Axial flux motors for EUCs

[Beowolve]

I have searched for Magnax / Axial Flux in the forum, and it seams this topic hasn't come up so far.

There is a new company (Magnax) specialized in axial flux motors. This is also a brushless motor design and can also be build as a wheel hub motor.

It is basically superb in all aspects and allows for higher efficiency and at the same time very thin / small designs. 

So my question Is this type of motor allready used in some EUCs (IPS comes into my mind), or is this something that could improve EUCs in newer generations?

I am not a motor expert but this seams to be a no brainer for every EUC company. As I understand it, there seams to be no disadvantage over radial flux motors.

https://www.magnax.com/

Whitepaper

 

Here is the basic design difference:

http://bioage.typepad.com/.a/6a00d8341c4fbe53ef0133ef5fb399970b-800wi

Edited September 6, 2023 by RagingGrandpa
(clarified title)

[The Fat Unicyclist]

Unfortunately Flux Capacitors require more speed than is available on EUC currently...   

[Keith]

21 minutes ago, Beowolve said:

I have searched for Magnax / Axial Flux in the forum, and it seams this topic hasn't come up so far.

There is a new company (Magnax) specialized in axial flux motors. This is also a brushless motor design and can also be build as a wheel hub motor.

Good question and possibly promising design, do you have any information are figures for its efficiency that are independent (I.e. not taking the company’s word for it)?

There is one word though that is likely to be a dirty word where uptake of this motor is concerned “Patents”. In reality efficiency increase is no more than about 10% (BLDC motors are 80-85% efficient) and it’s only real gain is likely to be in the motor being lighter. 

The company’s blurb suggests some manufacturing challenges I.e.

• Rectangular section copper wire, for the highest possible copper fill factor (90%).
• Concentrated windings, for the lowest possible copper losses (no coil overhangs).
• Grain-oriented electrical steel, lowering the core losses by as much as 85%.

This suggests it would be a case of buying the motors from the company not making them yourself.

In conclusion a possibility for high value, high performance vehicles like electric cars, pretty much likely to be a complete non-starter for a small EUC or PEV maker (IMHO)

Edited June 15, 2018 by Keith

[Beowolve]

Unfortunately I have no other information,  just read about that in on a german news site a while ago and instantly was thinking about  EUCs and wanted to share that info here.

Patents might me an issue, and if the motor cost is higher, it will have no success as well for sure.

[ir_fuel]

16 minutes ago, Beowolve said:

Patents might me an issue, and if the motor cost is higher, it will have no success as well for sure.

Not an issue if you buy them from the company that invented them. And it all depends on the motor cost indeed. Then again, what do you get in return? If the only return is that it will last longer no euc manufacturer will want to pay more. If you get a lot more efficiency/performance that might be different.

[Keith]

4 hours ago, ir_fuel said:

Not an issue if you buy them from the company that invented them. And it all depends on the motor cost indeed

...and thereby hangs the point I was making. You almost certainly would have to buy them from the patent holding company.

Using square insulated copper wire in order to increase packing density is hardly going to be cheap. It will be challenging for a manufacturer to ensure adequate insulation at the sharp edges and the slightest twist whilst winding will have it cutting through a lower layer and shorting so great care and precision will be needed. It also looks like might require twice as many rare earth magnets and very controlled steel production to have the correct grain properties and orientation. Ergo, manufacturing costs will rise significantly (IMHO) For what appears to be around a 10% gain - it doesn’t look cost effective. How much would you be willing to pay for a 10% range increase for example.

I doubt many, if any, of our current  EUC manufacturer’s make their own motors (with the possible exception of Uniwheel and, of course, the Pulse Glider as that must be using Warp technology ?) but they almost certainly have a company in China knocking them out very cheaply by the 1000 and winding them to suit the application. 

Thereby hangs another point, I haven’t read through the white paper but we would need to understand the Kv and torque range of this motor as well. If the Kv isn’t in the correct range for a direct drive EUC or PEV that would kill any effeciency gain and might make it unusable.

[Jon Stern]

This video on axial flux motors showed up in my Youtube feed today.

 

[mhpr262]

Those motors sure seem to be gaining in popularity. One of the biggest manufacturers of those motors (UK company YASA) was recently acquired by Mercedes Benz who will be using those motors to power upcoming electric AMG Mercedes vehicles. Two or three years ago I asked about outrunner(=hub motor) versions of those motors in the comments section under one of the company's videos. One representative of YASA even answered me and said that an outrunner topology would be possible but that they hadnt made such a motor yet.

I think it is only a matter of time though, because such motors would be ideally suited for outrunner configurations. The biggest problem with the inrunner configuration is reinforcing and stiffening the rotors with the magnets against the enormous and rapidly shifting magnetic forces generated by the stator with the coils. In an outrunner configuration the magnets would be embedded in the huge and (because it is fully closed) extremely rigid outer case of the motor, which ought to  get rid of all stability issues. It would also allow you to use only ONE stator with the  expensive copper coils in the middle and magnets on BOTH sides of the cover for maximum efficiency.

[RagingGrandpa]

It begs the question:

--> What are the drawbacks of the motors in our EUC's today?

[radial-flux permanent-magnet position-sensor BLDC outrunner direct-drive wheel motors]

My thoughts:

1. We've achieved just enough torque to make customers happy.
   We should treat today's Gotways with HB C38 @ 200A phase current as a 'minimum benchmark' for stall torque for an 18" tire size.
2. More speed is always welcome.
   Decreasing output power with increasing speed is just a fact of life (for any electric motor design).
   Expanding the speed range using voltage is already hitting practical limits of affordable IC's, and electrocution safety.
   Expanding the speed range using variable gearing is excessive complexity and goes against our minimalist ideal for EUCs.
   Expanding the speed range using (electronic) field weakening may be possible (and could be employed on many motor types, including today's BLDC's).
3. Motor overheating is almost unheard of.
   Our controllers burn first
4. Neodymium magnets are expensive, bad for the planet, and susceptible to field weakening when hot.
   If we could achieve our goals without them, that would be nice.
5. Mass reduction is always welcome... but you would have to cut the mass of the motor in half, to make a substantial difference in how an EUC performs.

So my proposal is: "We want more torque and more speed for the same mass and complexity."
(A man can dream, right?)
 

Axial-flux BLDC promises higher field strengths in the same package space. Field strength is good for torque and bad for speed... sounds like it shares the same drawbacks as the rest of today's EUC motors.

[Roadpower]

I'm only beginning to understand what has been done here but considering the subject matter I wanted to let the forum know about it so others could start wrapping their heads around it as well.

 

 

[mhpr262]

Frankly I would already be content with reliable MOSFETs...

No idea how that "raxial flux" thing actually works, but it will be a long, long time before we ever see one in a EUC. Normal axial flux motors would already be ideal with their extremely high torque and their pancake form factor that is like custom made for EUCs, but so far none have been built in an outrunner configuration, although that would be possible. Source: I once asked about that in the comment section of a promotional video by Magnax motors on Youtube and a representantive of the firm actually answered me. Their biggest advantage would only be less weight anyway as the big power output bottleneck are the batteries, and the control board/MOSFETs.

[Goonman]

I don't think they invented it. They just started making this type. It's been done before. They are using it and have refined it. 

[meepmeepmayer]

This is in the news again, because Mercedes bought an axial flux motor startup (not the one originally mentioned here) a bit ago, to explore using axial flux motors in their cars.

https://www.thedrive.com/news/why-axial-flux-motors-are-a-big-deal-for-evs

If you want to know what an "axial flux" motor is in practical terms (writing this because people are remarkably bad at explaining this everywhere I looked):

Our regular "radial flux" EUC motors are a circular disk (the unmoving stator) that has a rotating ring (the rotor) around it. (Due to the motor covers connected to the rotor, it looks like the entire disk is rotating from the outside, but behind the rotating cover is mostly the non-rotating stator.) An "axial flux" motor would be a static disk with a rotating disk next to it, like a sandwich of disks, connected by an axle. (You can vary, for symmetry reasons or whatever: a central fixed disk with rotating disks on each side, a central rotating disk between two static disks, etc. - anyways, it's just some sandwich of disks.)

The main advantage of axial flux motors seems to be their low weight, which is always good for EUCs. Their natural shape (large diameter but thin, vs. smaller diameter but wider) also fits the purpose. For EUCs, you would no longer need a motor cable going to the axle (because you have to go around the rotor ring), but you can go directly from the board on top to the static disk right below it. Pretty neat! (Though I'm sure Begode can achieve melting cables even when the cables are very short)

Hopefully this tech will filter down to generic Chinese electric motors. See you in 10-15 years, hopefully.

[onewheelkoregro]

https://www.ivtinternational.com/news/powertrain/ivt-expo-usa-turntide-showcases-axial-flux-motor.html the torque output alone on these things is very impressive and these can probably produce equal or more than a C40.

[alcatraz]

They're supposed to be lighter, right? That's a welcomed upgrade.

Only downside is lower max rpm. Might not matter for euc use.

I know people hate it when the chinese copy new tech but I guess there are some here now that wish they would. Ha!

Edited August 30, 2023 by alcatraz

[Punxatawneyjoe]

Mentioned on another thread awhile ago , cool tech.

[onewheelkoregro]

14 minutes ago, Punxatawneyjoe said:

Mentioned on another thread awhile ago , cool tech.

I just seen it on my phone. I didn't even look at the date on the article 😭😅

[onewheelkoregro]

20 minutes ago, alcatraz said:

They're supposed to be lighter, right? That's a welcomed upgrade.

Only downside is lower max rpm. Might not matter for euc use.

I know people hate it when the chinese copy new tech but I guess there are some here now that wish they would. Ha!

Give it a couple of months. How the US going to sue Chinese companies? And they aren't going to stop trading with China either so nothing is really stopping them.

[Circuitmage]

Nahh....we just get to keep paying extra for the tariffs that are still in place. 

<insert infinite political drama here>

 

[mhpr262]

The only downside is we would need one of those in a outrunner configuration, and I dont think I have seen such a motor, even though it would be ideal for how they are built. A while ago I posted a comment/question under a presentation video of such motor (made by Magnax) on Youtube and a representative of the firm actually answered me. He said there were no plans for an outrunner version.

[mhpr262]

An interesting article on thedrive.com about axial flux motors: Axial Flux Motors Are the Missing Link to Small, Fun Electric Cars (thedrive.com)

[skunkmonkey]

Yeah I saw that Mercedes-Benz was going to start using axial flux motors. They require tons of cooling though, so not very practical for EUC's.

[mhpr262]

On 9/9/2023 at 2:23 PM, skunkmonkey said:

They require tons of cooling though

I'm pretty sure those are just the extremely compact and at the same time extremely power dense motors for the automotive industry. A motor for an EUC would be very low powered, relatively speaking, and would have much more surface per volume. Cooling shouldnt be a bigger issue than our currrent radial flux motors. A much smaller issue, more likely.

[georeberven]

Axial Flux motors for EUCs are inevitable. Cost and time are the only delays. Lighter, thinner and more torque... what's not to love?  These motors were developed by a "backyard engineering" genius in England about 20 years ago and the first powered vehicle using his design was his electric bicycle, so they're completely reasonable for EUCs.  INEVITABLE!

[georeberven]

The most interesting aspects of the Axial Flux Motor result from the design flexibility possible from layering multiple motors with electronic gearing in between that would allow the equivalent of an infinitely variable transmission between counter-rotating elements. Why? Because the biggest limiting factor to EUCs being capable of safe 150mph speeds is not the energy available but more so the angular momentum of motor/wheel combination while riding at high speeds around curves. Overshooting curves is the largest source of single-vehicle motorcycle accidents currently and this effect is worse for current EUC designs. By having 3-4 controlled motors in one, the angular momentum could be variable between a maximum or minimum levels in proportion to the desired speed and agility. These benefits can be multiplied for higher stability (anti-wobble) or higher agility (even though weight remains the same).  If designed properly, self-driving, power-steering, fully self-balancing and anti-lock braking/traction control are al possible with Axial Flux motors combined with integrated mass-control gyros. {...which will likely be developed in about 10 years}. The BEST option for Axial Flux motors in EUCs (right now) is to create a new version of the 18XL or V12 that has the motor within 1" of the rim/tire, then have a bearing be at least 12" (Hollow bore).... then pack that hole full of batteries in order to keep it thin and light, which will make a light, agile, high speed commuter that is appropriate for beginners to intermediate riders... flanking the wheels with saddlebag batteries is unnecessary with an Axial Flux motor, imho.