Monday 17 May 2021

Cubic Octahedron

Anyone who’s vaguely interested in puzzles and 3D printing will be aware of the massive contribution that Aaron Siegel has made through his development of tools and techniques for making 3D printed puzzles that much more accessible. He’s not only developed some brilliant tools for helping puzzlers get their puzzles prepped for printing without support, he’s also been publishing print files for a huge variety of puzzles already in the public domain, bringing stacks of them to the attention of folks who might not otherwise have come across them…

One such puzzle is Christoph Lohe’s Cubic Octahedron which Steve Ali printed off a spare copy for me – thanks (again)!

Mine arrived as a bag of bits from the lads (probably the best way to ship it to avoid the spindly pieces possibly getting broken) so I had an extra little challenge to make sure I’d assembled the pieces properly. Once I discovered letters marking the various joints and realised there was only one orientation for the connectors to join up, I was pretty confident I was connecting the pieces up the right way… although at this point, I didn’t know what the puzzle was so had no idea what the pieces should look like – it added a little extra frisson.

With the pieces built my mind immediately went to a relative of Coffin’s Three-Piece Block – I knew there was a slightly larger four-piece version (I'm sure I have one in wood from John Devost - probably even blogged about it!) but I didn’t think the pieces were familiar so I just started trying to build something vaguely coherent… starting with a couple of pieces to see how they could be combined and when I found something that looked promising, try and introduce a third piece and so on…

I had (quite!) a few false starts (even to the point of wondering if I'd assembled things properly!) before finding something that looked promising – and at this stage I should point out that the whole premise of having these pieces where the joints are all quarter-face and offset makes for a deliciously confounding puzzle – we all know just how confusing Coffin’s Three-Piece Block is with just three, smaller pieces. This one adds a piece and they’re bigger…

Right about now I came to realise that Christoph has added a wonderful twist to this genre – Coffin’s originals are serial assembly puzzles – you had to insert the pieces in the correct order but when you got to the end, you simply inserted the last piece… Christoph doesn’t let you do that here… he makes you work some more, even after you’ve worked out where all the pieces need to be and what their relative orientations are – that extra little kick in the pants right at the end really makes this one stand out for me.

It's a great combination of confusing and puzzling!

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