Xenon, Tantalum and Fermium
Posted: September 24th, 2012, 5:51 pm
http://www.puzzle-place.com/wiki/Xenon
http://www.puzzle-place.com/wiki/Tantalum
http://www.puzzle-place.com/wiki/Fermium
Type : High level board burrs
Estimated solving time (taking apart) :
Beginner : 10 hours
Casual puzzlist : 5 hours
Expert puzzlist : 3 hours
The + : Exceptionnally well designed disassembling sequences (until the first piece is removed). Excellent manufacturing quality.
The - : Once the first piece is out, the rest of the disassembling sequence is chaotic. Reassembling the puzzle is difficult.
My rating : 5/5
The Xenon, the Tantalum and the Fermium are three different versions of a single design, by Donald Osselaer. It is a "board burr", that is a burr puzzle made of interlocking boards. It was first designed completely by hand, without the help of any real-world model, not to mention a computer. And that is probably why it is so interesting.
The number of moves needed to remove the first piece of the puzzles are respectively 42, 73 and 100. However, they are perfectly structured according to a certain plan that Donald had in mind from the beginning. It's not just a random succession of moves that has to be guessed by trial and error.
The name of the puzzles is chosen according to the atomic number of the chemical elements. 54 and 73 for xenon and tantalum, which represent the number of moves to get the first piece out without performing any rotation. 100 is the atomic number of the fermium, wich is the number of moves to get the first piece out using a rotation.
The goal is to disassemble the puzzle. To put it back together was not part of the initial challenge, and is usually done with the help of a computer running the Burrtools software, unless you learn by heart the position of each board.
In the beginning, I had no idea of what to do. I explored the possible moves from the start position, and it quickly turned out that one of them lead much farther than the others. This path, made of a long succession of moves, is not completely forced. You always have the choice between some minor variations, but these variations are not confusing enough to get someone lost.
Eventually, the logical sequence comes to an end. On the Xenon and Fermium models, a given piece can get out thanks to a rotation. It doesn't make much difference if you perform this rotation or not in the Fermium. However, in the Xenon, without using this rotation, things get quite complicated. You have 12 more moves to find, and they don't belong to the same logic at all.
In the Tantalum, the rotation is impossible, but the final part of the sequence is not as confusing as in the Xenon. Last, let's mention that a second version of the Fermium was designed by Donal Osselaer, but never manufactured. In this version, the rotation was forced. There is no other way to remove any piece, and according to the software, the puzzle has no solution. It follows that on this one, you would have to be extra careful when you disassemble it if you want to have a chance to get it back together one day! A third and final version was then designed, that is quite the same, but without the extra colours to force the solution. It was not manufactured.
The removal of the next pieces was not part of the initial design. It follows that the next moves to perfom do not obey to any particular logic. On the Fermium, it is escpecially difficult to get a second piece out. I'd say that it would be insanely difficult if the information that the number of moves needed is 80 was not available. Knowing this, it becomes obvious that you have to play back the sequence in the reverse order. That's the only way to perform so many moves.
The manufacturing quality is excellent for board burrs. All angles are beveled, which is very useful in order to perform smooth movements. The pieces are assembled using mortices for maximal sturdyness, and you don't even have to be especially careful to make any legal move. They come naturally, unlike in larger board burrs like the Ultraburr and the Millenium, where the pieces must be properly aligned for any move to be performed.
Two versions of the Xenon were made. The one in the first picture above is in maple, cherry and walnut. Here is the other one, in difou, padauk and wacapou :
The Tantalum was made in beech, cherry and walnut. Beech is darker than maple, but more textured. Fermium use the same woods as Tantalum, but with a part of the central pieces using an alternative colour. This was required to flag the central pieces, in order to avoid other, easier solutions, to be possible.
Because of the real reflexion that was put into the conception of these puzzles, and that results in very interesting disassembling sequences, I give them 5/5.
Link to the discussion about the conception of these puzzles : http://forum.johnrausch.com/cgi-bin/ult ... 1&t=000336
Related puzzles by the same author :
Natrium : http://www.puzzle-place.com/wiki/Natrium
Silicium : http://puzzlewillbeplayed.com/9BoardBurr/Silicium/
Ultraburr : http://www.puzzle-place.com/wiki/Ultraburr
Millenium : http://www.puzzle-place.com/wiki/Millenium