun, you'd find it only held 15psi. Just can't provide the volume of air needed and the air tank doesn't hold enough. Basically its one good stroke, give it a few seconds, next stroke and so on, which is quite painful when you are painting an entire car with multple coats.

But 2 x 1.5 = 3hp all up about $250
1 x 3 = 3hp all up about $800-$1000

+ guns, water traps, fittings etc. Mitre10 has the T-connector I need, was like $15 I think. However I think I will wussie out and pay someone. We'll see.

[Chryzla]

erm.... dude.... I paint using a 1.5hp compressor. I get no machinegunning, no loss in pressure, and the motor on the compressor isnt always running either... I think you need to look at your painting behaviour, as you arent doing something right.

[SpidersWeb]

Thanks for that, your the first person who said it outright hehe

Well if you are painting fine with 1.5hp, then that means its the gun. When using it, without giving it big breaks, the pressure drops to 30psi. Gun needs to be at over 50psi to atomize the paint properly, so everything would be nice and shiny then get worse fairly quickly.

So perhaps I should try a low pressure high volume gun first. What type of gun are you using? how long between strokes? how big was the reserve tank?

The one I had was a SuperCheap styles high pressure bottom feed. On average I was giving it about 5 seconds between sweeps. The motor was always on, and whenever I hit the trigger the pressure in the tank would go down rapidly until it hit 30.

[Chryzla]

I spray conststant, the air is always running when i paint (its the way you paint, you never turn the air off, hence why the gun has two stages, air and air/paint)

I cant remember the brand of gun i have. Grav fed.

I paint at 500kpa, tank takes 800kpa then motor cuts out.
If im continually painting it holds pressure with motor on, ant the motor stays on. but you do pause occasionally when painting. then if fills up

Compressor: 1.5 HP AirMate Tornado 21025

Bare in mind this is spraying undercoat, and then theres different paint types, i crank it up abit when spraying COB
Acrylic I use roughly 500-550kpa

[SpidersWeb]

Im painting at ~420kpA 1pak acrylic. At ~420kpa it comes out great, but the compressor drops to 200kPa rapidly. On idle tank is at ~850kPa.

Once the pressure gets too low (200-300kPa) it starts to spot, leaving a rough sand-paper like finish. If I just did a small sweep before the pressure dropped too far, it left a perfect shinny paint surface, but yeah, pressure dropped and hello sand-paper look.

Yeah I knew about the two stage thing, although I only learned about it about a week after I painted the car. Paint is still on it, no chips, crack or peeling or anything, just looks more matt black than gloss, and its rough when you run your hand along it.

We used a door to practice on, and adjust the gun, but when it came to the car, we were painting for longer, and the compressor could just not keep up at all.

[Chryzla]

hmm. you need a better quality compressor, if it cant maintain 420kpa it has issues!!

I dont know how you painted not knowing of the 2 stages, its what fades paint edge and brings out a nice finish on the paint.

Ah well, your only learning, takes patience/time/patience.

How many paint layers you apply?

To revove the rough finish buff the car :)

[CussCuss]

just to throw something into the mix, the price to hire a proper sized air compressor(12cfm) and spray gun is $110/day or $330/week.

[SpidersWeb]

hmm. you need a better quality compressor, if it cant maintain 420kpa it has issues!!

I dont know how you painted not knowing of the 2 stages, its what fades paint edge and brings out a nice finish on the paint.

Ah well, your only learning, takes patience/time/patience.

How many paint layers you apply?

To revove the rough finish buff the car :)

Yeah I did the 2nd stage when ending a stroke, e.g eased off before pulling away, but I didnt go back over it just blowing air, as I found was recommended after a stroke later on.

Anyway this compressor was providing exactly half of what I needed, so figured if I got another and T'd them up it'd be fine.

I did two layers of top coat, but no clearcoat. The layers appear quite thin too, tried doing a gentle light wet sand with 1000 grit, but got to the undercoat a little quickly.

Ultimately it was done in 3 hours with $60 of 1pak paint and thinners. So it wasnt a very pro job, just wanted the car to be one colour, but what worried me was the fact I could not get a shinny finish reliably. I was using the proper techniques with respect to equal distance, and speed, and using the door to adjust and find the best spray pattern/width. First strokes were perfect, but then it went to crap when the compressor dropped.

RE: rentals, local place only has the same compressor I have, and a 5hp gas powered one that costs a tad too much. Also if I can successfully paint a car, Id rather keep the gear for future toys :)