Dan, There something like that starting with a cone instead of cyliner. It's the spericon. Google gets several really nice hits, including some rollers. Robert Foote at Wabash College has turned spericons from wood - I'm pretty sure has some sphericons on his website. A sphericon with some animation can be seen at a Gallery of Space Curves that Peter Moses and I have at http://faculty.evansville.edu/ck6/Gallery/Introduction.html Clark Kimberling -----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Dan Asimov Sent: Wednesday, April 21, 2010 2:51 PM To: math-fun Subject: [math-fun] Trying to recall funny shape I recently read of an odd solid shape, with I think an odd name, that has recently been defined. It may be this: Take a solid cylinder whose diameter equals its height, cut it in half along a square, rotate one half 90 degrees, and glue the halves back together again. Does this shape have a name, or is there something similar that does? Apparently it has very interesting rolling behavior. --Dan ________________________________________________________________________ ________________ "Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read." --Groucho Marx _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun