It seems very fitting to put a 12-hour clock on a hinged puzzle that turns a 3-fold symmetric polygon into a 4-fold symmetric one! Jim Propp On Friday, December 5, 2014, Mike Stay <metaweta@gmail.com> wrote:

Here's a 10-inch one. http://boisselier.ca/en/products-page/curiosities/

On Fri, Dec 5, 2014 at 6:13 AM, Bill Gosper <billgosper@gmail.com <javascript:;>> wrote:

...

In at least one online recording (that I can't locate) of T. Tokieda's toy talk (e.g., Tadashi Tokieda || Toys in Applied Mathematics || Radcliffe Institute <https://www.youtube.com/watch?v=f07KzjnL2eE>), instead of his usual small plastic ones (with or without testudinal passengers) he had a large wooden (rosewood?) (outwardly) symmetrical one which he rubbed in his hair (ha ha) to reverse the preferential direction. Can someone suggest where to buy such a thing? Maybe not symmetrical. Maybe not wood. But fairly large? (I've heard of making them from old automobile bumpers. Maybe that's too large.) --rwg _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com <javascript:;> https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun

-- Mike Stay - metaweta@gmail.com <javascript:;> http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com

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