This is a talk I gave at the Bridges conference on mathematics and the arts (http://bridgesmathart.org/), on 28th July 2013, about my work with Saul Schleimer making the "triple gear". The slides are a little difficult to see on the video, but you can download them at http://www.ms.unimelb.edu.au/~segerman/talks/triple_gear_talk.pdf. The "Triple gear" sculpture won the "Most Innovative" People's Choice Award in the art exhibition this year.