well, this isnt the exciting update i had hoped to have, but:
the good news is: i was able to machine custom rotors for the dry sump scavenge pump on the big full size cnc mill I have access to. what a joy that machine is! i should have got it a valentines gift...sigh
all that i had laying around was 304 stainless, and it was 1/4" thick, so i set up the design software to come up with rotor geometry for 10 liters per minute per 1k rpm, with 1/4" thick rotors.. i arbitrarily chose 6 lobes for the inner rotor. i actually think 1/4" thick is right on target, so that this pump will fit in the shallow space available in between the psteer pump bracket and belt.
the bad news is, the rotors jam and dont rotate. i would have been pretty lucky to just dump the output of the design software into the mill and get something that rotated nicely.
the reason they jam could be a bunch of things. this is my first time going from the gerotor design software all the way to a machined rotor, and there are alot of links in that chain. just like machining anything really. the clearances are not outrageous here, in fact they are defined as 0.005" in the software, which the big mill can easily handle. i think the problem is in the way i converted the profiles into geometry was messy. sort of like converting a bitmap into vector, not ideal. much better to just draw the vector from scratch using the actual math that the rotor is based on. thats what ill do next time around.
BUT! its really not that far off, I took a dremel with sandpaper (not the grinding wheel) to the rotors and was able to get them to almost start turning. i can probably salvage them and use them in the initial prototype if need be.
on the other hand, my teeny sherline could make copies of these in aluminum without too much trouble, or maybe i can make another pair on the big mill.
i could really use some help on some of this, please chip in with your knowledge:
now to come up with a housing design of some kind. can someone help with this part? what do you all think should be the bearing system for this?
remember its low torque, because this is not a pressure pump, just a bucket brigade from the sump to the reservoir.
im thinking a pressed in shaft, with graphite impregnated bushings on both sides and a lip seal on the pulley side?
or would ball bearings make more sense?
all this stuff is available from mcmaster, shafts, bearings, bushings, lip seals..everything, so really once a good idea for the housing is figured out, its plug and play and i could have the parts in a day or two.