Quad motor vs locking diff

[zefram47]

For all those reasons it seems to me if some of their short comings can be mitigated, switched reluctance motors are better suited for this kind of application (i.e. four motor off/on road vehicle).

Though I suppose four ac types motors with a coil driver setup maybe workable as well.
link

Nonetheless it will be interesting to see if Rivian’s in house motor design will improve things when/if they're implemented in the four motor variants.

The Bosch motors they're currently using are permanent magnet AC motors.

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[escapee]

The Bosch motors they're currently using are permanent magnet AC motors.

Yep.

 

[RivianBowerbird]

And all your loud ranting is proving is you haven't actually read a damn thing in this thread. Theoretical operation is great, but when the rubber meets the road, ice, trail, etc...theory goes out the window. In certain situations Rivian's system is absolutely not properly calibrated. As many have already said in the thread, depending on the hardware they've actually used it may be possible to get a lot closer to theory...but if they haven't, then it may never get better. On-road performance does not equal off-road performance and no vehicle will excel at both. Rivian has attempted to make a jack-of-all-trades and it shows and does many things well...but they are a master of none of these realms.

Yes of course, but what I'm pointing out is that R.I.P doesn't know what he's talking about and that his criticisms should not be taken seriously. There's no better jack of all trades than the R1T, but no one is claiming it is the best in each category it's good at.

 

[R.I.P.]

Just the fact that you said, "cute video" in relation to Jason Fenske's careful explanation of how the quad motor system works (and its benefits and potential) is a reason to not take you seriously. You don't even understand how/why Rivians "feel" the surface and spin tires in the air in a controlled manner when they are free/off a surface and that their spinning is not a reason for criticism given the fundamental differences in how it all works.. All I see here is an old man shaking his fist at the modern world and ignoring realities and change right in front of him in favor of edge cases and misunderstanding.

Well gall dern it iffn I infuriated that I wer not tarrbly greatful fer yer settin us lads straight on thot thar tyre issue. I knowed my kin & I r not affortulated some of that thar higer lernin dat de white folk git, so I shudda knowed that it were a superior I were listin to, & right stern givn the thot a bit more of a ponderin.

Havin been sit strate on that particular issuance, me & the lads were hopin you could see yerself fitted ta do us a further solid. See, thar r 4x4/off-road/overland orgiginations like owrs all ovir the county. Iffin usins is too far fer ya ta help us with thisn request, we was hopin ya'll could find one farther local to yer perticulr bein an help those folk out. See, I am bettin that you could locatafy one of dem groups purty easy usin one of dose yeller & white paged telehone books.

Havin founded one of r sisterly groups in that perticuler fashion, we were hopin u culd correlate with dem rednecks n facilitate a propper timiliness for a gathering whar u culd shar the new-fangled terms n molicules that r gunna git dem dat better traction too. I recumend u bring dat fancy video wit ya so as they understand a bit more all da fancy trems fer why dey is about to git der butt whupped out on the trail wit dose sticky electrons dat make yer truk better den da truks dey built.

Aw, shucks. U know whut young fella, I shur wud tarably hate ta miss out on such a enlightemnet git together as dat is shur to b, so I gunna uphold my hand to my ol ticker, an make u a swerin. U do dis solid for my overland brothers, n I'll be there. I have ridden Pacific to Atlantic for less amuzin events, an I am old & retired. I till u whut, I wuld not miss such a knee-slapper, so I am off to git the ol power wagon prepared for da journey.

Oh, & son, thank ye agin for the tip on the tyres; I'll check dem while I am et it.

 

[racekarl]

Yes of course, but what I'm pointing out is that R.I.P doesn't know what he's talking about and that his criticisms should not be taken seriously. There's no better jack of all trades than the R1T, but no one is claiming it is the best in each category it's good at.

Please read the entire thread before tossing around statements like someone doesn't know what they are talking about, and do not bring the Tesla-style fanboy toxicity from those forums to this one.

 

[R.I.P.]

Yes of course, but what I'm pointing out is that R.I.P doesn't know what he's talking about and that his criticisms should not be taken seriously. There's no better jack of all trades than the R1T, but no one is claiming it is the best in each category it's good at.

Ah, shuks. I gist notified on de actuality dat der profile indicatates "R1T _soon_"

Well, slap my backside & call me thelma, see I had me the miscontaken enterpritation that I was communicatin wit a feller dat was drivin one uf dese mechanicl wonders as I am. Imagin my despondancy upon lernin dat he is not even an owner yet. Dis wood make it almost seem dat such a feller were not talkin frum 'sperience at all, but mayhaps takin his lernin soley from dem internet space waves.

Sits-in-puddles is all of the times tellin me to not judge a feller till ye have driven a mile in his R1T, but seein as this feller has no R1T, I feel a bit more righteousafied judging a certain Mr rivianbowstobirds ta b a keyboard warrior. I been tutaliged 'bout dem "KWs", n dose dat is smarter den me say dey all 'bout da attenten seeking behavioriges.

Well, fiddlesticks. I surely was hopin fer a showafication from Mr rivianbitsnbower wit his supiriorated machine. But, as me ol pappy useded to tell me, chickins seldom roost in da chimney. I gess dis is what I git for gittin on da space wave internet.

 

[wski441]

Hey R.I.P., how about you knock off the personal attacks.

 

[R.I.P.]

Please read the entire thread before tossing around statements like someone doesn't know what they are talking about, and do not bring the Tesla-style fanboy toxicity from those forums to this one.

It seems all threads eventually get taken down by the keyboard warriors, so why not have some fun with him lol.

I think we really have played this thread out anyway. I am hoping for improvements to report as updates come in, but more likely than not the off-road tires will not go back onto that truck. Mostly because it is not a "fun" truck to try to get through the obstacles. Most of our outings have a destination, and riding in somebody else's truck for the last half of the run because yours did not make it up a portion of the trail is not fun; it is a little humiliating lol.

This, I am sure, is not the case for all terrain types. The quad-motor seems to do quite well on rocky and hard pack surfaces. Most any surface where you are not dealing with soft ground, or ultra-low traction.

Unfortunately, we have those two things in abundance here.

 

[MountainBikeDude]

Well gall dern it iffn I infuriated that I wer not tarrbly greatful fer yer settin us lads straight on thot thar tyre issue. I knowed my kin & I r not affortulated some of that thar higer lernin dat de white folk git, so I shudda knowed that it were a superior I were listin to, & right stern givn the thot a bit more of a ponderin.

Havin been sit strate on that particular issuance, me & the lads were hopin you could see yerself fitted ta do us a further solid. See, thar r 4x4/off-road/overland orgiginations like owrs all ovir the county. Iffin usins is too far fer ya ta help us with thisn request, we was hopin ya'll could find one farther local to yer perticulr bein an help those folk out. See, I am bettin that you could locatafy one of dem groups purty easy usin one of dose yeller & white paged telehone books.

Havin founded one of r sisterly groups in that perticuler fashion, we were hopin u culd correlate with dem rednecks n facilitate a propper timiliness for a gathering whar u culd shar the new-fangled terms n molicules that r gunna git dem dat better traction too. I recumend u bring dat fancy video wit ya so as they understand a bit more all da fancy trems fer why dey is about to git der butt whupped out on the trail wit dose sticky electrons dat make yer truk better den da truks dey built.

Aw, shucks. U know whut young fella, I shur wud tarably hate ta miss out on such a enlightemnet git together as dat is shur to b, so I gunna uphold my hand to my ol ticker, an make u a swerin. U do dis solid for my overland brothers, n I'll be there. I have ridden Pacific to Atlantic for less amuzin events, an I am old & retired. I till u whut, I wuld not miss such a knee-slapper, so I am off to git the ol power wagon prepared for da journey.

Oh, & son, thank ye agin for the tip on the tyres; I'll check dem while I am et it.

I'm interested in SOME of the discussion happening in this thread, but this kind of response drags the entirety of it down to little more than shit posting back and forth.

It takes two to tango, I know, and I've been guilty of going down a similar path in the past, but developed some self control.

We are all here (in this thread, and on this forum for that matter) to understand the vehicle, it's technical prowess and limitations. But if you want to deal in absolutes, then just save yourself the time and don't bother posting a thread on a public forum inviting open discussion that may or may not align, then crap on people who think the potential may still be there to overcome your observed limitations.

Cheers.

PS For what it's worth, I appreciate your observations, it's furthered several fascinating discussions from the group on this.

 

[R.I.P.]

I'm interested in SOME of the discussion happening in this thread, but this kind of response drags the entirety of it down to little more than shit posting back and forth.

It takes two to tango, I know, and I've been guilty of going down a similar path in the past, but developed some self control.

We are all here (in this thread, and on this forum for that matter) to understand the vehicle, it's technical prowess and limitations. But if you want to deal in absolutes, then just save yourself the time and don't bother posting a thread on a public forum inviting open discussion that may or may not align, then crap on people who think the potential may still be there to overcome your observed limitations.

Cheers.

PS For what it's worth, I appreciate your observations, it's furthered several fascinating discussions from the group on this.

Ah, well, my attempt to deflect attacking behavior with humor appears to have fallen flat.

Apologies for any offense.

 

[graemebshaw]

@RIP I need to complete the math, but I think part of the issue with the Rivian on negative camber with low mu surface is that the center of gravity is lower (due to battery tray). This essentially puts more of the weight on the uphill tires than you would get on a higher CG vehicle.

A higher CG puts more weight on the downhill tires. If you are running in an open diff state, then these downhill tires will have little or no torque on them and all the available surface friction can be used to provide transverse support, keeping the truck from falling down the hill. The uphill tires, although having less friction to use, can slip under torque and impart some gradual forward propulsion (via slipping friction along the direction of traffic).

The Rivian with the low CG and lower normal force on the downhill tires may not have sufficient transverse friction to oppose the force trying to push the vehicle down the hill. Add to that the natural tendency of electric motors to break traction (even for a fraction of a second) and you could easily see a runaway situation where the vehicle starts crabbing down the fall line.

If I have time I will try to do the math later this week. But this is my suspicion.

 

[R.I.P.]

@RIP I need to complete the math, but I think part of the issue with the Rivian on negative camber with low mu surface is that the center of gravity is lower (due to battery tray). This essentially puts more of the weight on the uphill tires than you would get on a higher CG vehicle.

A higher CG puts more weight on the downhill tires. If you are running in an open diff state, then these downhill tires will have little or no torque on them and all the available surface friction can be used to provide transverse support, keeping the truck from falling down the hill. The uphill tires, although having less friction to use, can slip under torque and impart some gradual forward propulsion (via slipping friction along the direction of traffic).

The Rivian with the low CG and lower normal force on the downhill tires may not have sufficient transverse friction to oppose the force trying to push the vehicle down the hill. Add to that the natural tendency of electric motors to break traction (even for a fraction of a second) and you could easily see a runaway situation where the vehicle starts crabbing down the fall line.

If I have time I will try to do the math later this week. But this is my suspicion.

It would be fun, and quite useful to see the math behind the behavior. Thanks!

 

[graemebshaw]

It would be fun, and quite useful to see the math behind the behavior. Thanks!

And btw, some other posters have seen similar behavior on-road in snowy conditions with lots of camber. Snow mode may have helped some of that, but I don’t know.

I have been quite public about my fear of a 7000lb vehicle on icy highways at close-to highway speeds, especially if regen can’t be turned off entirely. High loads at high speeds with high rates of change in the forces involved (torque, traction, braking, regen, etc.) and super low-mu is terrifying.

 

[SeaGeo]

If I live in Denver, and I want to get to Kansas, there are a couple of ways to go. I can travel a short distance West, and I have achieved my goal. I can of course go East, and with a lot more work and expense get to Kansas by going around the world.

ummm...

Either something just whooshed over my head, or you are *really* bad at planning trips...

I think his elegant solution is to have a really bad sense of direction. Not very good when you're out in the middle of nowhere...

 

[R.I.P.]

And btw, some other posters have seen similar behavior on-road in snowy conditions with lots of camber. Snow mode may have helped some of that, but I don’t know.

I have been quite public about my fear of a 7000lb vehicle on icy highways at close-to highway speeds, especially if regen can’t be turned off entirely. High loads at high speeds with high rates of change in the forces involved (torque, traction, braking, regen, etc.) and super low-mu is terrifying.

I can attest to the terrifying part, and I am quite accustomed to some pretty hairy off-road stuff LOL. I have called the handling "evil," because the vehicle will just go completely sideways on you in ways I have never felt a vehicle do before. It just gets a mind of its own.

Edit:
Actually, I have been in vehicles before that acted this way. Vehicles that have a welded rear spool.

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