Thoughts on Heat Sinks on motors

How-Tos & Esk8 mechanics Esk8 Mechanics
#1

Unsure if this has been talked about but there’s been a new thing circling around the Facebook ESK8 group (I like to be plugged in to nearly all things Esk8) about heat fins on motors. See below:

After looking around a bit it seems the RC world has this too but I’m under the impression that unless you have a precise fit , you’re going to lose some heat to air if you don’t use thermal paste and since the motor can is metal and already exposed to air there’s not much benefit (Could be wrong physics is not my thing).

Thoughts ? Do you think this will assist in getting heat away from the magnets faster ?

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#2

A few thoughts from some here, posted yesterday…

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#3

Thanks Mooch! Haven’t been active recently

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#4

I think they’re better than nothing, but not by a whole lot for one reason: The can isn’t what needs cooling.

Yes, they will keep the can and thus the magnets cooler.
But, the can and magnets are already the coolest part of the motor. (And they need to be, since the magnets are the most heat-sensitive thing in the motor.)
Almost all the heat is being generated in the stator - Either as resistive losses in the windings, or eddy current/hysteresis losses in the steel.

The stator needs most of the cooling, not the can.

Unfortunately, the stator is harder to cool.

Fully sealed, low RPM motors (ebike hub motors) can use ferrofluid (or even regular oil) to cool the stator by transferring heat from it to the can, and then into the air, but high RPM open motors like those used in esk8 are unsuitable for this treatment.

Water/heatpipe cooled stators are possible, but fiddly and difficult to retrofit into existing motor designs.

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#5

But the motor fins won’t hurt?. Because they look cool, and that’s what really matters

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#6

Windage is a thing.

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#7

I mean technically the outside needs to be cooled since the magnets cant get hotter than 80 degrees right? So maybe it helps for that …

#8

Sure but are the magnets actually getting hot before the stator?

The steel flux ring and magnets are not exactly great thermal conductors so putting a heat sink on the can probably wont cool the magnets very much.

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#9

No but maybe the stator can get a bit hotter now since the magnets are cooled is what i meant.

Like 5 degrees :rofl: im just trying so see a use in these.

#10

Just depends on if the increased load in the stator due to windage doesn’t outweigh the cooling effects.

Someone will need to do some experiments but I doubt the can and magnets are limiting power on non hub motors.

#11

I doubt the increased rotational mass will make up for the small amount of heat loss

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#12

Yeah, motors like this turnigy 5035 just have fins built into the cans. That’s the real solution here.
image.

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#13

The magnets can’t run too cool, if that’s what you mean.

One possible edge case problem is the additional cantilevered mass. More mass means more force on the shaft connection point.

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#14

The part of the motor creating the heat is the stator as we know, so would cooling the rotor help? I mean, I feel like it could to a very minimal extent. But this is like turning on the AC in the upstairs bedroom when you are hot downstairs in the den.

Pulling heat out from the stator – the motor mount – might be more useful.

However, these things would work awesome on inrunner motors.

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#15

Only takes a small cnc to cut a watercooling loop onto something thicc like the new TB mounts or BN matrix

the area around the motor pulley is usually free and the ideal place for through-mount stator cooling

#16

Inrunners already have this. My fathers inrunners he bought came stock with a sleeve.

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