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Gear shift speculation

Discussion in 'Roadster: Technical' started by malcolm, Nov 2, 2007.

  1. malcolm

    malcolm Active Member

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    Am i correct in assuming that there are three options:

    1 Tesla gets the all-electronic(?) gear change working as intended

    2 has to install some mechanical doo-dad such as the zeroshift which carries a slight weight and efficiency penalty.

    3 has to install a clutch system ( A Clutch on top of Creep - Ugh!)
     
  2. WarpedOne

    WarpedOne Supreme Premier

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    I do not understand this fear from clutches.
    There is no need for it to be foot operated, it can be completely automatic and transparent.
     
  3. tonybelding

    tonybelding Active Member

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    It's an electro-hydraulic dual-clutch transmission. There is no manual clutch pedal, it's all controlled electronically. I believe that is similar in principle to the paddle shifters that are appearing on some cars these days.
     
  4. TEG

    TEG TMC Moderator

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    I wonder how much weight the dual clutches and electro-hydraulic actuators added to the transmission.
     
  5. WarpedOne

    WarpedOne Supreme Premier

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    Added?

    You think it was supposed to be clucthless? Sorry, but think again :)
     
  6. TEG

    TEG TMC Moderator

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    Well, what of all the talk of trying to do it without any clutches?

    http://www.teslamotors.com/blog3/?p=68
     
  7. WarpedOne

    WarpedOne Supreme Premier

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    I'd still prefer definitive statement from Tesla.

    Primarily because I do not know of a single case where clucthless transmission with fixed gear ratios was used in a car.
     
  8. donauker

    donauker Member

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    I'm not sure if you will get a definitive statement from Tesla at this point but based on my conversation with the Tesla people that were in New York City back in June of this year, this was indeed the initial design. While in theory this would work it did prove to be a huge challenge and they could not get the shift time down to an acceptable value. Also it would appear that it was rather easy to break the transmission when the shifting wasn't just right.

    I think it would be rather easy to do clutchless shifting with a permanent magnet DC motor but it proved to be too much of a challenge with an AC motor.
     
  9. malcolm

    malcolm Active Member

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    #9 malcolm, Nov 4, 2007
    Last edited: Nov 4, 2007
    I'm guessing that although it's easy to monitor the motor shaft rotation in both types, it's the electronic monitoring/prediction/control of the AC motor's torque immediately before and during the few hundredths of a second(?) change-over which is the tricky bit. Especially since a gear change can be initiated at any moment within quite a wide torque "window", including while the motor is decelerating the car/providing regen.

    Any delay between gear change initiation and actual change-over (while the electronics try to catch up with what's going on) would be very frustrating; e.g trying to minimize 0 to 60 times with TC off by trying to hit the optimum 52 mph change-over point.
     
  10. TEG

    TEG TMC Moderator

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    #10 TEG, Nov 10, 2007
    Last edited: Nov 11, 2007
    FYI, over here someone had said the original transmission was from Xtrac, then later switched to Magna.

    Here they said it was changed to get quicker shift times.
    Here they said the xtrac was "balky".
    Here Tony said the Xtrac was 'unreliable'.
     
  11. Kardax

    Kardax Member

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    The truth could be all of the above :)

    -Ryan
     

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