S9tim's 80100 direct drive

Maybe it makes sense to reduce friction, that was my motivation too. On the other hand we want turbulent flow in the winding gaps to maximize cooling efficiency. Also the head of the windings can take a lot of the heat away, so be careful not to cover it completely. I used low viscosity epoxy combined with vacuum to prepare the stator, and the coat is less than 0.1 mm thick. Someone wrote he uses a mm thick epoxy, i think this is contraproductive. The problem is there are many windings covered by others. The friction maybe costs you some watts, but the worser cooling can cost the motor. Put some more effort in reducing the friction on the inside of the rotor. This surface needs a good finish. But hey, do what you believe in, maybe its a good idea, but leave some water flowing. My motor was cooking inside. Also leave some outlets, so it is clear where the water is leaving with a distinct centrifugal pump effect. You can reduce the (number of) outlets later.
This did not work:

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I have sensors coming on my motor. Wasn’t sure if they are a good idea or not. If the sensors are useless, should we remove them to improve water flow and reduce the number of things that can turn into shrapnel?

I think the sensors are useless for this application. If I understand correctly sensors help to get the motor started when it’s under load at zero rpm (such as you are standing on your esk8 and want to start moving).

In that instance the motor in in open-loop because it is not spinning fast enough for the feedback to register at the processor. It’s only when the motor gets up to speed that it goes into closed-loop.

So when the motor is in open loop the controller has no idea what is actually happening. And that’s where the sensors help.

In our case unless the prop is blocked the motor should have no problem spinning it up enough to get to closed loop.

You gave me some motivation to get my direct drive done! Here’s a pic (just waiting for the corrosion X to arrive)…

The prop is 130mm and I’m not too sure of the pitch.


Nice Prop’ !
Is it a custom one ?
Did you try it already ?

It was posted on here a long while back and then I customised it for my needs.
It works well in a geared setup, but it will be interesting to see how it is in a direct drive.
I have other props I can test with too if this doesn’t do the job.

Short video from this past weekend.


Looks so nice on the water!


That looks great @Jezza , is that a 63mm motor and what KV?

Nice work! how are the stock bearings holding up?

So far so good. About 10 runs so far in saltwater with no signs of corrosion. Every few runs I soak the motor fully assembled in corrosionx for a few minutes.


Yes, its the 6384 100Kv with a claimed 4Kw of power. I have a lower pitched prop as well, but might as well try the higher one first :slight_smile:


Do you dip the whole motor into a bath of CorrosionX? Can you re-use it? Do you use the normal variant or HD?
Thanks :grin:

Yes, whole motor in the normal corrosionx not HD. It can be reused. The key is to make sure the motor is dry so you do not get water into the corrosionx or it starts to get milky.

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Hi @Jezza, is it custom 100kv motor that powerglider defined and bought from Alien power? Did you try it already in the water. How does it go? Power, amps? Please let us know and good luck!

It is the powerglider motor. My corrosion X arrived today so I will be able to submerge and then hopefully test over the weekend. I’m a little nervouse because the new shaft has no circlip and is only being held on magnetically, but I think it should be alright provided I don’t hit anything with the prop.

Be careful, the moment you release the power it will come off! Remember i got 30kg thrust at 2200RPM! You need under 10kg to remove the rotor from the stator when unpowered, i do it regularly by hand without any tools. You will loose it, thats almost sure. If you do not have a circlip, use a clamping ring!

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There shouldn’t be any reverse thrust on it except drag from the water. And the drag from the water definitely should not be anywhere near 10kg worth from the prop.

Why is it so? I do not believe it. I already lost a prop and rotor, because the circlip was mounted wrongly. And how can we know, that a spinning rotor produces the same magnetic holding force as a still standing prop?

Sadly CorrosionX is almost unavailable in Germany, I can only get the aerosol. So I will either use this to spray everything (no submerging) every once in a while or I need to use ACF-50 which should perform somewhat similar.