Tri-Track OpenSCAD Compatible tracks

This is a sub module of thing: https://www.thingiverse.com/thing:2832658

* 4 type track for selection.
* tight version chained with M3 12mm-15mm screw, no Nuts. (or longer screw with nuts)
* not verified yet, but hole to hole space is same. should be ok.
* SCAD ready and built your own design.

You need this library to running the module:
https://www.thingiverse.com/thing:2832698

Compatible with Tri-track bot:
https://www.thingiverse.com/thing:19170

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