Cars Live Axle

[ltcars]

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?

 

[Stereo]

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.

 

[ltcars]

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.

Is a panhard bar a solid axle?

 

[Stereo]

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)

 

[ltcars]

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

 

[Stereo]

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]

 

[ltcars]

Thanks a lot

 

[ltcars]

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]

[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.

 

[Stereo]

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.

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.

 

[ltcars]

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.

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.

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

 

[ltcars]

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!

 

[Tokki43]

if i copy the last one, and all, if i make my kn5 free axle, my rear axle is 100% free, it runs out of the car, alone

 

[GaryUK]

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.

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.

I am trying to model a car - de dion rear suspension - in one case with an open differential, and in the other case with a limited slip differential. At present the suspensions.ini file is using [REAR] TYPE=AXLE. Is this the correct suspension type for de dion? I don't see any lines within suspensions.ini that correspond to the differential type, e.g., LSD versus open differential. Any help with this is greatly appreciated.

 

[aphidgod]

The differential code is all in drivetrain.ini.

de Dion is a case that AC doesn't really handle gracefully with its AXLE implementation, so you'll have to decide on the compromise that you're most comfortable with. I tried a bunch of dumb stuff in the W125 but ended up doing something very similar to what Kunos did in the 250F, feel free to check out the Merc code if you like but it's basically just a 4-link with a panhard rather than the two trailing arms + central sliding locator pin on the diff housing.

Don't neglect to account for the diff in sprung rather than unsprung mass, assuming the de Dion you're implementing is designed as such.

 

[hedgehogg]

The differential code is all in drivetrain.ini.

de Dion is a case that AC doesn't really handle gracefully with its AXLE implementation, so you'll have to decide on the compromise that you're most comfortable with. I tried a bunch of dumb stuff in the W125 but ended up doing something very similar to what Kunos did in the 250F, feel free to check out the Merc code if you like but it's basically just a 4-link with a panhard rather than the two trailing arms + central sliding locator pin on the diff housing.

Don't neglect to account for the diff in sprung rather than unsprung mass, assuming the de Dion you're implementing is designed as such.

What about a watt linkage? Is [AXLE] still the best way to model it?

 

[Stereo]

Can't do a Watt's linkage with AXLE, if you really want it you'll have to use the CSP extended physics.