Advice wanted - novice HVLP spraying

[Nomad]

I'm looking for a compressor for occasional DIY use, mainly to spray a couple of project cars.
I already have a couple of HVLP guns, work will be 1 full respray + roof resprays on a couple of others.

My spraygun spec says 3 bar, 7-12cfm ( 200-340 liters/min), I guess this is for spraying different paints / viscosity / temps etc.


Will a compressor at the lower end be ok or do I need something that can deliver the higher end?
My guess is I'll be spraying a section - then pausing before I do the next section - so the compressor won't be running continiously.

Looking at a couple of links in the sticky thread they talk about the duty cycle - but the adverts I'm seeing don't list this

What Size Air Compressor for Spray Painting?

If you have a spray gun or you're looking to purchase one for a painting project at home or in the workshop, you may now be wondering what size air compressor you need to run your spray gun.

www.about-air-compressors.com

The smaller 25 litre air tank will be easier for me to store, will I regret not getting a 50 or 100 litre tank?

I can get a 2HP / 24 litre compressor locally, spec 8 bar max, 8 cfm. Will it do what I need?
There's quite a jump in price if I want anything that will deliver 12cfm.



Other uses will be :
Inflate a couple of pressure vessels (air tanks for a water system, volume 100 litres, pressure 3 bar)
Blow up car tyres occasionally (40 psi max)

Any & all advice appreciated

 

[Jack_K]

I wouldn't even attempt to paint a car with something that small (and rubbish). Most direct drive compressors will have a very low duty cycle. There are decent direct drive compressors (which even have proper brass fittings) but they are around the same price as belt driven ones. The HP ratings on the cheap direct drives are probably all massively inflated.

Even if you buy a small belt drive compressor it will likely be a better experience than a cheap direct drive one making lots of noise and cooking itself in the process.

a 2.5hp belt driven compressor with a 60l tank is the smallest I would want to use.

 

[Morrisman]

That little yellow one will give you 5cfm actual flow, if you're lucky.
I've sprayed with one before, though not a full size car. I had a big separate air reservoir tank and took my time, plus I had an electric fan blowing on the compressor to keep it cool. The extra volume gives time for the compressor to catch up.
I was running 22psi at the gun, little pressure gauge on the handle, so overall pressure could go quite low before it affected the spray pattern.

 

[dave h 2]

From the end of your gun box, last line.
the 1.3mm would need 7cfm and 2.0mm would need 12cfm.
Yours being 1.8mm is probably a 10cfm and maybe 9cfm if you turn the air needle down.
Big stetups like the 2mm are normally for thicker paints like primer
The 1.3 will spray gloss better

 

[Nomad]

The advice is all appreciated, many thanks

I've done bits of car spraying in the past but it was occasional jobs ( a handful of full resprays, several part-resprays after fitting new panels, a few roofs), but it was always using my old (long gone) set or borrowed equipment.

Looking around the budget will get me a new direct drive 2.5hp / 25 litre / 9cfm but I can't justify anything more expensive due to the infrequent use.

Any advice for buying used? It could be a way to get a lot more for my money or it could be an easy way to get another project that needs work - and I'm trying to avoid collecting any more projects

Worst case I need to accept that DIY spraying isn't an option for me but I'd like to make sure before I decide.

 

[RonMig]

I bought a LVLP gun to try out (but not done so, yet) - maybe look into those...?

 

[AVI_8]

These 2 bought second hand for under £300 the pair, had to put a new electric motor on one of them so around £400 in total, they’re each 3hp, I’ve one of those 25 litre ones, they’re only good for blowing up tyres or working a nail gun

 

[charlysays]

These 2 bought second hand for under £300 the pair, had to put a new electric motor on one of them so around £400 in total, they’re each 3hp, I’ve one of those 25 litre ones, they’re only good for blowing up tyres or working a nail gun

View attachment 427899

absolute bargain, don't look heavily used at all. If you wait around you can get air compressors for bargain prices. as a hobbyist I would personally never buy a new one unless it was a small direct drive one from Lidl which are usually pretty good value.
I got one of these with a job lot of stuff like work benches and a big vice for £100 which I was chuffed with but it was a lot grottier than those two you got.

To the OP get a 3HP compressor. If storage is an issue get a vertical air receiver so you have 200l storage.
You still won't be able to spray a whole car in one go with an HVLP (possibly could with a low CFM LVLP though) but you could spray a whole side of a car without running out.
Also worth bearing in mind that air straight from the pump is hot so you'll need something like a copper coil in a bucket of water to cool it to condense excess moisture out of the air. For space your best bet would be a vertical air receiver and a bin with water in it and coil of copper in there of decent length, then normal air separator , main regulator, coalescing filter (clarke standard coalescing filter did a good job for me), then an ongun filter too.

 

[carbon]

the 1.3mm would need 7cfm and 2.0mm would need 12cfm.

Fluid needle size on a spray gun has no effect on the air consumption. The possible explanation of the different air consumption values would be if the width of the sprayfan is reduced. Using the spray gun with no fan as a spot will reduce the air consumption. Usually different air caps will change the air consumption of a spray gun and will effect the paint finish to some extent.

 

[Jack_K]

Any advice for buying used? It could be a way to get a lot more for my money or it could be an easy way to get another project that needs work - and I'm trying to avoid collecting any more projects

I have five belt driven compressors. Two were purchased used and the other three I got for free. They all became small projects even though four did "work". If you just want something that will work straight away then new will unfortunately be the best option. On the other hand air compressors don't take much time to repair as long as you can get the parts.

Every one of them has needed new air filters, they are usually made of foam which falls apart. If the owner even notices they seem to replace them with something unsuitable, one of mine had scouring pads. The valves on that one all were blocked up with dirt so the three heads had to come off.

The other common fault is the air regulators, they start leaking out the vent constantly. These are available cheaply so it isn't much of an issue.

Two that I were given are SIP ones, they are the newest ones I have and both have needed the motor bearings replaced. They are made in Italy but they are cheaply made.

 

[charlysays]

I have five belt driven compressors. Two were purchased used and the other three I got for free. They all became small projects even though four did "work". If you just want something that will work straight away then new will unfortunately be the best option. On the other hand air compressors don't take much time to repair as long as you can get the parts.

Every one of them has needed new air filters, they are usually made of foam which falls apart. If the owner even notices they seem to replace them with something unsuitable, one of mine had scouring pads. The valves on that one all were blocked up with dirt so the three heads had to come off.

The other common fault is the air regulators, they start leaking out the vent constantly. These are available cheaply so it isn't much of an issue.

Two that I were given are SIP ones, they are the newest ones I have and both have needed the motor bearings replaced. They are made in Italy but they are cheaply made.

True, they do often need something or other doing but I would go for it if it is under £150 or so and charges up fine, kicks in and out without blowing the fuse and the pump doesn't sound knackered (knocking etc). Any issues are bargaining chips and there's often a good £300 to be saved.
The Clarke industrial 3hp 200 ltr I got for peanuts (technically free because it came with a vice worth £100 let alone the two huge work benches) needed a new airfilter and airfilter box (totally missing) but I didn't need to take the head off. Within a few months it needed new start and run caps. Maybe I got lucky on that one, about £30 worth of bits and less than an hour work (and a litre of straight 30 oil) and its been good for a few years now.
The other one I got for 30 quid and pretty much all of it was knackered- new pressure switch, new belt, new motor off the bat. It was 30 quid, probably too expensive but I was young and dumb. The pump limped on knocking away for many years but in the end it wasn't doing much pumping and I fitted a clarke pump which cost about £130. So that one wasn't the best bargain but has been in regular use for about 15 yrs now.

 

[Turbo]

HVLP guns are quite air hungry, I've used one supplied from 2 direct drive compressors linked together & you struggled to get a panel painted before running out of air.
I now have a 3hp belt drive & it is able to supply the HVLP gun.

Never used an LVLP gun but I've read that its tricky to get a good finish from them, orange peel is common.

 

[charlysays]

HVLP guns are quite air hungry, I've used one supplied from 2 direct drive compressors linked together & you struggled to get a panel painted before running out of air.
I now have a 3hp belt drive & it is able to supply the HVLP gun.

Never used an LVLP gun but I've read that its tricky to get a good finish from them, orange peel is common.

I wonder why direct drive is so inferior to belt drive... i know they're noisier but they seem to make less CFM for a given motor power and I don't really understand why- rpm issue?
When I was painting my car I used a 1.3mm hvlp with 40psi pressure at the gun with the trigger pulled, my long 1/4" air lines just about managed to supply this. I would usually run one compressor up but slave it into the other one, giving 350l of air. I'd usually let it sit a good while too before spraying so I had 350l of cool air to start with. Painting a couple of panels was fine and even one long side of a the car was fine, the pump would kick in doing a side but as you say it would keep up and even make headway slowly against the demand. Decent setup all in all and wayyyy preferable to forking out thousands to get a pro to do it.

 

[AVI_8]

I wonder why direct drive is so inferior to belt drive... i know they're noisier but they seem to make less CFM for a given motor power and I don't really understand why- rpm issue?
When I was painting my car I used a 1.3mm hvlp with 40psi pressure at the gun with the trigger pulled, my long 1/4" air lines just about managed to supply this. I would usually run one compressor up but slave it into the other one, giving 350l of air. I'd usually let it sit a good while too before spraying so I had 350l of cool air to start with. Painting a couple of panels was fine and even one long side of a the car was fine, the pump would kick in doing a side but as you say it would keep up and even make headway slowly against the demand. Decent setup all in all and wayyyy preferable to forking out thousands to get a pro to do it.

One reason is that the piston displacement is smaller as necessary because the motor has less power
My little direct drive has 2.5 hp, whereas my belt drive has a larger pump and 3hp

 

[Slowcoach]

Are you sure that’s a HVLP gun?
The manual seems to say it’s a conventional gun, although there is a discrepancy on air consumption between your box and the manual I found online.
Try some primer through it when you’re ready and see how you get on as it has a 1.8mm tip.

 

[Burdekin]

To get efficient paint atomisation you need volume of air going through the gun otherwise you'll get a poor finish; orange peel, lumpy, dull, dry, finishes etc. As a general rule times the gun cfm x 1.3 to work out the minimum compressor CFM. You should have at least 15.6 cfm rated compressor. Go smaller and be prepared to have a lot more work flatting after. You want to keep the paint wet when spraying so you don't want to be stopping waiting for the compressor.

 

[Burdekin]

These 2 bought second hand for under £300 the pair, had to put a new electric motor on one of them so around £400 in total, they’re each 3hp, I’ve one of those 25 litre ones, they’re only good for blowing up tyres or working a nail gun

View attachment 427899

Good score.

I have two of the Wolf Dakota's, cost me about £500. One was a refurbished machine and must be a returned machine they've fixed and sent back out. It runs perfect. The refurbished machine came a lot better packaged as well. I've never found a decent used compressor up this way for sale.

 

[pedrobedro]

I painted for years with a SIP V twin direct drive and had no problems, it would charge the tank while the gun was still spraying. My HVLP 1.3 runs happily on 30psi with the trigger pulled.

 

[AVI_8]

Good score.

I have two of the Wolf Dakota's, cost me about £500. One was a refurbished machine and must be a returned machine they've fixed and sent back out. It runs perfect. The refurbished machine came a lot better packaged as well. I've never found a decent used compressor up this way for sale.

I’d been looking for a descent second hand one for about a year, the ones that were being advertised the sellers were looking for too much money, then those two came up for sale a week apart both very cheap and fairly local. Still haven’t got round to building a compressor housing outside to put them and a copper pipe cooler, that’s a job for after the new year.

 

[carbon]

If you haven’t got a spray gun yet look at some of the smaller spot repair ones. I only have experience with some of the devilbiss range but find the sri pro to be very good and it only needs 4.8cfm. The fan is a good size and you can get adaptors to fit bigger pots rather than the 125ml standard one