Direct drive outrunner with direct water cooling



do you try to test insulation in water like powerglider indicates above but with the megohmeter ?

with a regular multimeter i get OL, but with the the megohmeter i get 0.something Mohm…

I ran the motor in water anyway, and it looked fine :slight_smile:


I took some measurement with 250V insulation tester in saltwater. For the epoxied stator alone i got OL, for the assembled motor including the solderings of the motor cables i got something less, hard to reproduce, minimum was around 100kOhm. I covered the soldering with Plastik 70 Kontaktchemie, sometimes i put a fat blob of MS Polymer around it, but made the experience it does not stick perfectly to the wires. It can help to increase resistance and to mechanically protect the underlying Plastik 70 furthermore. Theoretical a value of 10kOhms is sufficient, as it would limit the current to I=U/R=50V/10000=5mA, which is noticeable but not harmful. Such leakages can be caused by very small cracks where the water contact surface is very small. All these tests should be done in saltwater, i just solve salt in the water, so it tastes really salty.


thanks, i guess i’ll keep it as is then :slight_smile:
the water proofing i did was:
Remove the tubing around the wires
Cut the wires to length and solder the connectors
Cover the wires with some liquid tape between the connectors and the windings
Then apply a few layers of epoxy on the winding (the epoxy i use to make surfboards) end Thickness was no more than 1mm i think.
Then i sanded to get the outside diameter cleaned up, almost back to the metal.
Finally a couple coat of spray urethane to really seal everything (very thin)

after that i protected the wires coming out with adhesive lined shrink tubing… that seems pretty watertight. i’m using the same shrink tubing to cover and hold the connection to the wires going up the mast.

i just sanded the outside smooth and cleaned the inside with acetone. After that, it received a few layer of “appliance epoxy” … just because it was written waterproof and the can :slight_smile:

I replace the bearings with some SST ones, i have come completely open, some 2RS. for now i’m using the open as they are easier to clean / lubricate

Finally i replaced the shaft with a titanium one.


I waterproofed my cables by smearing silicone on the solder joint. Then I put a heat shrink tube over it and let it squeeze out the silicone. After it was cured, I added another layer of silicone and heat shrink so it’s overlapping.