Kossel 2020 tower braces for Folgertech and similar designs

Greatly reduces the dreaded "tower shake" when doing honeycomb and some other infill at high speeds. Noticeably improves the rigidity of the Kossel 2020 design. Also, this is a good upgrade if you are transporting your Kossel a lot. It will help ensure that the extrusions don't slip if the machine gets jarred.

I tried smaller braces that fit up tight against the vertex brackets, and they seemed to do almost nothing. These actually work.

I noticed an definite improvement in the surface