I have started working on a new plug in, for gh constrains. Its name is Skeleton. I am implementing reduced-coordinate kinematic solver for solving DOFs for different elements.
Right now only two components ready, and its on early stage, so i need testing. Please see if that is something interesting for you, I would appreciate the feedback.
You can download it in the Package Manager:
Updated to 0.1.4
Added push/pull node
Added gravity node
Updated to 0.1.5
Added support for gears/racks for ratio rotation/slide
Optimisations for heavy graphs
Example file
Skeleton_Example_0.1.5.gh (1.0 MB)
This is fantastic! 
How can I use these components to simulate a door opening using a hinge?
Skeleton_Hinge.3dm (5.9 MB)
Honestly i do not have full understanding on how these hinges work.. As i understand the screw should regulate how much the left part can travel. Maybe tomorrow i will have more time for that. But for now, here’s a quick example
Hinge.gh (413.5 KB)
Right click - show handles, right click - limits, to set limits of rotation.
