It is an 18 piece burr which requires 43 moves to remove the first piece. Jack designed this burr back in 2003 and at the time it succeeded Burrloon (33 moves by Goh Pit Khiam) in highest level. Indeed, it is a long way to Tipperary!
As you may imagine with this number of moves, it was fairly difficult to get it apart. However, the solution does have a pattern to it that makes it pretty easy to remember once you get the hang of it. I think it took me a good 30 or 40 minutes to get the first piece out, and after that it is fairly easy to disassemble the rest of the burr.
If you look at the cluster of six pieces going in the same direction, the two outer pieces and the two inner pieces are essentially the same, which gives the solution a nice symmetry. However, figuring out the location of the remaining six 'inner' pieces is still quite a challenge.
Jack actually wrote an article for Cubism for Fun that described his the design process for this burr, which was quite interesting to read. This "cage" concept for the outer pieces was actually created by Willem van der Poel way back in 1953! The article describes how Jack originally discovered a short sequence of move involving two pieces, and how he drastically increased the move count by adding in a second sequence of moves that interferes with the first sequence. This essentially multiplies the two move counts together, resulting in the length.
The real challenge was to figure out how to make the solution unique, and for this he used a computer to evaluate over a half-million potential assemblies for uniqueness. In the end, he did discover a version that had a unique solution, which is the version posted on Ishino Keiichiro's site, Puzzles Will Be Played. The version he sent me, however, is a bit easier to construct and has four solutions, all of level 43.
So, I was left with a bunch of pieces and no idea how to put them back. Fortunately, there's a great tool named Burr Tools that can solve puzzles like this quite quickly. To my surprise, it actually took a while to solve, about 20 minutes. Usually, it can come up with a solution to a simple puzzle after only a few seconds, so that shows you how complex a process it can be to solve an 18 piece burr!
Using the solution generated by Burr Tools, I carefully put the puzzle back together. It was a bit of a dexterity challenge though, since I had to keep reaching for the keyboard to navigate through the solution while holding the burr in my other hand, hoping it wouldn't fall apart! Eventually I did get back to a position where I could finish it off: I still remembered how the last few pieces went in. Phew! It was quite a relief to get it back together.
I had a great time with this puzzle, though burrs aren't my specialty, it was fun to play around with this one for a while. About a year ago, Jack developed the Burrly Sane series of 18-piece burrs, that have outrageously long move sequences to remove the first piece:
- Burrly Sane for Woodworkers (138 moves)
- Burrly Sane for Professionals (148 moves)
- Burrly Sane for Extreme Puzzlers (152 moves)