Sk3 motor waterproofing?

hard to tell what shape the blades are on that printed part but plain old radial and used to throw the air out is the way it wants to go. Probably just upped the motor continuous output by at least a hundred watts

@Hummie I noticed how the sk3 6364 and 74 have the built in fan. So one side the Fan pushes the air out the back, and one fan sucks Air in the back (in a dual set up because they are spinning opposite ways). So I was going to design one fan like you said so it’ll pull air through, and the other one to have blades that suck Air in to aid the built in fan. Think that would be a good idea?

i didn’t know those motors had a fan pulling and also pushing but I printed a couple different versions of forced air coolers similar to what you did and found if its spinning it will throw the air out radially. that need not be an obstacle and with the right shaping of blades it could pull the air into and across the motor but it wont pull towards the center and centrifugal forces override a scoop trying to pull in. so with your bladed blue fan above it would either throw air out successfully but trying to pull it in I doubt it would. a push and pull will work way better. But a truly passive cooling method these aren’t and current is lost just spinning the blades. Not much and insignificant really but it will only work with high speed and at that high speed it takes the most energy. ultimately I wonder how effective they really are. I gave up on them in the end and rather try a truly passive cooling method I’m trying to make some super thick motor leads with the most thermally conductive silicone insulation and see how that goes. no losses in its use there.

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@Hummie thanks for all of your experience and info… I might just end up making a mesh cover to keep rocks out then. The best cooling method is probably just some thick aluminum mounts and thermal paste between the motor and the mounts…

That’s exactly what I need, tell me when you share the files

motors get pretty hot, and most 3d printed stuff can’t take much heat? I think PLA/PETG/ABS deform in the 60-80c range? So then you’d be into nylon or polycarbonate?

theres high heat pla and abs. ive got pla I can make a teapot out of. but I doubt sk3 motors use magnets that are rated for much beyond 150f anyway

That’s so cool. LMK when the files are done :smiley:

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if you ever get around to modeling the fluid dynamics of the air and find how many blades and what shape is optimal at what speeds I’d love to know.

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turn down your volume please! its so misleading because foc on the road is so quiet.

looks very similar.

testing with just my infrared thermometer didn’t show much if any improvement. made a bunch of designs that never really got a full test. was disappointed in results generally. but never added scoops. just going bigger motors seems a better solution.

but your motor spins like 3x faster so could do more.

with the large amount of space inside the rotor of most outrunners it would be nice to design an air sucker of some sort that connected on the inside of the motor and got .1mm off from the windings. a turbine on the inside with many blades blowing out the holes. with a printer. temp wouldn’t be a problem. a clip on. I don’t have that motor and wont be making it but would if I was better at fusion. would take me too long. gotta watch more lars on youtube.

@Hummie thanks for sharing the videos… I do wonder if the extra rpm on belt drives would provide more airflow. I’m not sure what blade designs would be best… but looking at gives me some ideas. I’m going to look into some programs for fluid dynamics testing.

I think it’d be easier to make some different designs and test them than to learn some program and for sure accurate. If you can install a more accurate mounted temp sensor instead of the infrared because it’s so wild than it’s just riding around a route.
I think the ego motor has a fan on its outside.

But I like inside the motor and a snap on 3d print, maybe it’s more efficient being on the inside than the out with the air it’s contacting being only what its trying to move. there’s not much room inside but if it were to juuust fit that would be slick. that’s what I’d like to see.

or maybe if the printer were good enough could make a mesh of blades with .5mm holes to screen out rocks.

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Heres a new version of the fan cover. I made it so it has 30 backward curved blades as well as a second design with 52 blades. This is a rendering of how one looks. They just requires 4 3mm screws. Go ahead a download it and print it! It’ll be a work in progress, so if you have any ideas you would like me to implement just ask! @Caleb1 @fraannk


That’s cool, John! I’ll have to print one out

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I recommend the 52 tooth fan. It seemed to have more air flow. If you wait a few more days ill have a new version of it with larger fan blades as well as more optimizations.


What program is that?

This is a great mod! Perfect for my 4 motors on my mtb. Thanks !


@wmj259 it’s Rhino 3D for Mac. Its a really easy cad program to learn and work with.

EDIT @barajabali @Caleb1 @fraannk
Just finalized the design. V2.2 is the one I would recommend for an Emtb or backwards mounted motors. It has the best airflow of any I have made, but it isn’t as strong as the others. (2mm wider fan blades in same form factor, as well as larger openings for the motor holes) Print em out and let me know how they work for you :grinning:

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Gonna print it out now. I see left and right but from what point of view ?

right of this pic bring the front


What if you continued the fan portion to cover the whole motor all the way up the can.