how can one change the height of the sprung mass of a vehicle in Adams/Car ? 1

[josh m]

hi

I know that sprung masses in adams/car are a sum of multi-body situation and if we want to talk about changing the height of sprung masses we are talking about a bunch of masses …

but is there a simple way to do that ( change the height of the sprung mass ) in a simple way in your experience ?

 

[GregLocock]

Not a car user but either change the CGZ of a heavy part, or change your springs. Depending on how they are specified, change the free length or the preload.


Cheers

Greg Locock


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[josh m]

thanks a lot

 

[josh m]

thank you Greg Locock

I did what you said and I got results ! not accurate but much better than designing a vehicle from the scratch …

however I've got another question pertaining to the last one .

why can't I change the trim body.ges_trim_mass that is considered a sprung mass by the Adams/Car ?

why doesn't it have moment of inertia and only has a mass ? is the mass effective in the vehicle's maneuvers and tests ? if so how does the mass work without moments of inertia ? why can't I change the coordinates of the said sprung mass part ? because when I do it asks me for moments of inertias ( the moments of inertias of this part are zero by default and it turns yellow when I change the 0,0,0 coordinates of the said part ) ?

PS . thank you for you last good advice .

 

[GregLocock]

That seems very odd. The tpyical solver language statement for a part looks like this

PART/149,CM=14900,MASS=12.30,IP=5.0000e+05,5.0000e+05,5.0000e+05
, 0.0000e+00,0.0000e+00,0.0000e+00

M/14900,QP= 2340.000, 0.000, 501.000 CG - User Specified Location

where IP is Ixx, etc followed by iyz etc

AFAIK there's no such thing as a point mass in ADAMS, fundamentally. It would just look like this

PART/149,CM=14900,MASS=12.30,IP=0,0,0
, 0.0000e+00,0.0000e+00,0.0000e+00

M/14900,QP= 2340.000, 0.000, 501.000 CG - User Specified Location

I may get time today to look at CAR and see if the standard model has that part.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[GregLocock]

I found this in the MDI_CHASSIS.sub . So the real sprung mass part is called 'chassis', and has Ixx values. i don't know what trim_mass is for.

[PART_ASSEMBLY]
USAGE = 'chassis'
SYMMETRY = 'single'
MODE = 'rigid'
$ Rigid body data:
MASS = 663.0049
PART_LOC_X = 0.0
PART_LOC_Y = 0.0
PART_LOC_Z = 0.0
PART_ORI_ZP1 = 0.0
PART_ORI_ZP2 = 0.0
PART_ORI_ZP3 = 1.0
PART_ORI_XP1 = 1.0
PART_ORI_XP2 = 0.0
PART_ORI_XP3 = 0.0
CM_LOCATION_FROM_PART_X = 1452.643
CM_LOCATION_FROM_PART_Y = 0.0
CM_LOCATION_FROM_PART_Z = 356.0795
IXX = 2.204453E+08
IYY = 1.067216E+09
IZZ = 1.181078E+09
IXY = 0.0
IZX = 0.0
IYZ = 0.0
(COMMENTS)
{comment_line}
'Chassis Structure'
$------------------------------------------------------------------PART_ASSEMBLY
[PART_ASSEMBLY]
USAGE = 'trim_mass'
SYMMETRY = 'single'
MODE = 'rigid'
$ Rigid body data:
MASS = 0.0
$ Part location is dependent.
$ X,Y,Z location = 1452.643, 0.0, 356.0795
PART_ORI_ZP1 = 0.0
PART_ORI_ZP2 = 0.0
PART_ORI_ZP3 = 1.0
PART_ORI_XP1 = 1.0
PART_ORI_XP2 = 0.0
PART_ORI_XP3 = 0.0
CM_LOCATION_FROM_PART_X = 0.0
CM_LOCATION_FROM_PART_Y = 0.0
CM_LOCATION_FROM_PART_Z = 0.0
IXX = 0.0
IYY = 0.0
IZZ = 0.0
IXY = 0.0
IZX = 0.0
IYZ = 0.0

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[GregLocock]

as you can see in the demo vehicle you can assign any inertia you like to the trim mass.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[josh m]

hi Greg Locock

thank you for answering in detail and taking the time for replying accurately . you have done so much since I have met this site and for that I thank you …

the last picture that you have sent is exactly what my adams/car version says except for the mass that it is 603 kilograms , ofcourse, the file that i'm using is sedan_RWD and the trim_mass belongs to that … but surprisingly 0 values for inertias just as your pic implies ostensibly …

so does that mean that it has no effect on the vehicle sprung mass ? because in the sprung mass table it is taken as 100% sprung mass and it has a 603 kilogram mass … but as I said 0 inertias just as the model above …

So , does that mean that it has no effect on the vehicle at all ??

here's a capture of the said part :

 

[GregLocock]

You need to wander off into database navigator and find what other masses are associated with the sprung mass, and look at those. I don't have that model. The good news is you can enter the moments of inertia directly, if you know them. A part with no MoI is just a point mass. It will affect the model.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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