Direct drive outrunner with direct water cooling


We gonna get a better motor, better to build this thing, suited for our purposes. I put my requirements here to get your input.

So here is my specification:
6384 Motor with following changes:
Do not glue the stator iron to the aluminium hub.
Do not mount flexible cables to phase wires, just let the phase wires around 10cm long. Mount plugs there if you need it for testing. I do not need them.
Do not mount any sensor, sensor cables. Instead prolong the iron core by 4mm.
Adapt the winding: RPM/V shall be 100. 100kv.
Leave space between the windings like you use to do with the 6384 130kv. It is needed for cooling.

What is the sience behind?
Some space inside the motor is used for sensors we do not need. It can be used for iron core prolongation by 4mm which makes 54mm then. By this we gain some space for copper and iron and increase the powerdensity by 8% in the given volume, the weight is increased.
We want only 100kv. This means either stronger magnets and/or different winding. If it is only done by the winding, the current rating goes down. Too strong currents would overload the magnetic field and yield to higher power losses. On the other hand, with this knowledge, it is ok to make more windings with thinner diameter if they are cooled well. To ensure this, there has to be some space left between the winding packages on the full length for waterflow, which increases the resistance and powerlosses.
If you are searching for the highest possible power region with some given parameters you end up with some waterflow and some generalized averaged warming. I suggest high throughput, best possible cooling, from there you can optimize. The system is not going to crash because of overdimensioned cooling.

So if you see any improvements regarding the motor, tell it now.


Great description POwerGlider! Looks as very good concept. It the motor also can be water proofed in the fab then nothing else to do with the motor (probably put better bearings). Do you have any idea is alienpower can adapt such needs?


alien will not deliver it waterproofed, maybe they can do it.
As a first step i discussed a modificated 6384 motor, here are the specs:
6384 Motor with following changes:
Do not glue the stator iron to the aluminium hub.
Do not mount flexible cables to phase wires, just let the phase wires around 10cm long. Mount plugs there if you need it for testing. I do not need them.
Do not mount any sensor, sensor cables. Instead prolong the iron core by 4mm.
Adapt the winding: RPM/V shall be 100. 100kv.
Leave space between the windings like you use to do with the 6384 130kv. It is needed for cooling.
End of spec.

This will make it much easier to waterproof the motor and get the best performance. The motor shall be available per backorder end of this week, so typically you can receive it in 8 weeks. Lets see.
You need epoxy of two qualities, i used these: “Gießharz Wasserklar” with can-time 4-5hours for the stator using vacuum and a “normal” one with 20-60 minute can- time for the rotor, both from R&G.
To provide the vacuum i use a fridge compressor, apply vacuum for 10 minutes, than release, do it over until there are no air bubbles visible. You should have some experience with epoxy, its not a good idea to do it with such nice motor for the first time.

With the new motor you have disassembled parts, so it should be easier to handle and also the phase wire to other cables interfacing is much easier. Latter one i could not solve perfectly with normal motors.

If we figure out, how it is done with good repeatability we could try to get it done in the fabb. But it will be costly, as it is time consuming.


Great info! Awaiting to get this motor available in their site to order. Did you get the price perspective for this motor?


Price will be the same as other 6384.


How to build a simple vacuum chamber.
Building a vacuum pot is very easy.
Get these jam jar, they fit perfect for the 6384:
Get some hoses, which fit the cable bushing, a fridge compressor, and this:

Cut a hole in the lid of the jam jar
and mount the hose using the cable bushing.

The whole procedure takes some hours, but the result is outstanding and long lasting. Put the hose to the vacuum inlet of the fridge compressor and switch it on to generate vacuum. Check if it is tight by clamping the hose. Check the function with a swamp and water inside the jar.


Fridge compressor is good to use, if it is already available, if you need to buy, it is better to use a special compressor for vacuum, it creates a much deeper vacuum, for example:
I bought a similar compressor from local suppliers, because I plan to use carbon in my projects, I also plan to make an electronic pressure regulator to keep the necessary vacuum long enough and the compressor did not work all the time.


Nice device. Keep an eye on the vacuum and what it does. 2Pa sounds like space, maybe you stop when its getting milky way. I think its suited. Try it.


What do you think about using regular tyre pump, like this:,searchweb201602_2_10152_10065_10151_10344_10068_10345_10342_10343_10340_10172_10341_10541_10562_10084_10083_10307_10060_10155_10154_10539_10312_10059_10313_10314_10534_10533_100031_10103_10073_5680020_10594_10557_10596_10595_10142_10107,searchweb201603_2,ppcSwitch_5&btsid=a1700039-a2ae-4414-83f2-e7ef54fa4f34&algo_expid=be172508-68e2-4fbb-a668-afcc371648ca-2&algo_pvid=be172508-68e2-4fbb-a668-afcc371648ca&rmStoreLevelAB=0

and reverse the air flow direction?


or even cheaper stuff like this:,searchweb201602_2_10152_10065_10151_10344_10068_10345_10342_10343_10340_10172_10341_10541_10562_10084_10083_10307_5680015_10060_10155_10154_10539_10312_10059_10313_10314_10534_10533_100031_10103_10073_10594_10557_10596_10595_10142_10107,searchweb201603_2,ppcSwitch_5&btsid=bf6058cf-c4bc-4ba2-bc56-be3c6f5b287a&algo_expid=22658468-f940-419a-93b9-7a981ee2509b-0&algo_pvid=22658468-f940-419a-93b9-7a981ee2509b&rmStoreLevelAB=0


I bought a one-stage vacuum pump from a local supplier for $ 65. This pump has a residual pressure of 35 Pa. The 12V pump you offer has a residual pressure of 50 kPa, which is not enough to remove air from epoxy, judging by the forums, you need a pressure of less than 10 KPa, the less the better, according to information from the forums, this task can not be met by a converted car pump . I considered many options, but I bought a specialized pump, especially since it is not expensive. There is a very simple option that I got, perhaps this is the easiest way to save money:


Very nice, there is always one more possibility.


Doug Jackson from SV Seeker is building a 1000m ROV and a giant ship in his backyard. Crazy guy, cool project. He build almost everything from scratch. Here is his ROV thruster series:

While you are at it, feel free to check out my channel : )


Hello! Do you have any news about the updated 6384 motor for our purposes? The site did not have new engines of this size. Is there hope?


Well, how can we handle that? So you would directly buy a motor, without beeing tested by anyone. You can write a mail to bruno, give him the link to this thread and ask for a 6384PowerGlider. By this he can plan the demand.

Keep in mind it is untested so far and we still overload this motor so direct water cooling is crucial. Also voltage limitation has to be tested in depth if the phase current is unlimited. A lot of controllers only limit the phase current indirectly by their own resistance, the battery and so on, meaning everything gets dammed hot. All these toys are badly designed and built to break. The VESC seemed to be a chance for phase current limitation but is not powerful enough (yet).

If it is really urgent, buy any of the 6384 and rewind it according to your requirements.


I asked a question about the motor on the site of aliens, let’s see what they answer.
Regarding the VESC controller, I plan to buy it in Hobbyking and modify it as follows:
Remove the power transistors, bend their contacts so that it can be mounted at an angle of 90 degrees to the board, solder the copper bus sections on the reverse side of the transistors, and attach water cooling through the insulating gasket. It seems strange to me that the designer of the VESC controller used so powerful transistors that are capable of working with a current of 240A, if I’m not mistaken, and did not provide enough good cooling because of what the regulator operates at such a low current …


I am working on that, i.e. attaching a heatsink to the vesc for watercooling. So far i have flipped the Fets and added a copper bar to each fet as contact area for the watercooling. If you wait a few days I will report the results. I just have to find a way to dump the torque from the motor for testing without getting into the cool winter outside.


In place of prop I fitted a bar 420500mm and screwd vanes 30*50mm on the ends of that bar.
That gave me 80Amps 12s @ 3300rpm for testing esc.


It should be 4*500mm


After my call to Bruno, the motor appeared on the site, now it is available for pre-order:
I ordered myself one, I will experiment.