When will we see 3000 Watts?

[Planemo]

Ok cool so about 10Kw to achieve a 33 deg lean without wheelspin, and with Anetas further calculations the only problem we have is building the motor itself! With materials we have at the moment it doesnt sound feasible to build it without massive weight and size, which then needs more power to accelerate...ad infinitum

I would still like to see what Tesla or NASA could achieve

[Aneta]

11 hours ago, xorbe said:

If you raise V by 50%, then A also increases by 50% with the same resistive load, and 1.5*1.5 is 225%, so 2000W becomes 4500W.  You want to raise voltage by 22.47% probably... and none of that turns a 2000W motor into anything but a burned out motor probably, unless it's overbuilt.

Controller limits current in the windings by lowering voltage on them, serving as a dc-dc converter. We're not talking about applying full 84 or 126V to 0.1Ohm windings directly, that would produce currents ~1000amps and will burn those thin wires instantly.

[Nic]

On 12/17/2019 at 4:58 AM, Aneta said:

If you raise the voltage by 50%, the 2000W motor becomes a 3000W motor, max unloaded speed also increases by 50%. As long as the controller has a phase current limit, there shouldn't be any increase in heat. The torque will be the same, but the max speed will be higher. We "just" need to increase battery voltage from 84V to 126V (20s to 30s). Controller should have components rated for something like 150V, not 100V as 84V controllers typically do.

If you want the same max speed, but more torque (so that 2000->3000 increase comes not from speed, but from torque), then the only option is to make the magnets and stator 50% (?) wider (and thus, the motor will be approx. 50% heavier). Which translates to about 45mm magnets. Such motors are long available from Quanshun and are typically used in electric scooters (the "real" scooters, not electrified kick scooters) or "hot rod" e-bikes.

I had an interesting idea about improving the motor while keeping it compact ... the motor is basically a set of coils on the outer circumference of a set of magnets arranged in a circle. What if we sandwiched the magnets by adding another set of coils to the inside circumference of the magnets, so that we have now effectively doubled the electrical input. We could also offset those coils to give smoother power delivery with the outer set of coils. Just a thought. The weight would increase but the motor would still be the same physical size. No, I am not a motor expert, but I daydream a lot.

Edited December 18, 2019 by Nic

[Chriull]

5 minutes ago, Nic said:

the motor is basically a set of coils on the outer circumference of a set of magnets arranged in a circle. What if we sandwiched the magnets by adding another set of coils to the inside circumference of the magnets, so that we have now effectively doubled the electrical input.

The electrical input would be really doubled, but by the second row sitting on inside they produce with the same force less torque (=force x radius)

So this would be very inefficient...

[Mono]

On 12/17/2019 at 4:21 PM, Chriull said:

Accelerations above some 0.7g (~7m/s²) are not reachable

0.7g acceleration is equivalent to 35º lean. Leaning 30º forward needs tan(30º) = 0.58 g acceleration to counter the lean. This pic shows something around 25º:

Of course, one can just make the pedals much longer (OneWheel cough) and make a 50cm (= 100cm x sin(30º)) forward step instead of leaning. The 0.7 g acceleration limit remains as it is by tire limitations (0->100km/h in 2.2s is 0.63 g, like the fastest accelerating production car).

__
There are two fundamentally different EUCing cultures populating this globe.
One for which 40km/h is not exactly speeding and the other for which surpassing 25km/h is simply off limits. Always good to keep this in mind 

Edited December 18, 2019 by Mono

[pico]

For those interested in Compact and Efficient Electric motors.

Axial flux motors:   Ours are Radial Flux.

https://www.magnax.com/magnax-blog/a-new-generation-of-axial-flux-ev-motors

 

 

Edited December 18, 2019 by pico

[Nic]

4 hours ago, Chriull said:

The electrical input would be really doubled, but by the second row sitting on inside they produce with the same force less torque (=force x radius)

So this would be very inefficient...

The rotating magnets are still in the same location so radius doesn't change, also efficiency ... is that related to torque? If it is then why aren't all motors designed for highest torque rather than highest power? Is velocity a factor here?

[Chriull]

11 minutes ago, Nic said:

The rotating magnets are still in the same location so radius doesn't change, also efficiency ...

By putting the magnets in the middle of the two coil rows they are at a smaller radius as if they were at the outer circumference. So the radius at which the force acts does change.

 

15 minutes ago, Nic said:

is that related to torque?

Yes. Torque is force times radius.

A motor output at the axle best descirbed with torque, as the rotation and forces are produced/"transmitted" and used at different radii (moment arms).

18 minutes ago, Nic said:

If it is then why aren't all motors designed for highest torque rather than highest power? Is velocity a factor here?

Power is torque times rotational speed. (1)

I do not see the real difference between designing a motor for torque or power. Every motor with higher (max) power has higher (max) torque. Every motor with higher (max) torque has higher (max) power. And vice versa...

You meant desinging for speed vs. designed for torque? Or better at which rotational speed (range) max power/high torque can be used without transmission?

Also highest torque for an electric motor is the stall torque (when the axle/the motor is stalled and cannot turn). This is also the point of least efficiency for the motor - huge currents are flowing causing high losses. And normally one does not need stalled motors but wants to use the rotation.

 

Another point could be that the magnets are on a different part of the motor as the coils - so the force by the magnetic field can turn them. So interleaving/sandwiching coils and magnets makes the construction more complicated.

Also the commutation of both coil rows has to be synchronized.

Imo (gut feeling ) the permanent magnets are just strong enough to "counter" the force of one coil row. So the permanent magnets would be needed to be doubled anyway.

So imho with all this points (or some mixture) it is easier/more efficient to just build motors with one row of stronger magnets and bigger coils than making two rows...

Could also be that these hub motors developed for ebikes and now used for EUCs are just a compromise as they are already a wheel fitting perfectly in the overall construction.

High performance/efficiency electric motors are build differently.

(1) Rotational speed is (mostly) proportional to velocity. Velocity is in regard to a motor a "squishy" term. The motor "only" rotates - but it is often used to move something in very different ways...

[mrelwood]

2 hours ago, pico said:

For those interested in Compact and Efficient Electric motors.

Axial flux motors:   Ours are Radial Flux.

https://www.magnax.com/magnax-blog/a-new-generation-of-axial-flux-ev-motors

I want that one in my EUC! Anybody have contact info for Mr. Gotway? They’d still have time to make the first batch of ”MSX Axila” by the end of the year... 

[Mono]

1 hour ago, Chriull said:

Also highest torque for an electric motor is the stall torque (when the axle/the motor is stalled and cannot turn). This is also the point of least efficiency for the motor - huge currents are flowing causing high losses.

The loss at stall torque is as much caused by the current flowing as by the lack of any mechanical power output which makes all current a 100% loss. At half of the no-load speed we still see half of the stall torque current flow but we also see the maximal mechanical power output, instead of zero.

Edited December 18, 2019 by Mono

[Nic]

Who'd have thought motors and batteries could be so interesting.

Just makes me wonder how our EUCs will look 10 years from now ... assuming people are still wanting to ride these things. or something better has replaced them.

[Aneta]

6 hours ago, Nic said:

I had an interesting idea about improving the motor while keeping it compact ... the motor is basically a set of coils on the outer circumference of a set of magnets arranged in a circle. What if we sandwiched the magnets by adding another set of coils to the inside circumference of the magnets, so that we have now effectively doubled the electrical input. We could also offset those coils to give smoother power delivery with the outer set of coils. Just a thought. The weight would increase but the motor would still be the same physical size. No, I am not a motor expert, but I daydream a lot.

There are no spinning coils in a BLDC (Brush-Less DC motor). They are on the inner, stationary part (stator). Spinning coils require brushes to deliver power to them, these are called brushed DC motors, and they are useless for us. 

[Chriull]

31 minutes ago, mrelwood said:

I want that one in my EUC! Anybody have contact info for Mr. Gotway? They’d still have time to make the first batch of ”MSX Axila” by the end of the year... 

Unfortionately they have the wire outlets at the "rim", which is the rotating part for EUC motors  Don't know if a redesign of the connections is feasible for the quantities needed for EUC manufacturers - or they already have such a solution?

But there are still enough other "conventional" hub motors with power outlets through/beside the axle with much better build quality than the currently used for EUCs.

As one sees in @EcoDrift's teardowns alone the coil windings look horrible... And there are so many scientific/technical papers about wire forms/how to wind coils/coil forms and their impact on magnetic flux/efficiency. ...and this is already knowledge since decades (...almost centuries )...

Would be really excited to see (or just hear/read) once of such a state of the art prototype. Especially what would be possible weight/power/efficiency/price wise!

<Daydreammode on>.... and with a _real_ "center mount block (not to be called axle anymore) to have an outlet for _real_ motor cables and a _real_ pedal mount... <Ddm off>

[Aneta]

59 minutes ago, Mono said:

The loss at stall torque is as much caused by the current flowing as by the lack of any mechanical power output which makes all current a 100% loss. At half of the no-load speed we still see half of the stall torque current flow but we also see the maximal mechanical power output, instead of zero.

Available power is max at about half of no-load speed, but efficiency is max near NLS. (but the mechanical losses grow as a square of speed, so it's still wasteful to ride at high speeds)

The more and more I think about it, "power" is almost useless concept for us. For example, my wheel's NLS is something almost 70km/h, so max available power will be at about 35km/h. I typically ride at 20-25. Will something magical happen if I hit 35? Nope. I'll lose ~30% of available torque, so I'll simply rob myself of a significant chunk of thrust margin. But the power will increase, shouldn't it tackle steep inclines or bumps better? Nope. It can tackle 30% less steep grades. The fact that my wheel has max available power at 35kph is completely useless.

PS. See also Justin L-E's rant: https://www.ebikes.ca/learn/power-ratings.html

Edited December 18, 2019 by Aneta

[Aneta]

18 minutes ago, Chriull said:

<Daydreammode on>.... and with a _real_ "center mount block (not to be called axle anymore) to have an outlet for _real_ motor cables and a _real_ pedal mount... <Ddm off>

This has been done in a prototype by the genius Rockwheel CEO:

This can also be found in GoldenMotor Magic Pie and Smart Pie motors for e-bikes - the whole controller fits inside the bearing:

It's just that EUC manufacturers are cheapskates and buy cheapest bike motors, with only minor custom mods to axles (like no threads, but with flattened ends, or vice versa (GW)).

Edited December 18, 2019 by Aneta

[Chriull]

10 minutes ago, Aneta said:

This has been done in a prototype by the genius Rockwheel CEO:

I had some slight memory of such a design, but could not remember from where! Such a design looks really great!

... Just the coil windings (the next picture in the link) are again a real mess ...

Quote

This can also be found in GoldenMotor Magic Pie motor for e-bikes - the whole controller fits inside the bearing:

Wow! Even better! 

With the possibillity to mount the mosfets on a real massive heatsink!

And the possibillity for _real_ thick and short motor connection wires! 

Quote

It's just that EUC manufacturers are cheapskates and buy cheapest bike motors, with only minor custom mods to axles (like no threads, but with flattened ends, or vice versa (GW)).

Maybe @Jason McNeil and @EcoDrift could push them in stereo - one from the west, one from the east ... until the manufacturers make us really happy!

[Aneta]

9 minutes ago, Chriull said:

... Just the coil windings (the next picture in the link) are again a real mess ...

They are wound by hand, very fast, no time to sweat the neatness:

But technically speaking, we know from physics that total flux through the coil is only determined by the current, not the shape. I don't think there's much flux escaping being captured by ferromagnetic teeth of the stator, so it's mostly a cosmetic thing, plus there could be a bit more coil whine from loose wires.

[Aneta]

13 minutes ago, Chriull said:

Wow! Even better! 

With the possibillity to mount the mosfets on a real massive heatsink!

And the possibillity for _real_ thick and short motor connection wires! 

And the IMU will be mounted directly on the stator, eliminating any tremors from pedals or shell being loose on their mounts.

[Aneta]

15 minutes ago, Chriull said:

Maybe @Jason McNeil and @EcoDrift could push them in stereo - one from the west, one from the east ... until the manufacturers make us really happy!

Current (not IPS and Rockwheel, which are dead now) EUC manufacturers are not interested in core innovation, only in making more money by gimmicks like led lights, speakers, 21700 vs 18650, and incremental increase in battery capacity and power, nothing groundbreaking. Motors with large diameter bearings will cost 10-20 dollars more for them to buy from motor factory, that's a big no-no for them! They won't even double the connectors (which would virtually elliminate the possibility of one connector going bad resulting in a crash), which is only a couple of bucks total!

The race to the bottom won, true innovators don't survive in such a rat race. Sad...

[Chriull]

11 minutes ago, Aneta said:

But technically speaking, we know from physics that total flux through the coil is only determined by the current, not the shape. I don't think there's much flux escaping being captured by ferromagnetic teeth of the stator, so it's mostly a cosmetic thing, plus there could be a bit more coil whine from loose wires.

Let's hope so.

But still besides aestethics packing density is bad (unnecessary thick coils, more "distance" from wire to iron, worse heat transfer from outer wires to iron,...) and the magnetic ?field/flux? lines interfere unnecessary before beeing "gathered in the iron".

Hopefully this are really all just minor effects not worth the effort to make the coils pretty!

12 minutes ago, Aneta said:

They are wound by hand, very fast, no time to sweat the neatness:

Pfff... Pushing the coils with the ?chissel/knife? and hammer looked really ... äm ... interesting...

[Aneta]

9 minutes ago, Chriull said:

Pfff... Pushing the coils with the ?chissel/knife? and hammer looked really ... äm ... interesting...

All e-bike motors made in China are produced like this. We live in barbaric times of PEVs, with very poor engineering and quality. And we pay $2-3K for this crap. But we pretty much have no choice...

(I don't think Elon Musk will ever start making EUCs, built from the ground up with the best engineering practices, simply because the possibility of massive lawsuits for injuries. Several thousands of enthusiasts using Chinese cr@p is one thing; a million of Americans riding Tesla EUCs and 500000 injured each year and suing will obliterate Tesla and put Elon in jail.)

[Aneta]

47 minutes ago, Chriull said:

Maybe @Jason McNeil and @EcoDrift could push them in stereo - one from the west, one from the east ... until the manufacturers make us really happy!

Jason already wrote in Mten3 thread that it's futile. They can only do minor improvements by request, like put some loctite on the screws or sealant in the gaps. They seem to be uninterested in real innovation. They don't jump up and down from the thought of

50 minutes ago, Chriull said:

And the possibillity for _real_ thick and short motor connection wires! 

 

[Mono]

1 hour ago, Aneta said:

Available power is max at about half of no-load speed, but efficiency is max near NLS. (but the mechanical losses grow as a square of speed, so it's still wasteful to ride at high speeds)

Sure, but near NLS is the most irrelevant operating condition for EUCs ever. Of pretty much zero use, at least for us. I also don't know the efficiency graph for less than maximum-torque-for-given-speed, do you?

[Aneta]

32 minutes ago, Mono said:

Sure, but near NLS is the most irrelevant operating condition for EUCs ever. Of pretty much zero use, at least for us. I also don't know the efficiency graph for less than maximum-torque-for-given-speed, do you?

True. But in the range of speeds where wheels are useable, the efficiency is constantly (and almost linearly even) rising, see Motor Simulator.

You can see power and efficiency curves for duty cycles less than 100% by varying the throttle in MS, like here, it's 50%:

https://www.ebikes.ca/tools/simulator.html?batt=cust_84_0.2_20&cont=cust_100_200_0.03_V&wheel=17i&frame=cust_1_0.01&hp=0&blue=Lbs&motor=M3540&autothrot=false&throt=50

 

[Mono]

OK, cool, so the efficiency graph is always increasing up to the point where load and power become the same. As if one could not have predicted that . But that means just choosing the optimal throttle should always give 80%+ efficiency. Why should we even talk about efficiency then?

Edited December 18, 2019 by Mono