Gerotor Oil Pumps

[osubeaver]

We have been manufacturing our own dry sump pump for our ZX-6R motors for a few years now that uses two stock ZX-6R oil pump gerotors. The guy who originally designed it put a tiny oil passage that feeds oil off the stock pressure pump into the side of the gerotor bore housing in the dry sump pump. This oil passage was also used to oil the 2:1 gear reduction for the pump. In one of the previous years reports it was stated that this oil passage was essential for the operation of the pump, and if it wasn't there the pump would lose its prime. I am wondering if this is really true, as the stock gerotor does not appear to have such a setup. I was under the impression that gerotor pumps were self priming and should do just fine, and should get a fair amount of oiling just pumping the oil itself.

[Psychosis]

id agree with you, the nature of dry sump pumps is that they draw a vaccuum. hence they dont need primed to run. id toyed with the idea of putting two cbr oil pumps together to make a twin scavenge pump and running it off the water pump feed as you do with the pace pump (except a hell of a lot cheaper!) has anyone done this? with regards to you 6R did you have any problems making your own shaft to combine the pumps. id really like to see a pic, cheers.

[osubeaver]

Cool. We have actually run our pump off of the crank shaft on the side with the trigger wheel, which required a 2:1 gear reduction, but I am actually working on a design right now that will run it off the water pump shaft and eliminate the need for the gears. The shaft has never really been a problem. It is just a steel shaft with two holes in the correct spots for a pin to engage (thats how kawasaki attaches the geroters to the shaft). Here's a pic of the pump shaft and gears and lovejoy joint, as well as the pump put together (this is from our '05 car).

http://web.engr.oregonstate.edu/~westonde/pictures/Pump%20Shaft%20and%20Gears.jpg

http://web.engr.oregonstate.edu/~westonde/pictures/Finished%20Pump%202.jpg

[Psychosis]

that looks well sweet. especially as its your own custom housing. how do the judges like it? how much does it work out on the cost report compared to the $500 for a pace pump?
cheers

[osubeaver]

Lets just say you have to be very careful with how you cost out the CNC machining http://fsae.com/groupee_common/emoticons/icon_wink.gif. The judges have always really liked our setup though. They usually just want to know that we understand its functioning and can back up that it does what its supposed to do.

[Brian Evans]

Couple of thoughts. If a gerotor pump stage is run totally dry, it has a hard time pulling vacuum and hence getting the oil to it to prime the scavenge stage (or the pressure stage, but the reservior should always have a level higher than the input to the pressure stage any way). In practice, the pump is assembled with a lube so that it's not totally dry, and once the pump is run once, residual oil leaves sufficient lube to allow the stage to draw at least some vacuum to get the oil flow started. so theoretically a way to pre-oil the scavenge stage is good, in practice it's not required.

other thought - why use a taper pipe thread for your fittings on that pump body? Surely you could have used an O-ring fitting or a crush washer at the very least. NTP is the last choice you would make for a race car...

Brian

[osubeaver]

it has a hard time pulling vacuum and hence getting the oil to it to prime the scavenge stage (or the pressure stage, but the reservior should always have a level higher than the input to the pressure stage any way). In practice, the pump is assembled with a lube so that it's not totally dry, and once the pump is run once, residual oil leaves sufficient lube to allow the stage to draw at least some vacuum to get the oil flow started. so theoretically a way to pre-oil the scavenge stage is good, in practice it's not required.

other thought - why use a taper pipe thread for your fittings on that pump body? Surely you could have used an O-ring fitting or a crush washer at the very least. NTP is the last choice you would make for a race car...

Thanks for the input. I actually did originally plan to use O-ring fittings on the pump, but the inlet ports are so close together that I ended up using the NPT ones on the inlets (the hex head is a lot smaller on the NPT fitting than the O-ring one (trust me, I really don't like taper fittings of any kind). You can't see it in the picture, but the outlet port is an O-ring AN fitting. I have found some nice flange style O-ring seal fittings that Pace Products sells that I may use this year.

[Psychosis]

Originally posted by osubeaver:
I have found some nice flange style O-ring seal fittings that Pace Products sells that I may use this year.
they're not cheap. last i checked they work out about $27 each i think. weldo-flanges are the way forward http://fsae.com/groupee_common/emoticons/icon_smile.gif

[osubeaver]

Originally posted by Psychosis:
they're not cheap. last i checked they work out about $27 each i think. weldo-flanges are the way forward http://fsae.com/groupee_common/emoticons/icon_smile.gif

Wow, that is pretty steep, but then again i'm kinda used to getting reamed on the price of any decent aluminum AN stuff.