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

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

(OP)
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 ?

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

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

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

(OP)
thanks a lot

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

(OP)
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 .

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

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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

(OP)
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 :

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

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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