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I was curious how this thing works and asked Claude to visualize it -- mostly to see how good Fable is and I have to say, what it made was good enough for me to get a gist of it. Posted it here

https://azimi.me/axial-flux-motor-explainer/

That was a good video, and I also liked the Munro video that does a nice job of explaining how these work: https://www.youtube.com/watch?v=m507ryWhc6c

I wonder how developing electric motors compares to combustion engines. My hunch says that it’s the main reason the Chinese high-tech electronics industry was able to develop and iterate leading electric vehicles so fast. (Edit: My more clarified point is regarding the machinery required + place to accommodate them to work on electric motors vs. ICE metal parts and all the intermediary parts transfering power in the drivetrain. The shop in the video is smaller than many would imagine.)

When these hopefully go to the next generation Formula E cars, we’ll see some crazy improvements in cornering. The newest generation already has active 4WD. I imagine this can bring even better torque adjustment improvements.

Great video!

So it looks like axial flux, the OG was introduced in 1820 something and it wasn't easy to manufacture. So radio flux came after that and has been around ever since. So axial flux is making its come back this year!

The video is very interesting too about decompounding returns when the motor is less with the other things need to weigh less too.

Especially the bit about potentially not needing brakes in the near future because the regen is so capable. Which would lead to less weight and less parts even again!

A few years ago I built a few small ones in my home lab. They are extremely efficient. With the right setup, have insane torque, and don’t require a lot of energy to do it. The best part for me was that they are completely brushless by design and are easily to keep clean.

Came here for this, thank you for providing a link

Edit.... Video doesn't seem to explain very well either

Click "More" and scroll down:

"In contrast to conventional radial flux motors, the electromagnetic flux in an axial flux motor runs parallel to the axis of rotation. The key components are arranged in a disc‑shaped layout: two rotors sandwich the stator from the left and right. This design enables an especially compact motor architecture, high power and torque density, and new freedoms in drivetrain packaging. In the new Mercedes‑AMG GT 4‑Door Coupe, the motor at the front axle is just under nine centimetres wide; the two motors at the rear axle each measure around eight centimetres in width. The three axial flux motors are integrated per axle into so‑called High Performance Electric Drive Units (HP.EDU), where they are combined with a compact input planetary gearbox in a single housing."

A very good YouTube video from Munroe Live (an engineering firm specializing in "design for manufacturing") explaining it: https://youtu.be/dCO633KE7RA "Axial Flux Motors Explained"

Edit: a video from them on this particular YASA tech being discussed : https://youtu.be/m507ryWhc6c

Visited Astrall Dynamics, a Chinese startup that builds quadrupeds with axial flux motors here in Shenzhen. Super cool to see the robots in actions, carrying 60kg of weight up over 20 flights of stairs quite rapidly. The high torque at the compact form factor was super impressive. As far as I understood they are more complex to manufacture, especially at scale.

It's a bit buried, but it does:

> In contrast to conventional radial flux motors, the electromagnetic flux in an axial flux motor runs parallel to the axis of rotation. The key components are arranged in a disc‑shaped layout: two rotors sandwich the stator from the left and right. This design enables an especially compact motor architecture, high power and torque density, and new freedoms in drivetrain packaging. In the new Mercedes‑AMG GT 4‑Door Coupe, the motor at the front axle is just under nine centimetres wide; the two motors at the rear axle each measure around eight centimetres in width. The three axial flux motors are integrated per axle into so‑called High Performance Electric Drive Units (HP.EDU), where they are combined with a compact input planetary gearbox in a single housing.

“What“ might be a long answer, but why anyone might want one is to have increased torque density for the given volume and diameter. So they are thin motors where the generated flux is parallel to the shaft. And they are like the standard PMSMs where you apply the same driving algorithm from the inverter side to use them.

Here's a great Instructable on building one yourself, much better explanations in there.

https://www.instructables.com/Designing-and-Building-an-Axia...

It's basically the V8 of electric motors. Different topology results in better power to weight ratio. From the outside they look pancake shaped.

Most motors have N-S axis of magnets aligned tangential to the axis of rotation. Axial flux motors have N-S poles parallel to rotation. This allows motors to be thinner and wider as well as anyhow more lighter and sometimes easier made. Whether they make sense depends, it seems.

Consider the thousand or so comments at https://hn.algolia.com/?q=axial for more details. While it’s no substitute for a well-written comprehensive article, it certainly is a smorgasbord of answers.

https://en.wikipedia.org/wiki/Axial_flux_motor

Here's a good video on it from my watch history: https://www.youtube.com/watch?v=dCO633KE7RA

https://backtothefuture.fandom.com/wiki/Flux_capacitor .

As far as I understand it's so small and lightweight you can put one on each wheel and remove brakes and still save weight (something something unsprung weight bad).

So the engines have the same size of a disk brake?

That's incredible.

do we need disk brakes?

All motors are generators. It's only a matter of how you are creating the magnetic field with the stator windings.

In order to generate a higher regen, you'd have to somehow get more energy in the motor first... and since its only rated for 200kW, good ol' physics limits you, IF thats all the energy you put into the system.

If you roll it down a hill, or do something exotic like inverting the magnetic fields .... you can exceed the motor rating. But thats usually not recommended because the motor driver itself isnt rated to handle that power.

Their founder/CTO discusses that here and their ability to match the braking power density of carbon ceramic brakes: https://youtu.be/B2Hl4c1iZK0?si=bCLQnfovjY7t-eYm&t=900

400kW regen is going to be a fairly alarming level of stopping for a normal vehicle. It's OK to leave emergencies to the friction brakes.

> can a car with 200kW propulsion have a 400kW regen

At the motor level it should be the same, in propulsion you’re converting current to torque and in regen you’re converting torque to current, with the same hardware. The high voltage wiring is the same and will set the same limit on current regardless of direction.

I believe bidirectional inverters are generally symmetrical as well, so that should not be a factor.

Which I reckon leaves two factors:

1. Battery C rates, afaik pretty much all chemistries have a higher discharge rate than charge rate, especially when trying to maintain them for a long time, so by that account regen power would at most be the same as propulsion (if the entire power train is sized for the battery’s charging rate).

2. Artificial limitations, obviously you could always artificially under-prop, though that seems unlikely outside of niche applications.

tldr: I don’t think so, except on a technicality (that you can artificially hobble propulsion).

Am I reading you right that breaking power (that you want to regenerate in the system) >> speeding power? Obvious now I come to think of it, and still pretty nifty new thing learned if true!

Or the same size and same weight for MORE POWER!!1!

There are fluid dynamic bearings which were used in VCRs and probably hard drives and definitely laser printer mirror motors - two sets of precise herringbone patterns cut into the ID of a bearing column and a tiny bit of oil that gets entrained between rotor shaft and that bearing column. As the motor speeds up the oil forms pressurized donuts. Only works at speed and generally only useful when there aren't side loads so applications are limited. Rolling element bearings are a quite developed technology and hard to beat in most applications.

Closest I can think of is flywheel "battery" storage tech many of which do have magnetic bearings and also some way to get power in and out of the flywheel so basically a motor. It's not exactly what you're looking for but there's prior art out there.

I think air bearings exist? Maybe some prior art to consider

maglev but those do linear acceleration instead of rotational. seems tricky though for cars with such uneven surfaces.

I wonder if that is even possible since the whole point of the motor is an imbalance of magnetic forces.

Probably not. A huge disadvantage of axial flux motors is they have a large number of poles, which means that they get less efficient at high speed because they require say 5x as much switching.

This makes them kind of unsuitable for power generation and really high power motors (despite their power density) where the main way you get more power is just to spin really fast.

The other disadvantage is they have such a low amount of material in them, that the stator overheats really easily. And the topology of the motor makes it really difficult to get the heat out efficiently, which again limits their maximum power.

Yasa is a British company, for the record.

Their advantage was mechanical engineering. They have historically not done well with electrical systems. So this is a change - hopefully for the better.

And reversed the polarity of the neutron flow.

Britain didn't abandon it's space programme. It abandoned a launch rocket programme though. That was over 50 years ago and the rocket was less capable and more expensive than alternatives at the time.

> Brought to you by the only country to have a space programme and abandon it.

I mean, so did France; they both essentially folded theirs into ESA.

Did they have to? My impression is British companies sell out as soon as they can these days. Is this something that could be changed with policy? Does Germany incentivise running companies more? Or is this cultural, e.g. British people are more risk averse?

Actually, 137 years behind Tesla ;)

https://spectrum.ieee.org/axial-flux-motor-yasa

... Eh? No. No current large-scale production car uses axial flux motors. You're talking concept cars, plus a few oddities like https://en.wikipedia.org/wiki/McLaren_Artura

My understanding is that all current Teslas use radial flux motors

This entire product is easier to build than the existing technology, has more simple tooling and will be simpler and cheaper.

Designing the manufacturing machinery is exactly what happens in any manufacturing process. Those robots are general purpose that have been adapted for the required tasks, that's a normal process.

Why would you build a motor that's twice as heavy with copper and much wider when you don't need to?

China is working on the same type of engine: https://interestingengineering.com/ai-robotics/chinese-axial...

Efficiency and cost savings at scale usually involve an increase in complexity: in mass manufacturing, complexity is generally a fixed cost and so can be amortized over larger volumes.

A typical modern car is already hideously complicated and a different type of motor would not change this.

What is the current market sentiment? Share of EVs is slowly rising so having a good motor as important as ever.

He says, typing on one of the most hideously complicated things humanity has created.

By that logic we should all just be writing assembly manually. Screw hideously complicated higher level languages. Screw LLMs in particular, so complicated!

> Never become dependent on doing hideously complicated things

Is Mercedes stupid?

How did Carl Benz dare to do something as hideously complicated as building the first gasoline-powered car in history?

And why did they kept inventing complicated stuff that ended in all modern cars like ABS, adaptive cruise control, direct fuel injection, emergency brake assist, etc, etc?