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Gear Bracelet 7+5
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Eight Gears of different sizes on a foldable band.

Back in 2013, Ferdinand Lammertink showed Oskar van Deventer a puzzle prototype of this, made of lego. His prototype featured eight large lego gears connected in a cylinder. Ferdinand called it Gear Bracelet. The puzzle could be scrambled by folding the bracelet flat, and turning four out of the eight gears. Then, like any twisty puzzle, the challenge is to solve it and get all eight gears back into their original orientation. Unfortunately, Ferdinand's prototype was a failure for two reasons. First of all, the puzzle was trivial to solve, as four adjacent gears could be trivially solved one by one, and then the other side happens to be solved as well. Secondly, the puzzle could be easily cheated, as gears disengage too quickly, and one could easily turn each gear individually. Ferdinand abandonned the idea, and unfortunately there exist no photos of his original prototype.

Gear Bracelet 7+5 builds on this original idea by Ferdinand. It is also a gear bracelet with 8 links, each with a little gear. Some of the gears have 5 teeth, some have 7. The puzzle is scrambled by folding the bracelet flat and turning part of the gears. It was quite a design challenge to develop the 7-teeth and 5-teeth gears to mesh in the way that they do. The object is again to get all gear re-aligned again. The bracelet can be assembled in different ways. The photos show the 7-5-7-5-7-7-5-5 configuration, which is the hardest to solve. Other configurations are for example 7-5-7-5-7-5-7-5, 7-7-7-5-7-5-5-5 and 7-7-5-5-7-7-5-5.
Size: 25 x 105 x 125 mm
Weight: 62 grams



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