About this 3D model

[Video](http://www.youtube.com/watch?v=74ygvXzmrgk). This is joint work with Saul Schleimer. After making [Triple gear](http://www.thingiverse.com/thing:66708), we realised that there is a much easier way to design a mechanism with three pairwise meshing gears! Triple helix is also available at [Shapeways](http://shpws.me/nrXc).