I was just experimenting with ways to use one bones movement to affect anothers and making a chain of wacky bones that move in all sorts of directions and ways... and it sorta just sparked in my mind:
Tank tread movement is sorta an eliptical movement- if I can get a bone to move in an eliptical path (without using a path), half the battle would be over. The details and math I don't know, but visually I can speculate the angles and speed of things, which led me to Turn a bone at an angle so that the handle movement looks like an elipse. Now how do I get a bone to only travel in x,y of this handle movement? #1- child a target bone to that bone in line with the handle. #2- make another bone (tread bone) translated to the same spot of the target bone. #3- now you need translate limits constraint on this tread bone. set so the bone can move freely in (world) x,y movement but restrict z to "0".
WOW the tread moves in an eliptical path..... but if I limit (world) y movement the eliptical movement is cut off by this and looks more like a belt that is streatched across two drive wheels.
**BUT** we still need to have another bone closely follow this bone on the track (and many to follow that one too)- and the answer is simple: translate and orient a bone to the main tread and have it lag 1 in the orient and translate properties. then do the same with each tread bone you make... just translate and orient like the previous bone (piggy-backing).
I've provided a *prj* file that you can look at or for observation. anyone that wants to take this and build on it you have my permission... try to post here or link to this post so all the info is available to people.

Thanks.

Hey, that's cool!

Looks pretty interesting, though I see a few issues in the video.

Yes... the tread skips on the loop... and the timing is not perfect... I will be working on this again, but first I must work on the other two special rigs I've been trying to work out and it wasn't really my intention to work on this, it was just "happenstance" and I clumsily tripped into this idea. I have an I dea for non-penetrating armor rig and a muscle rig.
I will be back soon.

Looking forward to seeing your other rig ideas.

I don't think it skips, it's an illusion. What's happening is, the spacing is changing. Since the bones are actually moving in a circular path, limiting the translation causes them to be closer together when the limit is reached. For example, if you take a half circle spline with 8 cps, that are equally spaced around the arc, and scale it in one axis to flatten it out, the cps will not longer be equally spaced.

This causes the timing problem... to compensate I'm going to try something to control the speed. I don't want to use aan expression... actually an expression could solve this whole problem. A brainstorm is needed here...

Eventually all of the lagging upon the previous bone causes A:M to multiply the computation for each bone down the line- not the most economical way to do it... the answer to making it computationally easy is to make all the treads orient and translate to the main tread bone, but with each next bone increase the lag by one unit (to make things simple: my unit= 1). You can adjust the unit to be anything that makes the treads fit next to each other better. My tread belt needs 36 treads to complete the link.
I'm still working on a solution to the timing issue... and I'm close.