Stabilizer bar

[suspguy]

Hello everybody

i was looking up some formulas for calculating stabilizer bar roll stiffness, given things are:

Bar Diameter
Material properties
Lever arm length
Torsional section length

I found some data about it in thread108-40691

But the problem I was having the most formulas available dont take into effect the distance between mount bushings
To get more accurate results I was trying to take into effect the deflection due to rubber bushings as well

The methodology i am using is

1) Calculate the bending moment and torsional moment at bushing center due to vertical load at bar end.

2) Calculate bushing deflection due to bending and torsional load taking into account conical and torsional bushing rates.

3) Add thoose defections to the total deflection at bar end which can then be used to calculate roll stiffness

I am assuming a D-shaped bushing

If I did that would i be wrong??


I am a little confused if I should use radial deflection as well or my line of thought is totally messed up
In short i want to include bushing deflection also to calculate stabilizer bar roll stiffness

Any IDEAS or CORRECTIONS??

Thanks for your help!!!!!

 

[suspguy]

Well Ok lets talk about the complex situation where the links are inclined
How do you model that complex situation in ADAMS today lets just assume a ball-ball link
i would really like to understand how the load path is defined because I am assuming even in ADAMS you use beam elements to define your stabilizer bar and some kind of bushing or spring element for your bushings

and I think i can incorporate that into my FEA model since I am coding everything

The reason why I dont want to do that in ADAMS is because it is too complicated for a normal user to use and we r looking at a simpler tool without compromising the accuracy a lot

Thanks for all your help

 

[GregLocock]

The ball ball link can only generate axial forces (which is why we don't use a ball ball link to model it, but that is a needless complcation) so the direction of the force vector is defined exactly by the locations of the ball joints.

So, that is pretty straightforward.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[suspguy]

How about using a spool bushing at the ends
that can probable be modeled as a 6D spring element

I know there is another one the grommet kind thats complicated I have no idea how to model that

Thanks for your help

 

[GregLocock]

Yes, I use a 6 dof bush, with a non linear rate in the important direction. That's to represent the 'two rubber bungs with cup washers' type of joint. However, if you are really interested in the bar rate that is a needless complication.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[suspguy]

Well I was actually interestd in the effective bar rate at the wheel, i thought if i could get the effective bar rate at the link end and use the simple motion ratio formulas to get the effecting bar rate at wheel
I am not sure how accurate that would be but just a try

Thanks

 

[GregLocock]

Should work if you get all the geometry right.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[suspguy]

Greg

I am at a stage where my bar rate with bushings using a tool i created is coming out pretty close compared to Adams and Nastran.

But I am stuck at one spot, I want to model the links in the system as well and get the stabilizer bar system rate,

For a bayonet-bayonet (two rubber bungs with cup washers) joint which is perpendicular to the ground plane which are the important stiffness directions (I believe its 1) along link axis and probably conical ones also not sure though)

and also could you comment on bayonet -ball and spool-spool kind of joint too

I ahve a 6 dof spring that i want to use for the links and apply stiffness along the relevant direction

Thanks for all your help

 

[GregLocock]

Yes the axial rate is the important one. In practice I doubt you'll find the coning rate is a significant contributor except at extremes of roll, but you can check yourself, typical rate is 10 Nm/degree.

I'm not too sure what your various link types are, I've used the pair of rubber bungs with cup washers, and ball joints, only.

I think you'd be moderately insane to go with the rubber bungs in practice, except for off road use, or where cost is an overriding concern, or the articulation angle of the joint exceeds 24 degrees. Every time we fit ball joints in place of bungs we like the difference.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.