# Determination of the dynamic center of gravity of tractor/Rigid Dynamic

Member Posts: 1

Hello all,

i'm now working on my master thesis about stability system for tractor (e.g. avoid pitching). Here is a task in Ansys WB/Rigid Dynamic to determine the center of mass of the tractor. The tractor is moving and the left front wheel and also the left rear wheel are lifted by a ramp in such a way that the center of mass of the vehicle moves to the right edge of the stable triangle formed by the two rear wheels and the self-aligning bearing of the front axle.

The problem is, in Mechanical unfortunately I could not find the function to determine dynamic center of mass. Can someone maybe give me a tip what to do so that I can determine the center of mass? APDL also fits for me.

Best Regards

Hanwen

Tagged:

• Posts: 262Ansys Employee

Hello @Hanwen_Elmo,

Insert a position probe(solution>insert>probe>position) and select the body whose CG you wish to track over the simulation.

Regards,

Ishan.

• Posts: 4Member
edited February 18

Hi Ishan @1shan , thanks for your answer. I inserted a probe for Position and used "Box select" to choose my tractor but seemed like there were some problems in deteils:

This tractor has many parts, the method you mentioned works on when one part of tractor selected. So how could I do?

Hanwen

• Posts: 262Ansys Employee

Hello @Hanwen_Elmo,

Could you try creating a named selection with all the bodies in it and the scoping the position to this named selection.

Regards,

Ishan.

• Posts: 4Member

Hello @1shan ,

thanks for your kind tips. Unfortunately there is no option for named selection in probe position.

Regards

Hanwen

• Posts: 262Ansys Employee

Hello @Hanwen_Elmo,

You could create a coordinate system. (right click coordinate system select all 44 bodies) This creates a coordinate system at their CG. Then scope the position probe to this coordinate system. You could also try to combine all 44 bodies into a single multibody part using design modeler(https://forum.ansys.com/discussion/4116/how-to-find-center-of-gravity-and-moment-of-inertia) but you might loose the scoping attachments, so I think the coordinate system scoping method should be better.

Regards,

Ishan

• Posts: 4Member
edited February 19

Hi @1shan