OT - blasting on a budget

My immediate thought on reading the earlier paragraphs was to build a pump using a junk car engine and drive it from another engine, so you're not alone in your madness :-)

I have no idea how well it'd work in practice, however - I suspect you'd need an engine with separate cams for inlet / exhaust so you can screw with the timing and get optimal results, and it's perhaps a bit harder to find a sacrificial engine then (little old 80s single-cam lumps being ten a penny).

Hmm, if that's the sort of thing you want to do, won't a standard single-phase electric compressor manage it? I think the semi-pro stuff is supposed to be just about up to the job and isn't expensive new (or used

- I just bought one on this side of the Pond for the equivalent of £40)

cheers

Jules

On the engine that works as a compressor you take off the rockers, lock the exhaust valves in place, put weak springs on the inlet valves and take the air from the spark plug holes via non-return valves.

A 3hp single phase compressor might just be up to the job of mild blasting but I'm not confident our house electrical supply is up to the job and the cost of an electrician would make it unviable.

Pressure pot grit blaster, single phase electric compressor (small pump, big reservoir) and patience.

You can make your own pressure pot (gas cylinder & welder), or else buy for a hundred-ish.

Use the right grits, not sand.

I've bought a pressurised blasting pot. Just need the compressor sorted now. I can probably do a few 10 second squirts with my 1.5hp compressor until I find something more powerful.

michaelbrix wrote (snip):

How about one engine - half the cylinders driving and half compressing?

NHH

Gentlemen,

reading the following reminded me of my first compressor, it was a industrial job with a 40 in high, 18 in dia tank with a 3 hp 3 ph motor, I replaced it with an old 3 hp single phase motor with the points in to start it, I wired it into my 30 amp house supply and switched it on and away it went, this was closely followed by my wife coming out of the house to tell me the telly picture had died to a dot and then slowly recovered. I asked her to go back in doors and I stopped the compressor and then restarted it, again she said the telly had died so from then on I used the compressor when she wasn't watching the telly :-)) The only problem with it was the motor could not start against a full tank.

On Fri, 24 Jul 2009 14:56:23 +0100, Nick H finished tucking into their plate of fish, chips and mushy peas. Wiping their mouths, they swigged the last of their cup of tea, paid the bill and wrote::

Ruston's built one like that!

Brian L Dominic

Web Site:

Newsgroup readers should note that the reply-to address is NOT read: To email me, please send to brian(dot)dominic(at)tiscali(dot)co(dot)uk

Electric isn't out of the question you know.

I have one of those Machine Mart grit blasters - the one with the remote container that holds about 20KG's of sand. I run it with three compressors with all the outputs commoned up. I also feed them into a spare extra air receiver.

A 2.5hp compressor powered up from one shed/workshop, and the other two

1.5hp compressors powered via a separate ringmain from my other shed/workshop. The compressors are those cheap Clarke/Machine Mart things that I've acquired over the years and the beauty of this arrangement is that they don't all start together so not tripping any CBs.

Regarding these blasters of the type I have - they are very air hungry, forget what they claim to be the ''requirement'' for air, you need to almost double it. The blasters are only truly effective on seriously rusty metal if they are working at at least 100psi. With my set-up, if you try to blast continuously the pressure drops to around 60psi and much of the power is lost. So I have to play a waiting game for 50% of the time.

I'd love an old Diesel road compressor, or maybe one that fits onto a tractor PTO - like those old Tractair things that the councils once used. However I'd be struggling to justify it.

Julian.

3hp is only a tad over 2.2kW. You can pull 3kW+ from a single 13A plug. The inrush at switch on might be problematical, that is what soft start circuits are for...

Even ancient house supplies are rated at 40A (10kW) modern ones are more likely to be 80 or 100A (18.4 or 23kW).

Job done! I'm collecting a Clarke 6.5hp petrol compressor today. It will do 15fm at 100psi which should be sufficient for a 3mm nozzle. They are =A3800 from new but I got it down to =A3275. It only has a few hours on it. As they say: Let's have a blast!

Michael

I'm told that it makes a terrible mess & that the grit & resulting dust goes far & wide, being hooked out of crooks & nannies long after the task is completed.

I've no first hand experience though & pass the grift on FWIW

Regards,

Kim Siddorn

Yes it does a bit. I do it outside over some grass - the sand disappears without trace into the sod in a few days.

The article that's been blasted just needs a good dose of air blown over it to remove all the sand that hides itself.

Julian.