Setting up mechanical linkage of levers Since I'm new to Blender (I made the model and rigging with gMax), I find myself stuck trying to set up a linkage for the reverser of my steam locomotive. I was finally able to set the pivot point for the lifting arm using the iv constraint (reverser 1a).



When attempting the function the arm moved correctly but the bones disconnected and failed to raise the reverser arm. None of the constraints could remedy this (reverser 1b).



Further attempts kept the bones together.



However I was never able to keep the last bone attached to the linkage.



Any help would be greatly appreciated.
Have a great day.
TOM

Addendum:
I have been able to answer most of my questions through a lot of trial and error. I am trying to model this steam locomotive for use in TRAINZ.



A short video of my progress can be seen on Youtube.

I was able to do the linkage with an armature starting at the reverser lever. Using IK constraints with limited chain length I could connect to various objects. Everything works great when running forward: 



The problem is when shifting into reverse since the radius and valve rods are location constrained to the Y-axis of the expansion links pivot point, the motion is no longer correct. 



I have tried everything I could think of, including the clamp to constraint, without success. I would be grateful for any ideas. Have a great day. TOM
I've been at it over a month. I have a 99% solution.
The pictures show what I have done in Forward and Backward gear.
The solution isn't perfect because the travel between gears is on a circular route. I posted a video on Youtube. The first 30 seconds are still photos and then the action starts. If anyone has an idea how to make a straight route let me know. Thanks. Have a great day. 
TOM

https://youtu.be/L5k6kLqcca4