Air compressors

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  • #8931
    GSX Rat

    Just to be clear – this text is provided for information. This is what i have done and am using. I am in no way implying that it is correct or safe. that’s not to say it isn’t but if you kill or injure yourself or anybody else you were warned.

    Not really bikes, but thought this may be useful to somebody:

    Ever bought one of those cheap clarke or similar model air compressors with a little receiver built in – usally 25 litres. Found that when using an impact wrench or spray gun the air pressure rapidly drops off because the compressor cant keep up with the air demands of the tool?

    Me too! – So, what to do about it. Obviously you need a bigger receiver but to buy one costs mucho money, so my original idea was to get some 12 inch diameter pipe and weld ends on so off to the local industrial estate to purchase some i went, but on the way i spotted one of those 48kg propane cylinders that someone had dumped. I am not sure what pressure these cylinders are tested to, but at 27 degrees the vapour pressure of propane is 10 bar (150 psi) and i guess they must be tested to more than this but if anyone knows i would appreciate a reply – see below for testing. Well, they are the perfect shape, if stood upright they even have a dished bottom to collect the water that’ll drop out of the air!
    Firstly, checked it at the roadside to see if there was any gas left in it, there was none so i left the valve open and came back a couple of hours later just to be sure. Got it home and removed the valve with a pair of stillsons, all it needed then was a handful of pipe fittings and a safety valve (optional as the compressor will have one but recommended) to complete the air in/out/safety bit of the job. To allow water draining i drilled a hole in the bottom, tapped it 1/8 bsp and fitted a short length of copper tube and a valve.

    Testing – if you fill the cylinder with water, then pressurize it and it fails you get a bit wet, if its full of air and it fails it goes bang big time. I filled the cylinder to the top and pumped it up to 300 psi (we have a hydrostatic test pump at work) and it seemed fine, no leaks whatsoever. As i run my air at 80 psi normally, 100 psi max i figured that a safety factor of 3 would be more than adequate.

    Total cost – cylinder free, fittings a fiver, safety valve free…

    GSX750 Ratfighter / SR125 Rat / GSX600F / Beamish250 / Honda70 Rat

    Blackboard paint – Covers a multitude of sins!


    I read this 4 times and tried my best to understand it, think I’ve got it now. You are quite a genius! If I ever need a bigger receiver on my compressor you are the man!

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