Z thread stabilizer for printrbot simple

This is yet another add-on for the Printrbot Simple designed to limit wobble of the z axis threaded rod. The intent here was to minimize Z-ribbing in my prints. This piece is based on designs by others here and modified for the dimensions of the Pbot Simple (w large motors). Seems to work for me; your mileage may vary.

Note: beware that if you print anything taller than about 8.5 cm, the Y axis drive will hit this brace and try and force it up the poles, depending on how far up you place it.