For who try/have tried direct drive with outrunner


Would 22kg of thrust at 100kv be enough to get out of the water on a decent floater ?


Electro mechanically it should work, but this form factor is too bad. With a rotor diameter of 90mm the drag is rather high. Long and slim is rather unusual and harder to build but gives you much more opportunities to optimize the overall design and drag.


This is my first post. I have watched all the videos, I have read most of the posts. Thank you for all the information. I like this project because it takes you down so many paths. I am going down the path with a dry 83100 water cooled out-runner. First thing I am concerned with is motor cooling. Am I wasting my time trying to run this motor using the built-in water cooling only? Using the battery, I bought for my E-bike (36 volts at about 50 AMPS) and 45 degrees F cooling water, I had no problem.


This is a test tank I built. IMG_20171221_192138639

Propulsion System - Motors, Gears, etc

This is cool, keep me up!


You mentioned limiting your power to 24v to avoid excessive amps. Would the current consumed no go down with higher voltage? I imagine the total power would remain the same… ie: higher voltage = lower current and vise versa. Although I guess with higher voltage you would also run higher rpm which would load the motor more thus requiring more power and higher current. Did you test this at higher than 24v? How much current did you draw with leopard motor and solas prop at 24v?



Correct, this was the case.

I recall we were pulling well over one hundred amps at take-off with 24 volts. The amps would drop as speed increased and the prop unloaded…I don’t recall to what level the amps dropped, but I think at least half at about 9 or 10 mph.


hey Guys, so what ever happened to the brushless inrunner promised by Alien power systems? @pacificmeister @VeFoil


I’m not sure, to be honest. that motor is not something I’m using but was following along on its progress. We all know well all too well here, building something new is not quick nor easy.


I thought you wanted to test it and ordered already.


I haven’t ordered, I’ve asked for info, this is what he provided! Clearly an inrunner with water cooling !


I am astonished. I did not know this design.
Maybe you can drive it with a simple vesc 4.12? To get some data and safe usage?


No be never seen it before, looks like it has a water cooled jacket ! I’ll let you know more info when I know, don’t know when that will be seems 1 week can turn into 2 months with alien power


definitely water cooled jacket. over the initial pictures that were cycled around. The issue is then the OD is bigger than 56 and a new aluminium tube would have to be found.

If a VESC can handle spikes of 80A then it should be OK.


Can it be 100Kv or is it 500Kv like the sss?


I tested the sss 500Kv together with a Negart 1:5 against the 6385 Powerglide.
At 3500 rpm they used about the same power 2000W.
Will be interesting to what rpm I get at rated 4000W for the 6385.


What a great opportunity to test them side by side! How did you test them?


Airvanes + Eagelthree, I was surprised that the rpm became so low, with higher load it will become even lower. I only had about 45V aviable though.


I wonder how such a small inrunner can build up enough torque to drive a prop directly. If i look at the tables of tppower
i see their minimum Kv is 330 at 90A. 330RPM/V means a torque constant of 0.029Nm/A . At 90A you would get 2.6Nm. If you want a motor with 100Kv and the same style it means the winding has to be 3 times longer at 1/3 cross sectional area, meaning you can only drive less than 30A for thermal reasons and reach comparable Nm. With 30A and 48V you only have a power of 1440 W. Or 2.6Nm at an omega of 500.


Maybe slightly bigger diameter and double the lenght could do the trick?