13 ms·

The issue with this type of motor is that it is part of the unsprung weight since it is inside the wheel. This is probably why savings here matter a lot more (o

by nmehner 11mo ago

The issue with this type of motor is that it is part of the unsprung weight since it is inside the wheel. This is probably why savings here matter a lot more (or at least in a very different way) than the battery weight.

Kaibeezy 11mo ago
See also the Saab Emily GT project. Even with an older, heavier gen of these axial flux motors they found significant performance gains by controlling each wheel via its own motor. https://electrek.co/2023/04/27/saab-engineers-develop-secret-nevs-emily-gt-electric-car-project/ https://electrek.co/2023/04/27/saab-engineers-develop-secret...
- nmehner 11mo ago
  I didn't want to put the usability of the motor into question or go into a complete evaluation of advantages/disadvantages :) This was just an explanation that weight trimming the motor might be very much worth the effort - even if it somewhat "insignificant" compared with savings that are possible in battery weight.
close04 11mo ago
YASA doesn't call it a hub motor specifically but that's one place where it helps to save as much weight as possible. And for the cars most likely to have 1000+HP weight matters too. A Tesla motor weighs 100-200lbs, so saving that much weight down to 28lbs on a supercar is highly desirable. I think large drones will be another place where a downsized version of this motor will make a huge difference, assuming the power scales nicely with size.
rob74 11mo ago
Ok, now I understand why this motor is only used in supercars - installing four (or even only two - according to https://www.mercedes-benz.de/passengercars/technology/concept-amg-gt-xx-amg-ea.html#technology-and-innovation https://www.mercedes-benz.de/passengercars/technology/concep..., even the AMG GT-XX has "only" three of them) hub motors with twice the power of a Tesla Model 3 in any other car would be ridiculous. So, the actual challenge is to make this motor even smaller while keeping the same power to weight ratio, so it can also be used for regular cars? That is, if they want to build something for the mass market, not only for an exclusive clientele?
- eru 11mo ago
  Well, Tesla also started with the higher end of the market. That's where people are willing to pay more.
- thelastgallon 11mo ago
  But why limit only to cars? Can this be used for motorcycles, e-bikes, electric buses, train wheels, e-unicycles, electric golf carts, etc? There are probably a range of application where in-wheel makes perfect sense.
  - tckk 11mo ago
    Donut Labs markets a whole suite of axial flux motors. Sized from scooters through to large trucks. But no public pricing.
    - mlhpdx 11mo ago
      And thrusters for boats as well, IIRC.
    - doph 11mo ago
      I don't think their motors are axial flux, they're just large and narrow to fit inside wheels. Or at least all the images on their website depict radial flux designs.
  - exasperaited 11mo ago
    Motorcycles I could imagine. Do e-bikes really need significantly more power than they have? They already run arguably dangerously fast for their application. Is efficiency not the primary target there?
    - varispeed 11mo ago
      If engine can be produced cheaply, can it be limited "in software"? It's like saying people shouldn't use Rasberry Pi to blink an LED.
bidatzi 11mo ago
Why would it have to be unsprung? They are not unsprung in the vehicle shown in the article.
Zanfa 11mo ago
I might be wrong, but I don’t think these motors are intended to be used inside the wheel. That would add a ton of additional requirements in terms of physical durability as well as constrain optimal torque and RPM of the motor design.
- mbfg 11mo ago
  I believe the Aptera was originally going to have motors in the wheels... My understanding is the the first version will forego that, as there were challenges i guess, but i think they still to eventually do that.
Braxton1980 11mo ago
I believe caring about unsprung weight only matters for handling not efficiency
jama211 11mo ago
Where does it say it’s inside the wheel? Not sure about that
- scoobytuber 11mo ago
  He’s holding the motor in the picture. That format is in-wheel BLDC.
  - doph 11mo ago
    In-wheel application is possible, but it's important to understand that the pancake shape is only a consequence of the axial flux design and Yasa doesn't make motors in other "formats". Yasa motors shaped like this have been used in several supercars and all of them have been in-board on the axles, not in-wheel.
  - imtringued 11mo ago
    That format is the standard format for axial flux motors...
  - jama211 11mo ago
    I don’t believe it is in this case.
rdtsc 11mo ago
> This is probably why savings here matter a lot more (or at least in a very different way) than the battery weight. Wouldn't that make it worse or just ... different. Before this the unsprung weight wouldn't have had a motor in there and now it does. Increasing the unsprung weight doesn't seem a like a good thing.
jakogut 11mo ago
What current mass production EVs use hub motors? It seems a lot more sensible to have the motors inboard, mounted to the chassis, and drive the wheel(s) with axle shafts. It seems in my searching this is how nearly all EVs are currently designed and produced.

by nmehner 11mo ago

Kaibeezy 11mo ago

See also the Saab Emily GT project. Even with an older, heavier gen of these axial flux motors they found significant performance gains by controlling each wheel via its own motor. https://electrek.co/2023/04/27/saab-engineers-develop-secret-nevs-emily-gt-electric-car-project/ https://electrek.co/2023/04/27/saab-engineers-develop-secret...

nmehner 11mo ago
I didn't want to put the usability of the motor into question or go into a complete evaluation of advantages/disadvantages :) This was just an explanation that weight trimming the motor might be very much worth the effort - even if it somewhat "insignificant" compared with savings that are possible in battery weight.

close04 11mo ago

YASA doesn't call it a hub motor specifically but that's one place where it helps to save as much weight as possible. And for the cars most likely to have 1000+HP weight matters too. A Tesla motor weighs 100-200lbs, so saving that much weight down to 28lbs on a supercar is highly desirable. I think large drones will be another place where a downsized version of this motor will make a huge difference, assuming the power scales nicely with size.

rob74 11mo ago

Ok, now I understand why this motor is only used in supercars - installing four (or even only two - according to https://www.mercedes-benz.de/passengercars/technology/concept-amg-gt-xx-amg-ea.html#technology-and-innovation https://www.mercedes-benz.de/passengercars/technology/concep..., even the AMG GT-XX has "only" three of them) hub motors with twice the power of a Tesla Model 3 in any other car would be ridiculous. So, the actual challenge is to make this motor even smaller while keeping the same power to weight ratio, so it can also be used for regular cars? That is, if they want to build something for the mass market, not only for an exclusive clientele?

eru 11mo ago
Well, Tesla also started with the higher end of the market. That's where people are willing to pay more.
thelastgallon 11mo ago
But why limit only to cars? Can this be used for motorcycles, e-bikes, electric buses, train wheels, e-unicycles, electric golf carts, etc? There are probably a range of application where in-wheel makes perfect sense.
- tckk 11mo ago
  Donut Labs markets a whole suite of axial flux motors. Sized from scooters through to large trucks. But no public pricing.
  - mlhpdx 11mo ago
    And thrusters for boats as well, IIRC.
  - doph 11mo ago
    I don't think their motors are axial flux, they're just large and narrow to fit inside wheels. Or at least all the images on their website depict radial flux designs.
- exasperaited 11mo ago
  Motorcycles I could imagine. Do e-bikes really need significantly more power than they have? They already run arguably dangerously fast for their application. Is efficiency not the primary target there?
  - varispeed 11mo ago
    If engine can be produced cheaply, can it be limited "in software"? It's like saying people shouldn't use Rasberry Pi to blink an LED.

bidatzi 11mo ago

Why would it have to be unsprung? They are not unsprung in the vehicle shown in the article.

Zanfa 11mo ago

I might be wrong, but I don’t think these motors are intended to be used inside the wheel. That would add a ton of additional requirements in terms of physical durability as well as constrain optimal torque and RPM of the motor design.

mbfg 11mo ago
I believe the Aptera was originally going to have motors in the wheels... My understanding is the the first version will forego that, as there were challenges i guess, but i think they still to eventually do that.

Braxton1980 11mo ago

I believe caring about unsprung weight only matters for handling not efficiency

jama211 11mo ago

Where does it say it’s inside the wheel? Not sure about that

scoobytuber 11mo ago
He’s holding the motor in the picture. That format is in-wheel BLDC.
- doph 11mo ago
  In-wheel application is possible, but it's important to understand that the pancake shape is only a consequence of the axial flux design and Yasa doesn't make motors in other "formats". Yasa motors shaped like this have been used in several supercars and all of them have been in-board on the axles, not in-wheel.
- imtringued 11mo ago
  That format is the standard format for axial flux motors...
- jama211 11mo ago
  I don’t believe it is in this case.

rdtsc 11mo ago

> This is probably why savings here matter a lot more (or at least in a very different way) than the battery weight. Wouldn't that make it worse or just ... different. Before this the unsprung weight wouldn't have had a motor in there and now it does. Increasing the unsprung weight doesn't seem a like a good thing.

jakogut 11mo ago

What current mass production EVs use hub motors? It seems a lot more sensible to have the motors inboard, mounted to the chassis, and drive the wheel(s) with axle shafts. It seems in my searching this is how nearly all EVs are currently designed and produced.