Wednesday, 27 November 2013

Pennyhedrons galore

Ages ago I found myself chasing my own tail on an auction of Chinny’s set of Pennyhedrons – I’d been the only one bidding on a particular set and in spite of outbidding myself several times, I was still coming up short against the invisible reserve price and in the end I lost out to said invisible foe.

[As an aside, I love Chinny’s auction listings – where else will you find the Designer listed and “Stewart Coffin & Me” and the material simply as “wood”. Oh, and when he describes the fit as “Tight”, he means it!] 

I’d managed to snag something else by Chinny on the same auction so asked him how far away from the reserve price I’d been, and when he told me, I offered to buy it from him at that price and sent him the Paypal straight away (turns out I’d been reasonably close). 

A few weeks later I picked up a bunch of things from him in Narita… including this lovely set of Pennyhedrons, which were instantly shared around in the lobby of the IPP hotel and they kept several people amused for ages … actually they kept me amused for considerably longer! 

Pennyhedrons were first described by Stewart Coffin in his book “The Puzzling World of Polyhedral Dissections” as simple puzzles created by his children out of workshop scraps – the first variant needed an unusual grip to separate the two parts and had a hole in the centre that held a penny. They were sold at craft fairs as “Pennyhedrons” … not long after that the fertile mind noticed that he could produce very structure that looked identical on the outside, but required very different grips or movements to release them… and a family of Pennyhedrons was born. 

Chinny has produced an interesting variation or two of his own and in the course of his research had documented all of the known variations on the theme … but being an ace craftsman, there’s very little point in just documenting them, so he produced a couple of sets of all the variants that he could find and put some of them up for auction … and I suspect that one of the sets ended up going to Master Coffin as a gift from the nutty dentist. 

…and thus it came to pass that I collected a lovely set of hardwood rhombic dodecahedra from my Australian friend… complete with a list of the puzzles in the set on a page from his prescription pad. (Take two until the pain subsides and call me in the morning!)

The set starts out with the standard Coffin 3+3 grip Pennyhedron from the book, although Chinny’s done a superb job of disguising it by the way he’s combined the woods he’s used. There’s the trick version of the standard Pennyhedron that Coffin describes quite well as being quite simple, unless you’re expecting a Pennyhedron, in which case it might confuse you for a bit…

From there the set descends into some serious puzzling … including a few uneven grip designs from Coffin (2/4 and 3/4 fingered grips!) and ends up with Chinny’s own Rose Pennyhedron that comes apart in a rather unusual manner that actually looks like the petals of a rose opening …

One of them – a three-piece monster in the darker wood at the back right of the group photo has kept me out for several months. Chinny’s fit and finish is so good that when these guys are together, most of the time you cannot see where the joins are going to be coming from or which way to pull, or indeed push the various facets… and how the heck he gets them to snap together at the end, I have no idea! Anyhow, back to this dark and evil monster – I’d been trying to work it out for ages and had it up in front of my PC monitor so that I could try a new theory every now and then – usually with not luck whatsoever – until recently when I managed to get it to just about start opening – I changed grip a bit and instead of opening, it snapped firmly shut, biting me in the process… even knowing what I knew, it still took me a few more day to get it open … and working out how to close it properly took another few days – it is mean, and it bites too!

I’m not the best at remembering solutions to the puzzles I play with and this set has provided a lot of re-solving fun as I often find myself back at the starting gate as it were when I’m trying to open them…

It wouldn’t be Chinny if something didn’t explode, so there’s a spin-it-until-it-explodes-apart-into-a-bunch-pieces Pennyhedron as well. However – the piece de resistance is the undercover Pennyhedron, looks like all the others, however it IS glued together … sometimes I forget to mention that when I hand them out for puzzlers to play with…

Thanks Chinny – it’s a great set of the classics! Chinny & Coffin rule…


  1. Very nice write up Allard, THANKS. George Bell and I have rediscovered another 12 more Pennys, some of their openings will blow your mind. We'll play with them in London, see you then,,,SC,,,hey! we have the same initials!

    1. ...ANOTHER TWELVE! Hoo boy... hope they're easier than the Rose!