[HN Gopher] Hyundai Uni Wheel electric drive system could revolu...
___________________________________________________________________
Hyundai Uni Wheel electric drive system could revolutionize EV
design
Author : yread
Score : 246 points
Date : 2023-11-30 10:19 UTC (1 days ago)
(HTM) web link (www.autoblog.com)
(TXT) w3m dump (www.autoblog.com)
| thedrbrian wrote:
| So we could have a slightly bigger inside to the usual EV SUV.
| woo
| LargeWu wrote:
| A smaller battery would imply fewer resources required per
| vehicle, which will be important as demand for batteries
| increases.
| pornel wrote:
| Optimistically, we could have smaller cars without compromising
| on cabin space or storage.
|
| ...except when large SUVs are bought as a status symbol, or the
| race to drive the biggest tank on the road in defense from the
| other tanks or the road.
| estiaan wrote:
| I actually suspect part of the reason people keep buying
| larger cars is because larger cars are safer and sometimes
| get better safety scores because in a two vehicle collision a
| heavier vehicle will experience less acceleration in the
| crash. Also more space to absorb the impact, increasing the
| time over which the acceleration happens. This genuinely
| makes heavier and larger cars safer if they are designed
| properly and maintain the same braking performance, which is
| totally possible. However the issue is that a larger car is
| only a safety advantage if your car is large compared to
| other cars on the road, so if everyone else also buys heavier
| cars no one wins and pedestrians, the environment and so on
| all lose.
| acdha wrote:
| Also they're worse for everything else: the poor handling,
| especially with overpowering, means you're more likely to
| get in a crash, etc. Manufacturers have spent billions
| making them less likely to lose control, roll over, etc.
| but the physics are unforgiving.
|
| Drivers discount that because they like to think that those
| are things they control and just won't do, but every year
| some fraction of people will hit ice, be distracted or
| angry, etc.
| neuralRiot wrote:
| Bigger inside than modern SUVs? What does people transport? How
| many people ride regularly? What size are people?
| 4death4 wrote:
| Two adults, two kids in car seats, and a dog. With that, even
| a mid-size SUV has no space for cargo. If you drive a sedan,
| you have to leave the dog at home.
| neuralRiot wrote:
| Maybe if they don't put a foot-wide console in the middle
| there would be more space for people and cargo.
| IlPeach wrote:
| That's why station wagons and vans exist. SUVs do not
| provide more space, they just occupy more (on top of being
| dangerous to others)
| nradov wrote:
| Large station wagons no longer exist in the US market.
| The biggest one remaining is probably the Volvo V90,
| which is a nice car but can barely fit 5 people, and if
| you put a dog in the back then there's no room for cargo.
| It's also too expensive for most families; several large
| SUVs are actually cheaper.
|
| Minivans are a good option for some families. But they
| suck for towing trailers, and the ground clearance is
| terrible if you ever have to drive on a dirt road.
| doubleg72 wrote:
| Yeah really, like I'm gonna drive a minivan or station
| wagon out in the woods, or drive my four wheeler into the
| back when I need to take it somewhere.
| cnasc wrote:
| Well, this is why A6 Allroad and the newly bastardized
| E-Class wagon exist.
| xbar wrote:
| Right.
|
| I am all in on retrofitting a 1973 Ford Country Squire
| faux-wood-panel-in-green station wagon with a set of Kia
| uniwheels.
| steve_gh wrote:
| >> the Volvo V90, which is a nice car but can barely fit
| 5 people
|
| It's a lot bigger than my Prius, and that happily takes 4
| (5 with a squeeze) climbers with all their gear!
| redwall_hp wrote:
| The average number of occupants in a road vehicle is under
| two, yet they drive a massive tank. The typical pickup truck
| on the road also has an empty bed.
|
| Meanwhile, I can fit four people and some light cargo
| comfortably in my hatchback, or put all the seats down and
| carry more cargo than the typical SUV.
| semi-extrinsic wrote:
| I drive a small petrol powered MPV. It has a luggage capacity
| of 710 liters in the trunk with 5 passengers, 160 liters with
| 7 passengers, or 1900 liters with 2 passengers. Moreover the
| trunk is square, so I can go to Ikea and buy a whole new
| kitchen and fit it in the trunk. The cargo loading capacity
| with 5 adult passengers is 450 kg. It has a towing capacity
| of 1650 kg. It also has a large roof box. New price was
| around $30k depending on trim level.
|
| Now show me a modern EV that has similar specs, and you are
| talking about a large SUV that's up around the $100k price
| range.
|
| It's a simple fact that while modern EVs are often styled as
| SUVs, the inside is comparatively tiny since the battery pack
| takes up a lot of space.
| partiallypro wrote:
| I think more importantly is that you can add more battery
| capacity, making EVs much more competitive with gas vehicles.
| igor47 wrote:
| As a drivetrain nerd, this is awesome!
| mech987987 wrote:
| More mass inside the wheel increases unsprung weight and worsens
| some ride/suspension characteristics of a vehicle-
|
| that being said the tradeoff might not be too bad in this case.
| pornel wrote:
| It's just reduction gears, not the motor, so hopefully it can
| be made light enough. Shame that their promo didn't say a word
| about the mass.
|
| Quad-motor all-wheel torque vectoring sounds awesome tho.
| SkyPuncher wrote:
| My semi-educated guess is the heavier weight of the vehicle
| means the wheels can bear a bit more weight.
| sam_goody wrote:
| Is there some way that this or similar can be copied by all
| automakers, or is this all patented by Kia/Hyundai in such a way
| that most improvements are completely locked in?
| lovemenot wrote:
| Assuming the technology has actual value, Kia/Hyundai would
| likely be more incentivised to license it to other vehicle-
| makers, than to keep an exclusive license for themselves.
| metamet wrote:
| Especially considering how their name and brand are in the
| dumpster, and likely won't recover. Their cars will be
| targeted for break ins for a long time to come due to how
| viral the vulnerability is, regardless of whether or not the
| model is actually susceptible to it.
| almostnormal wrote:
| Manufacturers often buy gearboxes from suppliers instead of
| producing them. Hyundai does have Hyundai Transys as separate
| company for transmissions, and they would likely be happy to
| sell complete devices, not just licenses.
|
| https://en.m.wikipedia.org/wiki/List_of_Hyundai_transmission.
| ..
| olyjohn wrote:
| Maybe I can't tell from the video, or maybe they're not working
| on this yet... But what about the steering wheels? Surely the
| driveshaft will have to have a joint on it on the front wheels in
| order for the front wheels to turn? Also this doesn't look like
| it would deal with camber changes which are needed to keep your
| tires flat on the road when cornering...
| toss1 wrote:
| I also notice that unsprung weight was not mentioned. The
| "Uniwheel" clearly has advantages over CV joints, but it also
| looks like a significant increase in unsprung weight.
|
| They also gloss over "splitting the motor". It looks like 4
| individual wheel motors, which would indeed be optimal for the
| torque vectoring that they mention.
|
| Still, looks like a very cool development. I hope it works out
| to be a real advance
| bluGill wrote:
| It is a compromise - maybe slightly more unsprung weight vs a
| CV joint, but less than a hub motor.
| lttlrck wrote:
| Right, it seems like this will only work on non-steering solid
| axles, not with independent suspension.
| CodeWriter23 wrote:
| The front wheels still have a CV joint to facilitate steering.
| See 4:17 in the video.
| ChumpGPT wrote:
| This will work and you will still be able to steer.
| seltzered_ wrote:
| FWIW, there was recently a now-defunct car company (Lordstown
| motors) that utilized an in-wheel motor from the company Elaphe
| (https://in-wheel.com/en/technology/#in-wheel-motor-technolog...)
|
| I think the tradeoff is between more flexibility & fewer parts
| (no cv joints) but possibly more rolling resistance.
|
| But watch the video, this uni-wheel thing is different. It isnt
| an in-wheel motor, more of a cv-joint alternative?
| grogenaut wrote:
| unsprung weight I believe is also a big issue with hub motors
| esp as you get up to car size at speed
| jacquesm wrote:
| It is _the_ issue for in-hub motors. Solve that one and the
| world will beat a path to your door and shower you with
| money.
| throwaw33333434 wrote:
| The other issue is that potholes my get quite expensive.
| jacquesm wrote:
| Yes, the impact from a pothole can be substantial. Having
| an upset alignment is one thing, damaging the guts of an
| in-wheel motor is a totally different picture. But: when
| properly packaged and lightweight enough I think that is
| a secondary concern, you can design with that in mind
| given that it is more or less predictable from which
| direction and with which magnitude such an impact would
| happen. But every pound counts and the shocks+spring will
| have to be matched to the increased weight.
| benj111 wrote:
| Have you got a source. Everyone mentions this, but I've
| never come across anyone trying and failing.
|
| Motor scooters have unsprung motors, the motor is a
| significant proportion of the mass.
| jacquesm wrote:
| 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 relative to the vehicle body. The larger
| the mass the more energy gets imparted, and the more
| energy that gets imparted the bigger the impact and all
| that energy then needs to be absorbed so you'll need a
| stronger (and heavier) suspension system, roughly half of
| which is unsprung mass!, and a larger battery to
| compensate for the losses in the suspension which also
| adds weight (harder suspension -> bigger range but less
| comfortable ride). So it feeds back on itself and that's
| why it scales so poorly.
| benj111 wrote:
| 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?
| jacquesm wrote:
| 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.
| Beijinger wrote:
| You can buy a car powered with in-wheel motors here:
|
| We have developed the first production car to use in-wheel
| hub motors. https://mwmotors.cz/luka-ev/
|
| This car maybe too, as far as I understand it. A Russian
| UAZ on steroids:
| https://www.youtube.com/watch?v=RCOf_33C1qc
| jacquesm wrote:
| 815 Kg curb weight, aluminum chassis. It makes sense for
| a vehicle with that form factor (2 seater little sports
| car) but you can't really compare it with a full sized
| sedan, and note too that it has a tiny battery pack (22
| KWh), range is 'unofficial' 300 Km and likely will be
| adjusted down based on weight/pack size. The four motors
| together are less than half the rated power of what you'd
| find in a more conventional (is there such a thing
| already?) EV. But with that light total weight it will be
| a zippy little car anyway (most EVs are over-powered for
| their weight).
|
| Still, very impressive achievement and a nice testbed for
| this kind of tech, it may also make sense for motorcycles
| and for vehicles that are not meant for highway use.
| Beijinger wrote:
| What is the advantage of in-wheel motors?
| jacquesm wrote:
| That you save on a whole bunch of linkage and drive train
| components, four wheel drive without the associated
| complexity, that you can integrate the wheels, motors and
| brakes, cleaner airflow under the car and that the system
| as a whole can be lighter weight than the same package
| with motors near the centerline of the car, so you get
| somewhat better range. It also gives more space for
| batteries and/or more storage space. That's why
| manufacturers will keep trying to get this done, if they
| can get it to work cost effectively and without impacting
| that unsprung weight too much it will give them an
| advantage.
| Beijinger wrote:
| "cleaner airflow under the car"?
|
| Why should the airflow be cleaner?
| jacquesm wrote:
| Because that's automatically better range, cleaner
| airflow is less drag. That's why cars have all of those
| underbody skirts, it improves their mileage (and helps
| with not fouling up the more sensitive bits).
| 20after4 wrote:
| I think they mean smoother or less turbulent airflow, not
| cleaner in the sense of less pollution.
| tomcam wrote:
| That Luka has some pretty interesting tech and is so
| sharp-looking. I hope it's a massive success.
| jacquesm wrote:
| Gorgeous little car! Reminds me of the sports cars of the
| 50's and 60's. But they apparently dropped the hub
| motors.
| daemonologist wrote:
| There's another startup, Aptera, which is ostensibly still
| working towards producing a vehicle using Elaphe hub motors.
| Interestingly they are efficiency focused so I wonder how the
| motors are working out for them in that respect.
| jpecar wrote:
| Very well in fact, you have to look at the whole drivetrain
| efficiency, not just the motor. Elaphe has a webinar on this
| topic on their youtube channel, look it up.
| pkulak wrote:
| Yeah, it's not a hub motor, so the unsprung weight should be a
| lot less.
| robocat wrote:
| I'll be interested to see if the Elaphe in-wheel motors are
| designed into a high ground clearance 4WD. The site says added
| weight 25-65kg but maybe that is two motors for 2WD? A grunty
| 4WD tyre like a 33 inch (33/12.50R20) might weigh 33kg per tyre
| (not sure if rim weight), so the additional unsprung weight for
| the motor is comparatively reasonable per wheel? In-wheel would
| allow the suspension to be designed for much better clearance
| (since no shafts). Tyre might have a speed rating of Q (99mph).
| HeyLaughingBoy wrote:
| Pretty sure I measured a 33" BF Goodrich MT (mud traction)
| tire on an aluminum 15x8 wheel at 93lbs. However, it was
| about 25 years ago so memory's probably a bit fuzzy.
| Beijinger wrote:
| Is Lordstown defunct?
|
| As far as I know, this Czech company uses in-wheel motors:
|
| https://spartan.mwmotors.cz/ev-traditional-technologies/
| 20after4 wrote:
| Looks like they already abandoned that idea:
| https://mwmotors.cz/luka-ev-traditional/
| jacquesm wrote:
| Interesting, I wonder what the technical reasons were for
| the change. It has gone this way with pretty much every hub
| motor concept that I've seen so far, either they don't make
| it of the drawing board, or they end up abandoned at the
| prototyping stage. The GP had me wondering if someone had
| actually managed to conquer it but alas that doesn't seem
| to be the case. It's a neat little car though, reminds of
| the Daihatsu Copen that I had at some point.
| bluGill wrote:
| unsprung weight is what every engineer who looks at a hub
| motor will think. The less of that the better. Engineers
| would love to move the brakes off the wheel (there are
| safety reasons not to, but it would make the car handle
| notably better if you did)
| jacquesm wrote:
| Citroen DS/ID had that, SM as well. CX and XM did not.
| riversflow wrote:
| Don't even need to be an engineer just go ride some nice
| bikes, it is an amazing and very tangible lesson in the
| cost of unsprung weight.
| metadat wrote:
| Cc can you still do a burnout with these? It looks kind of
| fragile.
| prmoustache wrote:
| Have you ever looked at a gearbox?
| kelseyfrog wrote:
| Disappointed that they didn't explain how steering works. Seems
| like a major oversight.
| ChumpGPT wrote:
| A very simple and incomplete explanation. You have an
| electrical or hydraulic steering rack that spans your vehicle
| just behind the wheels behind your engine and close to the
| bottom. It connects to each wheel with a tie rod that has a
| ball joint on the end (not to be confused with your actual ball
| joints that are part of your control arms). When you turn your
| steering wheel it moves the tie rods to steer the car. Steering
| doesn't really have anything to do with the CV Joints or power
| to your wheels, it is a separate system.
| bluGill wrote:
| >Steering doesn't really have anything to do with the CV
| Joints or power to your wheels
|
| When you turn the wheels the axles need to flex somehow
| around that rotation. This is one of the things CV joints do
| well: they can handle not just moving up and down, but also
| the wheel turning left/right. This thing is a bunch of gears
| and seems to handle only wheels moving up and down and not
| turning.
| ChumpGPT wrote:
| My understanding is they can't shorten the CV Shaft/Joint because
| it causes problems.If they can move it into the wheel hub, it
| allows them to make the motor smaller which is where they save
| the room. By taking one big motor to drive both front or rear
| wheels, they now have smaller ones much closure to each
| individual wheel. This reconfiguration leaves more room for
| interior space or extra batteries.
| chris_va wrote:
| Seems like it's only in-plane motion, so the wheel can't
| tilt/turn?
|
| I assume that means they still need a CV joint for the front
| wheels regardless, and that it gains no camber when cornering.
| ChumpGPT wrote:
| Most likely they will have a ball joint (like the current inner
| CV Joint shaft has) on the end of the shaft that connects to
| the device in the wheel hub.
| modeless wrote:
| One of their animations indeed showed a CV joint in between the
| motor and the device. But you only need one and it can be
| absolutely straight when the car is not turning so the
| efficiency should be good.
| estiaan wrote:
| Correct me if I'm wrong here but this is just sort of an
| alternative to a cv joint, sort of because it can't handle
| rotation. It also has nothing to do with EVs specifically, a ICE
| could use this.
| ChumpGPT wrote:
| An ice could use this but there is no real purpose. The whole
| goal was to make the electric motor smaller and closure to each
| wheel so there is more room for other things.
| estiaan wrote:
| Yeah fair, though ICE cars also benefit from more space.
| Maybe I'm just salty because I had to watch 10 minutes of
| their video just for a clip that was about 1s long that
| actually shows what it is instantly, they should have lead
| with that...
| zardo wrote:
| You probably don't want to use a small ICE at each wheel
| though.
| bluGill wrote:
| An ICE still needs all the shafts connecting the wheel to
| the engine.
| nytesky wrote:
| I honestly thought that Tesla made a version of their sedan which
| had 4 motors -- one for each wheel. When I looked into it, all I
| can find is that the CyberTruck should have 4 motors. Wasn't
| there a quad and duel version of the sedans -- what are they
| referring to?
| eightysixfour wrote:
| They have dual and triple, the triple (Plaid) has two motors on
| the rear if I remember correctly.
| hooby wrote:
| 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?
| husam212 wrote:
| Maybe the motor is supposed to turn with the wheel, that
| doesn't sound like a good idea.
| justinclift wrote:
| That'd make the motor the pivot point. No idea if that's good
| or bad though. :)
| benj111 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| Cars already have traction control, and there's probably
| a thermal cutout already in the motor.
| tlb wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| > 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 wrote:
| 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 wrote:
| 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 wrote:
| Brake lines are a solved problem. Water lines wouldn't be
| any more difficult. If air cooled it could be a sealed
| unit.
| DennisP wrote:
| 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.
| deeg wrote:
| I've been under the impression that putting the motor on
| the wheels increases gyroscopic forces which can cause
| handling problems.
| benj111 wrote:
| It isn't rotational mass though, just unsprung.
| jillesvangurp wrote:
| 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 wrote:
| 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.
| audunw wrote:
| 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 wrote:
| 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 wrote:
| 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
| idiotsecant wrote:
| Hub motors have existed for a long time. The issues you'll
| have to overcome are the same.
| geoduck14 wrote:
| 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
| emilecantin wrote:
| It's been invented in Quebec 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%A9be... (in French only, sorry!)
| pxndxx wrote:
| 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
| reactordev wrote:
| newer designs are silent, weigh about 2lbs or a little
| under a kilo, can produce upwards of 100nm torque at 1000w.
| reactordev wrote:
| 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.
| metabagel wrote:
| 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.
| reactordev wrote:
| I'm sure it would. Any mechanical gears will produce
| noise at higher velocities so curious what this sounds
| like myself. Electric hub motors produce a wine from the
| EMF that is audible but that's a different sound (the hum
| of a tesla going by) or a Surron that uses a radial flux
| motor with chain link gears (this is my favorite hobby
| design, chain gears are super useful).
| pbronez wrote:
| Aptera is using in-wheel motors for their upcoming autocycle
| https://www.electrive.com/2022/06/23/aptera-orders-in-
| wheel-...
| atomicUpdate wrote:
| > 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.
| mulmen wrote:
| How do they keep this clean? A CV boot is compact, flexible, and
| fixed to the shaft. What kind of dust shield can cover the big
| vertical gap and handle a spinning shaft?
| esaym wrote:
| Yea I don't see how this will work. Just a little bit of sand
| or water in there and it is a goner.
| trabant00 wrote:
| Unsprung weight is a clear disadvantage to the solution. It will
| significantly affect ride quality, no way around that. Those
| planetary wheels look more fragile than the traditional solution.
| You also need to keep that entire thing closed and lubed as well
| and even so it looks like added friction, wear and a more
| expensive repair job when it goes bad.
|
| All that being said it could be a good niche solution. A small
| city car would benefit from the space savings and does not need
| to go high speeds over less than perfect roads. Nor does it rack
| up that many miles in wear and tear. In general I think electric
| will bring more diversity in car designs depending on purpose.
| nixass wrote:
| > Unsprung weight is a clear disadvantage to the solution. It
| will significantly affect ride quality, no way around that.
| Those planetary wheels look more fragile than the traditional
| solution. You also need to keep that entire thing closed and
| lubed as well and even so it looks like added friction, wear
| and a more expensive repair job when it goes bad.
|
| But uni-wheel changes paradigm!
| JoeAltmaier wrote:
| At least they are nine identical gears? So just keep a barrel
| of them handy!
| bluGill wrote:
| I expect the bearings wear out before the gears. So just
| replace the whole thing. Then rebuild it with new gears and
| bearings later.
| nabilhat wrote:
| 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 will be turning at a large multiple of wheel speed, so
| will require roller bearings except for low power and speed use:
| a radial and thrust bearing for each end of each gear, or 22 of
| each per wheel. Increasing torque also increases the level of
| thrust support required for the moving gear carriers handling all
| of those helical gears.
|
| It's a neat idea for highly space constrained applications that
| have to package a drivetrain very close to a wheel, which does
| end up being a rather niche use case. Mars rovers, perhaps.
| Trying to compete against CV joints in passenger vehicles with
| this would be quite difficult.
| benj111 wrote:
| 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 don't already have them)
| nabilhat wrote:
| If the drive source is attached directly to the uniwheel,
| then handling radial drive inputs isn't required and the
| uniwheel isn't necessary. It's effectively a hub motor with
| reduction gears at that point. Once the motor is mounted
| remotely from the uniwheel and the uniwheel is handling
| radial offsets, then we need to prevent the axle from getting
| pushed around radially. Rotating shafts that deflect
| introduce off-balance vibration and destructive mechanical
| loads. If the motor is located very near the uniwheel,
| keeping the shaft's free length very short, the motor's
| output bearing does effectively provide that support. Then
| we're only constrained by relocating the suspension elements.
|
| Thrust bearings are for the gears. The depictions show
| helical gears, which would surely be necessary when operating
| at transportation speeds for noise reasons. Helical gears
| experience axial forces, which would need to be handled for
| each gear. Mainly on one side for ICE drivetrains, since
| coasting loads are small, so one side could get away with a
| ground and hardened rub surface. EV's using regenerative
| braking would need robust thrust handling on both sides.
|
| Herringbone gears would eliminate the axial thrust issue, at
| substantially more expense. The easiest method is to separate
| the gear areas with a central runout groove so you'd have a
| hope of grinding in a decent surface on the faces, then it's
| only a little more than double the work; effectively cutting
| two gear shapes per gear plus the runout.
|
| https://en.wikipedia.org/wiki/Herringbone_gear
| governmentdude wrote:
| > 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).
| aidenn0 wrote:
| > Worth noting, placement at the wheel is somewhat arbitrary
|
| You're suggesting placing the ring-gear in the chassis and
| running the axle to the wheel? That would involve two reduction
| gearsets in the chassis instead of the current "one plus a CV
| gear," which kind of defeats the purpose of reducing chassis
| space usage.
|
| > The gears will be turning at a large multiple of wheel speed,
| so will require roller bearings except for low power and speed
| use: a radial and thrust bearing for each end of each gear, or
| 22 of each per wheel. Increasing torque also increases the
| level of thrust support required for the moving gear carriers
| handling all of those helical gears.
|
| I imagine the final product would use herringbone gears, since
| the large number of thrust bearings would all add to unsprung
| weight.
| wildekek wrote:
| An axial flux wheel motor is a much simpler and less fragile
| design for ev's. I'd like to see more experiments with that.
| BHSPitMonkey wrote:
| Regardless of the merit or practicality of the idea, I really
| loved the video and the animations. I'd happily watch a series of
| cars and other complex machines explained in the same style.
| kibwen wrote:
| The video is good, but I couldn't help but draw a parallel to
| the famous Rockwell Retro Encabulator:
| https://youtube.com/watch?v=RXJKdh1KZ0w
| konart wrote:
| I wonder how long will it take this to break if use on real (not-
| so-perfect) roads.
| JoeAltmaier wrote:
| My first thought, too. All those unsealed tiny gears. One
| fragment of metal filing in there? Perhaps a cascade failure of
| teeth chipping and flinging fragments until total breakdown.
|
| Reminds me of the head of a waterpic toothbrush - a packet of
| tiny gears, the weakest point in the device, constantly wearing
| out.
| tlb wrote:
| This wouldn't have worked for ICE cars, because in order to have
| a reasonable range of up-and-down movement the gear ratio needs
| to be quite high (ie, the pinion gear has to be much smaller than
| the ring gear). It's 6.2:1 in the article, about 2x what's
| appropriate for the top gear on an ICE car.
| teamonkey wrote:
| I wasn't clear why this couldn't be used on all vehicles but
| that makes sense, thanks.
| bluGill wrote:
| In and ICE you have the transmission - just put different gear
| ratios in the transmission if you need to get a different
| output speed.
|
| I think this could have worked with an ICE, but there is no
| real point: the CV joint is simple and the advantages to this
| don't apply when you have a single large power source.
| audunw wrote:
| This mostly makes sense if you have four individual motors
| right next to the wheels, that turns with the wheel. That's
| obviously also not viable with ICE cars.
| KaiserPro wrote:
| I love innovation.
|
| There still needs to be a CV joint to allow steering, but short
| of hub motors[1] There isn't much you can do about that.
|
| What I would be interested to see is how lubrication works. Do
| you think they just have a bunch of oil in the bottom and rely on
| centrifugal force to fling it to the ring gear? Then let surface
| tension transmit it to the sun gear?
|
| [1] They are heavy and heavy wheels affect ride quality, as
| suspension works essentially by allowing a light wheel to move up
| and down dampening against the mass of the heavy body. If the
| body is light, then you need to have less dampening, which means
| more shock/impulse is transferred into the main body of the car/
| tlb wrote:
| The hard thing with lubrication is sealing it so it doesn't
| leak. Considering the pinion gear and shaft moves in 2 axes
| relative to the housing, that could be tough.
| audunw wrote:
| > There still needs to be a CV joint to allow steering
|
| Naw, because if you look closely in the video you can see that
| the motors turns with the wheel. With small EV motors that's
| not unreasonable.
|
| Presumably the motor is free to tilt up and down a bit as well
| to deal with changing camber.
|
| > but short of hub motors[1] There isn't much you can do about
| that.
|
| I mean, it is pretty much a hub motor that has been decouple in
| the vertical motion so it doesn't contribute to unsprung mass,
| and with a good reduction gear as a bonus.
| spacecadet wrote:
| More or less a portal. But neat.
| nottorp wrote:
| Hmm steering and ride quality questions aside - i'm no mechanical
| engineer...
|
| How much would damaging a wheel cost?
| layer8 wrote:
| I was wondering if it would increase the incentive to steal car
| wheels.
| nottorp wrote:
| s/wheels/engines in this case :)
| drsopp wrote:
| Looks similar to https://507movements.com/mm_222.html
| iampivot wrote:
| I guess they will still need a cv joint, just because wheels get
| out of alignment all the time.
|
| That aside, it would interesting if someone made a 3d model one
| could print to try this out at home for small robots.
| mtrovo wrote:
| Looking at the video on their website it seems the EV motors
| are supposed to be mounted directly into each wheel, then you
| only need to account for oscillations on the X and Y axis.
| bluGill wrote:
| I got that impression at first, but looking closer, the motor
| isn't in each wheel. It is on the frame of the car - just
| much closer to the wheel than a CV joint allows.
| redandblack wrote:
| Will competitive racing adopt this? Assuming they seek out every
| advantage. Maybe their adoption will move this further to
| consumer space
| 55555 wrote:
| I don't know anything about cars but the video said the max
| speed was 120km/hr
| bluGill wrote:
| (Assuming the max speed issues the other post mention are
| resolved!).
|
| For a regular car this is useful because the space all the
| shafts taking power from the ICE to the wheels can be used for
| something else. For a race car there is plenty of space for
| those shafts and you don't have anything else to put into that
| space if you could. This the reason this was developed doesn't
| apply to race cars.
|
| Of course for race cars they are concerned about weight and
| performance. Not having those shafts may be better for weight
| and thus worth it (assuming a EV race care), or it might not
| make a difference. This might have some other advantage in
| racing applications that the designers haven't even realized
| yet.
| Justsignedup wrote:
| A question to someone who understands the physics involved
| here... Does this benefit ICE cars as well? Is this a generally
| good tech that reduces weight / space / cost for cars in general?
| ChoGGi wrote:
| Probably not, this is using four motors that are close to each
| wheel. ICE cars route energy from a central motor.
| Justsignedup wrote:
| can this not use a single center motor with a shaft, just
| replacing the current structures? It won't be that big
| savings as it is in electric vehicles, but it could reduce
| some complexity and unify architecture of electric and ICE?
| ElectricalUnion wrote:
| This proposed power transfer mechanic linkage can't handle
| angular differences between the power plant and wheel, so
| you would end up with broken mechanic linkages and torn
| shafts.
|
| Non-spinning-shaft power transmission (doesn't really need
| to be electric, could as well be something like fluid power
| transmission like hydraulic or pneumatic power) dodge this
| by putting the power plant in a way the angle between power
| plant and wheel can't change.
| bluGill wrote:
| If you have a single central motor and shaft, then existing
| CV joints work just fine. This is useful when you want to
| have a separate motor for each wheel, because it lets you
| put those motors closer to the wheel. There is then space
| in the middle (where the shafts went with the single
| central engine/motor) that can be used for something else
| not related to the drive train.
| ElectricalUnion wrote:
| As ICE cars are right now, no, because unlike electric engines,
| combustion engines and the clutch can't be made efficient,
| cheap and compact all at once.
|
| If you have to end up with 4 "normal sized engines" or "normal
| sized clutches" to implement this, you now are in net gain of
| wasted weight/space.
| wasm123 wrote:
| The HUB takes up all of the space where you disk or drum brakes
| would be. ICE cars don't benefit from regenerative braking so
| you'd have to come up with another solution of how to stop the
| car.
| adolph wrote:
| Inboard brakes exist in specialty applications such as F1 and
| vehicles with portal axels like the Humvee.
| bluGill wrote:
| Not really. You can use this on an ICE, but this really is
| useful (compared to a CV joint) when you have very short axles.
| On a ICE the axle needs to cross the entire width of the car
| anyway in some form, so you may as well use a CV joint. With an
| EV they want to use 4 small motors as close to each wheel as
| possible and thus free up space in the middle of the car where
| the axle used to go. A CV joint has a longer minimum length
| axle compared to this, so the motor has to go that much closer
| to the middle. When they use this they get useful space in the
| middle of the car (between the motors) that can be used for
| something else.
| Tor3 wrote:
| It looks interesting. But how do you change wheels? From the
| video there's no obvious way, and I'll assume the wheels must be
| very expensive - if all we see in the video is built in. Where I
| live I change wheels twice a year, for winter and summer (vastly
| different tires, and there's no way around that). So, to start
| with, I have to buy 8 wheels (9 actually, as my car has a spare
| wheel too, and that's also necessary here). That will cost a lot,
| it seems, and then - can I even change wheels?
| zdragnar wrote:
| You could probably get away with changing the tires, rather
| than replacing the entire wheel.
|
| The more interesting question to me is what happens if you get
| a flat tire? Does everyone need to carry a spare uniwheel, or
| wait to get towed?
| kwhitefoot wrote:
| Most people wait to get towed these days on those rare
| occasions that they get a flat tyre. In over forty years of
| driving I've only had three flats. One I changed the wheel,
| the second I just drove slowly for twenty miles because the
| tyre was at the end of its useful life anyway, the third was
| on a narrow rural road on a slope so in the winter in the
| dark so I just waited for the car to be taken away on the
| back of a lorry.
|
| A lot of cars don't have a spare wheel now, why would they
| start carrying one in the future?
| zdragnar wrote:
| I have yet to buy a car without one, but I suppose that'll
| be changing soon enough.
| bluGill wrote:
| Back in the 1950s tires went flat often, so a spare that
| you knew how to put on was a must. These days tire
| technology is much better and so getting a flat is rare
| kit does happen of course, but it is not very common.
| Many cars will go through their entire life without using
| the spare even once. Since a spare takes up a lot of
| space and weight, it makes sense to get rid of it if it
| isn't needed much. Tow trucks have always existed, just
| call one to fix the tire when you have issues.
| dagmx wrote:
| Most EVs don't carry a spare tire anymore due to weight and
| space
| pmdarrow wrote:
| It looks like the wheel is mounted on a hub, just like normal
| cars.
| c54 wrote:
| Adding to this: when you change your tire you're not
| replacing your brake assembly.
| simne wrote:
| Excellent for sales/mechanic! Now wheel will cost more than
| chasis $)
| simne wrote:
| Well, in reality, Forward wheel drive become typical, when it
| become cheap.
|
| And gears close to wheel used in off-road vehicles looong time,
| to create more clearance but they was headache, because need
| much additional mechanic time, and there was huge losses.
| metabagel wrote:
| How much additional noise will this produce compared to CV
| joints?
| mannykannot wrote:
| My first question, on seeing a picture of the drive, was how this
| allowed the wheel to be turned for steering - this is, after all,
| the difficult part of driving the front wheels (if you are not
| using an in-hub motor) and is why a CV joint, and not just any
| universal joint, is needed (when turning sharply, the wheel axis
| is nowhere near parallel to the motor axis.) Neither the article
| nor the video mentioned steering, however, and neither did the
| video demonstrate it, despite showing an all-wheel drive
| installation. It even has an animation of vehicles going around a
| curve with all the wheels resolutely pointing straight ahead!
| atomicUpdate wrote:
| It also (conveniently) ignores that a wheel's camber changes
| when it moves up and down, due to suspension geometry. It's
| certainly an interesting idea for sure, and any efficiency
| improvements here could help ICE vehicles as well. There's
| likely a reason these are just renders in a video though.
|
| Hopefully they are able to work out these details, and
| eventually provide a real physical demonstration of these use-
| cases.
| Descon wrote:
| I just assumed that the drive shaft between the motor and
| their uni wheel system would have a universal joint in it
| that would solve both of these issues, would it not?
| https://en.m.wikipedia.org/wiki/Universal_joint
| audunw wrote:
| In the video you can see the motors turning with the wheels. So
| there's no problem there at all.
|
| I think this would make most sense with an axial flux motor.
| That'd keep the package quite compact.
|
| I'm guessing the camper changes mentioned could also be handled
| by the motor pivoting up and down as well. But I can't say for
| sure if that makes sense.
| mannykannot wrote:
| I just replayed it on a big screen, and I see what you are
| saying - it is visible between about 5:15 and 5:20.
| einpoklum wrote:
| The video says the motivation is clearance for the vehicle's
| cabin. Does this have benefits in term of energy efficiency?
| Longevity/reduced wear? Overall weight?
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