This is a belt tensioner for the Y axis of the printrbot GO, designed to bolt in place of the original belt clamps (replaces both of them) using the same screws to mount it.
The mount contains TRAPPED NUTS (modeled for M3 nuts by default) so put in two "@pause insert nut" commands into the g-code at the layer transitions where the nuts will be sealed in so that you can insert them mid-print.
This design employs a grippy, toothed channel to hold the belt securely and the channel is inside a wedge shaped piece that holds it tightly pressed together inside the tensioner when installed.
I found that I had to print it with a 0.35 mm nozzle or smaller in order to get the grippy teeth in the wedge to properly resolve.
The customizable SCAD file can theoretically be used to make a version compatible with the original printrbot GO belt, but I have only made the GT2 version, so let me know if you try the other one and it needs work.
There are lots of parameters you can play with, but the included STL (GT2 version) is the one I am using.
8-20-13 - Added relief channel with grippy teeth to underside of mount to allow it to sit flatter and still clamp the belt securely.