For who try/have tried direct drive with outrunner

Isn’t a 500Kv + 5:1 reduction the equivalent of a 100Kv motor with no gear ?
The Max “no-load” speed for both setup at 12S is identical: 4800 RPM. Or am I missing something here ?


Correct, the RPM will be the same. However the motor torque probably will not be the same. The gearbox has a multiplying effect on the torque from the motor. Im not sure how much torque the low KV motors are getting. This torque is needed to maintain RPM under load.

Can’t we use the “P= C x Omega” formula with Brushless motors ?

If I am not mistaken the SSS 56104 500kv at 44.4v and 5:1 reduction should have roughly 50% more torque that the 6384PG (in theory).

Hi guys new to the form hear Long time reader first time poster I am thankful for what you all are doing this is very exciting I come from Ebike world. And now I definitely want to build a efoil!
I would like to know if anybody has ever tried Astro flight motor? They are one of the most powerful weight two ratio motors I have ever experience. I am thinking of disassembling one of my bikes to give this motor a try.
Definitely want to go for a direct drive i would like some input .

Stock number P/N 3220
Winding 5 Turns
Speed Constant 137 rpm/volt
Torque Constant 10 inch ounces/amp
Winding Resistance 50 milliohms
No Load Current 1 amp
Max Continuous Amps 75 amps
Peak Amps 1 minute 100 Amps
Typical Voltage Range 24 to 80 volts
Typical Power Range 4,000 to 6,000 watts
Typical Efficiency Range 90 to 95%
Typical Speed Range 6,000 to 10,000 Rpm
Stator 24 slot 8 pole winding
Rotor 8 pole Sm Cobalt
Bearings Two Ball Bearings
Motor Diameter 3.2 inches
Motor Length 3.4 inches
Motor Weight 4 lb.
Motor Shaft 3/8 inch diameter

I will be running astro 3220 4T KV 169 on 12s well run 6500 RPM
Maybe a Yamaha 7 1/2 x 7 prop?


see my post on rpm drop : Rpm drop under load, Rm I

to spin the solas propeller at 3000rpm you need about 6NM

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you are reffering: Any interest in a custom e-foil ESC?
Yes, its profiled, the outside is almost a straight cone, while the inside collects water and accelerates it to have the motor running at higher speed.

Well, our setups are quite different: You have it running in an oil filled tube with additional friction from oil and eddy currents, additionally you have higher induced losses because of the higher cross section area. BUT: you have a vesc delivering 3500W, thats good.

To all the plastic prop printers: What happens if you put the prop with its blades onto the end of a tube, so the blades touch the tube at 2/3 of their radius and than apply 30kg onto the hub? Does it bend or break?

At benjo:

What theory do you have in mind? A lossless gear? More amps possible for the SSS?

Well, same KV (at the prop shaft, you can do that, since the gearbox is linear) is same KM and KM unit is Nm/A, so (if you oversee the <5% difference in efficiency) it is exactly the same torque (in theory) at a given power level (I don’t think it makes sense to compare different power levels e.g. max power since max power really depends on your motor cooling and max power is no point where you want to drive your motor (permanently), because the efficiency is ~50% (in theory)).

Yes, lossless gearbox and maximum power as stated in the datasheet. So a rough estimate. I am also not a mechanical engineer or physicist :smile:

I believe that using a gearbox will actually reduce the torque, as the motor needs to use extra power to turn the gearbox as well.

You are right about the gearbox consuming a bit of the power. The Neugart PLE40 5:1 runs about 97% efficiency from memory. I dont think you understand how a 5:1 gearbox multiplies torque. It takes the 25000 RPM at 2Nm from the motor and turns it into 5000 RPM at 10Nm, minus your 3% power loss. Obviously there are other things going on to effect RPM and torque to the prop, but in a nutshell, that is what the gearbox is doing.

As michion said, a gearbox basically lets you trade RPM for torque and vice versa. A 2:1 gearbox should give you twice the torque with half speed, a 1:2 gearbox doubles the speed and halves the torque. Thats the reason you can go really fast in 7th gear in a car but struggle to accelerate. First gear is the other way around. Lower gears in a car are reducers, higher gears multiply the motor RPM.

Any update on your high efficiency propeller ?

Many thanks,

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If you can spend the amps, the geared motor seems to be more powerful, but tell me, why do you cool gearings?
With direct drive concept, the motor bearings are used directly, in the way they were designed. The force comes from the magnets inside the rotor. They translate directly into the propeller thrust. I should have patented some aspects of this, instead i gave it to everyone. :wink:
If i count it right, the direct drive has 3 deep groove ball bearings, how many has the geared one? And how many seals? I would suggest one for the direct drive as well. Although the sealed ball bearings are holding strong with standard grease. And a thight 3D printed cap for the circlip bearing.

Hi WNT did you ever manage to get this done? thanks

Yes, I can pull 3500W for a maximum of 1 minute. After that, the Vesc starts limiting the current.

Regarding plastic props, they are pretty stiff. It bends a bit but doesn’t break. Same for 3D printed PLA props.
I don’t know if using an aluminium one makes a huge difference though.

I have read here that you managed to go up to 16km/h using 2200W battery. Any Idea on how much Amps were pulled by the motor at that speed ?
Eventhough I managed to pull 3500W, it seems that your setup is way more effective than mine ! At 3500W, I’m only cruising at 10kph for now !

Not only will you find slippage in the prop due to bending, but you will also lose power due to oscillation in the bending. In a long-term application, aluminum is the way to go.

@Flo, i am PowerGlider being on vacation and i cannot use my usual account , can you please send me a private message, i need some support regarding your fantastic program espap you gave me some time ago. I got huge amount of data now, but struggle to analyse it.
Thanks a lot!

I read through a couple of threads now and I’m still wondering if anyone has ever successfully “foiled” with the 6384N @PowerGlider motor ? Power Glider, you’ve only used it to propel your surfboard, but not actually on a foil or am i mistaken?
I’m about to order a pair of 6384N Motors, but just want to make sure it’s actually possible to foil with these. Otherwise I’d order a spare 80100 just so I have a motor that I can foil with for sure.
Also, if anyone has ever foiled with that motor, did you change any bearings ? Or how long do the stock ones last (approx.)?
I was planing to do a 6384N Powerglider - ARC200 direct drive setup, Prop: Not sure yet
I’d be thankful for any info

Hi, foiled with both, the 63 may not suit if you weight more than 75kg

For the 80 the bearing got rusted instantly, needed replacement