Oil cooling your hub- NOT snake oil!

[Sancho's Horse]

Strike that, chlorinated and non-chlorinated brake cleaner both create corrosive byproducts when combined with oil.

My feeling is that this technique would be far more successful if the oil is moved out of the motor to convect heat.

Does the necessity of replacing bearings move this strategy to this more intensive and rarified plateau?

John in CR makes good points about simpler air displacement strategies (although ineffective, poorly designed hole drilling patterns reflecting zero understanding of modifying air flow will greatly outnumber examples of good execution). Has anyone started a "hole repair" thread?

 

[GCinDC]

well, the jury's back in for me, folks: air cooling wins!

for the past couple days, i've been testing out my second hs3540 with a varnished stator, lots of 1/2" holes drilled mainly over the windings and the same motorcycle wheel laced to the magnet ring. i couldn't believe it! riding hard, stopping hard, medium regen, hard accellerations, WOT up long hills, the vented motor stays cooler than the oil filled. the one possible exception may be while going slow, drawing a lot of current, when the motor is already pretty hot.

i still plan on plotting the temps on that route i did w/ unvented and oiled, just to see it on a chart.

so my unofficial conclusion is that oil splash can't compare to fresh air flow.

before i drill out my other hs3540 sidecovers, i just have to decide if i'm willing to ride salty winter streets with an exposed vented motor. otherwise i'd be drilling!

 

[ian.mich]

well, the jury's back in for me, folks: air cooling wins!

for the past couple days, i've been testing out my second hs3540 with a varnished stator, lots of 1/2" holes drilled mainly over the windings and the same motorcycle wheel laced to the magnet ring. i couldn't believe it! riding hard, stopping hard, medium regen, hard accellerations, WOT up long hills, the vented motor stays cooler than the oil filled. the one possible exception may be while going slow, drawing a lot of current, when the motor is already pretty hot.

i still plan on plotting the temps on that route i did w/ unvented and oiled, just to see it on a chart.

so my unofficial conclusion is that oil splash can't compare to fresh air flow.

before i drill out my other hs3540 sidecovers, i just have to decide if i'm willing to ride salty winter streets with an exposed vented motor. otherwise i'd be drilling!

Yes it is better, but i want to be able to sell a cooled hub motor, and having an open motor with hand drilled holes would not fly. I think using mineral oil, sealed bearings from mcmaster carr, lots of silicone around bearings and the covers, would do it.

 

[grindz145]

Wow, that's really surprising Greg. Looking forward to seeing the data. It makes sense though, it all depends how those thermal resistances add up!

 

[GCinDC]

Temp C on left and minutes on bottom axis:

dang it. i can't find original video of oil-cooled run, to compare with longer vented run! :x i'm pretty sure the oiled motor started cooler, but got hotter and stayed hotter than vented, tho i should shut up till i find that vid.

notes:
the 'no oil' line is for the unvented/unoiled motor.

ambient temp was ~5C hotter when the vented run was conducted.

except for a couple sections, i was trying to pull as much current (4kw) as possible, esp going uphill, to make the motor heat up as fast as possible.

 

[grindz145]

Awesome data Greg!!

You said that it takes longer to cool down with the oil, but the oil doesn't look like it's doing too bad though on this graph anyway. Maybe a good winter solution, to keep the salt out?

 

[John in CR]

GCinDC,
AFAIC your vented motor is still running too hot, and I believe it can do much better. I think you're leaving at least 50% on the table that can easily be obtained with less than 10% of the effort put into trying to make oil work, and that's before going to Arlo's approach with fans inside (though I think blowers would be a better choice because you can direct the air at the stator easier). I'd suggest putting some effort into managing the air flow you already have, and then decide whether you need to go the fan route. The type of riding determines whether fans are needed or not. They're easy enough to add later, and aren't an either/or kind of thing.
John

 

[electr0n]

Nice info there GC. I've been running my unmodified HS3540 at 88.8v nominal 35 to 37 amps in my 26" wheel here and there and it gets really toasty after about 10 to 15 minutes of hard riding. I back off the throttle on hills and when the side cover gets hot to the touch I give it a rest. I want to throw a thermometer in there and drill out the side covers after seeing your results. I would love to be able to run 5 to 6kw bursts and 3 to 4kw continuous without worrying about having a meltdown.

 

[itchynackers]

I haven't posted the details yet, but in my run to the top of Pikes Peak Saturday, I peaked at 118C, and saw a quick drop in the short downhill section to 103C. I'm running 400ml of atf dexron III in a 9c 6x10. Ambient was 5c at the top of the mountain. That is the hottest I've ever seen my motor get. I've never been over 80C in my normal riding in Wisconsin summers.

Adam

 

[GCinDC]

the oil doesn't look like it's doing too bad though on this graph anyway. Maybe a good winter solution, to keep the salt out?

yes, i think so! i posted about the salt we have in DC with any possibility of snow:

and i posted on it's effect on relatively new (and unvarnished or unmodified) hs3540 (that was far worse than 9C's i've had through several winters):

so i'm not concerned about dirt getting in the vented motor (or fresh water which will evaporate), but i doubt an unvented motor could survive that much exposure to salt for long. and oil cooling would be a great alternative for a sealed motor.

And an idea I had to prevent damaging the disc pads in case of leakage - an absorbent cylinder, such as a cymbal felt washer, but preferably white:

cut a slice in it to slide over the axle, then check from time to time... might at least save the expensive pads from getting ruined...

 

[GCinDC]

btw, i was so shocked at the corrosion, and it being my first xlyte, i had no idea of the cause, but have come to believe that the salty water, perhaps even slush was sitting on the wires and after the ride when the motor was cooling down, it all got slurped right in. :x :| :lol:

 

[korpin]

I have been reading this thread with great interest and it seems like the bearings are a source of leakage...I am in the swimming pool industry,and sometimes work on ponds and fountains which have submerged pumps (submerged in water)..these pumps have obviously have no air cooling and are filled with oil....the point being they have bearings and a shaft coming out of one end to turn impeller and must be sealed somehow?

 

[korpin]

I would like to hear from a few people who have tried oil and vents on the same motor....most of the comparisons were done verses standand non vented motors it seems?

 

[amberwolf]

Many of those pumps probably don't need to seal the shaft coming out; they probably use magnetic coupling between the motor and the pump itself. It's common in aquarium and koi pond stuff, probably in lots of water-circulation stuff.

 

[cheetor]

as I'm rebuilding my bike at the moment from 12S to 27S of LiFePO4, I figured hell, why don't I give this a try. so I added a breather/filler hole and put her back together... another 200mls of ATF in tomorrow.. I'll post back here with my results when my new Lyen controller arrives.

 

[ian.mich]

I think i've nearly figured this out. get:
some mineral oil laxative (cannot conduct electricity!),
two of these
http://www.ebay.com/itm/Bearing-6202RS-11x35x15-Sealed-Gas-Scooters-Go-Carts-Pocket-Bike-ATV-Quad-Buggy-/390447917652?pt=LH_DefaultDomain_0&hash=item5ae8826a54
a small titanium drill bit,
find an aerosol can straw,
some silicone gasket maker,
and epoxy.

1. drill one tiny hole in one of the covers, near the axle
2. install new bearings
3. silicone one of the covers shut
4. epoxy the two entrances for the wiring, and pop the stator back into the magnets and sealed cover
5. put on and silicone seal the 2nd cover
6. pour 100-150ml of the oil into the hole, maybe use a funnel or syringe?
7. insert a tiny piece of aerosol can straw (~2cm long), and silicone in place.
now every year or two when the amount of oil has decreased due to minor leakage through the bearing and the straw, the straw can be pulled out (silicone is weak), oil added, and the siliconed back in place.

 

[GCinDC]

that's for a 9C? i know those bearings won't fit an hs3540...

fwiw, my brakes that 'mineral oil', and i was about to use pharmacy stuff, but read that it wasn't up to the heat of the hydraulic mineral oils...

 

[ian.mich]

that's for a 9C? i know those bearings won't fit an hs3540...

fwiw, my brakes that 'mineral oil', and i was about to use pharmacy stuff, but read that it wasn't up to the heat of the hydraulic mineral oils...

Pro 901. ID 15mm, OD 35mm, width of 11mm. I was planning on using this http://www.ebay.ca/itm/Mineral-Oil-Laxative-Durvet-Gallon-/271021456035?pt=LH_DefaultDomain_0&hash=item3f1a233aa3
or something from steoil. pharmacy mineral oil is used for computer cooling so it seems like the right choice.

 

[neithermovingnorstill]

I'm curious if adding oil or coolant would reduce the noise of the motor?
I would think it would muffle the sound a bit, but I wonder if anyone has experience to verify if it actually makes it quieter?

 

[ian.mich]

I'm curious if adding oil or coolant would reduce the noise of the motor?
I would think it would muffle the sound a bit, but I wonder if anyone has experience to verify if it actually makes it quieter?

maybe a bit, but if your running enough power to merit cooling, you want to hear the roar! nonetheless, oil cooling is pretty simple compared to the physics of air cooling so that's probably what i'm going to do, especially considering the bearings are a mere $10 each

 

[GCinDC]

I'm curious if adding oil or coolant would reduce the noise of the motor?

yes, i meant to mention this. my oil cooled motor was noticeably quieter than when vented. i can't remember how much quieter my oiled motor was than stock.

 

[amberwolf]

In my Fusin geared motor, the oil cooled seems a bit quieter than just greased, but I don't yet have my pro-audio recording interface back from a friend yet (he has finally moved and is unpacking boxes slowly), and nothing else I have to record with does a good enough job to compare sound levels properly like this (most of them have auto-levelling, so they make all audio sound the same volume, whihc is worse than useless in this case).


I haven't tried a DD this way yet; the one from Ohzee will be the first of those, after I fix the rubbing issue with the hall wires (or whatever it is).

 

[neithermovingnorstill]

I don't mind the growl of a gas engine, it's high pitched whine that I can't stand, which electric motors seem to make as a rule.
I'm aware that DD hub motors are quiet, but they have drag, weigh more, and can't climb as well. I still might go with them though, just want to see how quiet a geared motor can be.

 

[neithermovingnorstill]

Oops, didn't see the other replies verifying that it's quieter, I just followed the link from my email alert and it led me to page 18, didn't see page 19.

That's great news (that oil reduces noise), I guess it's to be expected, but I'm really glad to hear it helps.

I just found this: "Super Low Viscosity Pure Silicone Fluids" (the one I found was clearcoproducts)
It is used by the military as damping fluid.

Not as good at thermal conduction as vegetable/petroleum oil though... ( at Engineering Toolbox their thermal conductivity chart shows that silicone oil is .1 where olive oil is .17 and engine oil is .15)
The same table lists glycerol at .28, and ethylene glycol at .25. They might be a bit thick, but maybe they could be mixed with the silicone? I'll do my homework, they're probably hygroscopic and could lead to rust, or migh not even mix with the silicone.

And, silicone has a high molecular weight, and I'm thinking that the ideal thing to reduce high frequency sound, would have the lowest molecular weight, (as well as low viscosity to reduce drag) since it would resonate more easily with the sound waves.

 

[ian.mich]

i think pure white mineral oil from walgreens, or shoppers drugmart for us canadians, is the best bet. clean, cheap, simple, and doesnt conduct electricity. they use a highly refined version to cool transformers.