For who try/have tried direct drive with outrunner


I had a lot of screw ups, i learned a lot. I have manage to rewind my 80mm out-runner motor from 187KV to 115KV Delta. I used 9 strands of #24 wrapped 8 times. I brought all 6 winding ends out of the motor so if I chose to, I could go with a star configuration. That would give me about KV=67 star. I have not tested it under load yet because I was having a cooling system leak. Hopefully tomorrow.


I have looked at a similar idea too you and suggest putting a copper coil connected up to the water cooling at the back of the motor and then put a small prop on the shaft in front of the coil blowing the cooled air in towards the motor. this will blow cooled air into the rear of the motor and create a high pressure in around the motor for additional cooling.

sounds complicated but would be very simple and might be enough to keep the motor cool.

let me know your results with this motor, im interested.


Very interesting.
How many amps was it drawing at cruising speed ?


I’m traveling at this time. I’ll be home in a couple of days. The last tests with RC aircraft propellers combined with this motor is showing great promise. I’m hoping to run some more tests this weekend and will share the results.


I have the Eon Unlimited Skateboard kit, which I want to use for my Efoil.

The specs are:
Motor: Max. power: 840 W, Max. torque: 3.5 Nm, Motor type: Brushless
Battery: Lithium-ion, Voltage: 36 V, nominal | 42 V max, Capacity: 2.5 Ah
Charger Specs: Input: 100 V – 240 V | 50 Hz / 60 Hz

I realize I will need a “replacement” motor for an Efoil application. Any Recommendations of an 840 W Motor?
Does this motor wattage seam low?


i cant see 840w being anywhere near powerful enough. you need something in the 5k watt range, the eskate board battery and esc wont handle that kind of power. maybe a duel 2k watt setup could be possible.


The motor and ESC heated up much less at the new 115 KV. In my test set up the motor runs in the very cold air outside of the water. So I don’t really know how well the cooling is working. I am building the motor enclosure now. I will probably fill it with oil to aid in cooling. I’m thinking of using automotive brake fluid for oil because it is very thin. Opinions?


Rather than using air for cooling, how about having one end of the copper tube face into the oncoming water and one facing away. This will use your movement through the water to cool the motor. There will need to be good contact between the motor and copper tube. I wonder how well JB Weld with extra copper shavings added to it could conduct heat from the motor to the tube.
Blowing air is a very inefficient way to transfer heat.


blowing air over a water circulated copper pipe would be an efficient way? no?


My plan is similar to that. On the built in core cooling I will run a tube forward to scoop up water and send it into the core of the motor. The water exiting the motor is heading up the mast and cooling the ESC. Then the warmed water will then squirt out of the board. Currently I have a self priming pump in the plumbing between the motor and the ESC.


The photo shows I have removed the original end of the motor and made my own. This will be the fwd end of the motor, It has threaded holes for attaching to the mast eventually. I’m attempting to print the aft motor end now. Too much snow brought down power lines last night, so I lost 8 hours of printing.


This is my idea for holding the outrunner motor in its place inside the fuselage, the slit on the bottom is to run the wires back through the mast. Open to any suggestions and critiques on it design. The mounting wall is 1.5cm thick, hopefully enough to hold my motor. fuselage thickness 4mm

second picture is end that connects to mast piece


Hi @MantaRay. I assume you plan to run the out runner dry in a sealed pod. I would use much thicker aluminum for the mounting plate to transfer the heat out. 1.5mm sounds thin. Also make the cable gab as small as possible, you need max outside wall attachment surface to transfer heat out. What do the other parts look like and how are you going to make that piece? Good luck!


Yep, the c80100 80 kv dry in the PLA pod. I was debating on printing that mounting wall (1.5 cm thick btw, not 1.5 mm) just as PLA with the rest of the piece, but adding a aluminum wall to the print is a good idea too. Another user mentioned that the motor doesnt run too hot, but do you suggest at least having some type of heat transfer for it?


some pics of the other pieces


I would suggest at least sme active cooling for your motor within the tube. I have been running a smaller 6374 type outrunner enclosed before and the heat transfer via the mounting flange was not enough. I had polished this flange and screwed it to a 8mm thick aluminium plate with a thin layer of thermal paste. On the other side I had cooling channels and direct waterflow over the aluminium plate. With the plate staying apparently at about water temoerature my thermistors on the motor windings reached 75C fairly quick anyway. Mayby your motor is more efficient and you need less power than me. I would assume no more than 85% efficiency for thermal estimations with an outrunner. I used 1kW of Input power during my tests back then, the 150W of heat will go somewhere and probably weaken your PLA if you don‘t provide another sufficient path.
I would suggest to at least provide some airflow and transfer fins, but you have to decide with your own estimated losses. I just want to give you an example datapoint to help your design.


Would you not be best getting the 80mm internal water cooled version and use pump to aid cooling ? I feel the motor will melt the pla with only heat transfer out the back plate


I burned a SK3 6374 outrunner in less than 30s in an enclosed PLA case. I just wanted to test power before spending more time on cooling, that didn’t work out well. Your motor is a lot bigger and will probably generate less heat but I am still skeptical that it will be happy in a PLA. I am afraid that adding an aluminum mount plate inside the PLA case won’t do much good either, you want to have it connected to some bigger aluminum that gets cooled by water, either the tube or the mast (like torqueedo does it). Active cooling as suggested would be even better if the motor supports it.


We are using the same 80100 motor but in 50 kv. Our plan is an aluminum mount plate welded to an aluminum tube that covers the motor. Play front and rear to finish and seal the pod. We expect this will provide adequate cooling as we are expecting 40a max and less than 25a cruise.


My initial design was to run a SK3 mounted to an aluminium mount plate. The mount plate would be around 20mm thick, have two grooves for o-ring seals and would fit tightly inside an aluminium tube, allowing heat transfer from windings to mount plate to tube to water.

Then mount the aluminium tube via PLA printed mast clamps.

Your APS motor would be well suited for that as the shaft is long enough to accommodate a seal.

I don’t think that a pure PLA housing is going to work.