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These compressors sufficient for blasting?
- Thread starter Tehrawk
- Start date
Just bear in mind you'll need a hefty supply for that 6hp unit, I guess 32 amp?
Yet another variable to bear in mind. Ill look into that tomorrow, thanks for the heads up.
FranV8, yes, any engine could be used as a self-powered compressor. With air cooling, 4 driving cylinders, and a quad compressor, a Tatra V8 would be ideal!
For the VW, that Dunn-Right kit does have a special camshaft to convert the two "pumping" cylinders to 2-stroke, but I think that the easy way to do this is by just disabling the inlet valves ( removing the pushrods/rockers ) on the front two cylinders, and then as you said, making the exhaust valves suction-operated by replacing their springs with very light ones. These valves will then open on every piston downstroke, drawing air through air filters fitted to what were the exhaust ports. The compressed air can be collected from the two cylinders via a couple of modified spark plugs, fitted with non-return valves. For sandblasting with a pressure-fed tank, an air receiver may not even be needed - just size the blast nozzle appropriately to the expected CFM.
For the VW, that Dunn-Right kit does have a special camshaft to convert the two "pumping" cylinders to 2-stroke, but I think that the easy way to do this is by just disabling the inlet valves ( removing the pushrods/rockers ) on the front two cylinders, and then as you said, making the exhaust valves suction-operated by replacing their springs with very light ones. These valves will then open on every piston downstroke, drawing air through air filters fitted to what were the exhaust ports. The compressed air can be collected from the two cylinders via a couple of modified spark plugs, fitted with non-return valves. For sandblasting with a pressure-fed tank, an air receiver may not even be needed - just size the blast nozzle appropriately to the expected CFM.
I looked at this a couple of years ago and found an article (which i cannot find now of course) that suggested there were 2 basic methods, both used 2 cylinders as an engine by removing HT leads and blanking manifold.
Version 1
modify either inlet or exhaust valve to be a one way valve as already suggested (intake would be routed to air filter) and replace spark plug with a non-return valve which would be routed to receiver.
Version 2
replace one cylinder head with a 1" thick plate with 2 non return valves per cylinder (inlet and exhaust)
Version 2 although more costly and difficult to do was more efficient due to the higher compression ratio and produced much more CFM and PSI (though i cannot recall the figures)
I also seem to recall that the article stated that the 2 cylinders of the 'engine' produced more than enough power to drive the 2 cylinders of the 'compressor' which led me to think that you could possibly use different size cylinders e.g 1300 cc cylinders for the engine side and 1600cc for the compressor side.
The other thought that i had (dangerous) was rather than making a custom cylinder head out of flat plate could you bore out the register of the VW cylinder head and use the original head as a clamping fixture to hold your flat plate in place, this would also save the hassle of blanking off pushrod tubes, modifying studs etc.
Hope this helps or provides food for thought
Regards
Frank
Version 1
modify either inlet or exhaust valve to be a one way valve as already suggested (intake would be routed to air filter) and replace spark plug with a non-return valve which would be routed to receiver.
Version 2
replace one cylinder head with a 1" thick plate with 2 non return valves per cylinder (inlet and exhaust)
Version 2 although more costly and difficult to do was more efficient due to the higher compression ratio and produced much more CFM and PSI (though i cannot recall the figures)
I also seem to recall that the article stated that the 2 cylinders of the 'engine' produced more than enough power to drive the 2 cylinders of the 'compressor' which led me to think that you could possibly use different size cylinders e.g 1300 cc cylinders for the engine side and 1600cc for the compressor side.
The other thought that i had (dangerous) was rather than making a custom cylinder head out of flat plate could you bore out the register of the VW cylinder head and use the original head as a clamping fixture to hold your flat plate in place, this would also save the hassle of blanking off pushrod tubes, modifying studs etc.
Hope this helps or provides food for thought
Regards
Frank
KemppiFrog
Member
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- Aquitaine
Just found this thread and it is just what has been going through my mind for a while.
In the shed I have a spare 1250cc Renault engine. Outside I have a Ford P100 with the 1800cc TD engine in good nick (rest of truck is past economic repair: gearbox, steering and front suspension need changing.)
Plan was to pull the Ford and mount it on a tube trailer with Renault suspension. Now the difficult bit. The Renault would pump say 1.000cc per rev (250cc guess for losses) That is 1,000 lts/min 100cfm at 1,000 rpm. Up that to 1500rpm and I am in the ball park for blasting (already made the pressure pot)
Problem is, I would like to direct drive the 'compresser' as the easiest option, but prob need to run the diesel at 2,000rpm, which might be too much for the compressor. But judging by the VW stuff perhaps not. I was looking at my existing 2hp units and they run at 1200rpm.
I was also expecting to have to make a new valve head to get rid of the combustion chambers and have two chunks of ally plate for this. But again, using the inlets with soft springs and spark plug non return valves, it looks like I can save myself the hassle. I will probably have enough air without needing to refine it too much.
The mechanics do not worry me, I have built a couple of cars from scratch, but does the assembled wisdom have any thoughts on this?
Big plus is that I have all the bits on hand.
I can hire sand blasting kit for €180/day. But having my own would save a lot of trouble and time. Currently resoring some heavily scrolled 80+year old gates and getting the paint off was a pain. Another lot booked in for next month too.
KF
In the shed I have a spare 1250cc Renault engine. Outside I have a Ford P100 with the 1800cc TD engine in good nick (rest of truck is past economic repair: gearbox, steering and front suspension need changing.)
Plan was to pull the Ford and mount it on a tube trailer with Renault suspension. Now the difficult bit. The Renault would pump say 1.000cc per rev (250cc guess for losses) That is 1,000 lts/min 100cfm at 1,000 rpm. Up that to 1500rpm and I am in the ball park for blasting (already made the pressure pot)
Problem is, I would like to direct drive the 'compresser' as the easiest option, but prob need to run the diesel at 2,000rpm, which might be too much for the compressor. But judging by the VW stuff perhaps not. I was looking at my existing 2hp units and they run at 1200rpm.
I was also expecting to have to make a new valve head to get rid of the combustion chambers and have two chunks of ally plate for this. But again, using the inlets with soft springs and spark plug non return valves, it looks like I can save myself the hassle. I will probably have enough air without needing to refine it too much.
The mechanics do not worry me, I have built a couple of cars from scratch, but does the assembled wisdom have any thoughts on this?
Big plus is that I have all the bits on hand.
I can hire sand blasting kit for €180/day. But having my own would save a lot of trouble and time. Currently resoring some heavily scrolled 80+year old gates and getting the paint off was a pain. Another lot booked in for next month too.
KF
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Interesting variation there. Are you going to couple the two engines flywheel to flywheel end? Assume you will use some sort of rubber coupler to stop diesel vibrations transferring across to the petrol engine / air end.
Blasting doesn't generally need more than 100 psi so I think increasing compression ratio on the petrol engine air end is pointless it's already in excess of what's needed. In fact reducing the compression ratio say with double or triple head gaskets may be worthwhile.
Have you considered any form of aftercooling for the compressed air it is going to get very hot after a short while.
Blasting doesn't generally need more than 100 psi so I think increasing compression ratio on the petrol engine air end is pointless it's already in excess of what's needed. In fact reducing the compression ratio say with double or triple head gaskets may be worthwhile.
Have you considered any form of aftercooling for the compressed air it is going to get very hot after a short while.
KemppiFrog
Member
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- Aquitaine
Thanks for coming back Stormin. I was thinking of using the 1st motion shaft out of the g/box to take the drive from the clutch of the Diesel to the compressor, might even use the vac pump to control the clutch with a remote. Another catch: I need to drive the Renault from the pulley end to retain the correct rotation and oil pump supply. In the drive train of the Ford there is a rubber coupling, That would do for the vibration and help in the alignment.
I was thinking of a big blow off valve set to 90psi, then run a coil in a drum of running water to cool it some. The compressor would retain its pump and cooling system.
It would be a chunky bit of kit, but mobile. I am in the country, with no trouble with space or noise.
It seems worth trying the head as is, then modding if needed re:extra gaskets.
Cheers,
Andrew
I was thinking of a big blow off valve set to 90psi, then run a coil in a drum of running water to cool it some. The compressor would retain its pump and cooling system.
It would be a chunky bit of kit, but mobile. I am in the country, with no trouble with space or noise.
It seems worth trying the head as is, then modding if needed re:extra gaskets.
Cheers,
Andrew
