it appears to be possible to machine a dry sump oil pump (gerotor type) on my teeny sherline mill. the consequences of this could be VERY good for us who want an economically priced, bolt on dry sump oil system for our cars!
why: because we could use the stock pump as the pressure pump by redirecting its pickup to an external reservoir, and then i could machine a single stage pump to use as the scavenging pump. that means only one pump needs to be purchased to make the system (along with the reservoir, oil pan, hoses, etc..)
but why make a custom dry sump pump when you can buy used multi-stage pumps for $125? because i can make a custom pump bolt into the right place and use an existing belt, saving money by eliminating brackets, belts, and multiple custom pulleys. at least thats the idea.
and since we wouldnt be designing the pressure pump, our job is easier because the scavenging pump doesnt need to generate high pressures since its just sucking up oil and relocating it to the reservoir. this means just about every specification of it is just easier i.e. easier to machine, easier to power, etc..
-since the scavenging pump draws very little power (about a 1/10th of a horsepower, see chart), we may be able to mount it so it uses an existing belt, i.e. it could act as the idler pulley for the AC compressor! this would further lower cost and make installation simpler!
-the pump style im talking about machining is a "gerotor", just like our existing stock pump. these are commonly used in commercially available dry sump pumps, along with another "spur gear" style, that im not talking about.
-it would be made of aluminum (just like moroso dry sump gerotor oil pumps)
-the rotors would be about 1/2" thick
-the pump I would make would be used as the SCAVENGING pump, and we would reuse the existing stock pump as the pressure pump, but reroute its intake to the external oil reservoir
-using some BAD-ASS gerotor design software, a 1/2" thick rotor design with 4 inner lobes could move 11 liters per minute at 1000rpm at 3psi. i am not sure how much oil we need to move, it may be much less than this. does anyone know what the flow rate of our stock pump is at a given rpm? that would put us in the ballpark of determining the required flow rate for the scavenging pump.
-the machining requirements seem fairly easy. i put in 0.005" of axial and rotor tip clearance, and we are getting what seem to be good numbers still. this geometry is very similar to my 4th cyl coolant adapter plate,i.e. 1/2" thick aluminum, so i am confident i can do a good job machining it. and I already have the material and end mills for it!
-since this is a scavenging pump, we could test it without actually using it to do anything important. i.e. it could just suck fluid from the oil pan, and deliver it to an external reservoir which gravity-feeds back into the oil pan, to demonstrate proper flow rate and function, before we actually use it in a dry sump system (i guess all these "we's" really are "me's" hehe)
-if we really want to go ultra-economical, we could just use the existing oil pan as our dry sump pan. we would modify the pan to have ports for the stock pickup to reach the external reservoir, and have a pickup for the scavenging pump to suck from the bottom. if you dont need the extra clearance that a dry sump system could give you with a shorter pan, then this would work. installation could be drilling two holes and installing the new pickup. then you connect the hoses and you are done with the oil pan.
so a kit using the above ideas would be:
-new oil pickup for stock pump $20 (cut stock pickup, bead, and run hose from it to bulkhead nipple fitting on wall of pan)
-external oil reservoir $40 (simple tank made of steel or aluminum with built in bracketry to bolt in some convenient spot on our cars)
-custom machined oil pump with pulley...i dont know..id have to actually make one before i could be sure. material cost is not a big deal, its the machining time. lets say $150
so a dry sump system for $270 that bolts up with minor modification to the oil pan and pickup?
this obviously assumes alot, but its within the realm of possibility. and if i can get the cost of the fittings or machining down, it could be even less..