High Torque and High Speed Wheel

[Scottie]

Are both possible?

Right-click the links and "open in new tab" to preserve the flow of the question.

I am interested in the V12 and recently watched a Wrong Way review of the wheel. A comment he made, starting at about 42:00 of the video, got stuck in my head. Adam wants a high torque version of the V12 to make it competitive with the 16X in that regard. Since I am a slower, heavier rider ... that comment sticks in my memory. And then I started thinking, which can be dangerous!

The video is set to start just before his comment.

 

I remembered what was said about the windings of a torque vs speed motor, in particular about the 16X - V12 motor here and here by @RagingGrandpa. Knowing this, I began to wonder if it is possible to engineer a way to have both speed and torque select-able in one wheel.

Is it possible to design a control board, firmware, and app that can let the rider select torque mode or speed mode ... much like the way pedal soft - medium - hard mode is selected? Can the board be wired separately to the 4th winding of the motor, so that it can switch the 4th winding on or off, thus operating in a 3 winding speed mode or 4 winding torque mode?

And ... can the control board and firmware be designed to automatically make the switch between torque and speed mode based on settings the rider selects in the app? The rider may want to set the wheel to automatically switch between torque and speed mode at 20 mph (32 kph).

It does not seem like it would take a whole lot of engineering or expense on behalf of a manufacturer. It is just a fancy new board and firmware along with controllable separate wiring to a 4th motor winding. But I know just enough to be dangerous and ask a question!

[yoos]

Yes, this is a good and absolutely workable idea called variable-winding BLDC, see this presentation and this paper. As the latter states, there are apparently some problems with deadtime -- the switch from one winding regime to another has to be pretty seamless in a self-balancing vehicle.

Anyway, quick googling reveals this technology is still in its infancy (i.e. there is little to be found on "variable-winding BLDC"). I doubt reliable and inexpensive specimens will hit the market soon. However this might just be the future for PEVs. At the moment, a poor mans solution in a several-wheel drive EV is to use a high-speed motor on one wheel (or pair of wheels) and a high-torque on the the other. 

Edit: to answer your questions more precisely: this would involve a lot of engineering and a novel, significantly more elaborate winding and wiring layout. This would definitely require a rebuilt motor, and there would be more than three phase wires -- at least 6 for a dual winding solution (if I understand the concept correctly). On-the-fly switching (which would be the main breakthrough) would require especially extensive testing and tuning.

 

Edited November 21, 2021 by yoos

[Bizra6ot]

His wish in the video is not your solution, he asks to have the choice to buy hs or ht as begode does

[RagingGrandpa]

On 11/21/2021 at 2:08 PM, Scottie said:

Can the board be wired separately to the 4th winding of the motor, so that it can switch the 4th winding on or off

 

On 11/21/2021 at 3:21 PM, yoos said:

Yes, see this presentation

Thought provoking!

The topic implies comparison of a few design options:

• Today's 100V ~100kph motors like V12
• Today's 100V ~75kph motors like RS:T
• Future 128V ~100kph motors like S20
• Hypothetical 100V ~100kph dual-winding motors

You can compare the results they would offer, using the data from the presentation above:

(that data showed a small motor that was not current-limited by its controller like EUCs are, but its notions are valid)

Based on this, I think the higher voltage system gives better performance, than a lower-voltage dual-winding system of the same freespin speed.

 

Edited August 17, 2023 by RagingGrandpa
(img url)

[Scottie]

8 hours ago, yoos said:

there are apparently some problems with deadtime -- the switch from one winding regime to another has to be pretty seamless in a self-balancing vehicle.

I am not an expert, and barely qualified to ask a question. But in my mind, I imagine that the 3 windings per magnet would always be in use. And that the 4th winding would be turned on or off by the board. So if we were riding such a wheel, we would feel it become stronger as we slow below 30 kph (if that speed was selected) and the 4th winding is turned on. Or if we accelerate above 30 kph we would feel the raw torque fall off a bit as we continue on with just the full time 3 windings and the 4th winding alone is turned off.

 

8 hours ago, yoos said:

this would involve a lot of engineering and a novel, significantly more elaborate winding and wiring layout. This would definitely require a rebuilt motor, and there would be more than three phase wires -- at least 6 for a dual winding solution (if I understand the concept correctly). On-the-fly switching (which would be the main breakthrough) would require especially extensive testing and tuning.

With the hollow bore motors there is lots of room for wiring. I am still a fan of the standard solid axle due to the bearing issues. But I think a slightly thicker axle would allow drilling for wiring to go in from both ends rather than one end. This should make room for additional wiring that is needed.

Could we start with the design of the current 4 winding torque motor (16X) and work out a circuit that de-torques it to a 3 winding speed motor (V12) by just dropping out a winding, and turning it back on as desired.

I was hoping that on-the-fly switching would be naturally seamless as envisioned above. But again, I do not know enough of the details of circuit design to say what is possible in a real world motor and control board. I am just dreaming and wishing and thinking out loud.

 

1 hour ago, RagingGrandpa said:

Thought provoking!

That is all I hope for! Well that and a dual stage motor that does not cost much more!

The guys that like to ride fast on good pavement and go off road too, should like such a setup.

 

2 hours ago, RagingGrandpa said:

The topic implies comparison of a few design options:

• Today's 100V ~100kph motors like V12
• Today's 100V ~75kph motors like RS:T
• Future 128V ~100kph motors like S20
• Hypothetical 100V ~100kph dual-winding motors

The S20 may turn out to be the beast that everybody wants. Hopefully it runs cool and can do well on Overheat Hill.

But it would be interesting to see what a dual torque / dual winding mode RS, EXN, Sherman, V12, Nik, etc. might be like without having to go to 128V.

[yoos]

3 hours ago, RagingGrandpa said:

higher voltage system gives better performance

Indeed, and it's also more straight-forward - that's why KS are doing it. The variable-winding improves performance for given voltage and current are limits (which are more or less set in stone once the battery packs are decided). Like any serious design, all aspects should be optimized, BLDC design included. The improvement is perceivable enough since people do feel the difference between HT and HS versions of the same wheel. The only reason the various-winding design is not used, I guess, is that these motors are still not widely produced (if they are produced at all). The concept and implementation seem quite simple: just have two independent winding circuits within the motor (i.e. two motors in one), each with its one phase wires and mosfets. Use both at low speed and just one at high speed. E.g. use all four windings at low speed, 3 at high speeds and just 1 at even higher speeds. 

[Tawpie]

You still have to pack those extra, sometimes unused windings into the motor—I'd rather increase the operating voltage than pay for unused cross sectional area.

[RagingGrandpa]

10 hours ago, Scottie said:

he S20 may turn out to be the beast that everybody wants.

I want 126V!

But I don't want a >80lb EUC with only 2200wh

Hopefully other >110V models follow, some with emphasis on range rather than suspension...

.02

[Scottie]

When the costs associated with building (or even repairing) an EUC are broken down, is the battery one of the most expensive parts? Just looking at current replacement part costs, the control boards and motors (with tire rims) do not seem so costly. If King Song, or any other brand, were to mass produce a special dual torque board and motor, I think the costs would be reasonable and similar to current costs, just a bit more.  

Thinking about a 16X (since it is the 4 winding cousin to the 3 winding V12), the 4 windings are already there. Can a control circuit be designed that is able to turn off the separately controlled 4th winding when desired and now it becomes a faster wheel? And also turns back on when desired for hill climbing etc. The re-imagined 100V / 2500 watt / 1800wh V12 could then be able to surpass the 84V / 2200 watt / 1554wh 16X when it is time to climb. And range would improve if riding around in torque mode (4th winding on).

 

9 hours ago, yoos said:

The variable-winding improves performance for given voltage and current are limits (which are more or less set in stone once the battery packs are decided). Like any serious design, all aspects should be optimized, BLDC design included.

Even the S20 could be more of a performer, especially for heavier riders.

For myself, the current HT wheels are fine since I am old, heavy and slow, so I do not suggest that the current HT and HS designs stop being produced because there is a market for simplicity. Thinking of younger, lighter, experienced riders that want more from their wheel in all aspects, like Adam, then I agree with @yoos.  Adam, and similar riders could go out for a day and blast and climb to their hearts content on their wheel that performs as an HT and an HS on demand. 

Disclaimer: I am not an engineer, nor do I pretend to be one on TV. I am just a dummy with an idea for the people that can do things ... if it is doable.

[Tawpie]

38 minutes ago, Scottie said:

Can a control circuit be designed that is able to turn off the separately controlled 4th winding when desired and now it becomes a faster wheel?

That certainly would be easy enough to do, but you have to get 2x the wires out of the motor because now each phase has two sets of windings. And you will increase the real estate on the control board for the motor drive circuitry. But still, an interesting idea for a hollow motor!

Edited November 22, 2021 by Tawpie

[Scottie]

17 minutes ago, Tawpie said:

That certainly would be easy enough to do, but you have to get 2x the wires out of the motor because now each phase has two sets of windings. And you will increase the real estate on the control board for the motor drive circuitry. But still, an interesting idea for a hollow motor!

That is what I was thinking. Yes, a hollow motor is an easier deal. They came out with those so they could run thicker wires ... now more wires.  Even with traditional axles, they could a little thicker so holes can be drilled from both ends and still have a strong enough axle.  Wires can then enter from both sides. We retain confidence in our wheel bearing with a more standard size rather than those large diameter ones. Isn't there a smaller center bore hollow motor introduced with smaller diameter bearings? That would be the thing if those bearings prove to be reliable.

[Tawpie]

You could always think about putting the switches for the torque winding inside the motor cover too. May I just invented something. There will have to be additional control feedback/changes to the control loop but we already have wye-delta motor starters so it can't be impossible.

 

(if putting the switch inside the motor cover is indeed novel, consider this public disclosure and prior art. just saying NO to patent trolls)

Edited November 22, 2021 by Tawpie

[Scottie]

1 hour ago, Tawpie said:

You could always think about putting the switches for the torque winding inside the motor cover too. May I just invented something.

Intuitively, I think you have something there. But my limited knowledge will not give me a visual. But whatever form it takes under the cover, we would need to protect it, or package it in such a way that it does not get damaged like @Mike Sacristan hall sensor wiring.

 

[mrelwood]

4 hours ago, Scottie said:

Can a control circuit be designed that is able to turn off the separately controlled 4th winding when desired and now it becomes a faster wheel?

I'm not an expert on the matter either, but as far as I understand things, the base theory in the quote above does not work. The number of windings is not what solely determines the amount of torque available. HT and HS motors also have a difference at least in the winding wire thickness and magnet wdth. If you simply take a turn of wire offline, more than anything you decrease the efficiency of the motor since the overall diameter of the windings gets smaller.

The diameter of the windings is explained here, starting at the most relevant spot. Although the video is definitely a worthy watch all the way through:

 

Edited November 22, 2021 by mrelwood

[Scottie]

34 minutes ago, mrelwood said:

The number of windings is not what solely determines the amount of torque available. HT and HS motors also have a difference at least in the winding wire thickness and magnet wdth.

I agree that the magnets of C30 and C38 Begode motors play a big role in torque, or lack of. And the wire thickness video makes sense to me about total cross section. But in the 16X > V12 motor comparison, I was theorizing based on the motor discussion found here, here, and here where I learned that the magnets are the same and it was the windings making the primary torque difference. This caused me to think about adding and controlling a 4th winding for this motor separately, in the case of a wheel like the V12.

1 hour ago, mrelwood said:

If you simply take a turn of wire offline, more than anything you decrease the efficiency of the motor since the overall diameter of the windings gets smaller.

Agreed. My understanding is that the HT motors (more windings, among other things) are more efficient. They run cooler and have better range. So if the theory holds, the V12 would gain some range and maybe run cooler when the hypothetical 4th winding is turned on ... and climb a steeper hill better. It would be a 100V 16X, probably even stronger. Then when turned off, it will roll along as fast as it does now and loose a percentage of range ... like it appears to do now. 

As a layman, I do not know all the factors at play. But this one hit me like a ton of bricks. I am leaving plenty of room to be wrong about all this, but I am not ready to admit to it yet.

These 1st two copy/paste would not do the standard Forum quote for me. The above links will take you there.

"Ecodrift teardown noted the v12 motor has the same motor serial code as a 16x motor"

"V12 has 3 turns per pole.
16x had 4 turns.
Otherwise, same pole count, same size pm."

On 7/1/2021 at 5:04 PM, RagingGrandpa said:

Speed vs Torque.
V12 and 16X have the same motor design, except that 16X uses four turns per pole, and V12 uses three.

 

[RagingGrandpa]

On 11/22/2021 at 5:51 PM, Scottie said:

magnets
wire thickness
windings

These are some of the many ways to increase the magnetic field strength.

Physically larger magnets -> stronger field from the rotor.
Thicker wires (and higher current) -> stronger field from the stator.
More winding turns per pole -> stronger field from the stator.

Doing any one of these design changes will increase field strength, which increases torque at low speeds.
(And doing more than one of these changes will increase the effect further.)
 

On 11/22/2021 at 5:51 PM, Scottie said:

HT motors are more efficient

Well, only a tiny bit.

BLDC motor efficiency is generally like below.

If you change the motor to be "HT" (stronger magnetic field by whatever method you prefer), you will squeeze this picture horizontally, pushing that peak-efficiency zone down to a slightly lower speed, and also reducing the maximum speed accordingly.

So if the HS motor operating at 25mph put us at the 92% efficiency site, changing to an HT motor at the same 25mph might get us 94%.
A 2% improvement... unlikely to be noticed by most riders

 

Edited August 17, 2023 by RagingGrandpa
(img url)

[Scottie]

It is interesting to haunt the older areas of the Forum. There is a similar desire or thought there, but with a different execution ... theoretically speaking. 

 

[yoos]

10 hours ago, RagingGrandpa said:

Thicker wires (and higher current) -> stronger field from the stator.

Field is proportional to current indeed, but thicker wires do not affect the field directly. What they do, however, is reduce the resistance of the circuit, meaning less heating, which in turn means slightly higher efficiency and allows the motor to tolerate higher currents without overheating provided the controller+battery can deliver those currents.