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Cars Live Axle

Discussion in 'Assetto Corsa Modding Discussions' started by ltcars, Jul 26, 2017.

  1. ltcars

    ltcars

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    I know how to do the rough suspension but how do you change a suspension to a live axle?

    I know that it has to do sth with this:
    [REAR]
    TYPE=DWB
    , but can you just change it to a live axle or are there things I have to look out for?
    And what would I have to write instead of DWB?
     
  2. Stereo

    Stereo

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    set TYPE=AXLE, then something like this

    [AXLE]
    LINK_COUNT=4
    ATTACH_REL_POS=0.6298
    LEAF_SPRING_LAT_K=300000
    J0_CAR=0.555, 0.04, 0.62 ; front half of leaf since rear floats
    J0_AXLE=0.555, 0.08, 0.0
    J1_CAR=-0.555,0.04,0.62 ; other leaf
    J1_AXLE=-0.555, 0.08, 0.0
    J2_CAR=0.555, -0.08, 0.62 ; parallel bars for the leaf, allows more squat
    J2_AXLE=0.555, -0.04, 0.0
    J3_CAR=-0.555,-0.08,0.62 ; other leaf
    J3_AXLE=-0.555, -0.04, 0.0
    ;J4_CAR=-0.555, 0.08, -0.05 ; panhard basically
    ;J4_AXLE=0.3, 0.08, -0.05

    LEAF_SPRING_LAT_K is optional, for cars w/o panhard bar. Link coordinates are relative to the midpoint of the rear axle.
    I have a 5th link commented out that would behave like panhard bar.
     
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  3. ltcars

    ltcars

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    Is a panhard bar a solid axle?
     
  4. Stereo

    Stereo

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    No, live axle and solid axle are synonyms. A panhard bar is a link that goes across the car to position the axle laterally and make the suspension more consistent during corners (you can adjust roll center with it, without it roll center's just kinda all over)
     
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  5. ltcars

    ltcars

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    So I'm doing the physics of the Caterham 165 on the base of the Mod by @Ben O'Bro at the time and it has a live axle at the rear. I copied the values into the susension.ini file like this:
    [REAR]
    TYPE=AXLE
    [AXLE]
    LINK_COUNT=4
    ATTACH_REL_POS=0.6298
    LEAF_SPRING_LAT_K=300000
    J0_CAR=0.555, 0.04, 0.62 ; front half of leaf since rear floats
    J0_AXLE=0.555, 0.08, 0.0
    J1_CAR=-0.555,0.04,0.62 ; other leaf
    J1_AXLE=-0.555, 0.08, 0.0
    J2_CAR=0.555, -0.08, 0.62 ; parallel bars for the leaf, allows more squat
    J2_AXLE=0.555, -0.04, 0.0
    J3_CAR=-0.555,-0.08,0.62 ; other leaf
    J3_AXLE=-0.555, -0.04, 0.0
    ;J4_CAR=-0.555, 0.08, -0.05 ; panhard basically
    ;J4_AXLE=0.3, 0.08, -0.05
    BASEY=-0.04 ; Distance of CG from the center of the wheel in meters. Rear Wheel Radius+BASEY=Rear CoG Actual CG height =(FWR+FBasey)+(RWR+Rbasey))/CG_LOCATION%
    TRACK=1.301
    and so on...

    When I want to drive the car and start a session it says that here is a problem with the setup. As I wanted to end the session the game crashed
     
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  6. Stereo

    Stereo

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    Oh, it should be pasted in after all the [REAR] section, so it's
    (...)
    DAMP_FAST_REBOUNDTHRESHOLD=0.075 or whatever's the last line.

    [AXLE]
     
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  7. ltcars

    ltcars

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    Thanks a lot
     
  8. ltcars

    ltcars

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    [AXLE]
    LINK_COUNT=2
    ATTACH_REL_POS=0.6298
    LEAF_SPRING_LAT_K=3000000000
    J0_CAR=0.355, -0.04, 0.42 ; front half of leaf since rear floats
    J0_AXLE=0.355, -0.0, 0.0
    J1_CAR=-0.355,-0.04,0.42 ; other leaf
    J1_AXLE=-0.355, -0.0, 0.0
    [GRAPHICS_OFFSETS]
    WHEEL_LF=0.0 ;Left front graphical offset of the wheel positioning in the x axis (width). + is left - is right movement
    SUSP_LF=0.0 ;Left front graphical offset of the suspension positioning in the x axis (width). + is left - is right movement
    WHEEL_RF=0.0 ; Right front as above
    SUSP_RF=0.0 ; Right front as above
    WHEEL_LR=0.0 ; Left rear as above
    SUSP_LR=0.0 ; Left rear as above
    WHEEL_RR=0.0 ; Right rear as above
    SUSP_RR=0.0 ; Right rear as above

    So this is what I made out of this.
    I have a problem with the car just bouncing around at starting and I have a feeling it has sth. to do with this: LEAF_SPRING_LAT_K=3000000000
    I tried very high numbers and very low numbers with no difference. Second problem I have is that the car sinks with half of the tyre in the ground.
    I noticed that the jumping was softer when the LEAF_SPRING_LAT_K- Value was lower. (It was undriveable anyways).
    If you want that I sent you a link where you can download the car, PM me.
     
  9. Stereo

    Stereo

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    Kinda tricky to explain how solid axle geometry works in general, I think copying 4 links is the way to go to get a reasonable handling car to start with though.
    [​IMG]
    Essentially the inner 2 form a triangle so the axle can't move side to side, and then the outer ones prevent the wheels moving forward/backward while still allowing suspension travel.

    It's important that 2 attach at the top and the other 2 the bottom of the axle, that prevents it twisting when you try to accelerate.
     
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  10. ltcars

    ltcars

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    Are they all attached at the car in one line? Are the red and green things in the image all horizontally even?
     
  11. ltcars

    ltcars

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    IT works!!!

    [AXLE]
    LINK_COUNT=4
    ATTACH_REL_POS=0.6298
    LEAF_SPRING_LAT_K=300000
    J0_CAR=0.4, -0.08, 0.62 ; front half of leaf since rear floats
    J0_AXLE=0.4, 0.0, 0.0
    J1_CAR=-0.4,-0.08,0.62 ; other leaf
    J1_AXLE=-0.4, 0.0, 0.0
    J2_CAR=0.355, -0.08, 0.62 ; parallel bars for the leaf, allows more squat
    J2_AXLE=0.155, 0.04, 0.0
    J3_CAR=-0.355,-0.08,0.62 ; other leaf
    J3_AXLE=-0.155, 0.04, 0.0
    ;J4_CAR=-0.555, 0.08, -0.05 ; panhard basically
    ;J4_AXLE=0.3, 0.08, -0.05

    Thank you very much!
     
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