This is an extension of the three-way joint (https://www.thingiverse.com/thing:4919115). We take a three-way joint , mirror it, and then adjust the space in between so that it is the length of the face diagonal of the base cube (which is also the side length of the equilateral triangle). Now we get a double-joint bar. Twelve copies of the bar will make a 14-faced solid or a tetradodecahedron, which has 6 regular octagons and 8 equilateral triangles. It is an interesting structure. However, they do not lock into a sturdy solid unless the joints are really tight or glued.
####Among the Files 1. Version 85mm: Based on a 25mm cube 2. Version 117mm: Based on a 50mm.