Tinkering about with SystemModeler a little further, I’ve managed to finally build a sprung arch, complete with dampers on the revolute joints. I’m intending on using this principle in my research to create folded structures, so it’s interesting to see what effect the spring stiffness will have on the behaviour of the arch during the unpacking process – specifically looking at the accelerations on the masses at key points.

The thing that I was struggling with was creating a structure that had a set of equations that could be solved, the key concept I was initially missing was the closing of the structure with the special type of revolute joint to complete the chain. Without this special revolute chain the equations are essentially unsolvable, so it’s important that one of these joints sits in the system somewhere.

Another concept is that the structure in the video has 3 straight segments, each 1m long; but the supports are only 2m apart…. forcing the arch to pop into a stable shape that balances the weights at each of the joints. This is essentially what makes the arch wobble when solving the initial set of equations. Next step is applying external forces and measurement points along the structure for displacement etc…