Electric Hydrofoil/E-Foil

[Gege2000]

Another succes, but I think there is not enough thrust, and the foil seems to need optimization, but congrats to him! : https://www.youtube.com/watch?v=1-KyoMd6rcU

 

[parabellum]

to WHY some experienced cogging issues.

Sensor less is not up to the task of loaded start, most of more advanced controllers still rely on sensor feedback to start spinning a motor in loaded condition and switch to whatever sensor less algorithm when solid BEMF reading is available.

like an astro motor

Yup, IMHO, by now, it is the best candidate to do it right in this application. Astro with sensors + advanced e bike controller to be precise.

Who's LFP?

Google Liveforphysics

P.S. Astro 32xx series

 

[dirty_d]

Just following this thread, as I'm interested in building one. I built an electric kick scooter that is loads of fun on land, and now its on to water

A few questions. I see that there is discussion of using a gearbox - is that to keep RPM at target or mostly due to sync issues? Is sync basically an issue of insufficient starting torque or something else? I couldn't find whether you guys are having sync issues running sensored or sensorless. I had sync issues when starting from stopped on my scooter when running sensorless and with gearing/motor kv optimized for speed rather than torque. When I switched to a much larger motor and ran sensored, I was able to start from stopped with ease.

So I guess my question is, why not simply rewind the motor at a much lower kv, say 50kv or so and increase voltage? If you have a 200kv motor, rewound to 50kv, you've essentially gone 4:1 with no loss in energy from the gears.

My plan is to use a sensored alien tp100, which is supposedly rated at 12kw continuous, at 72kv and then use one of his 300A EV escs and a 20s20p battery pack. The tp100 is a 100mm motor, so that's pretty wide, but I think it will be worth it for the substantial increase in torque/power?

It seems like it's a problem of torque efficiency at low kV and a problem of weight and size. With a direct drive, the motor will be too big and too heavy for the good torque and rpm.

Not sure I understand/agree here. Why does lowering kv change the weight and size of a motor? Doesn't a lower kv simply increases torque at the cost of top end rpm, which is exactly what mechanical gearing does, but without the additional cost of the gearing itself, both in weight and efficiency? You simply have to provide more voltage, but consequently, inversely proportionally less current, resulting in the same exact wattage.

I think this is a common misconception. Rewinding a motor doesn't change its mechanical characteristics, that is, it's torque/speed relationship at a given output power. A motor's mechanical characteristics are determined by it's size, shape, magnet strength, and copper fill percentage. Changing the number of windings changes it's electrical characteristics. It allows you trade current for voltage or vice versa for a given power input. The power output stays the same, and the ratio of torque to speed at that power stays the same. If you have a 24V system and 500KV motor, and you rewind the motor to 1000KV, yes you will have more power available. You haven't changed the mechanical characteristics of the motor though. What you've essentially done is the same as leaving the motor at 500KV, and changing the system to 48V.

If you double the number of windings you approximately half the KV, which doubles the torque you get at a given current. However, to fit double the windings you need to use thinner wire, and you get approximately four times the winding resistance. You only need half the current, but since the resistance is quadrupled, you now need double the voltage to reach that current. It works out that you need the same amount of electrical input power to get the same torque out no matter how many windings you have. The only way around this is to use thicker wire with lower resistance, this is only possible if you make the motor larger so it can fit.

There is no free lunch. If you want more torque you need a larger motor or stronger magnets. larger doesn't necessarily mean larger in every dimension. A large diameter ring shaped motor with the prop in the center would have high torque due to the leverage of the larger diameter rotor.

 

[staska]

Found another good source of brushless motor. This is a motor from electric power steering pump. Core is 7 * 7 cm or a little more. This drives hydraulic pump directly. Few kilowats easily i could guess. Will try to figure out oroginal amperage of it. It from gm family.

Thanks for plywwod foils. Last question - why mast is hightb? Because of waves ? For calme water smaller is better ?

 

[aethyr]

Just following this thread, as I'm interested in building one. I built an electric kick scooter that is loads of fun on land, and now its on to water

A few questions. I see that there is discussion of using a gearbox - is that to keep RPM at target or mostly due to sync issues? Is sync basically an issue of insufficient starting torque or something else? I couldn't find whether you guys are having sync issues running sensored or sensorless. I had sync issues when starting from stopped on my scooter when running sensorless and with gearing/motor kv optimized for speed rather than torque. When I switched to a much larger motor and ran sensored, I was able to start from stopped with ease.

So I guess my question is, why not simply rewind the motor at a much lower kv, say 50kv or so and increase voltage? If you have a 200kv motor, rewound to 50kv, you've essentially gone 4:1 with no loss in energy from the gears.

My plan is to use a sensored alien tp100, which is supposedly rated at 12kw continuous, at 72kv and then use one of his 300A EV escs and a 20s20p battery pack. The tp100 is a 100mm motor, so that's pretty wide, but I think it will be worth it for the substantial increase in torque/power?

It seems like it's a problem of torque efficiency at low kV and a problem of weight and size. With a direct drive, the motor will be too big and too heavy for the good torque and rpm.

Not sure I understand/agree here. Why does lowering kv change the weight and size of a motor? Doesn't a lower kv simply increases torque at the cost of top end rpm, which is exactly what mechanical gearing does, but without the additional cost of the gearing itself, both in weight and efficiency? You simply have to provide more voltage, but consequently, inversely proportionally less current, resulting in the same exact wattage.

I think this is a common misconception. Rewinding a motor doesn't change its mechanical characteristics, that is, it's torque/speed relationship at a given output power. A motor's mechanical characteristics are determined by it's size, shape, magnet strength, and copper fill percentage. Changing the number of windings changes it's electrical characteristics. It allows you trade current for voltage or vice versa for a given power input. The power output stays the same, and the ratio of torque to speed at that power stays the same. If you have a 24V system and 500KV motor, and you rewind the motor to 1000KV, yes you will have more power available. You haven't changed the mechanical characteristics of the motor though. What you've essentially done is the same as leaving the motor at 500KV, and changing the system to 48V.

If you double the number of windings you approximately half the KV, which doubles the torque you get at a given current. However, to fit double the windings you need to use thinner wire, and you get approximately four times the winding resistance. You only need half the current, but since the resistance is quadrupled, you now need double the voltage to reach that current. It works out that you need the same amount of electrical input power to get the same torque out no matter how many windings you have. The only way around this is to use thicker wire with lower resistance, this is only possible if you make the motor larger so it can fit.

There is no free lunch. If you want more torque you need a larger motor or stronger magnets. larger doesn't necessarily mean larger in every dimension. A large diameter ring shaped motor with the prop in the center would have high torque due to the leverage of the larger diameter rotor.

You have described what I had originally said - that lowering kv is the equivalent of mechanically gearing down - total power either watts or HP is voltage x current or RPM x torque. If you increase voltage, you decrease current or decrease voltage and increase current, given a fixed wattage of the motor. Or given a fixed HP engine, I can gear it to have massive torque, but low speed or high speed but low torque. And yes, there is no free lunch, the constant is the wattage of the motor - you can play with the voltage and current, decreasing one increases the other and vice versa. And consequently, lowering kv increases torque proportionally, but decreases the top rpm, all within the constant of the motor wattage. So again, instead of using a gear box, why not just decrease kv?

 

[staska]

And consequently, lowering kv increases torque proportionally, but decreases the top rpm, all within the constant of the motor wattage. So again, instead of using a gear box, why not just decrease kv?

No. On same motor you may have same torque/ power on same rpm. With different voltage and amps ratio. If you go higher in power input - core will saturate and you will lost power. You cant introduce more flux into iron core. It has certain max value. Energy in flux change is constant. Changes per second - none. And only this can change power. And this is rpm.

 

[parabellum]

You have described what I had originally said - that lowering kv is the equivalent of mechanically gearing down - total power either watts or HP is voltage x current or RPM x torque. If you increase voltage, you decrease current or decrease voltage and increase current, given a fixed wattage of the motor. Or given a fixed HP engine, I can gear it to have massive torque, but low speed or high speed but low torque. And yes, there is no free lunch, the constant is the wattage of the motor - you can play with the voltage and current, decreasing one increases the other and vice versa. And consequently, lowering kv increases torque proportionally, but decreases the top rpm, all within the constant of the motor wattage. So again, instead of using a gear box, why not just decrease kv?

It does not mater how you wind your motor, torque capability stays same, this torque is just archived by feeding at different current. Torque constant is measured per Amp but your current capability decreases by every wind you add, because of raising R (wire length+you use less cross-section area wire to fit this extra wind). Every time you lower kv to get more torque per Amp, you also lower current, so died-end here.
Now to magnets:
Yes with stronger magnets you get higher torque but, you reduce your kv and as we all know HP is result Torque x angular speed, so you could have lil more torque with same Power output.

Its have been beat to death in several ES treads, consensus after tons of maths and tests is- Motor topology, volume and quality of active materials limits what you can expect on Power and torque and copper winds count does not influences any of those 2 factors. You always can take square wire to increase fill factor by 30% and use silver for other 5% conductivity.

 

[Jezza]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

 

[aethyr]

You have described what I had originally said - that lowering kv is the equivalent of mechanically gearing down - total power either watts or HP is voltage x current or RPM x torque. If you increase voltage, you decrease current or decrease voltage and increase current, given a fixed wattage of the motor. Or given a fixed HP engine, I can gear it to have massive torque, but low speed or high speed but low torque. And yes, there is no free lunch, the constant is the wattage of the motor - you can play with the voltage and current, decreasing one increases the other and vice versa. And consequently, lowering kv increases torque proportionally, but decreases the top rpm, all within the constant of the motor wattage. So again, instead of using a gear box, why not just decrease kv?

It does not mater how you wind your motor, torque capability stays same, this torque is just archived by feeding at different current. Torque constant is measured per Amp but your current capability decreases by every wind you add, because of raising R (wire length+you use less cross-section area wire to fit this extra wind). Every time you lower kv to get more torque per Amp, you also lower current, so died-end here.
Now to magnets:
Yes with stronger magnets you get higher torque but, you reduce your kv and as we all know HP is result Torque x angular speed, so you could have lil more torque with same Power output.

Its have been beat to death in several ES treads, consensus after tons of maths and tests is- Motor topology, volume and quality of active materials limits what you can expect on Power and torque and copper winds count does not influences any of those 2 factors. You always can take square wire to increase fill factor by 30% and use silver for other 5% conductivity.

Yes, I realize my error now. Its torque per amp that increases, but total torque remains the same. So with lower kv I can produce that same total torque with lower current (but at higher voltage), which tends to be easier in practice than trying to manage tons of current.

 

[parabellum]

So with lower kv I can produce that same total torque with lower current (but at higher voltage), which tends to be easier in practice than trying to manage tons of current.

Controllers are the limiting factor of our realm and ~100V is the best W per buck on the market. SIC Fets throw a ray of light in to dark semiconductors tunnel, we will see.
BTW, do not go to high in voltage, remember you are in water.

 

[Gege2000]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

Congrats Jezza

 

[parabellum]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

Nice.
Is there some exact spot on the mast, where thrust should be applied? Under or over the wing, something even more specific or is it something operator just get used to?
P.S, Do not forget to design in a little galvanic anode somewhere, just in case.

 

[Jezza]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

Nice.
Is there some exact spot on the mast, where thrust should be applied? Under or over the wing, something even more specific or is it something operator just get used to?
P.S, Do not forget to design in a little galvanic anode somewhere, just in case.

Thrust must definitely be above the wing. You don't want the wing coming out the water, and if its below it will make it a little more unstable.
I haven't really decided on whether I'm going to use an anode or not. The alu tube is cheap so if it does corrode I can replace it cheaply. I will also be washing the board thoroughly after each session so that will help.

 

[Hiorth]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

Hahaha, we are also just building! Gearbox is perfect to get proper rpm and torque.

 

[Jezza]

While everyone debates motors, I thought I'd set up all the electronics on mine and test them. Happy to report that everything is working as it should!

Now I need to get my alu rod on a lathe and manufacture the spacer/connector for the motor and gearbox and the rear motor housing. These will both allow the motor and gearbox to transfer heat to the tube and allow the water to cool the entire housing

Hahaha, we are also just building! Gearbox is perfect to get proper rpm and torque.

I saw the kort nozzle you printed on facebook, it turned out well!
Did you buy the foil new or get it second hand?

 

[Hiorth]

We bought the foil new, 500£ there was an offer on king of watersports, still pretty expencive tho.

 

[aethyr]

I have some basic mechanical questions:

How are you guys handling shock safety? Clearly the electronics need to be protected/waterproofed, but in the event the waterproofing fails and you have accidental contact of battery/live high voltage/amperage wires to the water?

How are you sealing the motor shaft from water?

 

[ropower86]

I have some basic mechanical questions:

How are you guys handling shock safety? Clearly the electronics need to be protected/waterproofed, but in the event the waterproofing fails and you have accidental contact of battery/live high voltage/amperage wires to the water?

How are you sealing the motor shaft from water?

You should look up on Direct Current and Alternating Current. The electric components will not shock you but you can get burned pretty badly if you make a wrong connection because of the high volts. However, all electrical components need to be isolated properly. If the ESC is exposed and the water makes contact to MOSFETs, it will be like 4th of July all over again and it can be dangerous meaning as spark and fire. Also, lithium batteries need to be handled with care and setup correctly.

 

[aethyr]

I have some basic mechanical questions:

How are you guys handling shock safety? Clearly the electronics need to be protected/waterproofed, but in the event the waterproofing fails and you have accidental contact of battery/live high voltage/amperage wires to the water?

How are you sealing the motor shaft from water?

You should look up on Direct Current and Alternating Current. The electric components will not shock you but you can get burned pretty badly if you make a wrong connection because of the high volts. However, all electrical components need to be isolated properly. If the ESC is exposed and the water makes contact to MOSFETs, it will be like 4th of July all over again and it can be dangerous meaning as spark and fire. Also, lithium batteries need to be handled with care and setup correctly.

If the electronics get wet, that is clearly an engineering failure and I fully expect components to break. However, I wish to not die because of that failure

AC supposedly kills "easier" because of its ability to fibrillate the heart, while DC "just" stops it. That doesn't mean DC can't kill you, I mean, it does stop your heart, lol. I'm saying, imagine if you put the terminals of a 96V battery, capable of 200A of current, into the water. Would you put your hand in that water?

 

[parabellum]

If the electronics get wet, that is clearly an engineering failure and I fully expect components to break. However, I wish to not die because of that failure

AC supposedly kills "easier" because of its ability to fibrillate the heart, while DC "just" stops it. That doesn't mean DC can't kill you, I mean, it does stop your heart, lol. I'm saying, imagine if you put the terminals of a 96V battery, capable of 200A of current, into the water. Would you put your hand in that wa

Just imagine terminal potential you would hold in your hands and feel OK, where you feel uncomfortable, it is about where you should stop. People have different body conductivity due to different minerals concentration and there is no specific Voltage that can kill a human but approximate current flowing through the heart. I see no sense and would not go over 50V in water. You could make the less resistive path in fresh water after all.

 

[Bazaki]

I once lifted a 92v a123 60ah batterypack. My left wrist touched the + and right wrist the -. by accident ofcourse it just was tinteling a little bit. But i would not recommend it.

 

[kiter_UK]

Well done to all making great progress on this. Very impressive. (Winter project for me I hope)

As an observer it seems to me the motor/prop creates a moment that isn't planned for in the foil design/position/angle. Especially during acceleration phase perhaps.

As a result the weight of the rider seems to have to be very far forward and ahead of the centre of lift.

Don't know if this is a) true b) an issue.

But interested in views or prior discussion on this.

 

[Jezza]

Well done to all making great progress on this. Very impressive. (Winter project for me I hope)

As an observer it seems to me the motor/prop creates a moment that isn't planned for in the foil design/position/angle. Especially during acceleration phase perhaps.

As a result the weight of the rider seems to have to be very far forward and ahead of the centre of lift.

Don't know if this is a) true b) an issue.

But interested in views or prior discussion on this.

I don't think this is an issue, I think it is more a case of the board design that has been used thus far. I just think the angles of the foil with relation to the board allows the nose of the board to point to high into the air.
I have a slalom board that I am converting into mine and what I have noticed is if I just attach the foil as is to the board, the angle will not be optimized and as a result I would have to ride with a very bent front leg and most likely face the same issues. Therefore I will be changing the angle of either the mast or the foil so that it runs parallel to the deck of the board. Then a bit of weight on the back foot should lift the foil easily instead of having a big surge upwards.

 

[kiter_UK]

Makes sense. I know some foils have some angle adjustment to the mast.

 

[waterfox]

Hey, does anyone have a CAD model or the measurements of the SSS 56104 motor. Specifically the bolt pattern diameter. Mine is on order but I would like to get to work designing before it arrives.

I've taken a crack at this already with a propulsion system based on the BPhobbies Cheetah A5330-9 on 6S but I didn't have enough power or enough cooling. It was a drive-train I had left over from another project and didn't have high hope for it anyway.

Now switching to something closer to the conventional build:

Motor: SSS56104 (in the mail)
Gearbox: Neugart PLE40-008 (in house)
ESC: Seaking HV V3 130A (in the mail)
Battery: 2X Tattu plus 6S 16Ah
Propeller: 3D printed for now, may switch to Kenzen 150mm MAU or ducted 126mm $$$
Controller: 3D printed enclosure for a Teensy + RC control gimbal. Not great. Going to try an AliExpress Eskate 2.4Ghz controller with extra waterproofing.
Foil: Slingshot Hoverglide NF2. I would like to switch to a Liquid Force hollow mast with an adapter plate once I prove this out.
Board: Slingshot Simulator for now: Will build another once the proof of concept is finished.
Enclosure: Pelican 1200

Good luck with your projects!