
Belgian startup Magnax has found a way to mass-produce the axial-flux motor - sohkamyung
https://spectrum.ieee.org/transportation/alternative-transportation/this-insideout-motor-for-evs-is-power-dense-and-finally-practical
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AdrianB1
I am very eager to find out what the price will be for these motors, this will
have a huge impact in General Aviation. A banal 4 cylinder 100 HP petrol
engine is ~$20,000 ("aviation price") and the weight is a bit over 60 kg, if
my math is right a Magnax motor can be as light as 5 kg (even 10 kg is
fabulous) but the cost needs to balance the huge price of batteries: the
$20,000 petrol engine with 140 liter fuel tanks gives a flight time of almost
10 hours, batteries for that flight time would be insanely expensive and
possibly quite heavy. But most people don't fly more than 5-6 hours, so a
reduction to 6 hours would be acceptable for 95% of the people.

Another positive impact to GA is you don't need to adjust for mass and balance
that much, batteries have a fixed center of gravity that does not change while
discharging, while fuel tanks impact the plane's center of gravity as they go
from full to empty. Less trimming, simpler flying.

And not the last, it is eliminating any problems with carburetors, mixture,
air density or inverted flight: none of these affect an electrical motor, but
it needs to be considered for the likes of Cessna where you need to adjust the
(fuel/air) mixture depending on the altitude.

And it improves propeller efficiency, simplifying constant speed propeller
operation. It can be easily fully automated.

All good news, but seeing it happen is a different story: it can take 3 to 5
years, more that a decade or never to reach mass availability and adoption in
general aviation. It has the potential to make the market explode (in the
positive way), but there is so much politics involved there are chances the
status quo will be maintained. Let's see.

~~~
qubex
I’m absolutely ignorant on the topic of aircraft propulsion, but I’d always
assumed that the diminishing mass of fuel that one was carrying around with
oneself as the flight progresses is a key advantage that electric-propulsion
aircraft can never hope to replicate (short of dropping battery packs with
parachutes as they become exhausted of charge).

Am I absolutely wrong or is it not actually much of a factor?

~~~
Filligree
I hope to hear actual pilots chiming in, but from first principles:

It shouldn't be a large factor. Drag is independent of mass, and while lifting
the fuel to cruising altitude takes energy, most of the flight should ideally
be cruising.

The rocket equation doesn't apply; that's for an entirely different regime.

~~~
skykooler
While drag is "independent" of mass, the lift required to maintain level
flight is affected by weight, and drag is affected by lift. A heavier airplane
will absolutely require more power to cruise.

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mr_woozy
Anyone else just impressed by the writing of the article itself? They made a
very good effort of providing benefits over traditional radial flux electric
motors and how theirs was difference as well as measurable improvement
numbers.

I hope they succeed.

~~~
ridaj
It reads like an ad to me. It's hard to figure out what the catch is, if any
(and in this world of tradeoffs, there usually is a catch).

~~~
ew6082
The catch is that radial motors are balanced magnetically and these are not.
All that magnetic force is added to axial pull between the stator and rotor.
That means they need a thrust bearing in addition to the guide bearings. This
causes increased heat and mechanical losses and probably limits efficiency to
somewhat less than a standard electric motor. Hi-E standard motors cap out
around 98.8%, these will probably cap a point or two lower.

~~~
nomel
I don’t have a firm grasp of the article, but isn’t the force balanced in this
case since the two rotors, linked together, sandwich the stator? If I
understood correctly, this would mean the thrust bearing would only feel the
imbalance between the two sides.

See:
[https://m.youtube.com/watch?feature=youtu.be&v=BTuCshX5bc0&t...](https://m.youtube.com/watch?feature=youtu.be&v=BTuCshX5bc0&t=36)

~~~
japanuspus
Agreed, this seems to be an incorrect conclusion. Maybe ew6082 just looked at
the asymmetrical figure without reading the text.

~~~
ew6082
Fair enough. They said that a double rotor version has been developed, but all
their prototypes and marketing material are single rotor. We can probably
assume that single rotor is all that would fit on an in-wheel design but there
are other ways to skin the cat.

They would still need to include a light thrust bearing on the double rotor
design since you can never assume perfectly balanced air gap and one side or
the other will dominate, but the losses would be much lower with that setup.

------
hristov
This is very interesting. And it is very good news that companies are finding
higher efficiencies in mass produce-able electric motors. It means that
electric cars will become more affordable and practical quicker.

But I do hope they do not proceed with the in wheel concept. In wheel motors
make the ride not only bumpier but more dangerous. This is because the wheel
with more un-sprung weight bounces more and tends to lose contact with the
road more, which in turn makes the car more likely to spin out of control,
miss a turn, etc.

Electric cars, being still relatively new, cannot afford to get a reputation
for danger.

~~~
hinkley
Might work out if it’s paired with active suspension.

The idea with motors at the wheel seems to be that the moving parts are all
concentrated there. No mechanical distribution. Compartmentalization. But that
is not incompatible with active suspension systems.

~~~
adrianmonk
What would be the advantage of doing it that way instead of just putting the
motor on the car frame and connecting it to the wheel with a CV axle? From
what I could dig up, mechanical losses in a CV axle are on the order of 1%.

An active suspension requires power, too. And a heavier wheel would presumably
require a more power-hungry active suspension than a lighter wheel, so you're
not getting something for nothing in terms of efficiency.

I guess it is a matter of numbers, though. A CV axle also gives a wheel
inertia, as it has mass and moves when the wheel does (partially). If you can
make an insanely light motor, maybe you could make it so light that it's
actually contributes less inertia than a CV axle would, in which case go
ahead.

~~~
davidgould
The small diameter of the CV axle makes the inertia small compared to the rest
of the wheel, tire, brake assembly.

------
abyssin
> "If yokeless axial-flux machines replaced only a fraction of the older
> machines, we would save our customers some money and make the planet more
> livable while we’re at it."

The engineering feat is impressive and exciting, but this conclusion doesn't
account for the Jevons paradox. In itself, a technical progress that improves
the efficiency with which a resource is used doesn't lower the demand for this
resource, but instead increases it. The solution to a more livable planet is
political, and this is why it's so difficult to find.

~~~
jessriedel
If you make it cheaper to use a less polluting resource than a more polluting
one, this can still work. Improved solar technology, for instance.

~~~
vanderZwan
Yes, but the point GP makes is that you need carrots _and_ sticks. One or the
other alone will not be enough.

~~~
jessriedel
He's claiming that, I guess, but he doesn't actually provide any support. It
seems totally possible, depending on the technological specifics, to require
zero political coordination.

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mkoryak
Here is a video of one in operation with some techno music:

[https://www.youtube.com/watch?v=rGu7XDapR58](https://www.youtube.com/watch?v=rGu7XDapR58)

~~~
alanbernstein
That's cool, but I was hoping to find a video detailing the difference in
design between axial and radial motors. You know, with exploded 3d models and
such. And also with techno music.

~~~
wideasleep1
[https://youtu.be/BTuCshX5bc0?t=36](https://youtu.be/BTuCshX5bc0?t=36)

~~~
mkoryak
That techno music makes me feel very empowered.

~~~
Jommi
I'm sorry to say but that is not techno music at all.

~~~
mkoryak
What is it called?

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extropy
A concise and technical summary from their blog:

[https://www.magnax.com/magnax-blog/axial-flux-vs-radial-
flux...](https://www.magnax.com/magnax-blog/axial-flux-vs-radial-
flux.-4-reasons-why-does-axial-flux-machines-deliver-a-higher-power-density)

------
FlynnLivesMattr
> "One of our designs has a peak power density of around 15 kilowatts per
> kilogram. Compare that with today’s motors, such as the one in the all-
> electric BMW i3, which delivers a peak power density of 3 kW/kg—or just one-
> fifth as much. And the Magnax machine is also more efficient."

It will be interesting to see how Moore's law will materialize in EVs.
Understanding that the majority of time and effort spent in the automobile
industry has been aimed towards combustion engine design as opposed to
electric motors, it will be equally interesting to follow the efficiencies to
be discovered in the imminent future, taking into consideration how blazing
quick they already are today.

~~~
Gibbon1
15kw is about 9hp/lb. If you can get that maybe you can design a wheel motor
that doesn't suck. Two 75 hp motors would weigh about 8 lbs each.

No gear box, differential or CV joints. Potentially really cheep.

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zamalek
The most I understand about motors is how they typically work and that
innovations are possibly more lucrative than battery innovations; this seems
like a major innovation. I must be missing something? What's the healthy
skepticism here?

~~~
namibj
Emrax sells this technology for years now. This isn't new, and I couldn't find
a datasheet to meaningfully compare them with what else is available on the
market.

I do know of axial flux motors that couldn't have had iron teeth, but I think
it was a single-side design with a metal backplate to support the resin-soaked
stator windings. I recall a nice discussion about them using GaN power
electronics to reach very high efficiencies. Those machines were still hand
made last year, however...

~~~
Robotbeat
You can, of course, make an ironless axial flux motor with the resin and wire
itself acting as a structural composite. Two-sided. I think commonly were used
for solar cars (i.e. for student competitions).

~~~
namibj
The prototype I touched was for/part of a 200kW pair (I don't recall if each
or total) for a demonstrator plane...

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elihu
> "Motors and motor systems account for approximately 53 percent of global
> electricity consumption. We estimate that improving the efficiency of all
> the world’s motors by just 1 percent would reduce the motors’ power
> consumption by 94.5 terawatt-hours and shrink their carbon dioxide footprint
> by the equivalent of 60 million metric tons."

I find this surprising. Perhaps a big chunk of this is air conditioning, which
is technically using a motor to run a compressor?

~~~
bboreham
And refrigerators?

~~~
basicplus2
slight tangent...

Interesting thing to consider is that reverse cycle airconditioners are
notoriously inefficient compared to dedicated cooling or heating units..

Reverse cycle units can use anything from 2 times to 5 times the power of a
dedicated unit on cooling

~~~
matthiasl
At least 2 times and as much as 5 times seems surprisingly bad.

Do you have a source or a concrete example for that?

The most plausible explanation I can think of for what you're saying is that
you're comparing an evaporative cooling system to a heat pump based one, in
which case the 'reverse cycle' aspect is not the thing causing the
inefficiency.

------
ridaj
How much does motor weight matter in a modern long-range EV, vs battery
weight?

~~~
elihu
An AC motor for a car might be in the 100-200 pound range or so. DC motors
tend to be a little heavier. Along with the motor, you'd need a motor
controller and cabling.

Example conversion motors:
[https://www.evwest.com/catalog/index.php?cPath=8](https://www.evwest.com/catalog/index.php?cPath=8)

A general rule-of-thumb is that it takes about 100 watt-hours to move a
thousand pounds of car one mile. I just started on a project to convert a
Mazda RX-8 to electric. That's a 3,000 pound car (before the conversion), and
I'm planning to use a Netgain Hyper9 AC motor, which is 120 pounds, which is
pretty small compared to the rest of the car (or compared to the original
rotary engine). Battery weight is the bigger concern; if I can keep the pack
under 400 pounds I'm doing pretty good, and I'll be lucky if that gets me 100
miles of range.

~~~
nabla9
According to Magnax no-load losses reduce the effective range of the vehicle
by 10% to 20% (iron close to rotating permanent magnets equals braking when
there is no load) Magnax claims 85% less iron losses due to the low amount of
iron.

------
DrJosiah
Awesome design, makes me want to put one together just to see it work. :)

One concern: I saw some designs with the rotor outside the stator, physically
mounted to a wheel. I'm not a mechanical engineer, but as a guy who considers
himself not quite dumb enough to fail at everything...

I hope they build those motors tough. Typical electric motor mounts create a
situation where the only real stresses on the motor are rotational, along the
axis of rotation, or in the case of a pulley / gear-mount setup, you are
usually limited to 1-2 additional push/pull axis. But on a wheel? That wheel
is going to want to rotate and move on all axis, which now needs to be
supported by a motor, which also includes permanent electric magnets.

Awesome lighter motor, awesome that we can sandwich the rotor between stators
(more layers more torque!).

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rpmisms
My first thought is that Toyota needs to license this for their hybrids, and
mount it on/as the flywheel. Using something like this as either MG1 or both
MG1 and MG2 would seriously minify their hybrid drivetrain.

~~~
WhompingWindows
Why hybrids, Why not just go for full electric?

~~~
rpmisms
Because hybrids are the next step until EVs reach the junction of affordable
and practical for the average household. Toyota knows this, and is playing it
safe until there's a mass-market demand, when they'll step in with the most
practical and boring EV possible.

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tyfon
There was a lot of ifs, mays and hopefullys in that article, but maybe it's
just written in a strange way since it does say they have actually found a way
to mass produce this thing. It would be great if true.

One of the first questions that popped into my mind was how would this motor
with less mass (less structure) handle 5 times the power/mass of traditional
electric motors which are already pretty power full and sometimes break from
strain.

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ppf
> One of our designs has a peak power density of around 15 kilowatts per
> kilogram. Compare that with today’s motors, such as the one in the all-
> electric BMW i3, which delivers a peak power density of 3 kW/kg—or just one-
> fifth as much. And the Magnax machine is also more efficient.

>We believe that we can scale the design to whatever size carmakers (and other
customers) may demand.

Count the weasel words. I'm at 5.

~~~
baybal2
Even at 3kw/kg, an electric motors blows ICE out of the water.

~~~
ppf
Not my point, and an electric motor isn't going to do much without a battery.

------
JoeAltmaier
Complex issue. With this innovation they can rethink the whole
axel/brakes/rims/hub motor system and perhaps come up with more novel
solutions. E.g. Brakes/hubmotor integration to remove the unsprung weight
penalty? Rim/hubmotor integration? It's an exciting time.

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mark-r
> In tests at the University of Ghent on the first prototype, our yokeless
> axial-flux motor reached efficiencies from 91 to 96 percent. And that was
> just the prototype.

Wouldn't one expect a prototype to be better than a mass produced unit? It
gets individual care and can be optimized for the test.

~~~
JoeAltmaier
Nah. Prototypes have lots of compromises - wrong materials, crude circuits
etc. Maybe bolted to a plywood table top etc. The purpose of a prototype is
proof-of-concept and measurement/recording. Not a simulation of real
deployment.

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avmich
An electric plane with a motor like this, fueled with hydrogen like Toyota
Mirai... seems like it can improve the situation with range?

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longjowl
Looks lovely for drones.

~~~
namibj
You get by without the fancy iron teeth mechanical support they invented as
long as you remain small enough. The main issue is miniaturizing magnet
manufacture without per-magnet costs staying fixed.

I judge by COTS pricing, but the $/kW falling on magnets increases a lot below
5~15kW electrical.

~~~
Robotbeat
Yeah, if you have really tiny rare earth magnets, their cost-per-weight (for a
given magnetic energy product) goes up a lot. Just finicky to deal with
sintering a bunch of small things, I suppose.

------
quotemstr
But when will we see a motor powered by magneto-reluctance and capacitive
diractance instead of the relative motions of conductors and fluxes?

Seriously, though, this article is clear and well-written. I love it when I
see people solve problems we didn't know we had. I'd figured we'd basically
found the global optimum on electrical motors decades ago and were basically
stuck there by physics now, with advances happening elsewhere in the
powertrain. This development is like CPU vendors figuring out how to write 3x
more single-core performance out of the same thermal budget after our own
decade of stagnation in this area.

