How to determine joint axis of operation?

[jorm1]

To measure the forces on the bearings inside a MacPherson shock absorber (strut), I built a simple test model to test the behavior. In the first model I placed the strut vertically (lower and upper mounting point exactly above each other), so the axis of operation of the joints (bearings) were straightforward. R1: [1 0 0] R2: [0 1 0] R3: [0 0 1] P1: [0 0 1]

This model seems to work according to expectations. The normal forces on the bearings matched the ones determined by hand calculations.

In a second model, I placed the strut according to the real coordinates, so it will not be completely vertical, but under a small angle.

The question is now, what should be the axes of operation?

Vertical test model:

http://www.2shared.com/file/2EoCm68I/test_shockabsorber_MB.html

Inclined test model (also uploaded to this forum):

http://www.2shared.com/file/Eskbij2r/test_shockabsorber_MB_inclined.html

Picture of the test model:

http://imageshack.us/photo/my-images/84/testmodel.png/

Drawing of shock absorber:

http://imageshack.us/photo/my-images/10/shockabsorber.png/

 

[jorm1]

Nobody knows how to determine these axes of operation?

 

[GregLocock]

I wonder what the direction cosines of the upper shock absorber are from its base, in your chosen coordinate system?



Cheers

Greg Locock


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

http://eng-tips.com/market.cfm?

 

[jorm1]

The orientation of the base is just [0 0 0] (Euler x-y-z) with respect to the world coordinate system.
The world coordinate system is defined as follows, when looking to the rear view of a vehicle:
x -> inside the screen/paper
y -> horizontally to the left
z -> vertically upwards

Or isn't this what you mean?

 

[GregLocock]

I wonder what the direction cosines of the upper shock absorber are from its base.

Cheers

Greg Locock


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

http://eng-tips.com/market.cfm?