A/C Compressor as a Workshop Compressor

[TomG]

Been thinking about building an aircon air compressor for the garage running off a 240v AC motor.

At the moment I have a small workshop compressor, but isn't really upto running the air ratchet, etc. The Sanden A/C pump in the 90 runs the air tools surprisingly well, though the V8 makes an expensive compressor.. and the fumes are not so good.

Pro's i can see are:

Should be cheap, quiet and give a good CFM (so won't need a huge reservoir)

Reckon i need the biggest AC motor i can get (3KW?), perhaps an old vacuum cleaner motor? belt drive to the compressor with the pulley geared so it doesn't overload the motor or spin the pump too slowly (any ideas?)

Maybe use a valve / relay assembly off a compressor - guess i'll need 12volt to lock up the clutch on the pump or weld / bolt it solid.

I have considered a bigger 13CFM compressor but i don't have the space for it and i find they're quite noisy (piston ones anyway, not sure if you get smaller vane ones for reasonable money?)

Any thoughts?

Cheers

[BogMonster]

Buy some flexible exhaust pipe and route it outside from the V8

[orangemach5]

Ive been thinking of doing this myself, but i figured to make it worthwhile you should build a machine with at least 2 maybe 3 pumps! The problem you come across then is running them on startup, you need a capacitor drive motor. My current compressor which is 14cfm and 3hp which works out 2 1/4KW and wont run off a 13A supply, i had to add a stand alone 16A supply. Dont know what your power situation but bare this in mind! If you get a cheap used compressor from say fleebay which has a buggered pump then you could use the motor and resevoir along with the pressure switch relief valve for an easy build!

[orangemach5]

Forgot to mention ref cheap vane compressors! Hydrovane compressors are the dogs, but they are £1200 upwards!!!!

[simonr]

When my last compressor died, this is exactly what I did. I had an old 3hp single phase motor under my bench.

I found it needed gearing down a little roughly 2/3 so the pump ran at 2000rpm. At that, it was delivering about 6cfm at 100psi.

I added a delay start so the clutch would engage shortly after the motor switched on (Timer relay from Maplin). Otherwise, at full pressure, the motor would sometimes blow a 13A fuse when it kicked in. with a 1 sec delay it was fine.

Eventually the compressor gave up - it had already had a life as an AC compressor, then lived in my engine bay for a while as an air compressor.

Next I used a proper 3 phase Air Con compressor which delivered an easy 9cfm at 100 psi. It worked fine until the filter fell off the air inlet and it ingested lots of grinder dust!

Then went back to a £69 compressor from Aldi - which is surprisingly good.

May go back to the AC compressor next time one comes up!

Si