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Neutral gear

Discussion in 'Roadster' started by WarpedOne, Aug 26, 2006.

  1. WarpedOne

    WarpedOne Mainecoon Butler

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    I was wondering does it have one?

    I understand there is no clutch pedal, so computer decides on transmision configuration based on stickshift position. What if I want to glide down the hill without engine braking? Can I just disengage the 'gas' pedal, put in into neutral and glide? If there is no neutral it will be necessary to always 'search' for that optimal 'gas pedal' position that doesn't accelerate nor decelerate.
     
  2. Tesla2Go

    Tesla2Go Member

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    I guess gliding down a hill will still cause the car to accelerate, I think you would still have to touch the brakes once in a while.
     
  3. tonybelding

    tonybelding Active Member

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    I may be wrong about this. . . But I'm pretty sure I read a comment somewhere that it's programmed to use very little (if any) regenerative braking when it's in high gear. I would take a guess that you can put it in high and roll freely down the hill. Regenerative braking is programmed to simulate engine braking on a conventional sports car, which of course happens in the lower gears.
     
  4. tevvybear

    tevvybear New Member

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    i'm no expert on this sort of thing, but i would suspect that the car would effectively be in neutral whenever neither the "throttle" or brake pedal is pressed. if you've ever played around with a small DC electric motor (yes, i know the roadster uses an AC motor) you may have noticed that if you spin it with no wires attached, it spins fairly freely. But what happens if you put a wire across the terminals (short circuiting)? you get a braking effect. so what if you put a resistor across? you get braking, but not as much. I think the braking energy is relative to the electrical energy output. (so with the short circuit, a high power is generated, with the resistor, a medium ammount of power is generated, and with the open circuit, no current (and so no power) flows, and you get no braking force.)

    Whether the 3 phase AC induction motor works in a similar way i don't really know, but there's a good chance that it does.
     
  5. tonybelding

    tonybelding Active Member

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    Tesla have been pretty clear about how regenerative braking works on the Roadster. There's a certain position where you can hold the accelerator and it will maintain speed, but if you let off it will go into regenerative braking and slow the car. The mechanical brakes are only engaged when you depress the brake pedal. So. . . Unlike some electric cars, the Tesla lets you decide which type of braking you use.

    Regarding neutral gear. . . I believe you can physically put the shifter into a neutral position when the car is moving, just like any other sports car. I'll assume that until somebody tells me otherwise, at least. :)
     
  6. why would the Tesla require disc brakes, when the motor can handle all the braking needs? Can't the motor slow the car down from 60 to 0 all on by itself, without disc brakes being used. if disc brakes were discarded, it would be one less car part to have to maintain.
     
  7. asdar

    asdar Member

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    The government requires that a car has brakes to get certification. There's no way around that right now.

    I believe that regenerative braking isn't good at very low speeds, putting a lot of strain on the motor and also draining the battery. I'm no expert on this, but I read it on the web so it must be true. :)
     
  8. paco3791

    paco3791 TMC OG

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    I have helped design similar sytems on other types of transport and in my experience engine braking is used to brake the vehicle. when you let off of the "peddle" it would be very unnatural for the car to immediatly go into regen, regen can be a very hard braking, making that big of an AC motor into a generator is going to supply alot of power and would be similar to hard engine breaking on a normal car. It can be very hard even violent braking if not controled correctly.

    I would guess that if you let off of the accelorator the moror will stay in motor mode and you will simply coast, if you then hit the brake petal the motor switches to generator mode and the regen assits the brakes in slowing down the car. if anyone here has a prius or other hybrid car they might be able to shed some more light on this subject as I would assume that Tesla would use a similar kind of configuration. I think the main consideration they would have is making it feel like a regular car as much as possible. I can't wait until the Chicago dealership opens up and I can go ask some of these questions for myself.
     
  9. Michael

    Michael Member

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    Tesla folks indicate that they do not use regenerative brake assist on the brakes.
     
  10. paco3791

    paco3791 TMC OG

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    Interesting, do you a have a link by any chance?
     
  11. electrified

    electrified Member

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    One of Tesla's engineers made a responce to a comment in the blog. you have to read fairly deep into the comments to find it. If you search for the editor's comments, it might help, the editor posted his position in the company.
     
  12. tin-chicken

    tin-chicken Guest

    From the Tesla blog:
    #
    Mike Harrigan wrote on November 10th, 2006 at 7:16 pm e

    In response to david_42 on the combined accelerator/brake:

    The Tesla Roadster has regenerative braking linked to the accelerator. The regen braking is designed to emulate a manual transmission car with an ICE. When you lift off the accelerator the car slows down. The amount of deceleration is proportional to the amount you lift off the accelerator and regen is stronger in 1st gear than in 2nd gear (again to emulate a standard transmission car). We stayed away from things like pivot/push pedals because we want the car to feel as natural and normal as possible to drivers. I can say that when you drive the car it is very easy to adapt to it - the only real difference is that the regenerative braking will completely stop the car. Once you get used to it you can drive in normal city stop/go traffice without touching the brakes unless traffic stops suddenly. As a last comment, the brake pedal does not link to the regenerative braking in any way. It controls the power ABS disk brakes as it would in any normal car.



    Editor’s note: Mike Harrigan is Vice President of Customer Service and Support at Tesla Motors.
     
  13. tin-chicken

    tin-chicken Guest

    Oh, and I found this on the Tesla blog - the editor is a woman ;D
    #
    Bob wrote on September 30th, 2006 at 1:37 pm e

    ed wrote:
    “who is the zombie, censoring this blog site. his brain must be not very large.”

    Well, I’ve just come from the EV rally in Palo Alto and I met The Editor aka Engineering Director. *She* has a very large brain and exhibits no evidence of zombie behavior.

    Bob
     
  14. paco3791

    paco3791 TMC OG

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    thanks, chicken that is very interesting. I wonder if they disengage regen altogether when you hit the brake? I guess I'll just have to take a test drive and see what it's like ;D
     

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