Sk3 motor waterproofing?

Hi guys, I’m working on my first build and I noticed that my sk3 has very big holes on the motor. I was wondering if there is anyways to make that area more protected from small rocks or water. This is what I’m talking about,

. Please leave suggestions below.


Outrunner motors are inherintly water proof by design. as for protection, it depends on what you have at hand. if you have a 3d printer, thats super easy. if not, get a hotglueGun/adhesive and some mesh and glue it onto the end so nothing can get in. there are some good images on the forum somewhere, but either way, ive been running without protection for half a year now without problems.


Thanks for the tips!

A.) Can use wire mesh and use those 4 bolt holes to attach to. I saw a really nice mod by a forum member and it was also for a SK3, (and I just scrolled through all my replies to find that but can’t :frowning: )

B.) You can make a 3D printed cover for it. What kind of sk3 is that? Maybe in this thread >>

Actually I have some CAD drawings for 63XX’s.

Key thing to point out is that those vent openings actually help cool down the motor. Depending on what type of SK3 it is, it has a ram fan in the front portion behind the axle output.

For funsies:

Thanks for the help

Probably mid-way between post 1:

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Has anyone successfully swapped bearings in a motor with ceramic bearings?

I had planned on adding protection for the motor but decided it wasn’t necessary. I was wrong…

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Hi! just make a holes with threads and add mesh. Use loctite on threads.


I also added transparent heat resistant and vibration resistant glue around the edge, because in those areas around the edge of motor between screws- mesh was lifting up a bit.


@ninja That looks sweet and I’m taking inspiration from it though wondering about the mesh rubbing on the centre part of the back, doesn’t it turn independently? I’m not near my board atm so can’t check.

Nope. 10ch

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Nothing rubbing, it is fine. Also check your windings, on sk3 they not so good, i had a lot loose windings inside, they would rub from vibrations and lead to short. So then you need find some lacquer for windigs that can hold heat and ad few layers to glue them in place. I used this stuff on windings and magnets too, my friend using it for years for his e bikes. This stuff works like a charm:

I also experimented with this silicon type glue (bison-max repair), hight temp- same glue i was using to glue edges of mesh to motor. But its still in beta for me. Because I need more time proof that this silicon has no cemical reaction with copper in windings. But for now no issues 200km, no overheating, no cemical reaction, holds windings in place:

And one more thing- to make sk3 really good you need 4 things:

  1. silicon cable mod
  2. mesh on holes
  3. glue together loose windings
  4. replace bearings to better ones (i use skf bearings- they costed me about 20eur total. but except big bearing that is for inner fan- that one alone cost 27eur :scream:.)

I also took out that inner fan, because i f***ed it up when tried to open motor. Also it is useless and replacing bearings that bich can make it worthless(too expensive bearing for that fan).

Have a great modification! :wink:


@ninja Your the one I was looking for!!!

Wait so shaft side, the can is not supported?

almost no outrunners we use are supported on the shaft side except this sk3 and he just took it out. they’re all floating bells supported at the other side with the shaft in the middle only I like the gluing of the wires but the glue is so thick and will make the motor hotter and therefore get worse efficiency and you only get part of the windings coated and maybe there are unknown loose wires vibrating around you miss.


Thats why you use epoxy, its fluid (high viscosity), goes in every tiny slot. And its better thermal conductor than air. Just don’t make a 5mm thick seal^^ 0.5 to 1 mill is all you need. Indestructable then, magnets can still fuck up

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Depends what epoxy you use. Theirs a motor winding epoxy that hummie was able to get a sample of that worked very well. Ideally, you want as thin of a layer of epoxy on the windings as possible. It’s very possible the factory could be doing an ok job on this dipping, which will lead to problems for us due to the high vibrations.

Too much epoxy and your just insulating the motors, as hummie said.

Even the worst epoxy is better thermal conductor than air. Too much epoxy and your bell wont spin anymore. Factory does no dipping, wires are enamel coated thats all they do.

the lower the viscosity the thinner the resin On paper unfilled epoxy is close to the thermal conductivity of air but using even a highly filled and much more thermally conductive epoxy on windings it shows to hold more heat when I tried it. Theres other materials besides epoxy that can hold windings, maybe not quite as well, but that have much better thermal conductivity. The Tesla s car’s windings are potted in something. I bet if you wrapped the stator windings in thin copper foil and had that come out from under the motor bell you could get some great heat transfer. It seems the heat is stuck on the copper windings only to be transferred through the air as the stator steel is not conductive being laminates of high silicone stuff and with insulation layers. a block of steel in the oven vs a stator and the stator only gets warm and cant touch the true steel. If you could put some 6awg copper leads on the motor and if it’s possible to get some thermally conductive insulation on them instead of standard silicone theres a direct path to the source of most of the heat we produce. Or multistrand leads that splay out into the passing air.

the point of transferring the heat being to lower the heat in the motor so as to have the winding resistance stay as low as possible (increases with heat), so to have better efficiency and range and also have the motor winding insulation last longer and also avoid whatever temp would reduce the magnetic strength of the magnets or even demagnetize them at high temps potting of course being to hold the wires from vibrating and possibly shorting through each other or through the stator

If you are worried about stones and what not getting in the can; I’m designing fan covers that don’t extend the motors any longer then the shaft, and provide some added airflow for cooling I can share files once I finish a second iteration. I could just as easily make a solid cap if anyone wants that as well.