axis stepper motor pulley mount

This is a NEMA 17 (or 14) stepper motor mount which supports a 16t toothed GT2 pulley and fits on the end of OpenBuilds (or similar) 20x0 extrusion.

It has a mount for an MR105 bearing to take the belt load off of the motor spindle.

Change the beltVoffset variable in the OpenSCAD file to match the height of your gantry. I use this with the [belt tensioner](https://www.thingiverse.com/thing:2800314) and [GT2 belt clip](https://www.thingiverse.com/thing:2848858) for both the X and Y axes of my OpenBuilds extrusion i3 clone printer.