Flat towing Cybertruck?

[Stainlessbus]

Will the tri motor cybertruck be flat towable on the ground eg. behind a motor home?

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[Ehninger1212]

Most likely not. You cant even flat tow most ICE vehicles. Tesla's currently have to be towed by a trailer or a flatbed or it will void the warranty.

 

[Mammalian04]

Thank would be a bummer. I've already confirmed with Rivian (early reservation made) and Atlis (vaporware for now) that their trucks will be flat towable. We know that the F-150 is and there shouldn't be any reason the F-150 Hybrid is not. The F-150 full electric is still up in the air. I really want to keep my Cybertruck reservation but not being flat towable would kill the utility for me.
Does anyone know a way to get this answered? I was able to obtain an answer from Rivian pretty easily but the channels I've tried with Tesla have not resulted in any response.

 

[android04]

The answer will probably be no. As mentioned already, no Tesla can be towed on it's own wheels for a few reasons.

1st reason is for permanent magnet motors (in Model 3 and Y, Raven Model S and X) they will always generate electricity when spun and that has to go somewhere or else it will damage the inverter or battery. Cybertruck will most likely have at least 1 permanent magnet motor (a mix of permanent magnet and induction motors is what I expect for the Dual- and Trimotor). In the manual, Tesla warns of overheating that may occur if towed on it's wheels for more than 30 feet or more than 3 MPH. This is possibly related to generating electricity that goes nowhere if the car is off or the battery is full. With an induction motor, you can turn off regeneration but those are only on older (pre-Raven) Model S and X vehicles.

2nd reason is that all Teslas have an electronic or electromechanical parking brake that locks the rear wheels from spinning. You can put it in"Tow Mode" or "Transport Mode" to release the parking brake, but it re-applies them after 30 feet or if it starts to move above 3 MPH.

3rd reason could just be that Tesla doesn't want the added liability of increased wear and tear or risk of damage that may occur from flat towing. Remember that the battery and motor warranties for Teslas are 8 years and at least 100k miles (up to unlimited miles for some older Model S and X).

 

[ajdelange]

1st reason is for permanent magnet motors (in Model 3 and Y, Raven Model S and X) they will always generate electricity when spun and that has to go somewhere or else it will damage the inverter or battery.

Actually that is not a problem. WIthout going into the details I'll just point out that a generator (like the ones you buy at Home Despot) is a synchronous motor to which mechanical power is supplied rather than being withdrawn. Can you start a generator and run it without a load? Of course. Same with these motors.

Tesla is certainly adamant about not towing for more than even a few feet in their current cars. Obviously they could change their design or their policy but they seem hard and fast on this. To be honest, I don't understand it. I've made at least one 20 mile trip at the end of which the battery was at a higher SoC than at the beginning. Clearly the car was "towed" along the road by gravity over much of that distance. How would towing behind another vehicle be different? How is Rivian able to do it?

 

[android04]

Actually that is not a problem. WIthout going into the details I'll just point out that a generator (like the ones you buy at Home Despot) is a synchronous motor to which mechanical power is supplied rather than being withdrawn. Can you start a generator and run it without a load? Of course. Same with these motors.

Tesla is certainly adamant about not towing for more than even a few feet in their current cars. Obviously they could change their design or their policy but they seem hard and fast on this. To be honest, I don't understand it. I've made at least one 20 mile trip at the end of which the battery was at a higher SoC than at the beginning. Clearly the car was "towed" along the road by gravity over much of that distance. How would towing behind another vehicle be different? How is Rivian able to do it?

My point with #1 is that the permanent magnet motor will generate electricity when spun whether you want it or not, and it has to go somewhere. If the car is off or if the battery is full, it will probably just be converted to heat or a magnetic field that can damage or overheat components. For induction motors like what is in the pre-Raven Model S and X (and in the front motor only for Model 3 and Y) they can be turned off completely and spinning them will not generate any electricity. So if Tesla wanted to, they could enable a "TOAD" mode on pre-Raven Model S and X that keeps the parking brake deactivated and the induction motors off so there is no regeneration.

This is just due to the difference in the two types of motors that Tesla uses. The PMSR (what I call the permanent magnet motor) is newer and started being used with the Model 3 in 2017. It actually has magnets in the rotor to create a magnetic field, and those can't be turned off. So it will generate electricity when spun. The induction motor has no magnets, and it's what Tesla used on all their vehicles before the 2017 Model 3. It's also what's used for the front motor on all AWD Model 3 and Y, and for rear motor on Raven Model S and X. The induction motor has a field that is electronically controlled and can therefore be turned off completely. Thus it's possible to spin this motor without generating electricity and creating heat (except that due to friction).

The Rivian R1S and R1T most likely have 4 induction motors (one per wheel) and they can therefore completely power them off so there's no regeneration when spun.

 

[ajdelange]

This is just due to the difference in the two types of motors that Tesla uses. The PMSR (what I call the permanent magnet motor) is newer and started being used with the Model 3 in 2017. It actually has magnets in the rotor to create a magnetic field, and those can't be turned off.

Again I ask you to ponder why this isn't a problem in a generator. The answer is that the magnets can be turned off, or rather, they can be effectively turned off so....

So it will generate electricity when spun.

..that no electricity is generated when the rotor is turned. I was hoping to avoid the technical nitty-gritty but the fact is that the torque produced by or absorbed by a synchronous machine is the product of the magnitudes of the rotor and stator fields multiplied by the sine of the angle between them. The trick here would be to simply align the stator field with the permanent magnet field (sin(0) = 0) and Bob's your uncle. The motor would neither produce nor absorb torque and thus no electric energy would be generated. A simpler approach would be to simply close the bottom switches (all 3) in the inverter/rectifier bridge thus effectively shorting the stator coils. As the impedance of the closed switches is low little actual power would be generated. A small torque would be, however.

The motors (synchronous and inductive) in the Tesla are symmetric machines. They can produce torque in either direction and, as such must also be able to produce 0 torque, by controlling the stator field. This is the more elegant solution, of course, and, as these machines produce positive, negative and 0 torque as a matter of course in normal operation quite doable with the disadvantage that the motor control systems would have to be on line while towing. Again, I am most curious as to how Rivian pulls this off.

The induction motor has a field that is electronically controlled and can therefore be turned off completely. Thus it's possible to spin this motor without generating electricity and creating heat (except that due to friction).

As noted earlier the synchronous motor also has an electronically controlled stator field. If you like you could think of the 0 torque situation as being one where the stator field follows and cancels the permanent magnet field.

The Rivian R1S and R1T most likely have 4 induction motors (one per wheel) and they can therefore completely power them off so there's no regeneration when spun.

Well I, and I'm sure, a lot of other people here and elswhere, wonder what kind of motors are in the Rivian. PM motors are becoming awfully popular these days as they have no copper in the rotor (and thus, no copper losses making them more efficient) in addition to which the field in the rotor never reverses reducing rotor hysteresis loss. And they are cheaper to make. But I assure you there is no problem with free wheeling a PM motor.

 

[android04]

Again I ask you to ponder why this isn't a problem in a generator. The answer is that the magnets can be turned off, or rather, they can be effectively turned off so....



..that no electricity is generated when the rotor is turned. I was hoping to avoid the technical nitty-gritty but the fact is that the torque produced by or absorbed by a synchronous machine is the product of the magnitudes of the rotor and stator fields multiplied by the sine of the angle between them. The trick here would be to simply align the stator field with the permanent magnet field and Bob's your uncle. The motor would neither produce nor absorb torque and thus no electric energy would be generated. A simpler approach would be to simply close the bottom switches (all 3) in the inverter/rectifier bridge thus effectively shorting the stator coils. As the impedance of the closed switches is low little actual power would be generated. A small torque would be, however.

The motors (synchronous and inductive) in the Tesla are symmetric machines. They can produce torque in either direction and, as such must also be able to produce 0 torque, by controlling the stator field. This is the more elegant solution, of course, and, as these machines produce positive, negative and 0 torque as a matter of course in normal operation quite doable with the disadvantage that the motor control systems would have to be on line while towing. Again, I am most curious as to how Rivian pulls this off.

As noted earlier the synchronous motor also has an electronically controlled stator field. If you like you could think of the 0 torque situation as being one where the stator field follows and cancels the permanent magnet field.

Well I, and I'm sure, a lot of other people here and elswhere, wonder what kind of motors are in the Rivian. PM motors are becoming awfully popular these days as they have no copper in the rotor (and thus, no copper losses making them more efficient) in addition to which the field in the rotor never reverses reducing rotor hysteresis loss. And they are cheaper to make. But I assure you there is no problem with free wheeling a PM motor.

So then it sounds like my #3 is the main reason then, along with the small added battery drain of a "TOAD" mode. If this is true, then Tesla could update their firmware on the car and allow the motors (no matter if PMSR or Induction) to freewheel without generating electricity or magnetic fields that would cause issues. The only negatives would be more wear and tear due to friction (but not different compared to normal driving or regen braking).

Also, the Rivian might have a neutral if it has the ability to do different gearing (like for rock crawling). I can't remember if it does from all the videos and interviews I've seen about it.

 

[ajdelange]

AFAIK in the current models there are no gears or clutches that one can disengage. There is a neutral but I think all it does is prevent the parking brake from engaging.

 

[Mammalian04]

I'm still trying to find an answer from some avenue. I'll report back if I have any success.

 

[Pkbikeman]

RESTATING PLEASE HAVE APOSITION TO FLAT TOW WITH ELECTRIC INTERFACE FOR LIGHTS AND BRAKING PERHAPS AN OPTION?

 

[CanEHdian]

Why tow? With full FSD just let it follow. Even add some friends during covid. Just saying.

 

[Rhino5]

I'll add another +1 for flat tow capability. I would love to pull this behind my RV.

 

[Crissa]

While flat towing isn't a capability of any other Tesla, as a utility vehicle that will be away from services this would be a good feature to have, at least for short bouts.

-Crissa

 

[rick]

I'll add another +1 for flat tow capability. I would love to pull this behind my RV.

Add to that the ability to incorporate the CT's regenerative braking when the RV brakes, thus adding to the battery pack charge until it's full. on a longer trip.

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