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Differential

Discussion in 'Roadster: Technical' started by Curious, Feb 23, 2010.

  1. Curious

    Curious New Member

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    Hello,
    I have been trying to find out whether or not the Tesla Roadster has a differential on the rear axle. I have read in some places that it has a transaxle, whereas some say that the differential is incorporated into the borg warner gearbox. Can anyone definitively tell me which one of this is true?

    Cheers,

    ps. speculation un-welcome :smile:
     
  2. doug

    doug Administrator / Head Moderator

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    #2 doug, Feb 23, 2010
    Last edited: Feb 23, 2010
    That's what a transaxle is, the function of the differential and the gear box in the same package.
    In this case it's a single fixed gear ratio and an open differential.

    The drivetrain 1.5 transaxle is shown here mounted to the motor (with air cooling shroud).

    3472493838_afbf678e46.jpg


    See also here: Tesla Motors - Engineering
     
  3. Curious

    Curious New Member

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    The picture you have posted shows a motor attached to side of a gearbox. To my knowledge, this gearbox is the 31-01 Electric Drive Transmission supplied by Borg Warner. After reading more on the link you posted, the information I have gathered is that the axle goes at the bottom centre of the gearbox. In this picture, the reddish part at the bottom of the gearbox.
    How is the axle a transaxle? Doesn't the Borg Warner gearbox included a differential??
    Correct me if Im wrong,

    Cheers,
     
  4. mpt

    mpt Electrics are back

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    It does; imagine the other side of the red plug; that's the drive to the other wheel.

    What you're looking at is pretty much ALL of the oily bits in a modern car.
     
  5. Roger Reid

    Roger Reid Old but effective

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    I wonder if the "differential" shown earlier in this thread can have different ratio's. In autocross I'll never see 115 mph. Could a lower ratio quicken things up between 0-80?
     
  6. vfx

    vfx Well-Known Member

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    Or would it be easier to reprogram the firmware?
     
  7. TEG

    TEG TMC Moderator

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    The torque "curve" (er., elbow) is really stilted towards low end, so having shorter gearing isn't going to help so much. Once you are up above 9K RPMs (80MPH) the torque and power are dropping off. Of all the things to ponder trying to improve on the Roadster, the 0-80 performance seems like one of the things that is already well optimized!

    How about further improved braking? Carbon-ceramic rotors anyone?
     
  8. vfx

    vfx Well-Known Member

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    There are improvements that could be made that would benefit a short track with no long straights.

    Remember the original two gears were for getting up to a top speed around 130. In first gear the car could get 0 to 60 in 3.9.

    Then they dropped the second gear and fixed the gear ratio between one and two but tweaked and tweaked on the torque curves until they got it back to 3.9.

    This improvement is with a less than ideal gear ratio for 0 to 60. If 60 or 80 was your max speed on a track there are surely gear and/or firmware changes that would eek out a few fractions of a second on times.
     
  9. qwk

    qwk Model S P2681

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    How about just buying a smaller in diameter back tire/wheel combo for the track? Does the same thing. It will be much cheaper and you could use them whenever you want, then switch back for the daily driving.
     

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