jwz: Hoberman Switch Pitch

Hoberman Switch Pitch

This is a really neat toy! When you toss it, it sort of turns inside out, changing colors. The curved body panels that make it look like a sphere hide an internal structure that is a cube; or really, two tetrahedrons embedded in a cube; and when it hits its activation energy, the tetrahedron becomes its dual, swapping faces and vertices.

The profile of those body panels is really clever too, because they manage to just slide past each other while this is happening.

There have been a few papers written on this thing, but most of them are behind paywalls. Here's one that isn't, from the amazingly-named "Journal of the International Association for Shell and Spatial Structures", which contains this illustration of how the nodes move:

It's normal to buy a $9 kids' toy and then search for journal articles on it, right? Anyway, if this toy is patented, I'll bet the illustrations in there would be informative, but I haven't been able to find one. It's not quite "Bit" from Tron but it will do.

Previously, previously, previously, previously, previously, previously, previously, previously, previously, previously.

Andrew Klossner says:

5 years ago at 3:13 pm

See also this paper. Its first reference is to a patent application by the inventor.

jwz says:

5 years ago at 3:31 pm

That's actually a different edit of the same paper, but yeah, I missed the patent reference in there. It's "US7464503B2: Geared expanding structures". It covers a bunch of things based on similar linkages, but this toy is in there:

Dennis says:

5 years ago at 6:11 pm

I used to juggle three of these. Thrown just right they will stay the same color; thrown a little different they change. It’s a nice effect.

Also, this is the toy they use in the show Silicon Valley when they are saying, “Always blue! Always blue!”

Adam Lander Alpern says:

5 years ago at 10:40 pm

So cool!

David Konerding says:

5 years ago at 5:15 am

yes it's normal to buy a cheap toy and look for journal articles explaining it. at least, within my group. After I saw a self-balancing robot I got interested in PID loops. Actually though I didn't have to read any journal articles, as PID is nicely documented on the web, up to the point of optimal control theory.