5 ms·

> able to get a tow truck capable of transporting my car (turns out you need one that has a full bed because of the regenerative breaking Sounds incredibly sho

by dinom 3y ago

> able to get a tow truck capable of transporting my car (turns out you need one that has a full bed because of the regenerative breaking Sounds incredibly short-sighted that the regenerative braking can't be temporarily disabled by the driver... two people can push a "regular" car to a nearby gas station in a pinch. Even one person can push a smaller car around a parking lot if necessary. That said, they often send out full/flat bed tow trucks these days for almost any reason. Edit: fixed "breaking" to "braking"

sib 3y ago
If you put the car in car wash mode, you would be able to push the car: Controls > Service > Car Wash Mode And then "Enable Free Roll"
- dinom 3y ago
  thank you
- firesteelrain 3y ago
  ... assuming you have battery (which he didn't)
  - dinom 3y ago
    Yeah, that's a fair point but isn't it true that a mostly discharged battery will still have enough charge to perform some limited functions. E.g. even in a normal car I think a dead battery can power the lights even though the starter only "clicks". Nonetheless, I'm a rather conservative type of person and see your point so in my "dream car" I might want a way to manually put the car in neutral (or free-roll mode, whatever you want to call it). That's why locking hubs came to my mind in a prior reply.
    - firesteelrain 3y ago
      For the Tesla, it shut itself off in this story. Regardless of whether it may have had some juice left
purpleidea 3y ago
Tesla cars are way heavier. Nobody is pushing one with their friend. Unless it's downhill.
- reaperman 3y ago
  I'd need to do some quick math to double-check but very rough ballpark estimates still make me think Teslas can be pushed by a single person. After all, a single strongman can pull a passenger airliner, and any car is nearly impossible to push uphill -- you have to really get some momentum built up first to let them coast up driveways/etc.
  - Reubachi 3y ago
    It's not about weight or incline, it's the mechanical gearing in the "transmission" that can't turn the wheels without 100 percent power from the engine. You'll be able to push it and think it's really heavy, but it's just the transmission fighting you. standards and automatic trans have neutral that disconnects driveshaft from engine, removing any resistance from the engaged gear. Most EVs either don't have neutral or a poor implementation of it, because of single gear transmission/direct drive.
    - dinom 3y ago
      > Most EVs either don't have neutral or a poor implementation of it, I'm sorry, do you mean that neutral and "car wash/freeroll mode" are not 100% equivalent? This really confounds me... if my car has a problem while driving down the road, I'd really like to have a chance of pushing it onto the shoulder if necessary. A car that you can't do this with sounds very poorly designed to me.
      - stetrain 3y ago
        They aren’t equivalent. Most EVs have a free roll mode, where you can push the car or take it through a car wash. You are still spinning the electric motors though. This is fine for low speeds and short distances but is not advised for towing, like with tow trucks that leave two of the car’s wheels on the ground.
e136 3y ago
Most cars have one or more clutches to put the car in neutral. This is required so the engine can idle while the car stands still, among other reasons. Electric cars don't need to idle and therefore don't have any clutches in the drivetrain. Adding clutches just for allowing the user to push around the car seems needlessly complicated and over optimizing for a scenario that will not occur for the majority of cars.
- dinom 3y ago
  > don't have any clutches in the drivetrain Wouldn't a clutch be unnecessary in this case... a complete disconnect from the drive train should suffice, no?
  - caconym_ 3y ago
    That's exactly what a clutch does. They show up in all sorts of places besides the third pedal "clutch" drivers of standard transmissions are familiar with, e.g. in part-time AWD systems, traditional automatic transmissions with planetary gears, torque converters and hybrid transmissions with lockup clutches for efficient cruising, and so on.
    - dinom 3y ago
      I understand that... so you're saying something like "unlocking hubs" would not suffice? Or they'd add too much cost to the vehicle?
      - caconym_ 3y ago
        Locking (wheel) hubs could certainly be used to disconnect the wheels from whatever drivetrain trouble lurks within, but they come with a whole lot of compromises: cost, weight, complexity, space, etc. Standard industry practice for vehicles that can't be towed with only two wheels immobilized is (and has been for decades iiuc) to flatbed tow them, so Tesla isn't really going against the grain here. I think it's a fine choice.
- 3y ago
deleted 3y ago
[deleted]
caconym_ 3y ago
It's common for cars with AWD systems where the rear drivetrain can't be disconnected by a clutch to require flatbed towing, less because the car can't physically be moved with the power off and more because spinning the wheels at a sustained high speed will cause damage to the drivetrain and potentially the engine. E.g. my moldy old Subaru requires flatbed towing, because spinning the rear wheels while the fronts are immobile will destroy the limited-slip center diff, but it's totally possible to push it along with all four wheels on the ground. I think AWD Teslas have an independent motor and drivetrain for the rear wheels. Naively, one would expect that if you unload the rear axle motor/generator you could just tow the car with little resistance and no damage, but in practice the picture is probably more complicated. I would love to hear from an expert.
rdevsrex 3y ago
Yeah when I lived in South Africa, I saw people towing each other all the time with just a rope. Sure it was one of those flat threaded ropes, but it works.

by dinom 3y ago

sib 3y ago

If you put the car in car wash mode, you would be able to push the car: Controls > Service > Car Wash Mode And then "Enable Free Roll"

dinom 3y ago
thank you
firesteelrain 3y ago
... assuming you have battery (which he didn't)
- dinom 3y ago
  Yeah, that's a fair point but isn't it true that a mostly discharged battery will still have enough charge to perform some limited functions. E.g. even in a normal car I think a dead battery can power the lights even though the starter only "clicks". Nonetheless, I'm a rather conservative type of person and see your point so in my "dream car" I might want a way to manually put the car in neutral (or free-roll mode, whatever you want to call it). That's why locking hubs came to my mind in a prior reply.
  - firesteelrain 3y ago
    For the Tesla, it shut itself off in this story. Regardless of whether it may have had some juice left

purpleidea 3y ago

Tesla cars are way heavier. Nobody is pushing one with their friend. Unless it's downhill.

reaperman 3y ago
I'd need to do some quick math to double-check but very rough ballpark estimates still make me think Teslas can be pushed by a single person. After all, a single strongman can pull a passenger airliner, and any car is nearly impossible to push uphill -- you have to really get some momentum built up first to let them coast up driveways/etc.
- Reubachi 3y ago
  It's not about weight or incline, it's the mechanical gearing in the "transmission" that can't turn the wheels without 100 percent power from the engine. You'll be able to push it and think it's really heavy, but it's just the transmission fighting you. standards and automatic trans have neutral that disconnects driveshaft from engine, removing any resistance from the engaged gear. Most EVs either don't have neutral or a poor implementation of it, because of single gear transmission/direct drive.
  - dinom 3y ago
    > Most EVs either don't have neutral or a poor implementation of it, I'm sorry, do you mean that neutral and "car wash/freeroll mode" are not 100% equivalent? This really confounds me... if my car has a problem while driving down the road, I'd really like to have a chance of pushing it onto the shoulder if necessary. A car that you can't do this with sounds very poorly designed to me.
    - stetrain 3y ago
      They aren’t equivalent. Most EVs have a free roll mode, where you can push the car or take it through a car wash. You are still spinning the electric motors though. This is fine for low speeds and short distances but is not advised for towing, like with tow trucks that leave two of the car’s wheels on the ground.

e136 3y ago

Most cars have one or more clutches to put the car in neutral. This is required so the engine can idle while the car stands still, among other reasons. Electric cars don't need to idle and therefore don't have any clutches in the drivetrain. Adding clutches just for allowing the user to push around the car seems needlessly complicated and over optimizing for a scenario that will not occur for the majority of cars.

dinom 3y ago
> don't have any clutches in the drivetrain Wouldn't a clutch be unnecessary in this case... a complete disconnect from the drive train should suffice, no?
- caconym_ 3y ago
  That's exactly what a clutch does. They show up in all sorts of places besides the third pedal "clutch" drivers of standard transmissions are familiar with, e.g. in part-time AWD systems, traditional automatic transmissions with planetary gears, torque converters and hybrid transmissions with lockup clutches for efficient cruising, and so on.
  - dinom 3y ago
    I understand that... so you're saying something like "unlocking hubs" would not suffice? Or they'd add too much cost to the vehicle?
    - caconym_ 3y ago
      Locking (wheel) hubs could certainly be used to disconnect the wheels from whatever drivetrain trouble lurks within, but they come with a whole lot of compromises: cost, weight, complexity, space, etc. Standard industry practice for vehicles that can't be towed with only two wheels immobilized is (and has been for decades iiuc) to flatbed tow them, so Tesla isn't really going against the grain here. I think it's a fine choice.
3y ago

deleted 3y ago

[deleted]

caconym_ 3y ago

It's common for cars with AWD systems where the rear drivetrain can't be disconnected by a clutch to require flatbed towing, less because the car can't physically be moved with the power off and more because spinning the wheels at a sustained high speed will cause damage to the drivetrain and potentially the engine. E.g. my moldy old Subaru requires flatbed towing, because spinning the rear wheels while the fronts are immobile will destroy the limited-slip center diff, but it's totally possible to push it along with all four wheels on the ground. I think AWD Teslas have an independent motor and drivetrain for the rear wheels. Naively, one would expect that if you unload the rear axle motor/generator you could just tow the car with little resistance and no damage, but in practice the picture is probably more complicated. I would love to hear from an expert.

rdevsrex 3y ago

Yeah when I lived in South Africa, I saw people towing each other all the time with just a rope. Sure it was one of those flat threaded ropes, but it works.