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Oil pump rotor recommendation


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I'm hatching a plan to adapt one of these to use as a compressor for onboard air on my 300TDi. This will involve making an interface plate to provide a mounting which matches the aircon compressor mounts on the top of the timing chest and and a shaft which links the belt driven electric clutch off a standard 300TDi aircon compressor to the splined socket on the compressor. 

The compressor requires a pressurised oil supply to lubricate the con-rod bearings and the piston. It has ports to allow it to be fed by the Merlin's oil system, and I suppose I could plumb it into the 300TDi oil circuit, but that would mean pushing diesel-filthy oil through it which I don't much like the thought of. Instead I plan to give it is own oil supply using a small pump driven by the shaft.

I've looked at using the rotor parts out of a 300TDi oil pump - they are cheap, easy to get hold of and I kind-of like the symmetry of adapting 300TDi parts for this job. However, in practice the pump is far too big for this job, and a shaft to match its rather peculiar double internal keyway drive arrangement will be a bit of a PITA to make. 

Obviously I can do some looking about for something smaller but it would be a great deal quicker if someone here knew of a suitable alternative to the 300TDi pump. I think I'm looking for something with an outer diameter around 50mm and ideally with a single keyway round shaft drive about 20 - 25mm dia.

Has anyone got any ideas where I might find a suitable sized pump rotor set which isn't too spendy?

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Before anyone else gets in, I'll point out that I presume this project is for pleasure i.e. fitting a merlin engine auxiliary compressor to a 300tdi wont be the most time/cost productive way of sorting out some onboard air... personally I love the idea :D I've looked a few times at fitting some vintage aircraft instrumentation.

So a few thoughts - the Td5 uses engine oil to lubricate the vacuum pump i think so why not use engine oil? - you could take a tap off the blank port located on the oil filter housing.

Alternatively - how about repurposing a PAS pump?

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I've managed to knacker 4 aircon pumps using them for onboard air - and that's with mist oilers etc. I think the fact that my system runs at 15 bar may shorten the life. But yes, this is mostly about solving an interesting technical problem. Makes a change from sitting at a computer writing e-mails, which is mostly what I do in the day job. 

As I said in my OP, I don't really want to fill the compressor with black oil from the engine sump. An external pump is certainly a possibility but we have a rotating shaft and some space so having a crack at making a circulating pump sounds like an interesting possibility.

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I like the idea and appreciate what's driving you.  As Maverick mentioned the PAS pump, what about running a supply from that?  It would need a suitable size-reduced line to limit flow/pressure, but since you're probably unlikely to need on-board air while travelling it should have no impact on the steering and the plumbing would be relatively simple.

Mike

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