Separated Board Burr Set - Quick Summary
All three of Frans de Vreugd's separated board burrs in one set: ZigZag at level 7.8, Torture at level 17.4 and Extreme Torture at level 28-22-9-8-3. Eighteen flat boards, three separate builds, solved in that order. Hard through Expert. All three ship disassembled.
Best for: burr collectors filling a gap in their board burr shelf, and solvers who want to work through a family of designs in the order the designer built them rather than buying the hardest one and getting stuck.
One Idea, Taken to the End
In 2002 Jim Gooch suggested to Frans de Vreugd that you could take a standard six board burr and pull the two boards in each pair one unit apart. The resulting shape had far more room for complicated movement, and de Vreugd wrote a computer search to find piece sets that would still go together.
ZigZag came first and is the one you can reason about: seven moves and it splits into two identical halves. Torture came next, level 17.4, with 7,680 assemblies and exactly one solution among them. Extreme Torture was the last push, the hardest form found in de Vreugd's research, at 70 moves to take apart.
Solving them in that order is the point of the set. Each one teaches you something the next one takes away.
What Is in the Set
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ZigZag - level 7.8, Hard. Six boards in two colours. The first separated board burr ever made.
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Torture - level 17.4, Expert. Six boards. One solution out of 7,680 assemblies.
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Extreme Torture - level 28-22-9-8-3, Expert. Six boards, 70 moves to take apart. Produced commercially for years as Gordian's Knot, now discontinued.
They Arrive in Pieces
All three ship disassembled, as eighteen loose boards across three puzzles. There is no solved state to copy in any of them. Assembly is the challenge in every case.
Frequently Asked Questions
What is a separated board burr?
A standard six board burr has six flat pieces grouped in three pairs. In a separated board burr the two boards in each pair sit one unit apart rather than flush together. The gap opens the shape up and allows much longer move sequences than a normal board burr can hold. Jim Gooch suggested it in 2002, Frans de Vreugd designed the puzzles.
What order should I solve them in?
ZigZag, then Torture, then Extreme Torture. That is the order they were designed in and the order they get harder. ZigZag has a symmetry you can work with, and it prepares you for the other two.
Do they arrive assembled?
No. All three ship as loose boards. Assembling them is the puzzle.
Are these suitable for a beginner?
Not as a first mechanical puzzle. ZigZag is a fair entry point for someone who has solved a standard six-piece burr before, but Torture and Extreme Torture are Expert and will take repeated sittings.
