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Quad motor vs locking diff

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Good review, illustrating very well why quad motors can't really compete with full locking diffs. It is interesting to see in the comments that people believe this can be "fixed" with software updates. I guess it is just a factor of people not understanding the technology.

A traditional four-wheel drive with fully locked diffs turns all four wheels at exactly the same speed. One wheel can never, and this is the point that is so very important NEVER slip. Any slip can mean falling off a rock and impaling your truck. Any slip starts to create holes that you have to dig yourself out of. When it is critical that you don't slip any wheel, four wheels locked into identical rotation speeds can never be approximated by a quad motor or software.

While this creates a handicap the quad motor Rivian can never overcome off-road, it has a similar handicap on road. When conditions become super slippery, (snow and ice is an example), a traditional four wheel drive can lock both front and rear axles together while not locking the differentials. In this mode there are at least two wheels at any given time providing lateral stability while the other two attempt to either increase or decrease speed. Again, four disconnected wheels on motors and software can never really approximate this very important ability.

I doubt that Rivian will ever admit that there is more than just a cost savings motivation behind the new dual motor version. As cool as the quad motors are, and as useful as they are in some circumstances, they really do carry some very basic handicaps.

Thank you Kyle for a decent demonstration of at least the first concept.
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I need to watch this. I am still in the camp of “4 motors has the potential to be better” but isnt there yet.
If indeed you are in that camp, then you don't quite understand the mechanics at work.

If the axles are not physically tied, there is no way for any of the four wheels to know how much traction it actually has until it breaks free. Then, of course, it knows "too much" torque and it can apply traction control. But the damage is done. It has broken free, and any negative consequences have already happened prior to the computer being able to make any further calculations.

Again, if physically locked together with large gears and drive shafts, there is no possible way for one wheel to break free in that manner, unless of course something is broken.

I frequent a four-wheel drive Park where Rivians have started coming in, and I see people's mystified faces when they try to understand that sometimes software cannot duplicate a physical state of being. The best I can do, is that no back-massage app on your phone is going to turn out quite as well as an actual set of human hands physically massaging your sore muscles.

Sometimes, more technology does not equal better results on the ground.
 

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If indeed you are in that camp, then you don't quite understand the mechanics at work.

If the axles are not physically tied, there is no way for any of the four wheels to know how much traction it actually has until it breaks free. Then, of course, it knows "too much" torque and it can apply traction control. But the damage is done. It has broken free, and any negative consequences have already happened prior to the computer being able to make any further calculations.

Again, if physically locked together with large gears and drive shafts, there is no possible way for one wheel to break free in that manner, unless of course something is broken.

I frequent a four-wheel drive Park where Rivians have started coming in, and I see people's mystified faces when they try to understand that sometimes software cannot duplicate a physical state of being. The best I can do, is that no back-massage app on your phone is going to turn out quite as well as an actual set of human hands physically massaging your sore muscles.

Sometimes, more technology does not equal better results on the ground.
I watch the video and love this channel BTW.
If indeed you are in that camp, then you don't quite understand the mechanics at work.

If the axles are not physically tied, there is no way for any of the four wheels to know how much traction it actually has until it breaks free. Then, of course, it knows "too much" torque and it can apply traction control. But the damage is done. It has broken free, and any negative consequences have already happened prior to the computer being able to make any further calculations.

Again, if physically locked together with large gears and drive shafts, there is no possible way for one wheel to break free in that manner, unless of course something is broken.

I frequent a four-wheel drive Park where Rivians have started coming in, and I see people's mystified faces when they try to understand that sometimes software cannot duplicate a physical state of being. The best I can do, is that no back-massage app on your phone is going to turn out quite as well as an actual set of human hands physically massaging your sore muscles.

Sometimes, more technology does not equal better results on the ground.
I watched the video. I love that YT channel BTW. Very informative. Admitted, I still feel the same…4 motor tech isn't there YET, but absolutely can and will get there. I have 2 Landcruiser tripple locked and one with no lockers. The more modern cruiser uses technology (ABS, Traction control And others) called A-Trac. My a-trac equipped cruiser climbs better and its not even close. EV‘s will get there and surpass. When? we shall see
 

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Too bad all evidence points to no locking diffs in the dual motor R1 vehicles 😢
Agreed. Even without locking differentials, it will probably have advanced traction control. That, combined with an actual differential will probably give it better traction behavior on slippery surfaces then the quad motor has.
 
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I watch the video and love this channel BTW.


I watched the video. I love that YT channel BTW. Very informative. Admitted, I still feel the same…4 motor tech isn't there YET, but absolutely can and will get there. I have 2 Landcruiser tripple locked and one with no lockers. The more modern cruiser uses technology (ABS, Traction control And others) called A-Trac. My a-trac equipped cruiser climbs better and its not even close. EV‘s will get there and surpass. When? we shall see
Your Land cruiser has the massive advantage of having a differential (three of them actually). This provides unsurpassed automatic torque vectoring that the traction can control can then work off of.

The quad motor shortcomings are not because it's an EV especially, it is just the lack of a differential that handicaps it. I truly believe that the dual motor variant with effective traction control will probably out-climb it.
 

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True, but I'd rather drive my Rivian than my fully lockable Toyotas. It's plenty capable.

Regarding the future dual vrs. quad - the one upside to the quad right now is that the traction control is motor based which is unique to only the quad versus the dual which will go back to brake based traction control.

(Caveat I am not going to watch the video so maybe this was discussed)
 

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Your Land cruiser has the massive advantage of having a differential (three of them actually). This provides unsurpassed automatic torque vectoring that the traction can control can then work off of.

The quad motor shortcomings are not because it's an EV especially, it is just the lack of a differential that handicaps it. I truly believe that the dual motor variant with effective traction control will probably out-climb it.
Again, we agree, the LC “currently” has an advantage. I believe the rivian quad motor technology will catch up and surpass differentials in the very near future. time will tell
 

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I think this is a mostly silly argument honestly. Locking diffs may be better for a very specific set of circumstances that a Rivian driver may encounter. For many of the other use cases that the Rivian is capable of, the quad motors are a massive improvement over a solid axle.

Quad motors allow for optimum flexibilty depending on use case. Sure that makes the Rivian more of a Jack of All Trades, but that's also what makes it so unique.
 

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Good review, illustrating very well why quad motors can't really compete with full locking diffs. It is interesting to see in the comments that people believe this can be "fixed" with software updates. I guess it is just a factor of people not understanding the technology.

A traditional four-wheel drive with fully locked diffs turns all four wheels at exactly the same speed. One wheel can never, and this is the point that is so very important NEVER slip. Any slip can mean falling off a rock and impaling your truck. Any slip starts to create holes that you have to dig yourself out of. When it is critical that you don't slip any wheel, four wheels locked into identical rotation speeds can never be approximated by a quad motor or software.

While this creates a handicap the quad motor Rivian can never overcome off-road, it has a similar handicap on road. When conditions become super slippery, (snow and ice is an example), a traditional four wheel drive can lock both front and rear axles together while not locking the differentials. In this mode there are at least two wheels at any given time providing lateral stability while the other two attempt to either increase or decrease speed. Again, four disconnected wheels on motors and software can never really approximate this very important ability.

I doubt that Rivian will ever admit that there is more than just a cost savings motivation behind the new dual motor version. As cool as the quad motors are, and as useful as they are in some circumstances, they really do carry some very basic handicaps.

Thank you Kyle for a decent demonstration of at least the first concept.
👍😎
Unless I’m misunderstanding your explanation, the crux of the issue is that the quad motors work independently until slip is detected on one or more then power is pulled from the slipping wheel(s). This means the rotation of the 4 tires doesn’t stay in perfect sync as they would on a vehicle with 3 locking diffs. Is that right?
Edit:typo
 

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If indeed you are in that camp, then you don't quite understand the mechanics at work.

If the axles are not physically tied, there is no way for any of the four wheels to know how much traction it actually has until it breaks free. Then, of course, it knows "too much" torque and it can apply traction control. But the damage is done. It has broken free, and any negative consequences have already happened prior to the computer being able to make any further calculations.

Again, if physically locked together with large gears and drive shafts, there is no possible way for one wheel to break free in that manner, unless of course something is broken.

I frequent a four-wheel drive Park where Rivians have started coming in, and I see people's mystified faces when they try to understand that sometimes software cannot duplicate a physical state of being. The best I can do, is that no back-massage app on your phone is going to turn out quite as well as an actual set of human hands physically massaging your sore muscles.

Sometimes, more technology does not equal better results on the ground.
We get it, you much prefer your locking diffs over the quad motor setup.

I've watched literally every video Kyle has done on the T including some of the hours long live streams. The conclusions you can draw from not only those, but this singular video as well, is that the drivetrain characteristics have advanced dramatically from his first drive a year prior to the attempts in the video, and on top of that, to what they are as of today. Rivian is literally the only company building a 4 motor drive vehicle for the consumer, and as such, deserves a little leeway in getting that new tech dialed in.

I know. Locking diff is easy, quad is hard. Just furthering the discussion (because that's what we are doing here, not gettin all heated) watch/listen to the MotorTrend interview with Max Koff. To his credit I wrote him off as a legacy leftover of the Rivian old guard, but he has some decent credentials/background in vehicle development etc. Anyway, while quad motor is at a disadvantage currently in the odd use case, it's superior in its ability to deliver a far quicker precise reaction to changing terrains. https://www.rivianforums.com/forum/...n-the-inevitable-podcast-by-motortrend.11979/

I'll help you with your rebuttal "but full lockers will have perfect reaction time because all wheels turn at the same speed regardless of Mu etc" 😜
 

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Unless I’m misunderstanding your explanation, the crux of the issue is that the quad motors work independently until slip is detected on one or more then power is pulled from the slipping wheel(s). This means the rotation of the 4 tires doesn’t stay in perfect sync as they would on a vehicle with 3 locking diffs. Is that right?
Edit:typo
Rivian could simulate it by changing from torque control to speed control, making all the tires spin at the same rate, but you're still at the mercy of the substrate you're driving on. I've watched plenty of videos of Jeeps with locking diffs where they are still spinning all of their tires trying to climb up something very steep or slippery.
 

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Sure it might be marginally better to have the lockers off road but the 4 motors are leaps and bounds better on road. Since my R1 is a grocery getter and family truckster I much prefer the setup I have.
 

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Rivian could simulate it by changing from torque control to speed control, making all the tires spin at the same rate, but you're still at the mercy of the substrate you're driving on. I've watched plenty of videos of Jeeps with locking diffs where they are still spinning all of their tires trying to climb up something very steep or slippery.
I was going to suggest that, though less technically. I can see Rivian offering a virtual locker mode where all 4 wheels are kept at exactly the same speed regardless of reaction.
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