Oil cooling for hub motors

[flexy]

I read about an electric scooter (ZEV I think) where they had oil in the hub motor to help dissipate heat , has anyone tried this with their motors?
I guess if the cover plate is well enough sealed you can fill it up to just below the axle, once the motor is spinning the oil centrifuges to the outside, it would have to be non flammable oil like silicone of course.

 

[nebriancent]

not sure if anyone here has tryed it but i would like to
(once i get a spare motor) my main concern is as the oil heats the viscosity will drop
could be a problem for direct drive motors as the hall sensors could potentially be compromised
and for brushed motors it could for a layer between the stator and brushes killing the conductive path to the motor
could it become contaminated from use and become conductive? (small metal filings accumulating like in most oil filled mechanical thing)

i would still like to try it to see if this even becomes an issue
and of course to see if it helps cool in the first place

it would help keep the barrings lubed


neat idea none the less

 

[gensem]

I dont think its going to work...
Not because of the oil itself, coz you can cool a computer by filling it with oil (all but not the power supply and the dvd reader)
But a hub motor is much smaller than a computer case and does waste alot more energy as heat, that would force you to have a strong pump and a somehow big radiator.
for big power numbers i think the astro + reduction aproach is more straight foward.

 

[AussieJester]

Actually, I seen PCs submerged in mineral oil psu included, wouldn't do it myself but definitely psu
Was dunked...

If it was me, I would be more incLined to go with distilled water with some radiator inhibitor splashed in to stop any corrosion, use a inhibitor that's designed for both Ali and steel headed motors.

Hal has a watercooled frock no idea what he's running in it though, he's a clever chap our Hal gets the job done for sure....

KiM

 

[gensem]

I tought about speaking of Hals motor, but I dont even know if he´s watercooled hub is already rolling.
He had major delays in the ebike department because he was working alot with eletric cars. Recumpence could be an option for a ready to go rocket now.

 

[John in CR]

While it would work to some extent, because it's already been tried, there's not a chance in hell I'd do it to one of my motors. The viscosity of any liquid I know of would create to much resistance itself at speed. You wouldn't want enough fill for the spinning oil to reach the hall sensor wires, which are just too fragile. You'd need just enough oil that during operation the resulting ring of oil would just reach the perimeter of the stator. Sure that would help cool the stator quicker, but guess where the heat would be directed...much more directly through the magnets, which is the most thermally sensitive item on the motor. We try to cool our motors to keep the magnets cooler.

The thing that would really make it a waste of time is that it doesn't change the exterior of the motor, which is where all of the heat is transferred to the outside world. That means in continuous operation you haven't increased the motor's ability to dissipate heat by a single watt. In intermittent use, yes it speeds the heat transfer to the outer shell quicker, but that may be counterproductive, since in normal operation the motor will spread the heat fastest from the windings through all of the metal parts directly connected. That means the heat migrates fastest toward the axle. The oil would change that and send much more of the heat toward the perimeter of the the rotor, causing the magnets to typically be at a higher temperature than otherwise.

If you want to cool a motor with a fluid, then run tubes throughout the stator and have them exit the motor to flow to a heat exchanger on the exterior. The pumping losses, effort, space required, and complexity make this a losing proposition for a hubmotor IMHO. Good hubmotors cool fine as they are. Heat problems come primarily from improper gearing (too large a wheel for the load), and pushing the stator to saturation (eg Justin tested a 9C and it saturated at 90A, and that's phase amps, which are much higher than battery side).

John

 

[Kingfish]

If you want to cool a motor with a fluid, then run tubes throughout the stator and have them exit the motor to flow to a heat exchanger on the exterior.

If I were building a hub motor from scratch and I could dictate how cooling would be done, that is the way I would do it: Internal nickel-plated copper sink to pick up the heat, and an external radiator to dispose of it. The pump would be a simple electric motor that kicks in and ramps according to the temperature profile. This way the motor can still cool off when parked. The system would likely need forced-air fan on the external radiator as well. Fluid of choice – mineral oil cos it needs nothing special. Also there is the possibility of using a green-safe refrigerant, but then it would add weight and other dependencies.

I have always had a slight passion though to make a radiator appear as a fender with tastefully designed fins protruding from the sides like the old classic cars or Buck Rogers kind of look. Hmmm <rub chin…> 8)

Dreaming, KF

 

[John in CR]

If you want to cool a motor with a fluid, then run tubes throughout the stator and have them exit the motor to flow to a heat exchanger on the exterior.

If I were building a hub motor from scratch and I could dictate how cooling would be done, that is the way I would do it: Internal nickel-plated copper sink to pick up the heat, and an external radiator to dispose of it. The pump would be a simple electric motor that kicks in and ramps according to the temperature profile. This way the motor can still cool off when parked. The system would likely need forced-air fan on the external radiator as well. Fluid of choice – mineral oil cos it needs nothing special. Also there is the possibility of using a green-safe refrigerant, but then it would add weight and other dependencies.

I have always had a slight passion though to make a radiator appear as a fender with tastefully designed fins protruding from the sides like the old classic cars or Buck Rogers kind of look. Hmmm <rub chin…> 8)

Dreaming, KF

I'd just make a better more efficient hubmotor instead of making such a simple system more complex. Better and thinner laminations, more phases, and a sine wave controller would be a good start.

 

[flexy]

I've never had a problem with the motor overheating, but the first time I had to open it (to replace one of the halls) I was surprised by the amount of moisture that had worked its way in.
I was thinking this might help protect it from corrosion which is what ruined the hall sensor.
I might just drill a small drain hole on the outer rim and hope the bugs don't crawl in there.

 

[drunkencat129]

it will work u just fill the motor with a bit to cover the winding but to seal the thing u take ur sealed bearings apart and use silicone oil in them to keep it from coming out its a little thick but helps keep oil in ^_^ or u can just fill it and see where it takes u lol use minaral oil works good or baby oil works good to