MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
The metal is 8x22x7mm ball bearings: http://www.amazon.com/gp/product/B002BBGTK6
Base1 and Base2 are glued together (or just attached to wood/railing next to each other, they both have a nail/screw hole on the back side).
Base3 holds two copies of gear2.stl and it sits on top of Base1+Base2, moving freely to the left and right.
Base4 is glued to the back of Base1+Base2 to keep Base3 from falling off or moving in any direction other than left/right.
Put the bearings in the gears and slide them onto the the base pieces.
There is a model in the collection here that shows it fully assembled. You can use Thingiview or the 3ds Max file to see where all of the parts go.
Let me know which parts are too big for you and I'll split them up. I made this for the MakerBot 150mm print area, so most parts should work in your 140mm limit.
I'm collection ideas for version 2, let me know if you'd like to see anything specific!