Quad motor vs locking diff

[Ralph]

.. snip

This can easily be fixed via software because it is software that is controlling the quad motors.

...snip

You have indeed made this statement many times. And many times people have attempted to explain. Just *maybe* it is not as simple as a few lines of code? Assuming that the Rivian engineers are just too stupid, lazy or incompetent to do something so "simple" seems like lazy thinking (to me).

Perhaps the sensors are not sensitive/fast enough or there are other problems to solve with the feedback loop required?

Several people have attempted to explain why there *might* be "torque available" limits. Those same people or others have suggested that *perhaps* there are component design limits with regard applying all available torque from no traction to (potentially) a full traction condition. Half shafts anyone?

Varying degrees of traction with torque on a heavy vehicle with lots of travel *may* produce levels of stress Rivian is finding they did not fully appreciate.

We simply don't yet know and therefore maybe speaking in absolutes is not warranted?

I'm assuming like most owners, that Rivian will indeed, over time, continue to improve the system. It *does* seem (to me) like the problem Kyle shows in his video could be improved upon; at least to some degree. But I don't *know* that it can "solved" with what is on the truck.

I hope so. In any case I've no doubt that if Rivian does improve it, even limited success will be seen as total vindication by some.

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[White Shadow]

You have indeed made this statement many times. And many times people have attempted to explain. Just *maybe* it is not as simple as a few lines of code? Assuming that the Rivian engineers are just too stupid, lazy or incompetent to do something so "simple" seems like lazy thinking (to me).

Perhaps the sensors are not sensitive/fast enough or there are other problems to solve with the feedback loop required?

Several people have attempted to explain why there *might* be "torque available" limits. Those same people or others have suggested that *perhaps* there are component design limits with regard applying all available torque from no traction to (potentially) a full traction condition. Half shafts anyone?

Varying degrees of traction with torque on a heavy vehicle with lots of travel *may* produce levels of stress Rivian is finding they did not fully appreciate.

We simply don't yet know and therefore maybe speaking in absolutes is not warranted?

I'm assuming like most owners, that Rivian will indeed, over time, continue to improve the system. It *does* seem (to me) like the problem Kyle shows in his video could be improved upon; at least to some degree. But I don't *know* that it can "solved" with what is on the truck.

I hope so. In any case I've no doubt that if Rivian does improve it, even limited success will be seen as total vindication by some.

It's 100% controlled by software now. You're reading too much into my words. I'm saying that it would be easy to change (does that work better for you than the word "fix"?) the software from it's current state to a condition where it will provide more torque to the wheels tnat have more traction.

 

[White Shadow]

Please stop telling people why I started the thread. Your statements are not accurate. You seem to be watching a different movie than most of us, and you seem utterly hell-bound on drawing this conversation off-topic.

As the OP, I am asking politely; please stop.

Sorry, you don't get to start a thread like this with the words YOU chose and then act like you didn't mean what you said.

Anyone can go back and read the very first post in this thread and clearly see that you were directly comparing quad motors to locked differentials and claiming that quad motors can never be as good.

 

[White Shadow]

Actually no. In the case we have been discussing, we want power to the wheels with the least traction. We are trying to protect the reserve of static friction that the downhill wheels have (so they can protect us from sliding down the hill), so do NOT want to direct any power to them. As I'm sure you know, tires have a certain amount of friction they can use, which is shared between resisting driving torque and providing lateral support to prevent side slipping. So if you off-camber, the downhill wheels are the "rails" you are riding on. The uphill (slipping) wheels are providing the propulsion.

Limited slip behavior is what you want when you're stuck in an off-camber situation with one front and one rear tire spinning and the other two tires doing absolutely nothing. Sending power to the wheel with the least amount of traction is mimicking the behavior of an open diff, and open diffs are basically useless in low traction offroad situations.

 

[graemebshaw]

Sorry, you don't get to start a thread like this with the words YOU chose and then act like you didn't mean what you said.

Anyone can go back and read the very first post in this thread and clearly see that you were directly comparing quad motors to locked differentials and claiming that quad motors can never be as good.

Okay... the words "locking diff" imply a device that has three key features (which you seem to ignore):
(1) it is a differential
(2) it can be opened
(3) it can be locked

The OP repeatedly lamented the lack of a "locking" diff, for all three features. Not just a locked diff. Not just an open diff. But most definitely a diff.

 

[graemebshaw]

Limited slip behavior is what you want when you're stuck in an off-camber situation with one front and one rear tire spinning and the other two tires doing absolutely nothing. Sending power to the wheel with the least amount of traction is mimicking the behavior of an open diff, and open diffs are basically useless in low traction offroad situations.

lol. glad you think so. please procure life insurance if you ever plan to drive across a sloped surface with a cliff drop-off, like the OP has in his property...

 

[White Shadow]

Okay... the words "locking diff" imply a device that has three key features (which you seem to ignore):
(1) it is a differential
(2) it can be opened
(3) it can be locked

The OP repeatedly lamented the lack of a "locking" diff, for all three features. Not just a locked diff. Not just an open diff. But most definitely a diff.

Okay...let's at least make an attempt to be intellectually honest here, shall we? When someone is talking about a locking differential in the scenarios mentioned, they are indeed talking about it in a locked state. Of course a locking differential can be unlocked. Think about that for a moment.....if a differential were permanently locked, it would no longer function as a differential in any regard. Differentials were created to allow wheels on an axle spin at different speeds, right? Such as while turning.....the outside wheel needs to turn faster than the inside wheel, which is where the differential comes into play. So what's the point you're trying to make by saying that a locking diff can also be unlocked?

 

[popoga]

This thread is... kind of a shit show, should it be locked? It's hard for me to imagine anyone's getting anything new out of it after 18 pages.

 

[White Shadow]

lol. glad you think so. please procure life insurance if you ever plan to drive across a sloped surface with a cliff drop-off, like the OP has in his property...

Sure. Now you go to 10:00 in Kyle's video in the initial post of this thread and explain to me how and why you'd want more power going to the wheels with the least traction. And what good that would do in his real world situation.

What I'd want is for the Rivian to apply more power to the two wheels that aren't moving. Color me silly, huh?

 

[R.I.P.]

Okay... the words "locking diff" imply a device that has three key features (which you seem to ignore):
(1) it is a differential
(2) it can be opened
(3) it can be locked

The OP repeatedly lamented the lack of a "locking" diff, for all three features. Not just a locked diff. Not just an open diff. But most definitely a diff.

100%. You appear to be watching the same movie most of the rest of us are lol.

 

[White Shadow]

This thread is... kind of a shit show, should it be locked? It's hard for me to imagine anyone's getting anything new out of it after 18 pages.

You could just stop reading it. Thats what I do when a thread no longer interests me.

 

[White Shadow]

lol. glad you think so. please procure life insurance if you ever plan to drive across a sloped surface with a cliff drop-off, like the OP has in his property...

Forgot to say.....you do realize that a limited slip diff in no way behaves like a locked diff, right? If you're truly worried about sliding off the cliff of death, you most definitely would want limited slip over locked for sure.

 

[graemebshaw]

Sure. Now you go to 10:00 in Kyle's video in the initial post of this thread and explain to me how and why you'd want more power going to thd wheels with the least traction. And what good thst woulddo in his real world situation.

What I'd want is for the Rivian to apply more power to the two wheels that aren't moving. Color me silly, huh?

I think the problem is that you have assumed the issue in Kyle’s video is the same as that described by the OP (his scenario #2). In fact they are quite different. We are not talking about cross-camber situation with opposite wheels unsupported. We are talking about driving across a slippery hill.

You will become a better off roader if you go back and carefully read his post. And also read my attempts to explain the situation. We promise you we are correct in this. It is physics. Perhaps you have not experienced the side slipping if you break traction on downhill wheels (by applying torque or brakes), but I assure you it can be scary.

 

[White Shadow]

I think the problem is that you have assumed the issue in Kyle’s video is the same as that described by the OP (his scenario #2). In fact they are quite different. We are not talking about cross-camber situation with opposite wheels unsupported. We are talking about driving across a slippery hill.

You will become a better off roader if you go back and carefully read his post. And also read my attempts to explain the situation. We promise you we are correct in this. It is physics. Perhaps you have not experienced the side slipping if you break traction on downhill wheels (by applying torque or brakes), but I assure you it can be scary.

Don't look now, but there are multiple topics being discussed throughout this thread. What you are talking about may not be specifically what I'm talking about. That said, I've referenced Kyle's video several times already in my posts, so if you are initially going to reply to my comment, then the burden of understanding what I'm referencing is really on you.

So again, do you disagree that in Kyle's video that having the quad motors behave more like a limited slip diff would be more beneficial than behaving like an open diff (which is actually what they are doing in the video) to have helped him drive up that hill? Or are we not even agreeing on that?

 

[MountainBikeDude]

Interesting thought occurred to me.

Rivians obviously have some sort of MEMS gyroscope built in to determine levelness of the vehicle for uses of say camp mode for example. Why couldn't observations from such a device as well as observed Mu as the vehicle progresses along a trail, say the last 15 seconds, be used to determine appropriate force to the wheel likely to have the least traction, but most potential for forward motion (higher wheel) over the lower wedge wheel let's call it, and just provide those lower wheels with enough power to allow them to freely move with the vehicles forward motion?

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