On original FD Assist (+, max, slim) , Foildrive use 6374 130 KV 3200 W 5.6N.m to have 25kg of trust at 3000 rpm on the propeller. The system is limited to 1500W by the VESC (half motor power) so I wonder if we could use a smaller motor because I conclude it’s an overkilled size for this use.
I’m thinking about an APS 5065 90kV 1800 W 5.7 N.m at best to reduce drastically the drag
or
the APS 6355 100kV 1700W 3.8 N.m to reduce the weigh.
The assist has max power for an initial period to get the rider up. Then they limit the various iterations of FD to a safe continuous power limit because of battery longevity and lifetime.
The smaller 56mm motors can’t generate enough torque to get the rider up easily even at max power.
Then you need to take into account that guys are riding anything from 3ft to 10ft boards with an assist so there’s a massive difference in what is needed power-wise. If they decided to support a smaller motor, then it’s just an additional bunch of costs for a company with zero real gains…
That again has nothing to do with foil drive. Foil drive use a 11s3p battery.
The higher voltage push on assist units came from other companies like E-sea Foil and then FD one upped them on series count. Manta is the first company to use 12s2p.
Yeah it’s basically the smaller rotor gives you less torque that’s the issue. But that also comes down to each individual and the board size, weight etc…
You might be able to get going on a smaller motor. You might also just need that tiny assist…
Try it and record data and let us know the results.
What is considered required startpower for 70kg, 90kg, … takeoff weight for a given board type and volume/shape, anyone of you who has educated guesses from your testing?
I’m 95kg and can start a 27L 4’6 board with a very inefficient prop at about 3kw…
I was meant to test some new props this week but instead decided it was a good idea to lift a CNC machine and put my back out.
These examples makes one think you are onto something here. Finishing my first fd classic clone and already thinking what is next. Slimmer motor size sounds like a nobrainer candidate, along with subsurface/board battery and esc mount….
Regarding torque. It’s about saturated stator steel afak and enough stator/rotor length can also deliver required torque for a given diameter so the slimmer APS with 5.8nm but lower watts is the same torque design as any diameter motor with 5.8nm, so factors affecting takeoff and sucess would be more system overall design such as prop eff, proper rpm, stable voltage and getting enough current to the kv motor design to deliver required torque without heating etc?
Sound like lots of fun ahead.
Can’t trust rc motor specs, normally a fantasy number the seller just makes up.
A proportional comparison shows that a 56100 sized outrunner can be estimated to have equal max torque to a 6384 if the airgap flux is the same. In reality it’s unlikely to reach same flux density, with smaller diameter the area for steel in the stator teeth and room for copper between the teeth gets smaller. Efficiency will be also be lower at max torque.
What happens at smaller diameters is also that (for same power) the efficiency is shifted towards higher rpm so the smaller motors can have good power and efficiency but are not the best for direct drive where torque needs to be higher.
Wisdom is a strong word😀
I’ve tried smaller motors without success, they burnt without reaching foiling speed even though i tried a few props. Torque and power just wasn’t enough.
The EXACT genuine Foil Drive motor is Saite 6374, you can buy it waterproofed from Saite. No magic with Foil Drive Gen2 components. Flipsky 6374 or 6384 140kv motor is easier to source.
one more question, I’ve done some search and I see no one actually (or didn’t find yet) tried to make battery/electronic case at the mast base (similar to FDGen2), I would expect to find CNC files and STL to reproduce that, but everyone seems to be just throwing in the box on top of the foil… so no one done design for bat/electronics for mast base?
Hello, I have made a similar attempt for a friend (a box with everything between the mast and the board). He is currently putting it together. There battery is 14s3p, 50S Samsung.
I’m currently making a bigger one for myself, with a 14s5p battery.
I’m still in the fusion 360 stage, but I can send a picture if you’re interested.
When and if it works out, I’ll post info on the forum.