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Thread: 450-452 subframe - Converting a Roadster to electric power

  1. #11
    Join Date
    Dec 2015
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    Although the motor has an encoder output which goes into the curtis controller to control the motor speed, I think you are right and a separate line using the standard RPM sensor would be the simplest way.

    Had a look into the gear change, I think this will be ok as it appears to have a DC motor and encoder on the selector drum, so will probably build a separate controller to turn a button shift into a rotary position, question is can I crash the box?!, power will be momentarily off the motor at the time of changing but not sure if there will be too much inertia in the motor to allow the gears to change..

    In terms of using standard gauges, as I can also get a reading of the power going into the motor I thought I could simulate the turbo pressure sensor and make use of the Turbo boost gauge, 1.0 bar being the 100% continuous power reading, 2 bar max for 200% (although I think i can run at 300% for short times) and I also get negative bar readings when regenerative breaking kicks in... seems applicable.

    The guy I bought the motor off mentioned 12v vacuum kits.. one not to forget!.

    On a sort of related point, I was thinking of changing the steering wheel for a paddle shift but looked unnecessarily awkward for the small benefit so never did it, but wondered if it was easier to make 'stick on' paddles with wireless comms to a small board that you fit to the standard gear shift switches, so basically does the same job but with a lot less wiring... if this is a useful thing people might be interested in then I may do this as a separate thing?.

  2. #12
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    Quote Originally Posted by crispy View Post
    Had a look into the gear change, I think this will be ok as it appears to have a DC motor and encoder on the selector drum, so will probably build a separate controller to turn a button shift into a rotary position, question is can I crash the box?!, power will be momentarily off the motor at the time of changing but not sure if there will be too much inertia in the motor to allow the gears to change.. .
    There is a 6(?) page PDF online (in German) that details extensively the gearbox - including a schematic for gearchanging showing how all the sensors and actuators function WRT time. The shaft speeds are matched prior to executing the shift. If you can incorporate that level of control then a stand alone controller should work. If not you are dependent entirely on the synchro and how you configure the selector motor operation.

    NB. 1st and 4th, 2nd and 5th, 3rd and 6th ratios share pinions. The lower or higher (3) ratios are selected with a change of diff ratio. Choosing one of those pairings would permit that only the diff ratio requires shifting.

  3. #13
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    Dec 2015
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    Thanks, that's very useful info, although the ability to change gears isn't that important for the conversion as I can lock it into a fixed ratio I think it would be useful even if it wasn't very quick. I've had a look for the document but can't find anything, do you have a link to it?. The diff ratio shift sounds like it would be a good option. I'm sure the encoder position of the selector will be ok to read but I've noticed on pictures the the motor has 6 pins so not sure why. I need to buy a gearbox so might do that soon and have a look.

  4. #14
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    Both gear shift motor and clutch actuator motors contain rotary encoders. These generate two square waves 90 degrees out of phase. This type of signal is what they call a quadrature output.



    Two pairs of cables conduct the signal to engine control unit. These motors have a total of six cables. Two thicker cables for power and four thinner cables for quadrature output. The signal allows engine control unit to work out angular position, rotational speed and direction of rotation.
    Drives a Smart Cdi - 65 to 85 MPG

  5. #15
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    Quote Originally Posted by pinger View Post
    There is a 6(?) page PDF online (in German) that details extensively the gearbox - including a schematic for gearchanging showing how all the sensors and actuators function WRT time. .
    https://www.google.co.uk/webhp?sourc...F+smart+getrag

    Third one in the list (Smartclub)
    Last edited by pinger; 02-01-2016 at 05:22 PM.

  6. #16
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    Quote Originally Posted by pinger View Post
    file:///C:/Users/User/Downloads/smart_450_gearbox.pdf

    Don't think this will help much as is a link to a file on your computer.

  7. #17
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    Here it is. Got it from Pinger a few years ago so will be same document.

    https://onedrive.live.com/redir?resi...int=file%2cpdf
    Drives a Smart Cdi - 65 to 85 MPG

  8. #18
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    Here is gear change sequence info if you should ever need it:

    Using my WinStar diagnostics kit I have read raw data from drum turning angle sensor and corresponding gear position:

    TAS - gear
    978 - R
    897 - N
    822 - 1
    722 - 2
    555 - 3
    352 - 4
    226 - 5
    67 - 6

    This means gear shift pattern is R N 1 2 3 4 5 6.

    I also found drum does not move when moving gear stick into neutral at speed. Clutch is just moved to "off" position. Drum will shift into the most appropriate gear for the speed as car slows down when gear stick is in neutral. Confirmed all of the above by test driving with diagnostics attached.
    Drives a Smart Cdi - 65 to 85 MPG

  9. #19
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    Dec 2015
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    Thanks, I've got plenty of info now so should be able to make this work. The gearbox is actually quite 'smart'!
    The diff switch ratios are quite interesting, one option is to chose one of the primary ratios and lock it, then all I need to do is wack the motor one way for high and the other way for low (lock 1 and switch 5 and 6 gives me 2nd and 5th gear) but it's possible that 5th is too high a gear?.. adding stops to limit rotation and flipping between 2nd and 4th might give better ratios?!.
    Reverse is just a input on the controller to switch motor direction so that's easy. I'll get hold of a gearbox soon and have a go at full control.
    0 - 8000RPM in 2nd gear with 100Nm sounds good

    Time to buy some drive parts now!

    Cheers

  10. #20
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    Not as easy as you think. Existing gear shift drum only allows the gear shift sequence posted.
    Drives a Smart Cdi - 65 to 85 MPG

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