custom dry sump oil pump do-able!!

[acannell]

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..


some notes:

-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)

-hoses/tubing/fittings $60

-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..

[detobias]

wow you are doing some cool stuff !

I tip my hat to you, sir :)

[acannell]

Quote:

Originally Posted by detobias wow you are doing some cool stuff ! I tip my hat to you, sir :)

thanks! although I havent really done anything yet lol...but this does seem feasible, bizarrely..

.some more notes..

-the housing for the pump may actually be no big deal at all. literally two flat plates with ports milled in them. one or more of the plates could be extended and act as bracketry. the gerotor design software also designs the ports and even exports solidworks files (!!!!)

-i totally made up the idea of using the pump as the AC idler pulley without even looking at that area to see if it could fit. so i checked it out now..the AC idler bracket has an offset which pushes the pulley out to meet the plane of the other pulleys on its belt..the pump could fit right behind the pulley and the bracket would be basically the same...almost looks possible. i havent measured how much room there is behind the pulley though. with 1/2" pump rotors the pump itself may be about 1" thick..but with the fittings it could get big...

or maybe mount the pump on the outside of the belt and point it towards the engine? is that impossible for some obvious reason?

[acannell]

heres an exploded view of the moroso 22521 single stage gerotor dry sump pump..im actually not sure if the rotors are aluminum or not, but i dont see why they couldnt be. the design software even lets you input the material qualities and i entered 6061 parameters so i think it will be okay. besides my pump will have .005" clearance and not be generating much pressure at all so i think the material requirements will be quite lax..and 1/2" thick aluminum with the tensile strength of mild steel should be pretty stout..right?

parts 9 and 8 are the "rotors", which i will be machining, almost exactly as the ones in the picture..4 lobe inner rotor, but probably thinner than the moroso one, which looks to be 1" or thicker

the ports in the moroso design are a bit convoluted. the moroso pump has a built in "manifold" which connects multiple stages of the pump, seen as the rounded rectangular port at the top of part #1. the actual ports which the rotor dumps/sucks into/from appear to be on part #2, which connects one of the ports to the "manifold", and the other port to the lower fitting somehow..i think the center housing is just thick enough to allow some space after the rotor for the AN fitting to connect to

i think we can do away with the #17 pressure relief section since this pump will just be scavenging oil and moving it from one place to another..although for safety i suppose it should have some kind of relief valve if somehow the hose gets blocked or something..although it would probably just melt the AC belt worst case

the shaft and how it will connect to the pulley and rotor are unknowns right now..it would be nice to somehow reuse the existing AC idler pulley to save on cost..i have an extra one around, I'll see if that might be a possibility

[acannell]

heres a dry sump rotor that has ports in the rotor..this would make for a thinner pump..


maybe i was wrong about aluminum rotor gerotors..at least until i find an example..heres an aluminum rotored lobe style pump..similar to a gerotor..i think this is enough evidence..at least for me to go on lol..id make it out of steel but my mill cant do it..

Oil Pumps

heres how the corvette does it for their dry sump..thin and large diameter to compensate..

[D3NT]

this is looking awesome!!! keep up the good work. could you make it flow threw the oil galley on the side that you wanted to mount it on? (the one with the plug in it)
??
or am I missing the concept?

[detobias]

when (if?) I get my omni running this summer,
I'll volunteer to proof-of-concept test it with ya ;)

lol I think I'll wire in a low oil P -> fuel pump/injector shut off just in case

[acannell]

Quote:

Originally Posted by D3NT this is looking awesome!!! keep up the good work. could you make it flow threw the oil galley on the side that you wanted to mount it on? (the one with the plug in it) ?? or am I missing the concept?

hehe yeah the pump i would be making is just the scavenging pump, it sucks oil from the pan and delivers it to the external reservoir. i actually really liked your idea and it seemed like a really clean way...then i realized that this pump wont even be doing that job lol....

Quote:

Originally Posted by detobias when (if?) I get my omni running this summer, I'll volunteer to proof-of-concept test it with ya ;) lol I think I'll wire in a low oil P -> fuel pump/injector shut off just in case

i may take you up on that!

remember, the stock pump will remain and still be used to provide pressurized oil to the engine, so all its reliability and function wont change. except that its pickup will be rerouted to an external oil reservoir. so i would think (depending on how fast our stock pump flows oil), that we would get several seconds, if not a minute or more (maybe thats a stretch..?) of warning via the reservoir running low before oil pressure would drop..i.e. if the custom scavenging pump failed

heres a pic of the AC idler bracket with the pulley removed..

that space behind the offset is where im thinking the pump could go..ive barely done any investigation though..the alternator and its belt is behind there so there might not be room..i think i need to figure out exactly how much space there is to work with

also...the shaft and pulley needs to be figured out. my ac idler pulley appears to have a bearing pressed into it..maybe that bearing could be pressed out..and some kind of adapter (with shoulder)could be pressed in and secured with a washer and bolt, and somehow attached to a shaft...

this scavenging pump should have pretty low loads so the bearing system it uses for its shaft shouldnt be too demanding..

[Dr. Johny Dodge]

I'm not sure what moroso uses to make their pumps but aluminum may cause issues in terms of longevity - maybe

the problems with AMC V8 oil pumps comes to mind as they were made with an aluminum houseing that was prone to failure

it may be worth looking into finding a place that does anodizeing - re , military grade "hard" anodizeing (it's early did I spell that right ?)

[acannell]

Quote:

Originally Posted by Dr. Johny Dodge I'm not sure what moroso uses to make their pumps but aluminum may cause issues in terms of longevity - maybe the problems with AMC V8 oil pumps comes to mind as they were made with an aluminum houseing that was prone to failure it may be worth looking into finding a place that does anodizeing - re , military grade "hard" anodizeing (it's early did I spell that right ?)

i think you are on the right track here about this...

but just to be clear, this should simply be made out of steel. i just cant machine steel of this thickness on my teeny hobby mill (well, I could, but its a factor of 10 slower than aluminum), thats all. otherwise id make it out of steel just like the vast majority of gerotors are made.

but, i can get the entire system designed and up and running (lets just assume that hehe) and then literally just switch the material to steel and maybe change the feeds/speeds and use a bigger mill, without changing any of the design.

there are also many gerotor rotors you can just buy..since the rotors are so common, you could probably purchase them as parts for GM oil pumps. if there was one that had the right diameter and shaft hole, we might even be able to just use it as is, and all i'd make is the housing.

also, a stock oil pump might be modifiable to use as an external scavenging pump..the skys the limit really on how to do this. gerotors are simple and were invented in the 1800's...we just need to find a way to cram one into our pulley area..

this project is also serving as a way for me to increase my machining and fabricating skills by making a working pump, so I think im going to give the rotor machining a try at least once :)

heres a pic of the aluminum lobed dry sump pump (not gerotor as i understand it) pump..made of out 7075 aluminum

[Dr. Johny Dodge]

I totally understand workin with what you have and the challenge aspect you have set out for yourself with this project
I also am lookin forward to seeing how it turns out

[acannell]

i wish i had an oil pump laying around..it would be nice to design the first attempt of the gerotor to have flow as close as possible to the stock oil pump..

i figure the intermediate shaft runs at half the crankshaft speed since its on the same pulley size as the camshaft right?

but what is the gear ratio of the intermediate shaft to the oil pump rotor? hmmm..if anyone has one laying around and could turn it by hand or something to figure that out it woud be great..

also if you have the oil pump apart, if you could take measurements of the rotor (thickness, and maybe a ruler laying across the lobes to figure out approxinmate geometry)

this will help in matching the new gerotor pump flow to the existing stock flow..im assuming you dont want too much or too little otherwise you end up with intermittent flow as the sump goes below the pickup, or overflowing sump, respectively

[Dr. Johny Dodge]

thickness of the parts will prob be diff between the 85 and earlier pumps vs the 86 and later as the 86 &^ went to a high volume pump - usually done by makeing the part thicker

to bad your in CA and I'm way up here or I'd send you one of my "slightly" used pumps

[acannell]

okay did a reality check..

the spot behind the AC idler pulley is immediately occupied by the alternator pulley and belt...a couple inches rearward and there is some space..but right there there just isnt..

so...

near the power steering pump is lots of space..so the new gerotor could act as a tensioner pulley for the power steering pump (which currently swivels on its own for tension)..there is quite a bit of space..but im not sure if the geometry of the belt will work for a tensioner pulley...

perhaps it could push backwards and down on the flat side of the belt in order to tension it, like the water pump or the timing belt tensioner...so then we could use a flat pulley, like the water pump..maybe even a water pump pulley...or something i could make out of aluminum perhaps..a round pulley is easier to make than a v belt or timing pulley i would think

[Dr. Johny Dodge]

looks like you could use the power steering bracket to mount the pump somehow
under it

I'd think you could make the pump fixed in position and still use the same tensioning method already used by just tightening the belt by the ps pump position

say , push the new pump up under the lower section of the belt so the belt has to go over the hump of the pulley - might need a slightly longer belt though