Comment by rob74
6 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?
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.
Donut Labs markets a whole suite of axial flux motors. Sized from scooters through to large trucks. But no public pricing.
And thrusters for boats as well, IIRC.
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.
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?
e-bikes don't necessarily need more power but they could benefit from a smaller and lighter motor. If it becomes small enough to "disappear" in the pedal assembly for example, it would allow more design/parts commonality with normal bikes and fit more people's aesthetic criteria.
The lower weight would be definitely welcome, my ebike is comically heavy compared to a normal one and sometimes I have to carry it up flights of stairs (some German railway overpasses, grr).
Also in scooters it could fit in the wheel (since the wheel is tiny and has to spin quite quickly - no reduction gear needed vs a bike with 26-28" rims) allowing a simpler design and cost savings. But maybe in scooters they're already using in-wheel motors, I'm a bit ignorant there.
1 reply →
While more power may not make sense, less weight is an easy way to get more efficiency. And if you can keep the same power at a lower weight, that's a win.
Hmm. I am NOT an expert (though I ride and have owned 3 traditional motorcycles). IIUC, reducing unsprung weight is really crucial for handling -- which is why so-called "inverted" forks / front shock absorbers became basically the standard.
1 reply →
The motor to battery weight ratio on e-bike is much more than for cars. Having a lighter motor would improve the efficiency.
They don’t need this motor, but if it can be scaled down… at over 10kW/kg sustained, one could wish/hope to get 200W at 50g (disclaimer: I have no idea how this scales with size). Combine that with 1kg of a 600Wh/kg battery (https://news.ycombinator.com/item?id=45797452. Again, I have no idea how realistic that is), and you have a bicycle that’s only a little heavier than a non-electric one, but gives you a boost for 3 hours (more if you use it sparingly. If you’re cycling at leisure, 100W already is a lot of power)
1 reply →
Yes, all else equal, we want lighter motors in vehicles.
I'm always interested to hear about the latest in lighter and possibly more powerful and torque-y e-bike motors.
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.
2 replies →
Yeah, my first thought was racing EUC’s, lol….
End User Credentials ? Everyone Uses Cars ? Engineered Universal Conscience? (Since you seem to assume we all share your thoughts & context...)
2 replies →
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.
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] "
The fact that you CAN put it in the wheel doesn't mean it MUST to go in the wheel.
1 reply →
They’re investigating the potential for them to be placed inside wheels, but they aren’t at the moment, so my point stands.
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.
I guess if you can make the motor and a suitable reduction box lighter than the equivalent bearing and driveshaft combination you could make the suspension arms mechanically simpler.
By using motors at each wheel you'd eliminate the need for a differential, saving a good 40-50kg or so. Of course, if you kept the drive shafts and put the motor and reduction box in the middle, you'd be able to use inboard brakes and save a lot of unsprung weight!
5 replies →
Interesting! But yes in axel in this case then
I get your skepticism and I know nothing about the field, but if the round thing in the press release picture isn’t designed to fit in a wheel, I’m confused. https://yasa.com/news/yasa-smashes-own-unofficial-power-dens...
Not necessarily, cf: https://lammotor.com/wp-content/uploads/2024/12/YASA-400R.jp...
From https://lammotor.com/yasa-axial-flux-motor/
the shape is due to the change to the motor layout: https://www.thedrive.com/news/why-axial-flux-motors-are-a-bi...
It’s currently designed for the axel for now as far as I’m aware.
Well, Tesla also started with the higher end of the market. That's where people are willing to pay more.