Yes I did look at the 4 cylinder oiless compressor, it has a 4 litre receiver, on YouTube a video on it doesn't look to bad for noise. Price is £ 158 here in the UK, which is quite good. I've never done a side by side comparison of oiless verses oil compressor. I'm certain the tank and trap will remove any oil vapour. Most of the intended painting was going to be artist canvas or similar surfaces. I'm trying to get my Son interested also. He's got no interest in electronics sadly. Yes I can get hold of large propane cylinders that are empty, the problem there is finding someone to fill it with water before welding the feet and input output ports into it. Many welders are sceptical of welding old gas cylinders for obvious reasons, I know filled with water it's safe. As a retired diver, out of test cylinders look like an attractive option. Large twin set would do really well. They'd hold that pressure all day long, the walls are very thick indeed. But again it's the welding, welders see a cylinder and think oxygen, but it's not, it's compressed air or nitrox in it's previous use. EBay have a few sellers of air receivers but there expensive. There are also sellers of compressor / airconditoning motors I've found, but there not that cheap. A new bit of info above about the relay and PTC I was unaware of the PTC part of that, i knew it involved a relay, just asumed they used a centrifugal switch to disconnect the start winding and any capacitor. I'm wandering if there's a way to configure that PTC thermistor for frequent stop starts with out over heating any windings, but I doubt it...