I have a two force member, pin connection that's free to rotate at each end.  And its shape includes a couple of curves to clear other objects.

I can apply a force to the first pin hole that is directed at the second pin hole.  I can put a fixed hinge in the second pin hole, but how do I limit the motion of the first pin (the one with the force applied) to a plane in line with the second and still be free to rotate?