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Hello All,
I am thinking of making the step up from using pre-mix aerosol spray paint tins to the real McKoy. From a quick look online there seem to be two main types: gravity fed, which has the paint pot above the spray gun nozzle; and suction/siphon, that has the paint pot below the spray gun nozzle. I already have a compressor I have a range of pneumatic mechanic's tools - just not a spray paint gun yet. I would be mostly painting things like chassis and I might have a go at panel painting. I am a novice and do not intend doing spray painting for a living. I also noticed that some spray systems vary in price from $34 for a kit; to well over $500, just for the hand piece alone. What are the main differences and applications between gravity and suction - is one more advantageous than the other? Is one type more flexible than the other and better suited to smaller - occasional jobs? Is High Volume Low Pressure really the duck's guts like some of the advertising material suggests? What are the brands that people would recommend for each type gravity/suction? What sort of cost would get decent quality system? You know a spray gun where I am not encouraged to practice my swearing due to shoddy results directly attributed to tools with poor adjustments or weak componentry, awkward to hold. I have to compensate for my own lack of ability after all. Your thoughts would be greatly appreciated. Kind Regards Lionel
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1940 Chevrolet MCP with Holden Built Cab (30 CWT). 1935 REO Speed Wagon. 1963 Series 2A Army Ambulance ARN 112-211 Series III ex-Military Land Rovers x 2 |
#2
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Wow, that's a lot of Qs.
I only use gravity feed. There are many benefits of gravity over suction. The first one is simply the ability to spray in a very wide range of angles, and because no pot hanging below the gun, you won't accidentally drag it through the fresh paint while applying anothet coat. Imagine painting a roof panel, reaching across to mid line, and trying to fight against fatigue. Don't laugh. After the first two coats, that ackward position becomes rather tiring. Gravity feed allows you to get every last bit of paint out of the pot. You don't have the fear of pot coming loose or leaking when gun is tilted. The air hole on suction feed is always ABOVE the gun, so it is less likely to drip out, if the cap is turned towards the user. People assume the air hole on suction won't leak because of the negative pressure (suction), but this is not always the case in practice. The High Volume Low Pressure (HVLP, from now on) gives a much more consistent paint flow, and therefore, a noticably better result. HVLP is used almost exclusively when refinish shops are using the Poly paints, 2-Pack, etc.. I started my painting years with suction. The HVLP guns weren't common at that time, because we mostly used acrylic or plain old enamel (or 'jam' as we called it then). Once repair and resto shops started using the far superior polys, we went to gravity guns instantly. The range of fan adjustment and airflow will suit any situation. Different locations require minor changes to gun settings. I'm contantly adjusting my gun during use. If you are using acrylic or enamel, suction will do, but you will most definitely get better results with gravity (HVLP). As the name suggests, you don't waste any of your air supply in trying to draw up paint from botom of a pot! That suction level changes slightly as your full paint pot starts to empty. You won't notice it, but the gun will behave differently, I guarantee it. There are many brands of quality spray guns and equipment. Devilbiss, Iwatta, CIG, are just a few. You can pay into four figures for some of the very best guns. Most of the better brands will set you back in the vicinity of $200-400. Having spruked the virtues of gravity guns, and how the finish is better, in my opinion, I'm about to say something that sounds TOTALLY contradictory to chasing the best result. All of the spray work on my restoration has been done with a gun that cost less than $50, from Supacheap Auto. Now, I'm working on the assumption that you don't have a sterile spraybooth, and are not planning a full respray on an Aston Martin, so a gun which is setup correctly, and sound technique is all you will need to produce a great finish. Seriously! Everything I have painted so far, has been done outside in the elements, and I don't think anyone could tell. Some of the credit goes to a lustreless paint. Very little shine equals much reduced reflection, therefore any nibs in the paint don't draw the eye like gloss would. I know you're a fair distance from me, but if you are around this way in the near future (at least before you need to start painting), get in touch and call in. I'll show you how easy it really is to setup a gun correctly and get a good finished product. Once you are aware of WHY certain adjustments and technique are done, the rest just falls into place. So, in short, don't waste big bucks on a spraygun, but I would strongly recommend a gravity feed gun.
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Ford CMP, 115" WB,1942 (Under Restoration...still) Medium sized, half fake, artillery piece project. (The 1/4 Pounder) |
#3
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Thank you for your detailed reply Tony. It is much appreciated. Lots of questions ... I will quote Snoopy, "It is better to ask dumb questions than make stupid mistakes". Also I am working from a point where I know only what I have recently researched online. When I was young the only option was the suction type spray gun. Kind Regards Lionel
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1940 Chevrolet MCP with Holden Built Cab (30 CWT). 1935 REO Speed Wagon. 1963 Series 2A Army Ambulance ARN 112-211 Series III ex-Military Land Rovers x 2 |
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Hi Lionel and Tony
Would you guys mind if I use both your question and response in local club newsletter, because they really summarize the issue and advice around painting military vehicles. Cheers Phil The only thing I would add is protect your lungs, but that is a whole separate thread on shop safety.
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Phil Waterman `41 C60L Pattern 12 `42 C60S Radio Pattern 13 `45 HUP http://canadianmilitarypattern.com/ New e-mail Philip@canadianmilitarypattern.com |
#5
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Fine with me, Phil.
I didn't go into WH&S rant, because Lionel knows that stuff already, I expect.
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Ford CMP, 115" WB,1942 (Under Restoration...still) Medium sized, half fake, artillery piece project. (The 1/4 Pounder) |
#6
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It is fine with me to copy the post. ![]() As a former horticulturist I have sprayed lots of chemicals and I am aware of its related OH&S. So Tony is correct about that ![]() Kind Regards Lionel
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1940 Chevrolet MCP with Holden Built Cab (30 CWT). 1935 REO Speed Wagon. 1963 Series 2A Army Ambulance ARN 112-211 Series III ex-Military Land Rovers x 2 |
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Tony, Can you give us a run down on setting up a gun.
You are able to offset your cheap gun with your experience. A lot of us have the cheap gun and no one to guide us. A general run down on those two knobs on the back of a suction gun would be helpful. What is different on the gravity gun? What do we look for? Thanks. Lynn.
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Bluebell Carrier Armoured O.P. No1 Mk3 W. T84991 Carrier Bren No2.Mk.I. NewZealand Railways. NZR.6. Dodge WC55. 37mm Gun Motor Carriage M6 Jeep Mb #135668 So many questions.... |
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Sure, Lyn. There's no trick, it's just a matter of finding the right setting for each combination of gun and paint type. Acrylic paint will require entirely different settings to enamel, different again to 2-pack, etc. If, like me, you paint outside, temperature, wind, direct sunlight or shade, and paint type all combine in dictating the end results. Might be easier to explain if I use illustrations and possibly demonstrate what the various adjustments do. On Sunday I will find a suitable bit of metal to paint on, and I'm sure I have some usable paint that I won't use for anything, which I can put into the gun for the purpose. Bear with me until then. I recommend you find a nice big panel to practice spraying on, and experiment with changing gun settings and air flow rate, using the type of paint you intend to use for the 'real' job.
There are some things I will take as a given. Always follow manufacturers instructions, with regards to thinning ratio, and hardener additive, if applicable. Always clean the spray gun and pot immediately after you finish spraying. A dirty or partially blocked gun or nozzle will never give a good result. Usually any blockage can be cleared, but this may involve immersion of the gun for a period of time. I do the first clean of the gun with a small quantity of the thinner or reducer which is applicable to the paint which had gone through the gun, then another, more thorough, clean with thinners which I know as either "G.P thinner (general purpose) or "Gun Wash". As the name suggests, the latter is only good for cleanup of equipment, not for thinning paint. I recommend buying a multi scale measuring stick AND graduated (marked, not received a qualification!) mixing cup. Most cups come in a range of sizes, to suit any quantity of paint desired, and should be clear so you can watch the level of material from the outside. They usually have several different ratios marked on the sides. Mine I think have six ratios 1:1, 1:2, 1:3,........ you get the idea. The measurements usually include the ratio or hardener, if it is required. I cannot overstate the importance of mixing ratios. I know it is a pretty basic consideration, but you would be surprised how often i hear someone say they mix by 'sight' or close enough. Every part must be exact, at least until you know what you can achieve by altering the ratios. I won't go into that for now. Best left for later. I'll have a little play on Sunday, and post some info with photos. As i said before, there is no great mysteries, just some principles which must be observed, no matter what type of paint you are using. Those principles, once fully considered, will get a good result every single time. I recommend everyone wanting to refine their skills prior to the real paint job, to get their hands on a nice large vehicle panel. A decent size bonnet / hood would be perfect to practice on. Stand it on it's side, and spray your practice when the panel is vertical. There is no challenge in spraying a panel when it is laying horizontal. Paint won't run off it like it will when it is standing vertically. You will want to ensure you can avoid paint runs, so make your practice reflect the conditions you will be subjected to with the real thing. Once you can successfully spray without dry spots or runs in the paint, repeat the test again with straight thinners, no paint. If you can apply thinners evenly and it doesn't run, then you have achieved your goal. Any spray job after that should be a walk in the park, and you will be ready for the task at hand. It will make more sense when I demonstrate, trust me. Excuse any spelling mistakes in the above. I don't have my glasses on!
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Ford CMP, 115" WB,1942 (Under Restoration...still) Medium sized, half fake, artillery piece project. (The 1/4 Pounder) |
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