On the original design, the set screws on the lower vertex may get loose, and because the belts are under tension, the tower extrusion may push itself to through the bottom. I added a heel below the motor vertex to support the tower extrusion without relying on the two set screws. It also serves as foot pads for the machine. OpenSCAD file included but you have to get the other support files from Johann's github repository - https://github.com/jcrocholl/kossel