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Flat towing a Rivian

CommodoreAmiga

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Although I think this is great news, it confuses me even more.

Why would we be able to tow charge a Rivian in neutral to add range according to one customer service rep, yet not be able to tow a Rivian with any wheels on the ground according to a 2nd customer service rep, all in the same day?
Those are two different things. You could technically tow-charge the R1T behind an RV, but that is a different use case than the "flat towing" that RVers typically want.

Tow-charging involves pulling the R1T behind another vehicle, with the electric motors in the R1T being used as generators to charge the high voltage battery. This will create significant drag on the vehicle towing the R1T. There is also probably a limitation that you must stop tow-charging the vehicle once the battery reaches a certain charge state.

RVers want to flat-tow a vehicle not to charge it, but rather so that it can be unhooked and used as transportation when the RV is camped at its destination. Most RVers wouldn't want to deal with the huge hit to fuel economy caused by the drag of tow-charging. Also, the potential distance limitation imposed by tow-charging may not be acceptable for the RVers use case, anyway.
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srwaxalot

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There is the fact that tow charging at low speed for a short time is very much different then hours or days behind an RV at highway speed.
I can see them worried about battery over charge or some issue with the motors(over heat) after hours/days/weeks of towing vs. once a month or less tow charging in an emergency.
Could also be they didn’t have time or ability to long term test of flat towing to know if it’s safe and it’s better to error on the side of safety.
 

McRat

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I don't know how many of you have flat towed a 6000+ lb vehicle with no trailer brakes, but it's really not safe. In a panic stop, the rear of the tow vehicle lifts, and then the towed vehicle tries to lift and jack-knife the tow vehicle. Lightweight vehicles aren't that much of an issue.

While I did not have any problems doing this with a 7000lb pickup behind a motorhome, I only did it because I was out of options and only going 90 miles.
 

cwoodcox

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Yeah, this is what I was thinking. We’re talking about two different definitions of flat-towing. They demonstrated “flat towing in a pinch” to recharge on Long Way Up. They got a semi driver in Argentina (I think) to tow them a couple of miles and it added the 20 miles or so of range they needed to get to their destination. It’s possible and probably endorsed by Rivian.

Flat towing over long distances (decoupling the drivelines) might have been possible at one point, and was nixed. It makes sense that they would want to let the front wheels free-wheel for efficiency when rolling down the highway. But it could have also just been this mis-definition.
 

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StevieD

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Rivian R1T R1S Flat towing  a Rivian 2C760B5A-991F-4733-83B9-0CE613671574
 

StevieD

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I don't know how many of you have flat towed a 6000+ lb vehicle with no trailer brakes, but it's really not safe. In a panic stop, the rear of the tow vehicle lifts, and then the towed vehicle tries to lift and jack-knife the tow vehicle. Lightweight vehicles aren't that much of an issue.

While I did not have any problems doing this with a 7000lb pickup behind a motorhome, I only did it because I was out of options and only going 90 miles.
As far as braking is concerned, it’s easily solved. I tow my RAM 1500 behind my RV as I have done in the past with my Toyota TIndra, Scion xB, several Jeeps, and a few other vehicles. Because my RV has air brakes, I use Demco’s Air Force One to perform proportional braking action in the TOAD. It uses a small piston attached to the brake pedal to apply the brakes when needed and supplies vacuum to the brake booster to reduce the braking application force. Further, it has a breakaway switch to lock the brakes up if the toad separates from the RV. There are other systems that perform the same functions, including for those RVs with hydraulic brakes.
 

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2C760B5A-991F-4733-83B9-0CE613671574.jpeg
THIS IS A POSSIBLE SOLUTION — NOT THE ONLY SOLUTION — RIVIAN WOULD NEED TO SUPPORT IT IN PARTNERSHIP WITH AFTERMARKET SUPPLIER OR INCORPORATE IT IN ITS MANUFACTURING.



Problem Statement: EV motors and components are susceptible to damage when the EV is flat towed at the speed and distances normally experienced when towed behind an RV.



Proposed Solution: Manual Hub Locks will disconnect the drive wheel(s) from the entire line thereby inhibiting motion transfer to EV drive line components, including the EV motor.



Exemplars:



Manual Hub locks like the one shown operate at the wheel to set the configuration to “free wheel” or drive train “Hub”. Since flat tow already involves outside activities to attach the EV to the RV, the wheel configuration setting can easily be done at the same time.



Rivian R1T R1S Flat towing  a Rivian 1618322022508




One internal design that may likely be changed to suit Rivian EVs involves the drive line extending to the wheel hub housing to a termination point that allows its separation from the hub when selected. In the exemplar, the termination point is part #4049. The arrangement allows the wheel to free spin or be connected to the drive axle as the user selects.



Rivian R1T R1S Flat towing  a Rivian 1618322022567




The manufacturer currently offers the product in marine grade stainless steel, different appearance options, and different vehicle configurations.



A typical set of parts supporting 4 wheels purchased today on Amazon for the right vehicle costs less than $600 .
 

StevieD

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I don't know how many of you have flat towed a 6000+ lb vehicle with no trailer brakes, but it's really not safe. In a panic stop, the rear of the tow vehicle lifts, and then the towed vehicle tries to lift and jack-knife the tow vehicle. Lightweight vehicles aren't that much of an issue.

While I did not have any problems doing this with a 7000lb pickup behind a motorhome, I only did it because I was out of options and only going 90 miles.
Like this:
Rivian R1T R1S Flat towing  a Rivian 1618322221638
 

rickydsc

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@CappyJax - Have some good news about regen during flat tow. I found a recent article (posted yesterday!) stating regen IS possible during flat tow.

"Many people like to use their motor home or a 5th-wheel to tow a vehicle behind it. Rivian says that the R1T will be capable of charging its batteries while being flat towed behind an RV or another vehicle. This is an innovative idea, but it could and would add an extra burden on the vehicle that is towing it."​

Source - TFLTruck: "Now the Rivian R1T Electric Pickup Truck Comes with a Kitchen Sink and Can Be Charged While Being Towed Behind an RV" - May 20th, 2019
This was actually demonstrated in the series "Long Way Up" on Apple TV+. There was one occasion where one of the Rivian prototypes used on that trip ran out of juice. So they got a friendly Trucker to tow them for 30 minutes or so to get some charge. If I remember correctly, I think they said the battery could be charged to 80% with an hour of towing.
 

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StevieD

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There’s been a lot of discussion about flat towing ranging from the basics of what is needed by most people, including me, of being able to tow behind their RV to additional benefits of enhanced braking, battery charging, etc. Unfortunately, the most recent news from the Rivian team is that flat towing is not available and other features are limited.

I’ve presented some considerations to Rivian who have held out that it’s under review by the design team. We’ll see.

This is the most recent letter I’ve received from Rivian regarding current flat tow capabilites:

Rivian R1T R1S Flat towing  a Rivian BAF85ACB-CCF4-4B6D-B329-E8F0D1676B12
 
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Max

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Can someone that understands this stuff explain to me what is the difference between flat towing and putting a Rivian in energy saving mode where two of the motors are not working? If power can be cut off to two of the motors at 70 mph with no drag and no regen, why can't this be done to all four wheels? What am I missing or misunderstand here?
 

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Can someone that understands this stuff explain to me what is the difference between flat towing and putting a Rivian in energy saving mode where two of the motors are not working? If power can be cut off to two of the motors at 70 mph with no drag and no regen, why can't this be done to all four wheels? What am I missing or misunderstand here?
As I understand it, the two rear motors are disengaged from their axels by a what is essentially a single-speed clutch. The front motors probably don’t have those clutches.
 
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DeafPug

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Do not tow the R1T with another vehicle with either the front or rear wheels on the ground and rolling. From page 175 and 177 of the current R1T Owner's Guide:

Rivian R1T R1S Flat towing  a Rivian 1639538082605


Rivian R1T R1S Flat towing  a Rivian 1639538139060


There is no disengaging clutch on the rear axle that allows the rear wheels to rotate without damaging the motors on the rear axle. Edit: a couple people pointed out that there is actually a clutch on the rear axle. That's what I get for assuming the R1T is like every other EV out there and doesn't have a clutch.

Also as @Autolycus said, the reason this is a problem on EVs is that for almost all EVs, there is generally no clutch that can be disengaged or transmission that can be put in neutral. For neutral on an EV, you are just shutting down the field to the electric motor and letting the system coast. There is a gear reduction unit (single speed transmission) that is always engaged and ties the motor directly to the wheels. As you tow the vehicle, the motors are going to be spinning, and will be doing so without any supplemental cooling that the vehicle may have. In addition, no power will be applied to supplemental oil pumps/coolers for the gear reduction unit. Both the motor or the gear reduction unit could overheat due to lack of cooling or possibly suffer issues due to lack of lubrication.
 
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I wonder why there's no mode that allows it to be towed on a dolly with only the rear wheels on the ground, make a mode similar to conserve where the rear motors are disengaged, then you can simply just tow it behind an RV on a dolly, like a lot of people do already with some vehicles behind their RV's
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