Resin Printed Oil Pump

[KurtF]

Some of you may have noticed a photo of my 12v spray pump motor in the ThreadMaker post. My internal ATF pump has failed on my 20 y.o. car, and I'm hoping I can prolong the life of the car maybe past the covid economy, which has used car prices seriously inflated. Maybe this is a very cool idea; or maybe my amateur engineering skills are sorely lacking and this is more art than part. Either way, I'm officially welcoming any thoughts from people who know better.

This is the prototype I have built and ready to print and water-test in the kitchen sink. It is the same type of mesh-gear pump actually built into the transmission. If this pump can hold 60psi or better under zero or small flow rates, then I can drive again. I've already tested the theory with the original diaphragm pump which came with the spray pump. I got about 2 driving hours of useful ATF pressure before it's rubber elements warped under heat.

My design theory here is that so long as the pressure blowby in the gear mesh is greater than the blowby in the triple-O-ring drive shaft, then it shouldn't leak back into the motor. So 60 psi < Gear Mesh Pressure < Shaft Seal Pressure. Do you think this can actually work? My best resin has a Tensile Strength of 50 mpa. That works out to 1,125 lbs/cm^2. Pounds per sq. centimeter is a Kurt Standard Unit.

Prototype.jpg (500.15 KiB) Viewed 1688 times

ATF Pump.FCStd

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[KurtF]

Here's a funny little macro which rotates the gears until you type an 'x' into the document comment property. I learned this from MangoJelly video. Just save it to your macro directory, load the ATF Pump doc, run macro.

RotateGears.FCMacro

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By my calculation, each tooth cavity is approximately 16 sq. mm. Using 10 mm high tooth it works out to approx. 2.4 gal/min unrestricted output.

EDIT: Forgot to add, that's based on 3,600 rpm from pump motor.

[KurtF]

Just happened to have a packet of silicone O rings this size:

AddedORings.jpg (331.13 KiB) Viewed 1610 times

[herbk]

Hi Kurt,
what is broken at the original of the ATF pump?
Wich material you want to use for the print?

[chrisb]

I got about 2 driving hours of useful ATF pressure before it's rubber elements warped under heat.

This sounds to me as if the failure of the pump is not the reason for the failing transmission, but rather a follow up. My guess is that you have unwanted high friction somewhere so that things become much hotter than they should. Even with very bad rubber it shouldn't fail after two hours, at least not completely.

[KurtF]

Hello Herb, Chris.

what is broken at the original of the ATF pump?

I cannot access the ATF pump without removing the tranny. All I can tell is that the pressure at the pressure test port (on the front of the tranny case) drops from it's service limit, 120 psi, down to near 0 during the 20 min. warmup period. I've been driving it back and forth from grocery store past few months with a pressure gage sticking out from under the hood, near the windsheild where I can see it. It's gotten gradually worse since I've been monitoring, and now down to about 8-10 min. of usable drive time after cold start.

I will go ahead and confess how this started: owner negligence (owner depression). I drove over 100,000 mi. without once checking or changing ATF. It was almost black when I drained it. When my tranny first failed, it was pulling into driveway after about 50 min. of driving. First thing I did was replace ATF. Problem progressed anyway. I've tried 4 full-tranny flush procedures with 3 different flush agents... no impact. Enter the external 12v backup pump!

Wich material you want to use for the print?

Siraya Tech Build

Siraya Tech Tenacious

For final printing, I was going to use 75% Build and 25% Tenacious, which makes the cured product less brittle. Do you know of a good engineering resin for this?

My guess is that you have unwanted high friction somewhere so that things become much hotter than they should

I hadn't fully considered that: overheating ATF. It does fit most of the facts and I haven't thought to rule that out yet. I've assumed the pump gears/chamber is worn from operation in completely degraded ATF for so long. But something else overheating the oil is definately a candidate. Hey, thanks for stopping by! I'm going to re-visit the shop manual to see if there's anything related to tranny temp. I do know there's no ATF cooling loop under the radiator like many cars have. This tranny was designed without external ATF cooling.

The spray pump was only rated for 170 deg F. I broke it down after about 3 trips to the grocery store and driveway testing. At first it held up round trip, providing about 80 psi. It gradually dropped with each trip until it no longer held the absolute min. 40 psi needed for slow shifting. Inspecting and cleaning the pump diaphragm parts improved pressure slightly on the last trip, but nut much. It relies on little rubber disks to seal against backflow pressure against a plastic cage, and these just no longer seal. There's a nice drawing on p.2 of the pump manual. You can see the large, reinforced rubber disk in the center of the diaphragm, and the cage-side view of the 3 satellite valves.

This is the story of my life: Sitting at the stop light to turn left out of my grocery store, wondering if I'm gonna have 1st when the light turns green...

Printing prototype now (4:40 est. print time). Photographic resluts, one way or the other, coming soon!

[herbk]

Hi Kurt,

I have great concerns about using plasics for this...
First reason is, like Chris sugested to, the temperature the oil gets after a few Minutes of running. Plasics usuali changes it's dimensions very and looses strongnes much with growing temperature.
Second is the abrasion resistance. Usually gearwheels are made with hardened surfacees !

Each gearpump, used inside a motor or gearbox i know, is build with an valve to prevent about too high pressure. At most cases this valve is the reason for a behavior like you described.
The last 10 years i have had 4 old cars with similar storry (no oil change or not used vor many years) and dropping oil pressure if it gets warm. Each of it was to repair by taking the valves piston out and polish it.
Also use allways a ATF fitting to the age of the car ! Modern ATFs are much more liquid as the older. The reason for that is: the modern gearboxes are made with much more precision and smaler tolerances, that needs a more liquid oil.

[KurtF]

Hello Herb.

Plasics usuali changes it's dimensions very and looses strongnes much with growing temperature.
Second is the abrasion resistance. Usually gearwheels are made with hardened surfacees !

Yes, I understand this too. If I have to print a new set of gears every 5 weeks or so, I can live with that for another year. Although I have no clue what I can get away with using 3D resin; without a fun experiment.

is build with an valve to prevent about too high pressure.

I think you refer to what my shop manual calls the "Regulator Valve". The pump feeds right into it, it's a spring-piston valve which maintains 120 psi. Is that the one? If only I could reach in and clean it like you suggest, without removing the tranny. From your suggestion, I'm now considering the pressure loss could be from excess wear in piston valve, not necessarily the pump gears. Temp rises, viscosity drops, oil blows-by. What do you think?

In fact, from what both you and Chris have shared, I'm considering an experiment with a higher weight of tranny oil. Or a multigrade replacement which (I think) maintains viscosity better at full temperature.

RESULTS (SORT OF) I made a flawed decision to use resin from my resin-recycle jar, instead of the "good stuff". This and a minor support problem contributed to a bad print, with too much runout of the side-gear shaft D, and too much clearance around the gears. But since the parts fit together, at least, and the shaft seal printed with desired clearance, I tried it anyway.

The gears bound up on the first motor start (irregular side gear shaft), but it ran after I pushed the gear around a few degrees first. It did not even come close to self-priming (silly me, lol). It did pull oil up the tube about 2 cm above the liquid level, but after about 20 seconds, a tiny puff of smoke came out of the drive-gear side of the chamber cap seal, so I cut the power. Then I fully primed the pump chamber with oil, to see if that would pull any oil. There was no noticeable difference from the un-primed run. Investigation revealed the drive gear gouged the chamber wall, opposite the side gear, which also gouged the chamber wall on it's side. But the teeth all held up, and the shaft seal as well. I still feel the need to run this experiment again with a flawless print job.

3DP Printer.jpg (537.19 KiB) Viewed 1095 times

Drip-drying on the printer

3DP Experiment.jpg (803.16 KiB) Viewed 1095 times

My world-class machine shop.

[user1234]

This topic is interesting, but i also have my concerns, not only because of the weariness of the pump itself.

- a little edge(s) is breaking out of the the pump, it can close oil lubrication channels, which can destroy the whole gearbox. Even when it is closed and the gearbox OK, the cleaning can be an impossible task, because they are in channels, they are not accessible (depends like the gearbox is build up).

- similar as above, but it can wear make points

- i am not an expert in plastic material, but is resin solubility in oil? If yes, it can coat you whole gearbox and destroy it. And even it is not completely destroyed, the cleaning is maybe also an endless task.


Greetings
user1234

[KurtF]

Hello, user1234. Heehee... yes, I also imagined flying bits of acrylic plastic inside the gear chamber. I haven't designed the output fitting yet, but it will include both a strainer screen and a check-valve.

I've put this down for awhile to work on another FC project. I won't be away from it for too long, though.