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Hyundai Uni Wheel electric drive system could revolutionize EV design

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Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#131

Post by jacquesm »

benj111 wrote: post #127
jacquesm wrote: post #73

Earlier quoted context omitted.

Motor scooter motors weigh a fraction of what the equivalent motor for a car would weigh, and it's exactly the problem: The issue is that it scales poorly, unsprung weight is bad enough that on some cars the disc brakes live 'inboard' on the front wheels (older hydraulic suspension cars). Essentially the larger the unsprung mass the bigger the hit every time the road surface irregularities cause the wheels to move re…

I can sort of buy this at the upper end. But a small car with 4 relatively small motors with normal tyres v a range rover with run flat tyres and massive disc brakes?

In a small car it could work, but you'd be very much limited in power and weight.

See upthread links and subsequent updates

https://news.ycombinator.com/item?id=38485097.

Note that more unsprung weight has other effects as well, such as poor handling because the wheel bounces higher and so will be out of contact with the road for a longer time when it encounters an obstacle. If you think of the weight of the wheel as the weight on a pendulum it is easy to see why that would affect the period of the swing.

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#132

Post by governmentdude »

benj111 wrote: post #66
nabilhat wrote: post #51

Worth noting, placement at the wheel is somewhat arbitrary. There's nothing to prevent this contraption from working the other way around and being mounted at the chassis instead, aside from squeezing out every bit of space optimization. Axle support would be a concern either way. Controlling deflection of the drive axle adds a structural requirement, certainly a well supported bearing close to this device. The gears…

It's trying to compete against a CV joint and gear box. That seems like an easier sell. I'm not sure if we're talking past each other but you wouldn't need an axle to deflect. The motor drive could attach directly to the 'uni wheel' which is in turn connected directly to the wheel. If you're talking about the motor drive shaft, then surely you'd just be moving thrust bearings from the gearbox to the motor (if motors…

> you wouldn't need an axle to deflect

This is really cool for rear wheels. I don't know why their demo shows it on all 4, since it has to be able to steer (note that the demo does show a CV joint in the axle on the front, but that seems like it would limit steering angle severely, since it is just 1 joint. They're probably planning to apply torque to steer).

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#133

Post by benj111 »

consp wrote: post #92
benj111 wrote: post #65

Earlier quoted context omitted.

Why not? You'd have an added complication of making the shock absorber the pivot point, and attaching the motor to the top point. Or having a separate pivot point where the motor or wheel can slide up and down. This does raise the question of why not just attach the motor straight to the wheel. The standard response to that is a hand wavey "unsprung mass". But has it actually been tried and shown to be an issue?

> The standard response to that is a hand wavey "unsprung mass". But has it actually been tried and shown to be an issue? Afaik with high performance motors, if you want optimal performance and space efficiency you take the unsprung mass for granted and move everything in wheel and try to reduce the mass as much as possible. As a bonus you do not need joints, just a planetary gear system.

Why only high performance though.

A motor per wheel simplifies everything.

No diff, no CV joints, you don't need this, just a simple planetary gearbox.

You gain space, lower manufacturing costs (theoretically, assuming multiple motors doesn't offset the other cost reductions, although as you could base a 2wd and 4wd high performance version on the same motor, that's an even harder case to make).

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#134

Post by hwillis »

tlb wrote: post #90
benj111 wrote: post #65

Earlier quoted context omitted.

Why not? You'd have an added complication of making the shock absorber the pivot point, and attaching the motor to the top point. Or having a separate pivot point where the motor or wheel can slide up and down. This does raise the question of why not just attach the motor straight to the wheel. The standard response to that is a hand wavey "unsprung mass". But has it actually been tried and shown to be an issue?

Unsprung mass sucks. You don’t notice on smooth surfaces, but if you are cornering on a rough surface the wheel ends up losing contact with the ground after each bump. It’s extra-dangerous when its the rear wheels because the car can spin out.

It's not unsprung. The wheel and gear bit are the only unsprung parts; think of it like the motor attaching directly to the wheel bearing, and the wheel is able to move vertically on the bearing.

I think this only works with RWD, because the turning wheels can't be sprung without also having to rotate the springs.

It would be a better suspension (closer to racing suspensions) than standard, because wheels wouldnt toe in/out when they moved down/up. Looks expensive as hell though

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#136

Post by reactordev »

20after4 wrote: post #96
hooby wrote: post #47

The thing I see not mentioned in the article/video, is how the wheels can tilt/turn/angle - without needing a CV joint again. The designs seems to cover all the motion of the wheel in the suspension - but I don't see how this could accommodate steering. Is this for back wheel drive only? Curiously the animations shown in the video, show the uni wheel used in the front of a front wheel drive car - but without ever sho…

The next logical step would be integrate the motor directly into the wheel. With 4 wheel drive motors it wouldn't require huge motors, they could each be small enough to be packed right up against the inside of the wheel. I'm actually surprised they would even need the gearbox. Why not just put four Outrunner[1] motors, one on each wheel, and let the wiring be the only thing that has to flex when the wheel is steered…

I thought the same thing and was disappointed to see a planetary gear setup to turn an outer ring gear. Shame, we have come so far in EV motor design and yet Hyundai seems stuck on drivetrain power design.

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#138

Post by pbronez »

20after4 wrote: post #96
hooby wrote: post #47

The thing I see not mentioned in the article/video, is how the wheels can tilt/turn/angle - without needing a CV joint again. The designs seems to cover all the motion of the wheel in the suspension - but I don't see how this could accommodate steering. Is this for back wheel drive only? Curiously the animations shown in the video, show the uni wheel used in the front of a front wheel drive car - but without ever sho…

The next logical step would be integrate the motor directly into the wheel. With 4 wheel drive motors it wouldn't require huge motors, they could each be small enough to be packed right up against the inside of the wheel. I'm actually surprised they would even need the gearbox. Why not just put four Outrunner[1] motors, one on each wheel, and let the wiring be the only thing that has to flex when the wheel is steered…

Aptera is using in-wheel motors for their upcoming autocycle https://www.electrive.com/2022/06/23/aptera-orders-in-wheel-...

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#139

Post by metabagel »

reactordev wrote: post #136
20after4 wrote: post #96

Earlier quoted context omitted.

The next logical step would be integrate the motor directly into the wheel. With 4 wheel drive motors it wouldn't require huge motors, they could each be small enough to be packed right up against the inside of the wheel. I'm actually surprised they would even need the gearbox. Why not just put four Outrunner[1] motors, one on each wheel, and let the wiring be the only thing that has to flex when the wheel is steered…

I thought the same thing and was disappointed to see a planetary gear setup to turn an outer ring gear. Shame, we have come so far in EV motor design and yet Hyundai seems stuck on drivetrain power design.

My experience with a planetary gear in a bicycle is that it produces additional noise. I wonder if this would be noticeable for an automobile.

Re: Hyundai Uni Wheel electric drive system could revolutionize EV design

#140

Post by reactordev »

pxndxx wrote: post #117
20after4 wrote: post #96

Earlier quoted context omitted.

The next logical step would be integrate the motor directly into the wheel. With 4 wheel drive motors it wouldn't require huge motors, they could each be small enough to be packed right up against the inside of the wheel. I'm actually surprised they would even need the gearbox. Why not just put four Outrunner[1] motors, one on each wheel, and let the wiring be the only thing that has to flex when the wheel is steered…

Hub motors make wheels quite heavy, which means that there's more unsprung mass [1] in the vehicle, making it less responsive under acceleration/braking and more noisy and sensitive to vibrations. They're common in electric scooters, bikes and bicycles though. [1] https://en.wikipedia.org/wiki/Unsprung_mass

newer designs are silent, weigh about 2lbs or a little under a kilo, can produce upwards of 100nm torque at 1000w.
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