Powered tonneau fix = new dual motors setup

[blturner]

It seems that persons thinking the 2 motor method is a bad idea also seem to think the jack shaft will be gone. Adding a second motor to the other side and just driving it via torque/current would take much of the load off of the jack shaft. But the jack shaft would still be able to transfer force to a lagging side and keep things aligned. I don't see a need to add syncing or feedback to make this work because the jackshaft would do that.

To figure out the best solution requires seeing and replicating multiple failures. Not something I, or most of us can do. I have to trust the Rivian engineers to get this done.
Stacking detached panels into a too small square box above the gear tunnel so that everything was neat and pretty seems to be the bad idea. But at least it is neat and pretty.
I think that esthetics won and mechanical reliability lost.

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[Adventusaurus]

We are just visionaries in a sea of haters!

That should just be the tag-line for the whole internet.

 

[R1Tom]

Fwiw, my understanding is that components have changed, but it is still a single motor fix.

This is going to be interesting for sure!
Go Team Jackshaft!

(Also hold an undergrad in mechanical engineering if that is required to have an opinion on this).

 

[DaveA]

 

[JGard18]

Denver SC told me a few weeks ago that the dual motor fix for the tonneau cover would be done during a home visit, no requirement to bring it in, and I live about 2.5 hours away so that was great news. The time frame, however, was a different story, as he said they were "months away" from getting started.

I just got off the phone with the Boston SC, as my truck is in there awaiting front damper replacements. I asked if they have any powered tonneau replacements in yet, and he said no. I followed up with asking if they'll be able to install those via mobile service. He checked with a colleague and came back on saying no, it's too involved and they can only do it in the SC.

So basically, we still know nothing! lol

 

[HaveBlue]

Power window motors just use amperage lockup to detect when they are closed and they run pretty consistently from one door to another. Likely two stepper motors would work pretty well.

 

[Adventusaurus]

Power window motors just use amperage lockup to detect when they are closed and they run pretty consistently from one door to another. Likely two stepper motors would work pretty well.

All the ones I’ve seen use a single motor though. Usually they have a lift point on each end connected with simple cables.

The problem with the tonneau is its two independent teethed mechanisms and multiple sections. A big challenge to keep both sides in synch.

The best chance would seem to be beefing up, and making more symmetrical the current one motor system, and redesigning the teeth to allow the drive cog/sprocket to pass through the straight teeth to prevent jumping. Adding another motor only seems to make the chances of synching that much worse?

 

[R1Thor]

All the ones I’ve seen use a single motor though. Usually they have a lift point on each end connected with simple cables.

The problem with the tonneau is its two independent teethed mechanisms and multiple sections. A big challenge to keep both sides in synch.

The best chance would seem to be beefing up, and making more symmetrical the current one motor system, and redesigning the teeth to allow the drive cog/sprocket to pass through the straight teeth to prevent jumping. Adding another motor only seems to make the chances of synching that much worse?

This was already answered in the post above yours, and described in other posts. It's VERY easy to make sure 2 motors are turning at the same rate. Either by monitoring current draw, or using encoders.

It's also extremely rare that 2 identically built motors will spin at different rates if given the correct inputs. Therefore, if nothing else, having 2 is going to sensibly demonstrate premature wear and/or predictive failure.

 

[Adventusaurus]

It's also extremely rare that 2 identically built motors will spin at different rates if given the correct inputs. Therefore, if nothing else, having 2 is going to sensibly demonstrate premature wear and/or predictive failure.

I respectfully disagree. The only way two motors make sense to me is if there wasn’t enough space to fit a single motor that is powerful enough to drive the mechanism. In that case the two motors would need to be linked by gears or a beefed up torque bar to provide a unified output that drives both sides.

Two independent motors is very unlikely to be the solution imo.

Time will tell and I’m fully willing to be wrong .

 

[R1Thor]

I respectfully disagree. The only way two motors make sense to me is if there wasn’t enough space to fit a single motor that is powerful enough to drive the mechanism. In that case the two motors would need to be linked by gears or a beefed up torque bar to provide a unified output that drives both sides.

Two independent motors is very unlikely to be the solution imo.

Time will tell and I’m fully willing to be wrong .

I literally do, and have done, various types of automation throughout my career.
Disagree all you want. 2 identical motors are expected to behave the same, given the same conditions. And there are innumerable ways to control said motors to make sure they're behaving the same. Again, encoders. Again, current draw. You can drive based on distance you want a motor to travel. You can drive based on how much power you want to expend. You can set by jitter, acceleration, angular velocity. And you can use multiple feedback control mechanisms (read PID loops) to validate your equipment is moving the way you anticipate it should.

So, go ahead and disagree. You're welcome to your opinion. But this isn't a subjective thing--it's objective. Otherwise, the world of 'things that move' would be relatively uncontrollable.

Next time you happen by an FDM-type 3d printer, check out how it's setup. Especially the newer ones that have 3 or 4 stepper motors per rail to move in the Z-axis. It can be reliable because those motors will turn (set displacement) the exact same reliably. When there is misalignment, it's generally due to belt tensioning in this instance. And the beauty of this system is it can re-balance itself by auto-leveling. Which is ALSO a benefit of this type of system--if, somehow, the bed rails would become misaligned, they can be re-aligned with the right instructions.

 

[Adventusaurus]

I literally do, and have done, various types of automation throughout my career.
Disagree all you want. 2 identical motors are expected to behave the same, given the same conditions.

Can a tonneau assume “same conditions” on both sides though? These trucks have to work in unideal conditions where one side of the truck bed may heat up a lot more from sitting in the sun while the other is shaded, for example. Mine sounds like it is straining when the weather is over 90F. Now what if the cover is 140 on one side and 100 on the other?

I have no doubt you are an expert and two motors that are not physically connected *can* be made to turn at the same rate for some applications, even with significantly different resistance on each side. What cost is involved in that, and are those costs viable for this product, however?

I lack any years of mechanical engineering experience, but with those factors in mind I would expect a mechanically linked drive to power both sides, whether it has one motor or two.

Again happy to be 100% wrong, but I just don’t see two independent motors being the solution here, even if it *could* be done.

 

[R1Thor]

Can a tonneau assume “same conditions” on both sides though? These trucks have to work in unideal conditions where one side of the truck bed may heat up a lot more from sitting in the sun while the other is shaded, for example. Mine sounds like it is straining when the weather is over 90F. Now what if the cover is 140 on one side and 100 on the other?

I have no doubt you are an expert and two motors that are not physically connected *can* be made to turn at the same rate for some applications, even with significantly different resistance on each side. What cost is involved in that, and are those costs viable for this product, however?

I lack any years of mechanical engineering experience, but with those factors in mind I would expect a mechanically linked drive to power both sides, whether it has one motor or two.

Again happy to be 100% wrong, but I just don’t see two independent motors being the solution here, even if it *could* be done.

Yeah, you're making mountains out of molehills. The delta in resistance you might see from one motor somehow getting heated in direct sunlight and another in shade is going to be a millimeter over tens of meters at most.

Furthermore, if there are concerns as such, it's REALLY easy to assign compensation tables to that behavior. The circuitry required to see a difference in current draw is pretty standard. Almost every motor is paired with a drive. Drive's are pre-programmed to handle all of the characteristics of these drives, as there have been learnings over time that help whomever is building the steppers/servos/dc motors make them work in various applications. Even if Rivian is using some onboard module to trace the logic and is using something more akin to a 'relay' to drive these motors (doubtful, as it'd save pretty much 0, and introduce worlds of needless complications), there are still various sensors all over the truck that can be used to compensate if necessary.

Flip side: if you have a direct-linkage and one tooth jumps, how are you resolving that binding without pulling the entire system apart? I'd argue that using 2 motors is smarter than using a mechanical linkage. Mechanical linkage also has to deal with torsional stress over time. And your mechanical bearings are also going to undergo thermal stress from environmental and thermal cycling, so you're not gaining advantage there either. AND they have to maintain axial linearity over the linkage (or introduce some type of joint to prevent binding otherwise--which is another potential area of failure).

For every argument you present, I am finding more confidence that the 2-motor setup is better. If you ever find yourself looking for a career change, you're EXACTLY the kind of 'devil's advocate' a lot of research groups are looking for! (Afterall, if you design away all the ways a thing might NOT work, you find the best path!)

 

[Adventusaurus]

Yeah, you're making mountains out of molehills. The delta in resistance you might see from one motor somehow getting heated in direct sunlight and another in shade is going to be a millimeter over tens of meters at most.

Furthermore, if there are concerns as such, it's REALLY easy to assign compensation tables to that behavior. The circuitry required to see a difference in current draw is pretty standard. Almost every motor is paired with a drive. Drive's are pre-programmed to handle all of the characteristics of these drives, as there have been learnings over time that help whomever is building the steppers/servos/dc motors make them work in various applications. Even if Rivian is using some onboard module to trace the logic and is using something more akin to a 'relay' to drive these motors (doubtful, as it'd save pretty much 0, and introduce worlds of needless complications), there are still various sensors all over the truck that can be used to compensate if necessary.

Flip side: if you have a direct-linkage and one tooth jumps, how are you resolving that binding without pulling the entire system apart? I'd argue that using 2 motors is smarter than using a mechanical linkage. Mechanical linkage also has to deal with torsional stress over time. And your mechanical bearings are also going to undergo thermal stress from environmental and thermal cycling, so you're not gaining advantage there either. AND they have to maintain axial linearity over the linkage (or introduce some type of joint to prevent binding otherwise--which is another potential area of failure).

For every argument you present, I am finding more confidence that the 2-motor setup is better. If you ever find yourself looking for a career change, you're EXACTLY the kind of 'devil's advocate' a lot of research groups are looking for! (Afterall, if you design away all the ways a thing might NOT work, you find the best path!)

Haha - happy to play devil’s advocate. I do so in my current line of work, but at least there I have some knowledge vs armchair quarterbacking.

Thanks for all the cool information. Most of the failures I’ve heard about, and the one mine suffered was a tooth skip. Those seem inevitable going forward if the “new” design uses the same panels, so decoupled systems that can correct *do* seem superior for sure if that is the case. I was hoping they’d beef up the teeth to be less likely to skip - but that remains to be seen.

Now I’m genuinely excited to see what they have come up with .

 

[R1Thor]

Haha - happy to play devil’s advocate. I do so in my current line of work, but at least there I have some knowledge vs armchair quarterbacking.

Thanks for all the cool information. Most of the failures I’ve heard about, and the one mine suffered was a tooth skip. Those seem inevitable going forward if the “new” design uses the same panels, so decoupled systems that can correct *do* seem superior for sure if that is the case. I was hoping they’d beef up the teeth to be less likely to skip - but that remains to be seen.

Now I’m genuinely excited to see what they have come up with .

You and me both! If this batch fails, you and I will put together a consulting proposal to Rivian, and we'll solve it for them

 

[R1Tom]

Anybody get a new and improved cover yet?

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