8 ms·

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 th

by hooby 3y ago

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 showing how the wheels steer. How is that supposed to work?

deleted 3y ago
[deleted]
husam212 3y ago
Maybe the motor is supposed to turn with the wheel, that doesn't sound like a good idea.
- justinclift 3y ago
  That'd make the motor the pivot point. No idea if that's good or bad though. :)
- benj111 3y ago
  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?
  - hooby 3y ago
    Well, if the motor is unsprung mass, you no longer need this contraption at all, and you can just directly connect the motor to the wheel... So, that's probably not it.
  - dist-epoch 3y ago
    I'm no mechanical expert, but I wonder how you prevent damage to the motor if the wheel encounters an obstacle when it tries to rotate (against a curb for example) or if it's forced to rotate by an exterior force.
    - benj111 3y ago
      Cars already have traction control, and there's probably a thermal cutout already in the motor.
  - tlb 3y ago
    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.
    - hwillis 3y ago
      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
      - schiffern 3y ago
        tlb was replying to this part: "This does raise the question of why not just attach the motor straight to the wheel. The standard response is ...unsprung mass"
  - consp 3y ago
    > 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.
    - benj111 3y ago
      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).
      - lstodd 3y ago
        Everyone says "unsprung mass" but you also have to provide cooling without ingesting all the dirt and water off the road. It's not that simple.
        benj111 3y ago
        Brake lines are a solved problem. Water lines wouldn't be any more difficult. If air cooled it could be a sealed unit.
  - DennisP 3y ago
    The wheel can move up and down relative to the motor, so you can still attach a shock absorber to the wheel, without the motor being involved. The video shows this at 2:36.
    - benj111 3y ago
      Yes my point is, why have the complication of this set up at all.
      - DennisP 3y ago
        To me it doesn't seem any more complicated than a pair of CV joints. Benefits according to the article: "reduced packaging size, improved ride quality, greater durability and, importantly, increased efficiency."
  - deeg 3y ago
    I've been under the impression that putting the motor on the wheels increases gyroscopic forces which can cause handling problems.
    - benj111 3y ago
      It isn't rotational mass though, just unsprung.
jillesvangurp 3y ago
Probably a combination of having some way to rotate wheel + motor around some axis and the ability to simply vary the motor speeds on each wheel independently.
- hooby 3y ago
  But then you need empty space around the motor, so that it can rotate there. That somehow seems a weird choice for a device that's all about improving space efficiency.
  - deleted 3y ago
    [deleted]
  - audunw 3y ago
    You can see the motors turning in some empty space in the video yes. But it’s mostly in the space that would be taken up by the CV joint. Just look closer at the animations in the video if you want to see how the space is being used
chakintosh 3y ago
In the video there was a brief animation at 5:06 showing the entire motor rotating with the wheel. So the CV joint (if you can call it that) wasn't really removed, just moved to the part between the motor and the chassis.
20after4 3y ago
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. 1. https://en.wikipedia.org/wiki/Outrunner https://en.wikipedia.org/wiki/Outrunner
- idiotsecant 3y ago
  Hub motors have existed for a long time. The issues you'll have to overcome are the same.
- geoduck14 3y ago
  I agree, hub motors [0] have been around for over a decade and are used to power EVs in races. I don't really know why these aren't being considered here. [0]https://www.explainthatstuff.com/hubmotors.html https://www.explainthatstuff.com/hubmotors.html
- emilecantin 3y ago
  It's been invented in Québec in the 90s[1] by our national utility company, they had demo cars and everything. Then it was all swept under the rug after some secret deals with car manufacturers... 1. https://fr.wikipedia.org/wiki/Moteur-roue_d'Hydro-Qu%C3%A9bec https://fr.wikipedia.org/wiki/Moteur-roue_d'Hydro-Qu%C3%A9be... (in French only, sorry!)
- pxndxx 3y ago
  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 https://en.wikipedia.org/wiki/Unsprung_mass
  - reactordev 3y ago
atomicUpdate 3y ago
> The designs seems to cover all the motion of the wheel in the suspension - but I don't see how this could accommodate steering. It actually doesn't. A wheel's camber changes as it moves up and down, which is why race cars typically have negative camber when going straight, so the tire's entire contact patch is used when going around a turn, which compresses the suspension of the outside wheel. This design doesn't appear to handle this case at all. I'm not sure how a traditional suspension setup could be modified only move a wheel up and down, without any change in the camber, considering the fixed attach points of the various control arms.

by hooby 3y ago

deleted 3y ago

[deleted]

husam212 3y ago

Maybe the motor is supposed to turn with the wheel, that doesn't sound like a good idea.

justinclift 3y ago
That'd make the motor the pivot point. No idea if that's good or bad though. :)
benj111 3y ago
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?
- hooby 3y ago
  Well, if the motor is unsprung mass, you no longer need this contraption at all, and you can just directly connect the motor to the wheel... So, that's probably not it.
- dist-epoch 3y ago
  I'm no mechanical expert, but I wonder how you prevent damage to the motor if the wheel encounters an obstacle when it tries to rotate (against a curb for example) or if it's forced to rotate by an exterior force.
  - benj111 3y ago
    Cars already have traction control, and there's probably a thermal cutout already in the motor.
- tlb 3y ago
  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.
  - hwillis 3y ago
    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
    - schiffern 3y ago
      tlb was replying to this part: "This does raise the question of why not just attach the motor straight to the wheel. The standard response is ...unsprung mass"
- consp 3y ago
  > 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.
  - benj111 3y ago
    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).
    - lstodd 3y ago
      Everyone says "unsprung mass" but you also have to provide cooling without ingesting all the dirt and water off the road. It's not that simple.
      - benj111 3y ago
        Brake lines are a solved problem. Water lines wouldn't be any more difficult. If air cooled it could be a sealed unit.
- DennisP 3y ago
  The wheel can move up and down relative to the motor, so you can still attach a shock absorber to the wheel, without the motor being involved. The video shows this at 2:36.
  - benj111 3y ago
    Yes my point is, why have the complication of this set up at all.
    - DennisP 3y ago
      To me it doesn't seem any more complicated than a pair of CV joints. Benefits according to the article: "reduced packaging size, improved ride quality, greater durability and, importantly, increased efficiency."
- deeg 3y ago
  I've been under the impression that putting the motor on the wheels increases gyroscopic forces which can cause handling problems.
  - benj111 3y ago
    It isn't rotational mass though, just unsprung.

jillesvangurp 3y ago

Probably a combination of having some way to rotate wheel + motor around some axis and the ability to simply vary the motor speeds on each wheel independently.

hooby 3y ago
But then you need empty space around the motor, so that it can rotate there. That somehow seems a weird choice for a device that's all about improving space efficiency.
- deleted 3y ago
  [deleted]
- audunw 3y ago
  You can see the motors turning in some empty space in the video yes. But it’s mostly in the space that would be taken up by the CV joint. Just look closer at the animations in the video if you want to see how the space is being used

chakintosh 3y ago

In the video there was a brief animation at 5:06 showing the entire motor rotating with the wheel. So the CV joint (if you can call it that) wasn't really removed, just moved to the part between the motor and the chassis.

20after4 3y ago

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. 1. https://en.wikipedia.org/wiki/Outrunner https://en.wikipedia.org/wiki/Outrunner

idiotsecant 3y ago
Hub motors have existed for a long time. The issues you'll have to overcome are the same.
geoduck14 3y ago
I agree, hub motors [0] have been around for over a decade and are used to power EVs in races. I don't really know why these aren't being considered here. [0]https://www.explainthatstuff.com/hubmotors.html https://www.explainthatstuff.com/hubmotors.html
emilecantin 3y ago
It's been invented in Québec in the 90s[1] by our national utility company, they had demo cars and everything. Then it was all swept under the rug after some secret deals with car manufacturers... 1. https://fr.wikipedia.org/wiki/Moteur-roue_d'Hydro-Qu%C3%A9bec https://fr.wikipedia.org/wiki/Moteur-roue_d'Hydro-Qu%C3%A9be... (in French only, sorry!)
pxndxx 3y ago
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 https://en.wikipedia.org/wiki/Unsprung_mass
- reactordev 3y ago

atomicUpdate 3y ago

> The designs seems to cover all the motion of the wheel in the suspension - but I don't see how this could accommodate steering. It actually doesn't. A wheel's camber changes as it moves up and down, which is why race cars typically have negative camber when going straight, so the tire's entire contact patch is used when going around a turn, which compresses the suspension of the outside wheel. This design doesn't appear to handle this case at all. I'm not sure how a traditional suspension setup could be modified only move a wheel up and down, without any change in the camber, considering the fixed attach points of the various control arms.