Tri-Rodspan Puzzle

A puzzle designed by Bruce Patterson. Twelve identical pieces assemble into the final shape.  This puzzle apears on the cover of Cubism For Fun #120 (CFF 120), a puzzle newsletter.

Assembly is a challenge, but you do not need 12 hands.  I like to add one piece at a time, but the structure is unstable until about 8 pieces are in place.  If you are having trouble, I can add a solve video.  The final assembly is quite stable.

Print 12 copies of the basic piece, no supports are needed.  I have included the puzzle in two sizes, the larger size (76.2) is easier to assemble.  I like to print it in 4 colors, 3 pieces per color.  This way you can assemble the solution with color symmetry.  

The small puzzle fits in a 2.5" cube (63.5 mm), the large version in a 3" cube (76.2 mm).  The offset used is 0.08 mm.  The assembled puzzle is hollow and the void has the shape of a rhombic dodecahedron.  I added both sizes of this core.  Using the core actually makes the puzzle easier to assemble, because you can assemble the pieces on top of the core. The core is wireframe but prints file with no supports (bridging test).