Brushless Motor Fans

Alright guys, I am trying to lower the working temperature of my turnigy sk8 6374 192kv motors.


I want modify an existing 3d model of these fans that can be mounted on the end of my motors.

I am trying to figure out how the fans need to be oriented to facilitate the cooling of my motors. I am also more than open to looking at other fan designs in order to optimize cooling.

Trying to wrap my head around fluid dynamics and would love input.

I doubt these will have any impact on a sealed motor such as the one you linked, motor with an open end sure…

as for your question take a look at this pic

the 3d file you linked doesnt seem to have any angle to the blades at all, not sure how effective they would be

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Has anyone tried ferrofluid on their motors?

Supposed to do wonders for hub motors.

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I thought the same at first.

I’ve seen them used on sealed motors and they supposedly make a difference.

I don’t get these motors. The cans are designed to be heatsinks( not that this will really cool the stator) and there are fans built into the internals, yet they run hot. I still need to put thermal compound between motor and mounts.

In all fairness, though.I have gained 25 pounds since the quarantine started and am running pretty damn high motor amps.

If I can’t figure out how to cool them down, I’ll just have to decrease motor amps.

I want to know whether the fans should push air towards the can, or away.

I would be inclined to think since you’re using this fan attachment on a sealed motor, air would have to be pushed towards it. Pulling air away wouldn’t make sense since there is no opening to pull air from the sealed can. This is only if we are talking about this specific thingiverse fan design. Others could work if designed differently.

Looking at the thingiverse pictures, it seems thats what the designer had in mind also as the flat side of the fan is pointed outwards away from the motor. Otherwise if the flat side were flush with the back of your sealed motor, there wouldn’t be any intake airflow at all and it would just be a decoration. Going from this, i think its safe to assume air travels from the flat base to the extruding fins and probably what you should do as well.

Like I said previously though, the fan blades dont have any noticeable angle to it so its hard to tell which direction it has to spin to push air. Assuming we’re looking at your board form the back, the left fan attachment will be spinning clockwise while the right spins counterclockwise when you are rolling forward. So either way, one fan will pull, the other push. If it were designed properly, there would be two separate files, one for left and one for right.

Im not an expert, just a nerd whos built a couple custom PCs and watched a bunch of videos on proper airflow/cooling.

I’m not entirely sure I’m comprehending the orientation/referencing of everything you said. I’ll take a look tomorrow when I’m not about to fall asleep.

In the mean time, here are some other alternate designs it would be cool to get your opinion on.

Sk3 63mm Motor fan cover by JohnAlbrecht - Thingiverse

The first one you linked by benbeboy is the best designed one imo. Just mount them according to the link in my first post and you should be good. Be sure to tell us how they work out for you!!

Thanks man. Think there would be any benefit to making the fan a little wider in diameter than the can itself?

Aside from more air flow, it could be possible that air would hit the sides of the can rather than just rebounding off the bottom. Im not sure though, you’d have to ask someone more versed in physics :sweat_smile:

Thats what I was thinking as well. Didn’t make a whole lot of sense to me for it just to hit that one end of the can.

I’m thinking about sealing my motors and using it.


Please let us know if you do.

If Luna weren’t out id buy some now.

I’m worried that it will eat at the epoxy on the magnets and the epoxy I’m going to use to seal intra motor phase wires and hall sensor

That could be a valid concern, I have no idea.

seal how? I feel like the outrunners we use will just sling it out the edge between the can and stator.

" On this skateboard wheel, the air gap diameter is more like 45mm. For this we have

500 rpm = 6.3g
800 rpm = 16g
1250 rpm = 39g

On a skateboard wheel, 1250 rpm is about 20 kph / 12 mph. Not super fast, but not a useless speed either and well in the ballpark of what these hubs would be doing up a hill climb.

Going in the other sense to bigger hubs, I also tested the large diameter BionX D motor, see

On that one, the 300 rpm test corresponds to a force of 16g on the motor.

Anyways I’m hoping that by collecting more info like this over a range of wheel diameters and rpm’s, we can also come up with some good rule of thumb guidelines for Statorade fill levels based on some simple equations given

a) diameter of the motor
b) width of the stator
c) the motor RPM.

And also have a reasonable max RPM number where modest amounts of FF cease to have much of an effect as the acceleration is just too high. For instance, an 80mm outrunner motor spinning 4000 rpm? G force at the magnets is over 700g, and for sure that’s way too much for FF to bridge the gap.

Dammit man. Normally ,I take a scientific approach to things. This time I was just going to seal the damn things and put some ferrofluid in there monitor the temperature.

Now that I’ve seen this data, though…

With Ferrofluid there is only a thin layer, and obviously it is attracted to the magnets.

Maybe a different fluid that essentially fills the entire space could handle that force and actually transfer the heat.

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