Use of Grasshopper to simulate Pivot mechanisms

Hello Everyone!

I'm a new user (one-week) user of Grasshopper and kangaroo physics. For a project that we currently have at the office, I'm looking at recreating a pivot mechanism (as such found in the scissors) using Kangaroo.

Just to get started, I modelled a simple system consisting of a 4 beam crossing (2 parallel beams on top, 2 on the bottom) which form a square. Then top and bottom layer of beams are attached using small beam elements which have no torsion resistance (very small GJ constant values).

Finally, as boundary conditions, I'm applying a anchor in one edge and a tensions force, with the intention deform the square as it was acting in shear.

However, when I run the solver, it looks like the model is unstable as it starts to deform out-of-plane when I apply the force.

I have spent several days trying to figure out how to correct it but I have been unsuccessul so far. Therefore I wanted to ask you if someone could take a look at my GH file to maybe find out what I'm doing wrong.

Any help would be greatly appreciated.

Thanks a lot and best regards,

Gerard