There are two main concerns I have with the Theo Jansen linkages, which have shown up in rough prototypes.
If the node that I have labeled as F in my drawings, referenced in the previous blog post, can get even a little bit out-of-plane, it can collapse towards the fixed node, B. I will certainly try to ruggedize the hinges at F, and hope that solves the problem. I am already planning to make linkage BH and GH extra wide (out-of-plane) to establish some degree of out-of-plane stability... i.e. keep the walker from collapsing if it gets pushed sideways.
Another tricky issue is that in a practical build, with some width and depth to linkages, segment CH comes very close to fixed point B. This can be an issue for me since I was planning to give the axle at B a large diameter since it would extend out as a structural component for out-of-plane support. Worst case, I might need to curve linakage CH a bit to make sure that it does not contact anything connected to the main axle at B.
I hope there will be no need to make motion-stops around some nodes, or guides to keep linkages in--plane.
https://www.youtube.com/watch?v=JrNtSyH4_1o