This shows a 3d print I produced using shapeways.com. This model is available at http://shpws.me/mQ6F. A smaller version is available at http://shpws.me/mX9t. This is joint work with Saul Schleimer. The three gear images are from http://www.lhup.edu/~dsimanek/whoops.htm#gears. Here is a paper Saul and I wrote on the mathematics behind the Triple gear: http://arxiv.org/abs/1304.6859.