Quad motor vs locking diff

[R.I.P.]

UPDATE:

Now that the UbTube crowd has soundly confirmed what we learned last winter, I thought I would update our findings with the new dual motor variant of Rivian's drivetrain.

To recap, I sold my quad motor R1T after becoming frustrated with the handicaps of the quad motor design. To be fair, we are hard-core off-roaders, and we were expecting too much of it. That said, I documented how even open-diff pickups were beating the quad motor in areas that seemed ridiculous. In the end we concluded that removing the differential from the design hurt it more then it helped it, and hypothesized that simply putting the differential back into the vehicle would make it better on common slippery surfaces we experience in the PNW.

I am happy to report that this assertion has proved correct, as we have now had the opportunity to play with a couple of dual motor "Enduro" equipped Rivians in scenarios that completely defeated the quad motor machines this past February. In fact, I am so impressed with the Enduros that I just purchased one, scheduled to be at the Portland SC in 2 weeks.

Kudos to the Rivian team on the progress, and for those who may be on the fence; the Enduro is the real deal. Do you want the best drag-racing power possible? Do you drive exclusively on high traction surfaces? Quad motor is for you. Do you want the most mannerly truck on snow and slippery surfaces? The dual motor Enduro can't be beat, as it does not sacrifice lateral traction the way the quad does.

Neither is a "hard-core" off-roader that can truly compete with a locked diff rig, but the Enduro actually gets a little closer... it actually has a physical diff that maybe in the future could gain a locker.

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[kylealden]

Do you want the best drag-racing power possible? Do you drive exclusively on high traction surfaces? Quad motor is for you. Do you want the most mannerly truck on snow and slippery surfaces? The dual motor Enduro can't be beat, as it does not sacrifice lateral traction the way the quad does.

 

[MountainBikeDude]

UPDATE:

Now that the UbTube crowd has soundly confirmed what we learned last winter, I thought I would update our findings with the new dual motor variant of Rivian's drivetrain.

To recap, I sold my quad motor R1T after becoming frustrated with the handicaps of the quad motor design. To be fair, we are hard-core off-roaders, and we were expecting too much of it. That said, I documented how even open-diff pickups were beating the quad motor in areas that seemed ridiculous. In the end we concluded that removing the differential from the design hurt it more then it helped it, and hypothesized that simply putting the differential back into the vehicle would make it better on common slippery surfaces we experience in the PNW.

I am happy to report that this assertion has proved correct, as we have now had the opportunity to play with a couple of dual motor "Enduro" equipped Rivians in scenarios that completely defeated the quad motor machines this past February. In fact, I am so impressed with the Enduros that I just purchased one, scheduled to be at the Portland SC in 2 weeks.

Kudos to the Rivian team on the progress, and for those who may be on the fence; the Enduro is the real deal. Do you want the best drag-racing power possible? Do you drive exclusively on high traction surfaces? Quad motor is for you. Do you want the most mannerly truck on snow and slippery surfaces? The dual motor Enduro can't be beat, as it does not sacrifice lateral traction the way the quad does.

Neither is a "hard-core" off-roader that can truly compete with a locked diff rig, but the Enduro actually gets a little closer... it actually has a physical diff that maybe in the future could gain a locker.

Without reigniting a flame war, the Enduro motors have better stall torque than the Bosch quads, something Rivian's engineers touched on when @OutofSpecKyle was at their plant for the Enduro test drives.

 

[R.I.P.]

Without reigniting a flame war, the Enduro motors have better stall torque than the Bosch quads, something Rivian's engineers touched on when @OutofSpecKyle was at their plant for the Enduro test drives.

Yes, they do. But beyond that, lets look at this recent vid, where the driver is saying "I have it floored"...



Anybody with a half-day of off-roading experience would agree that the vehicle the R1T was pitted against is by no means a "mean off-roader", and no, it does not even have lockers, rather it has GMs "grenade" LS diff. It is still declared the "winner", because the diff in it was able to transfer some torque.

As you pointed out, the quad runs out of "stall torque" pretty quick when subjected to even the moderate loads tested in the vid. Not only does the Enduro have better stall torque, but in actual tests, it does not even need it... because the motors never stall. The wheels lifting off the ground are spinning, as such, so are the motors, so they are not stalled! Instead, they are spinning at RPMs that give them massive torque, and as the brakes are applied to the spinning wheels, that torque is applied to the wheel with traction.

Again, no stall occurs, and that "stall power problem" is gone.

Of course, that is only one of the problems caused when you delete the diff, but it is a good example of how putting the diff back in the truck helps it.

 

[HaveBlue]

UPDATE:

Now that the UbTube crowd has soundly confirmed what we learned last winter, I thought I would update our findings with the new dual motor variant of Rivian's drivetrain.

To recap, I sold my quad motor R1T after becoming frustrated with the handicaps of the quad motor design. To be fair, we are hard-core off-roaders, and we were expecting too much of it. That said, I documented how even open-diff pickups were beating the quad motor in areas that seemed ridiculous. In the end we concluded that removing the differential from the design hurt it more then it helped it, and hypothesized that simply putting the differential back into the vehicle would make it better on common slippery surfaces we experience in the PNW.

I am happy to report that this assertion has proved correct, as we have now had the opportunity to play with a couple of dual motor "Enduro" equipped Rivians in scenarios that completely defeated the quad motor machines this past February. In fact, I am so impressed with the Enduros that I just purchased one, scheduled to be at the Portland SC in 2 weeks.

Kudos to the Rivian team on the progress, and for those who may be on the fence; the Enduro is the real deal. Do you want the best drag-racing power possible? Do you drive exclusively on high traction surfaces? Quad motor is for you. Do you want the most mannerly truck on snow and slippery surfaces? The dual motor Enduro can't be beat, as it does not sacrifice lateral traction the way the quad does.

Neither is a "hard-core" off-roader that can truly compete with a locked diff rig, but the Enduro actually gets a little closer... it actually has a physical diff that maybe in the future could gain a locker.

I came to the same conclusion and ordered a dual motor. After having a 4Runner with dual air lockers and even my GX with a single, there's nothing that compares to speed and traction control. Locking diffs can definitely be built for the Rivian even if it has to be a lunchbox locker.

I'm not shy about giving that a shot.

 

[R.I.P.]

I came to the same conclusion and ordered a dual motor. After having a 4Runner with dual air lockers and even my GX with a single, there's nothing that compares to speed and traction control. Locking diffs can definitely be built for the Rivian even if it has to be a lunchbox locker.

I'm not shy about giving that a shot.

Locking diffs can be built for the Rivian... _if_ it has a diff. Kyle's cries for an aftermarket locker for his quad are not likely to come to fruition, as trying to "connect" the rear wheels would involve having to add....


wait for it.....


Yes.... a diff lol.


All that said, I am thrilled to be getting another Rivian, as there is so much I really did like about the truck. The latest update push with all the beautiful data access is making me even more eager to be back in an EV truck.

 

[MountainBikeDude]

The main advantage to an ICE drivetrain over a direct drive or even differential equipped EV is gearing that changes. Yes an Electric motor can spin at far greater speeds than an ICE counterpart, giving it low speed toque, but also high speed output, unfortunatley the fixed gear ratios mean it can't do both perfectly.

If I have one wheel with an opportunity to move a vehicle forward, but all others are bound, unless the gearing is there to allow the electric motor to more effortlessly spool and drive that wheel, a differential is in the same situation as the quad. The low end gearing isn't present because the transmission has fixed gearing that caters to majority situations especially efficiency over low end crawl control.

You could overcome the inherint issue with better low range gearing, but if fixed like the current setup, would severly cap the vehicles top speed. Porsche worked out into their Taycan's, a 2 speed transmission that helps improve efficiency, but also top speed. Rivian could do the same, but it increases the complexity of their product, and only panders really to the rock crawling Rivian owners out there.

For what it's worth, Rivian patented a bolt on crawler gearbox that could address this issue, but have yet to implement it.
https://www.rivianforums.com/forum/threads/cool-rivian-patent-trademark-info.554/post-275472

 

[HaveBlue]

Locking diffs can be built for the Rivian... _if_ it has a diff. Kyle's cries for an aftermarket locker for his quad are not likely to come to fruition, as trying to "connect" the rear wheels would involve having to add....


wait for it.....


Yes.... a diff lol.


All that said, I am thrilled to be getting another Rivian, as there is so much I really did like about the truck. The latest update push with all the beautiful data access is making me even more eager to be back in an EV truck.

That's why I ordered the dual. The picture I posted on top IS the differential in the dual motor Rivian. The bottom is a Toyota 8" with an ARB. I've done a few of those.
Here's another pic with output driver in place.

 

[R.I.P.]

The main advantage to an ICE drivetrain over a direct drive or even differential equipped EV is gearing that changes. Yes an Electric motor can spin at far greater speeds than an ICE counterpart, giving it low speed toque, but also high speed output, unfortunatley the fixed gear ratios mean it can't do both perfectly.

If I have one wheel with an opportunity to move a vehicle forward, but all others are bound, unless the gearing is there to allow the electric motor to more effortlessly spool and drive that wheel, a differential is in the same situation as the quad. The low end gearing isn't present because the transmission has fixed gearing that caters to majority situations especially efficiency over low end crawl control.

You could overcome the inherint issue with better low range gearing, but if fixed like the current setup, would severly cap the vehicles top speed. Porsche worked out into their Taycan's, a 2 speed transmission that helps improve efficiency, but also top speed. Rivian could do the same, but it increases the complexity of their product, and only panders really to the rock crawling Rivian owners out there.

For what it's worth, Rivian patented a bolt on crawler gearbox that could address this issue, but have yet to implement it.
https://www.rivianforums.com/forum/threads/cool-rivian-patent-trademark-info.554/post-275472

All that accurately said, the electric motors used in these vehicle have massive torque down low; it is when you get them cogged/stalled that high temps and problems occur.

The two Enduro equipped riggs we tested this last week had none of the issues the quads displayed when pushed over the same obstacles. There was a fair amount of wheel spin (fun), but they powered thorough things that stopped the quads in their tracks.

The feeling is much more like a gas-powered vehicle with traction control. That awkward feel from the quad trying to figure out where the traction is does not happen in the Enduro. Even with the wheel spin, it is a much more controlled feeling for the driver.

 

[HaveBlue]

Could you feel the traction control kicking in and grabbing brakes? I wonder if you can give both brake and throttle simultaneously or if it will cut power if you touch the brakes. On Toyota open diffs, applying brake forces the carrier drivers outward by loading the diff to act like a limited slip. The Rivian has a similar design with that huge friction surface on the output pinion.

Basically what happens is the pinions gears are beveled to change rotation 90 degrees. Applying torque to the carrier from the motor and not allowing the torque to escape to a spinning wheel forces the pinions away from each other an imparts drag against the carrier housing. This locks up the carrier a bit like a spring load limited slip.

Those MOSFETS must get super hot at lock up when they are essentially shorted. What we've learned is that electric motors have about the same amount of torque at zero rpm as an ICE.

 

[MountainBikeDude]

Could you feel the traction control kicking in and grabbing brakes? I wonder if you can give both brake and throttle simultaneously or if it will cut power if you touch the brakes. On Toyota open diffs, applying brake forces the carrier drivers outward by loading the diff to act like a limited slip. The Rivian has a similar design with that huge friction surface on the output pinion.

Basically what happens is the pinions gears are beveled to change rotation 90 degrees. Applying torque to the carrier from the motor and not allowing the torque to escape to a spinning wheel forces the pinions away from each other an imparts drag against the carrier housing. This locks up the carrier a bit like a spring load limited slip.

Those MOSFETS must get super hot at lock up when they are essentially shorted. What we've learned is that electric motors have about the same amount of torque at zero rpm as an ICE.

You should give this a watch, @OutofSpecKyle goes into depth on some of the characteristics between the two while driving on and off road

 

[zefram47]

I wonder if you can give both brake and throttle simultaneously or if it will cut power if you touch the brakes.

Interestingly, I found out recently that the R1 will allow you to get on the brakes and the throttle at the same time. I was able to put the brakes on enough that I could get almost half the blue curve (accelerator application) without increasing speed. It will definitely chop throttle if you apply too much brake, but I was pleasantly surprised.

 

[R.I.P.]

Could you feel the traction control kicking in and grabbing brakes? I wonder if you can give both brake and throttle simultaneously or if it will cut power if you touch the brakes. On Toyota open diffs, applying brake forces the carrier drivers outward by loading the diff to act like a limited slip. The Rivian has a similar design with that huge friction surface on the output pinion.

Basically what happens is the pinions gears are beveled to change rotation 90 degrees. Applying torque to the carrier from the motor and not allowing the torque to escape to a spinning wheel forces the pinions away from each other an imparts drag against the carrier housing. This locks up the carrier a bit like a spring load limited slip.

Those MOSFETS must get super hot at lock up when they are essentially shorted. What we've learned is that electric motors have about the same amount of torque at zero rpm as an ICE.

Yes, you can feel the brakes grabbing much like any comparable traction control system out there. It feels familiar, it feels predictable, and I have no issues handing this to my wife on icy roads; which was a requirement for me with the truck in the family. And yes, you can "compound" the torque transfer with brake pedal application.

I agree that we will see lockers for the Enduro unit soon. I it is reasonable for Rivian to offer it as an upgrade soon, but because this is a pretty traditional differential we may see aftermarket offerings even sooner.

I just pre-ordered the Atomic 20x9s and am quite looking forward to putting the Enduro through the same paces we put the last truck through (a quad) with some Toyo ATs on it.

 

[GogglesPisano]

Don't mean to kick this back up, but I've only seen a couple of people mention my thoughts on the whole topic. I went with a quad motor because I feel the potential is there even if it isn't there now. I'm coming from a Wrangler with lockers and do some off roading. Nothing crazy or rock crawling, so I'm looking forward to putting my upcoming R1S through it's paces.

That said, I see absolutely no reason Rivian couldn't "lock" the wheels simply by forgetting the slip control and forcing both front or rear wheels to rotate at the same speed. That is all a locker is doing anyway. There's no hocus pocus that gears do that the software can't if they program it correctly. They can actually make it better by taking into account the steering angle and biasing that side of the rig to spin slightly faster overcoming some of the downfalls that actual lockers have.

Let's not forget physical lockers don't like taking turns and you end up pushing more than turning. With the proper software tweaks, Rivian could essentially perform even better.

Are you listening Rivian? Let's get some proper off roaders in your software crew and not the type of people that think a forest road is "off roading" like the Subaru commercials depict

 

[Proxy]

The QM off road is significantly better with the recent updates. However I believe the DM will outperform the QM in 98% of off road situations. I’ve mentioned this before, but the DM can put over 400 ft-lbs of torque to any wheel with traction control doing its thing. The QM can send less than 250 ft-lbs max to any individual wheel. Overheating with a QM on a long sandy uphill is a bad situation to be in (personal experience).

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