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Comment by nmehner

5 days 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.

53 comments

nmehner

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rob74  5 days 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/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?

  • thelastgallon  5 days 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.

  • jama211  5 days ago

    I don’t see anything inside the article that says it’s designed to be inside the wheel. I’m not sure where they got that from.

    • Enginerrrd  5 days ago

      From Wikipedia on Axial Flux Motors: >"Mercedes-Benz subsidiary YASA (Yokeless and Segmented Armature) makes AFMs that have powered various concept (Jaguar C-X75), prototype, and racing vehicles. It was also used in the Koenigsegg Regera, the Ferrari SF90 Stradale and S96GTB, Lamborghini Revuelto hybrid and the Lola-Drayson.[9] The company is investigating the potential for placing motors inside wheels, given that AFM's low mass does not excessively increase a vehicle's unsprung mass.[10] "

      3 replies →

    • hylaride  5 days ago

      I think they misspoke when they said "in" the wheel, but supercars can have a separate motor for each wheel, and the closer they are to the wheel the better the torque as it's not also driving a longer shaft. The smaller the motor, the closer you can get.

      7 replies →

  • eru  5 days ago

    Well, Tesla also started with the higher end of the market. That's where people are willing to pay more.

close04  5 days 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.

Zanfa  5 days 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  5 days 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.

bidatzi  5 days ago

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

rdtsc  5 days 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  5 days 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.

Kaibeezy  5 days 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...

  • nmehner  5 days 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.

jama211  5 days ago

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

  • scoobytuber  5 days ago

    He’s holding the motor in the picture. That format is in-wheel BLDC.

    • doph  5 days 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.