I am hoping someone can give me some pointers on rigging this valve gear. I’ve got a start on it, but now I’m stuck. For the non-train people, this is what all the parts are called:
I’m having trouble with the radius bar and everything it interacts with. One end connects to the combination lever, the other end to the lifting link, and a connection point in the middle moves with the expansion link.
This video shows the final result. Importantly, around the 3:50 minute mark you can see him adjust the lifting link so that the radius bar touches on a different part of the expansion joint.
It seems like I need two IK constraints interacting with each other in order to get the valve stem guide moving correctly, but I’m not sure about it.
The bone parented to the expansion link sticking out to the left roughly orthogonal to it is along the radius of the expansion link. I’m fairly certain I’ll need a bone there (maybe flipped the other way?) for shifting the radius rod up and down the link.