Hell's Gate in my R1T

[GhostAndSkater]

I'm envisioning a different way to thinking about the accelerator pedal. Usually we think of it as controlling the amount of force applied to the wheels. Perhaps in very low speed rock crawling situations it should instead by a simple speed control: push down, the wheels spin faster; each wheel's controller applies the amount of torque to achieve the desired rotation rate. The goal is simply to make all 4 wheels spin at the same rate. It doesn't have to be perfect. It would be OK for there to be a few milliseconds of lag and a few rpms of difference between the wheels.

This is quite hard to do, mostly because traction control is reactive, while lockers are proactive. As it takes time to react, you also have all the rotational inertia to take into account

I know this forum isn't fond of it, but I'm really looking forward to seeing the Cybertruck in a similar scenario, because Tesla traction control is usually really good, mostly because it's reaction time is fast due to the inverters talking with each other without a middle man, traction control is done at a inverter level, while in afaik most if not all other EVs it's done in a VCU, and that leads to more delay

This is something that Rivian could probably implement via an update, because all of the videos I've seen so far, for something that in theory should be updated multiple times every second, it takes too long to react to traction changes

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[pntbllarea51]

This is quite hard to do, mostly because traction control is reactive, while lockers are proactive. As it takes time to react, you also have all the rotational inertia to take into account

I know this forum isn't fond of it, but I'm really looking forward to seeing the Cybertruck in a similar scenario, because Tesla traction control is usually really good, mostly because it's reaction time is fast due to the inverters talking with each other without a middle man, traction control is done at a inverter level, while in afaik most if not all other EVs it's done in a VCU, and that leads to more delay

This is something that Rivian could probably implement via an update, because all of the videos I've seen so far, for something that in theory should be updated multiple times every second, it takes too long to react to traction changes

You bring up a decent point about the response time of the traction control system and the location of control within the vehicles network. We could estimate this if we can gain access to the internal network. I think I read somewhere (when rivian was still a dream) that they were planing on using TCIP protocol for the internal network. That way they could engineer the modules to have crazy amounts of data throughput overhead. Idk if this ever happened though. We would also need to break whatever encryption, if any.

either way, I too am excited to see a tear down report of the cybertruck. Should be enlightening.

 

[pricedm]

Great discussion...

And the summary from @pntbllarea51 "I bought the R1S because it can get me through the Rubicon trail if needed, beat almost any car off the line at a stop light, and is comfortable on road trips."

 

[Dirtcom_AJ]

Hell yeah nice send!

With the info we've gained from our simulated roller tests on how the Rivian reacts to "crawling and low traction situations there is definitely room for improvement. If it is true that the Electric Motors react the way they do to prevent overheating, then we cannot gain a "simulated" locker due to this fact and a software update won't do much for us. Punching the accelerator pedal will have to suffice for now.

If overheating prevention is the case, then higher gear ratios would be the only solution. Currently the Rivian is on a 12.6:1 gear ratio. To put this into perspective, the Honda Passport has a 20.39:1 gear ratio when locked in first gear. Very capable for its class of vehicle, but still not smooth at crawling. A true 4x4 would be in the 30 - 50:1 gear ratio. This gives a much higher resolution of control at slower speeds.

That being said, the Rivian is still amazing at offroad situations.

 

[HaveBlue]

Another thing to keep in mind in a Rivian compared to a conventional 4WD that I'll expand on is braking. On the Rivian quad, each caliper brakes one wheel only. On a 4WD, each caliper brakes the other wheels in addition to the one it's mounted to because all wheels are mechanically locked together and even more so on a 4WD with locking differentials. Don't underestimate this effect to control wheel speed equally (in 4WD mode) also when slowing down as ABS is, again reactive to an issue instead of proactive in preventing one. Brakes do not apply with equal force when you step on the pedal. First off, the rears always apply first and then with less force over all since on the pavement, the fronts have more stopping power.

 

[jplblue]

Hell yeah nice send!

With the info we've gained from our simulated roller tests on how the Rivian reacts to "crawling and low traction situations there is definitely room for improvement. If it is true that the Electric Motors react the way they do to prevent overheating, then we cannot gain a "simulated" locker due to this fact and a software update won't do much for us. Punching the accelerator pedal will have to suffice for now.

If overheating prevention is the case, then higher gear ratios would be the only solution. Currently the Rivian is on a 12.6:1 gear ratio. To put this into perspective, the Honda Passport has a 20.39:1 gear ratio when locked in first gear. Very capable for its class of vehicle, but still not smooth at crawling. A true 4x4 would be in the 30 - 50:1 gear ratio. This gives a much higher resolution of control at slower speeds.

That being said, the Rivian is still amazing at offroad situations.

Is it possible to change gearing on the Rivian? (Ignoring all the potential software related issues)

 

[jimmyb2]

I bought the R1S because it can get me through the Rubicon trail if needed, beat almost any car off the line at a stop light, and is comfortable on road trips.

Amen!

 

[jimmyb2]

thanks. That backs up my intuition that to make it up Hell's Gate I had to not stop.

Maybe not. In this climb the Rivian actually positions itself and stops part way up to take photos. Then they back up slightly to reposition again to continue the climb to the top.



I think you did great … especially since you didn’t have one or more guides, but instead did it with only your own eyes picking the track which is often extremely difficult from inside the vehicle.

 

[zgStevieD]

Quick video of my R1T going up Hell's Gate in Moab. I could have taken a slightly better line. And it might have been better going a little faster to maybe avoid some of the tire slipping. But this is a lot harder than it looks, going fast would be terrifying. Lockers would help a LOT.

BillArnett after this:

 

[_R1S_]

Exactly. Mentioning brakes...for any not aware, Rock Crawl mode is the only one where you're able to turn off Brake Hold. Coming down a rocky trail this summer I was getting pretty pissed off about how grabby the brake hold was while trying to negotiate some large rocks with the aid of gravity. Finally remembered I could turn off the brake hold and the truck was *way* more controllable on the descent.

I get pissed about brake hold pulling into and out of my steep driveway! Having to "accelerate" downhill in reverse is unpleasant. Thanks for the tip.

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