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R1T vs. R1S in snow?

Phatman113

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Right. Maybe for the very specific use case of off camber ice the DM has an advantage over QM....but other than that, it's highly debatable and very dependent on the details of each scenario (deep snow, packed snow, ice, flat, incline, off camber, etc...) and most importantly...THE TIRES
dOn'T aRgUe WiTh RIP, He KNOWS what's up... just trust him.

SeRiOuSlY
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R.I.P.

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Also, do you think Rivian could emulate a diff by only applying power at opposite corners? That way there would always be two tires that aren't slipping. A "No side slip start" type of mode.
No.

A computer cannot "emulate" the physical characteristic of a wing and make a cinder block fly. The wing reacts with the physical world to create lift by differentiating air speeds above and below it.

Likewise, the differentials in my truck are reacting in real time to the physical characteristics of the traction each wheel is experiencing, in real time, in the real world, and adjusting with the physical conditions as they change; not reacting to them. Blindly applying power to one side w/o having any reference to which wheel actually has the most traction at that split second would be a clumsy way to try to overcome the handicap, but would not have the real-time advantage of absolutely anchoring the wheel with the most traction. The more slippery the overall condition, the worse this "emulation" would work.

In 1872 a "no side slip start mode" was invented by Onésiphore Pecqueur. To this day, the most capable off-roaders in the world use it. I have had the opportunity to now own and use two otherwise very capable vehicles that tried to get away without using one, but they just don't do very well when pushed hard in low-traction situations.

I am back firmly in the "give me a differential please" camp.
:cool:
 

R.I.P.

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Right. Maybe for the very specific use case of off camber ice the DM has an advantage over QM....but other than that, it's highly debatable and very dependent on the details of each scenario (deep snow, packed snow, ice, flat, incline, off camber, etc...) and most importantly...THE TIRES
It is actually flipped from this. The QM has some advantages is some very specific scenarios. Racing on high traction surfaces is such an area. The ability to vector power can get you some advantages as well.

However, in most scenarios outside racing, the advantage moves to the differential equipped machine. Yes, good tires help mask the QM's poor manners in snow and ice, but I would rather have the good tires and the inherent stability of a differential. Trying to rock-crawl a QM is miserable; it gets herky-jerky with all 4 wheels flailing trying to find where the traction is, and the stall-characteristics of the motors makes matters even worse. The DM machine simply acts like any other diff-equipped rig, because the diff can feel where the traction is and make good adjustments. All the while the DM machine has none of the motor-stall headaches that the QM suffers, because the diff allows the motors to never actually stall (along with the fact that the larger motors have higher torque).

The below article asks the question. Having owned both, and wheeled both extensively, I can answer that question; DM shines everywhere. QM struggles once outside a pretty narrow comfort zone.

https://www.autoevolution.com/news/...ited-for-off-road-than-quad-motor-224772.html
 

usofrob

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No.

A computer cannot "emulate" the physical characteristic of a wing and make a cinder block fly. The wing reacts with the physical world to create lift by differentiating air speeds above and below it.

Likewise, the differentials in my truck are reacting in real time to the physical characteristics of the traction each wheel is experiencing, in real time, in the real world, and adjusting with the physical conditions as they change; not reacting to them. Blindly applying power to one side w/o having any reference to which wheel actually has the most traction at that split second would be a clumsy way to try to overcome the handicap, but would not have the real-time advantage of absolutely anchoring the wheel with the most traction. The more slippery the overall condition, the worse this "emulation" would work.

In 1872 a "no side slip start mode" was invented by Onésiphore Pecqueur. To this day, the most capable off-roaders in the world use it. I have had the opportunity to now own and use two otherwise very capable vehicles that tried to get away without using one, but they just don't do very well when pushed hard in low-traction situations.

I am back firmly in the "give me a differential please" camp.
:cool:
Thanks for the reply.

Since we're having fun here. What about a QM with an LSD in rear and maybe front? It would still allow slip on one side and power to transfer, and unlike a locker, it would allow the opposite motor to get out of motor-stall (similar to DM).
 

R.I.P.

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Thanks for the reply.

Since we're having fun here. What about a QM with an LSD in rear and maybe front? It would still allow slip on one side and power to transfer, and unlike a locker, it would allow the opposite motor to get out of motor-stall (similar to DM).
Yeah, lots of workarounds have been proposed, to include the step down gearing that Rivian was looking at for a hot minute.

At the end of the day, some might work, some might not. I'm betting none as well as an actual differential.

On a similar topic, there are experiments trying to make wheels work that are not actually round. Fun experiments for sure, but in 10 years, I'll bet that the most capable vehicles will still have round wheels and real differentials in them.
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usofrob

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Yeah, lots of workarounds have been proposed, to include the step down gearing that Rivian was looking at for a hot minute.

At the end of the day, some might work, some might not. I'm betting none as well as an actual differential.

On a similar topic, there are experiments trying to make wheels work that are not actually round. Fun experiments for sure, but in 10 years, I'll bet that the most capable vehicles will still have round wheels and real differentials in them.
😎
My point was that you can still put a differential in between the rear two motors. In fact, it'll probably be easier than putting in lockers as you wouldn't have to get the RPMs to match exactly.

Although, as I think about this, I'm not sure what that would actually look like. A normal diff would have one input power and two output. The contraption I'm thinking of is just two outputs connected to the same diff. So, they'd act like both inputs and outputs. Would you lock the normal input, or maybe let it freewheel, or would it have to be a totally different sort of design?
 

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dOn'T aRgUe WiTh RIP, He KNOWS what's up... just trust him.

SeRiOuSlY
I don't think i've ever been more aware of anyone's opinion on something in my life than that guy's. Had to block him. Got tired of reading the same freakin thing over and over again.
 

R.I.P.

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I don't think i've ever been more aware of anyone's opinion on something in my life than that guy's. Had to block him. Got tired of reading the same freakin thing over and over again.
It is interesting how facts, and how things really work don't really change all that much, isn't it?
🤷‍♂️

Test gravity 100 times, and you'll get some pretty consistent results.
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OrthoBlock

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I think the easiest way to think about it is that when 3 wheels lose traction on Quad-Motor the most power you would have available is 25% at the remaining wheel. Because lefts and rights are not connected.
While on Dual Motor, through engagement of traction control, you could get up to 50% of that power applied to the wheel with traction.
Lets assume there is a guy with g-wagon and all of his lockers are engaged, he would be able to put down 100% of available power to the wheel with traction.
ut it would be fun to test this theory.
In an effort to make sure the reader does not get the wrong impression here (as 25% sure sounds less than 50%):

Ignoring the fact for a moment that the QM total output is greater than the total output of DM, and just focusing on the percent of power available at each wheel, it is directionally true that the QM can only put down ~25% of the power there. Technically, the motors in front/rear are not identical so it's not exactly 25%, but either way the maximum is equal to what a given motor can give out, which is about 25% of the total.

Now in case of the DM, making similar simplifying assumptions about motors being roughly equal between front/rear, each motor represents ~50% of the available power. However, with an open differential, a brake based differential aid can at most transfer 50% of torque to a wheel, so this would be 50% of the 50%, which gets us right back to 25% of total torque available to single wheel.

So in the end both the QM and DM can each get about 25% of the total available torque to a single wheel.

The observations that a triple locked vehicle can in fact get 100% of the available torque to a single wheel is true.
 

240vPlug

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T and S are pretty comparable on snow. Ultimately it comes down to whichever has the better tires.
I agree with this. The difference in wheelbase, in the snow scenario, is not likely to be very noticable in most situations.

As far as QM vs DM there will be situations where each will outperform the other. I believe quad motor is the future for a software defined vehicle because of the control at each wheel. It gives the software folks more control over the experience.

In most situations the tire choice will play a more important role in how the vehicle performs in snow/slush/ice.
 

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RivAW

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DM performs better in the snow than QM does. Otherwise, yes, the difference is just going to be the wheelbase issue.
What are you taking about? Why would a DM perform differently than a QM? Aside from that, OP asked about the R1T vs the R1S….i don’t think very many people (if any) had delivery of an R1S while there was still snow around so there’s very little comparison available
 

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I suspect that dual motor isn't always better. I believe it's better for lateral stability to keep you from sliding off a cliff on your side. But what about going up a slippery hill? Seems like that would depend on how quick the stability control is as slowing the slipping wheel vs the motors doing it themselves.

What about driving around a snowy track?

Also, do you think Rivian could emulate a diff by only applying power at opposite corners? That way there would always be two tires that aren't slipping. A "No side slip start" type of mode.

I wonder if braking down a hill is actually better with DM as well, because the QM can't perfectly emulate free wheeling, so the regen will always cause more problems with QM than DM.

Also, back to the OP's original question, often times tires are the ultimate decider of more grip. If one of your vehicles has more tread depth, that might be the best one to take.

I did a "drag race" in the snow with my Lotus Elise with fresh Blizzak tires (open diff, no traction control) against my uncle's 4WD Chevy Avalanche (probably AT tires), and it was pretty even to about 30-40 mph where we let off.
:( that poor elise...with blizzaks!! :)
 

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It is actually flipped from this. The QM has some advantages is some very specific scenarios. Racing on high traction surfaces is such an area. The ability to vector power can get you some advantages as well.

However, in most scenarios outside racing, the advantage moves to the differential equipped machine. Yes, good tires help mask the QM's poor manners in snow and ice, but I would rather have the good tires and the inherent stability of a differential. Trying to rock-crawl a QM is miserable; it gets herky-jerky with all 4 wheels flailing trying to find where the traction is, and the stall-characteristics of the motors makes matters even worse. The DM machine simply acts like any other diff-equipped rig, because the diff can feel where the traction is and make good adjustments. All the while the DM machine has none of the motor-stall headaches that the QM suffers, because the diff allows the motors to never actually stall (along with the fact that the larger motors have higher torque).

The below article asks the question. Having owned both, and wheeled both extensively, I can answer that question; DM shines everywhere. QM struggles once outside a pretty narrow comfort zone.

https://www.autoevolution.com/news/...ited-for-off-road-than-quad-motor-224772.html
RIP - I wanted to thank you for the information shared in these posts. Very helpful. I'm in Colorado, drive to the mountains regularly, and waiting to lock in. I've been waffling about QM v DM. This is great information. Appreciate it. 👍
 

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Follow up:

On an off-camber, slippery surface, it is helpful to focus on where is vehicle is _not_ trying to apply power rather than where the vehicle is trying to _apply_ power. By default, an open differential will always attempt to apply power (both "going" and "stopping") to only the wheels with the least traction on each axle. This is highly desirable when you want the wheels with the most traction to keep you from moving sideways, into a ditch or a tree, etc.

The QM has no option but to always at least attempt to apply power (both "going" and "stopping") to all four wheels, going into traction control mode when it senses slipping. Current software iterations have made behavior better, but the QM is always going to be working at a disadvantage attempting to overcome a problem the DM simply does not have.
it is the same with most (all?) four wheel drive vehicles. I used to unlock my front wheel hubs on icy surfaces. In normal four wheel drive mode, my Jeep would become a hockey puck. Technology can help, but when it is super slick, four wheel drive becomes a handicap. Of course, the opposite is true in snow.
 

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I don't think i've ever been more aware of anyone's opinion on something in my life than that guy's. Had to block him. Got tired of reading the same freakin thing over and over again.
OH thank god! I had no idea that was even an option! The fucking arrogance that just radiates off of him is suffocating.

He's someone that has enough info to form an opinion, and enough intelligence to make it a good opinion. But after that, he just groups his opinions and facts together and can no longer separate them in reality.

Now I can blithely ignore him and my world will be 100% better!
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