this post was submitted on 02 Dec 2023
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I'd be concerned with the amount of unsprung weight this adds, too. You're basically taking the transmission and adding that mass to the hub. Seems like it would be pretty crashy on rough surfaces.
Isn't the ring gear the wheel body (or whatever it's called), that is, even a fixed axle would have weight there, the gearteeth even provide stiffness. CV joints also contain unsprung mass, I'd say there might be a bit of a difference but nothing drastic. With modern fancy biomimetic wheel body geometries and everything you'll probably definitely be lighter than 80s steel rims. What happened to spoked wheels, anyway.
The CV only contributes half it's mass to unsprung weight, and this system still requires a drive shaft and either a CV or u-joint. But with more mass at the hub.
Typical hubs are still lighter than this, because this setup still requires the hub structure, it's just adding gearing out there.
Half of the hub is unsprung, the transition between sprung and unsprung is at those fancy articulating planetary gears. The drive shaft is definitely sprung, it and the motor is completely static relative to the battery and everything.
Yep.
Trucks used these as far back as pre-WWII. It a great solution for off road vehicles to gain clearance. At low speeds, even universal joints work fine for this setup, because the shaft rotates at 1/3 wheel speed, like a drives haft does going into a differential.
This puts a diff at each wheel.
Edit: These are called Portal Gears
Not quite portal gears, that has the input shaft fixed at the top. This is like an adjustable portal gear.
Meh, it's still a portal hub, where you put the input shaft is a minor difference. It's still putting the gearset in the hub, increasing the total weight of the vehicle, and increasing unsprung weight.
Calling it a new thing is a lie. All they've done is switch it to planetary gears. I'd bet lots of money this was tried a long time ago, and was shelved in favor of an offset input shaft.
I noticed they conveniently didn't talk a lot about steering..
The claim of "one wheel drive" I think is meant to highlight what happens if traction is lost. It sounds like something I have heard on 4wd off-road forums. I agree the phrase "one wheel drive" is perhaps not a great way to explain the disadvantages of differentials vs limited slip differentials vs locking differentials vs individually driven wheels.
The idea of "one wheel drive" as I have seen it used, is that in a vehicle with one powered axle assembly (what we normally call 2wd-- either front or rear wheel drive) is that if you lose traction with either drive wheel, the vehicle no longer moves because all power is diverted to the slipping wheel.
If you have a limited slip differential, there is a limit to how much power is diverted to the slipping wheel. With a locking differential, you only stop moving if you lose traction to both drive wheels.
Anyway...
The design is really interesting.
You also bring up a good point about how camber changes with suspension position. Also the effective track width changes, such as with my 4Runner which has upper and lower control arms, a Double wishbone suspension. If the motor remains in a fixed position, the wheel will move onboard and outboard relative to the motor depending on suspension location.
I don't quite get how these two effects are addressed with this new design. Or are the suggesting a different suspension technology that they didn't discuss?
As for steering, I wonder if the design rotates the motor along with the wheel. In that case no CV is needed but I would guess there are some downsides to such a design.
I agree the video seems kind of... premature. The mechanism is cool but I don't get the sense that its applications haven't exactly been nailed down yet.
The axis of the motor doesn't need to be parallel to the axis of the wheel.
If the axis of the motor is vertical, you could use a ring and pinion gear to transfer the torque to the driveshaft running out to the wheel, and have the steering wheels pivot around the axis of the motor.
But you need a CV or Universal on that drive shaft to accommodate suspension travel (or steering if needed on that wheel).
What for? The axis of the driveshaft would always be parallel to the axis of the wheel and perpendicular to the axis of the motor.
Look at this hand drill:
The hand crank is the electric motor. If you rotate the drill about the hand crank axis, you don't change any angles between the drivetrain components and don't need CV or universal joints
Now imagine there is a handle sticking out of the crankshaft that needs to rotate around the shaft with the hand crank as it gets turned. That is the motor.
The video never showed the motor moving along with wheels turning, only the up and down part. In fact, when they showed space savings they showed the motors as stationary with no clear way to turn.
What are you referring to as the crankshaft?
Suspension movement still requires flex in the shaft. There's no way around it unless the engine moves with the suspension
Yes, there is.
Take a conventional front engine, rear wheel drive drivetrain. Rotate the drive train 90 degrees about the rear axle, as if the automobile has its nose in the air, with the driveshaft oriented vertically.
You can steer the vehicle by rotating the entire axle around the axis of the driveshaft, though it isn't perfect or space efficient, it would require no universal or CV joints. It would behave sort of like a vehicle with an articulated frame.
The axle could be fixed vertically with uni wheels at the ends of the halfshafts allowing the wheels to travel vertically independent from the axle.
Do you understand so far?
Unrelated comment, but holy shit I am a huge fan of the M8. So wild to see you on Lemmy, and this comment section is exactly what I'm here for.
TIL there is a musician with the moniker of Trash80... https://en.wikipedia.org/wiki/Trash80
Sorry to disappoint, but I picked my username because of the TRS-80.
https://techland.time.com/2012/08/03/trs-80/
With how small the motor is you could also pivot it alongside with the wheel, after all, something pivoting with the wheel doesn't mean that it has to be unsprung.
As to the rest- you're wrong. Sorry.
But the real reason this tech won't be very important is because it's a lot more complicated and expensive than a cheap ass cv joint and is minimally more efficient. I can buy both sides of my vehicle for like $80 and don't have to worry about em again for ages. I think this new hyundai stuff could be reliable, but it's going to be a lot more expensive.
Also, they look like they'd be noisy.
Yeah the amount of BS or confidently incorrect in tech articles about automotive engineering is crazy.
And while gear-sets are really efficient, adding 8 to each of the 4 wheels 32 total, in leu of 2-4 at each end of the car, plus 4 CVs (assuming it’s AWD) has to be close in efficiency. And as a DIY+ car restorer in New England. I wanna see how they seal this thing. And with steering wheels it’s either gonna have to swing the motor around or put the CV back in anyway.
NVH (noise vibration harshness) is also going to be a huge factor. That and cost and weight is why we don’t have gear driven camshafts except on a select few exotic motorcycle engines and F1 engines.
Helical gears are the cost effective way to reduce gear noise, but they impart axial loads which would be difficult to overcome in this hinged joint. Herringbone fears eliminate the axial load, but are much harder to make, unless you go with powdered metal sintering. Which I barely trust in a cordless drill, let alone a Kia.
Edit: And no accounting for wheel castor, or camber changes along the suspension travel (way more basic and important for handling than torque vectoring). This video is pure marketing wank.
Lol, what?
My RSX was made two decades ago in '03, so the newest that would be multiple decades old. It's also a Type-S, the sporty model. It's got an open diff.
My '93 Subaru Loyale, which is 3 decades old, has two open diffs, with a locking center diff. No limited slip.
My '04 (almost decades old) Crown Vic PI doesn't have an limited slip. It was an option on Interceptor that the city didn't opt for.
My '07 (not decades old) Volvo XC70 has no limited slip diffs. It uses the traction control to try to imitate them, but no actual limited slip differentials.
My partner's '07 (still not decades old) Kia Spectra5 has an open diff.
The only car in my fleet that has a limited slip is my '02 Subaru Legacy Outback, and it was an option that the person who bought it new opted for, and it's just the rear that's limited slip, the front is still an open diff. Apparently the limited slip isn't even that good either, you can still get stuck with two wheels spinning. I haven't tested that yet, I just got the car.
If you go out and buy most cars today they'll come with open differentials. The traction control system will likely try to compensate for this, but they do not have limited slip differentials.
Yea, companies love to tout their "electronic differential" that's nothing more than an open diff and traction control via the brakes (Toyota Tundra comes to mind, as recent as 2017).
Yeah. I guess the person I replied to fell for their marketing? However, even traction control wasn't terribly common 20 years ago. I'm not sure what they're on about.
Me too, it was super late. However, holy crap it's different in quality between manufacturers.
My RSX has great ABS, even on gravel or in the snow. It does way better than I could in most situations. Coming from my '98 corolla (without ABS) to the RSX was a massive improvement in braking.
The ABS on my Crown Vic, which is one year newer than my RSX, just doesn't work. You don't lock up the wheels, so I guess by the definition of ABS, it works. However, the ABS also increases your stopping distance by a lot. I need to figure out the best way to disable it. Pulling a fuse doesn't work, as that's also the fuse for the dash instruments. When I do it I'll do a test to make sure that the stopping distance is improved by as much as I think it will be.
Yeah, the ABS "works" as far as I can tell. The wheels don't lock up. It pulses. It's just way too generous towards not locking up the brakes, and doesn't pulse with a high enough frequency, from what I can tell. My vic is lifted for offroading, so it's a real issue stopping on gravel.
I'm thinking pulling a wheel speed sensor would be the easiest, but I haven't looked into it yet.
In the RSX one came lose, and it disabled the entire system, so that's how I assumed it worked in the vic as well, but I guess I'm not sure.
All wires are sustained from when I bought the vehicle, some could've been compromised previously.
I have an OBDII BT scanner, I might check out Forscan, thanks!
Just how many cars do you have, exactly??
The RSX is on the chopping block. I want to get a more dedicated sports car, since I'm privelaged enough to own multiple vehicles.
The Outback and Volvo are wrecked title purchases from copart that I'll get salvage titles for, then enjoy for a bit before selling to break even, or even for a possible profit.
The crown vic is my beater. I drift it. I take it on logging roads. I take it on the Gambler 500. It's fucking awesome. I'll always have one, probably.
The Loyale is something I've wanted since highschool. I love the push button 4WD. I love how comically slow it is. I love the interior. I get quite a few compliments on it. It needs some work, but that's part of the fun. I dunno if I'll own it forever, but I really like the thing.
I, as of recently, own my grandpa's 1984 Oldsmobile Delta 88 Royale. I've gotten similar compliments to the Loyale on it. My grandpa is about two weeks away from dying of cancer. I'll own that car forever.
My partner owned a Spectra5 when I met her. It's our economy car, which every household needs. I'd like to upgrade it to a Volt at some point.
I definitely own too many vehicles, but I love the variety and unique characteristics of each of them.
Sort of related, but I'm not one of those dickish gearheads, I use and support public transport, and think that the world as a whole would be better off with fewer cars. If one doesn't want to drive, then they shouldn't fucking have to.
Hey don't let me take your fun away from you. I just think it's an unusual amount of cars, but if you enjoy it then that's great! Sounds pretty cool tbh