A couple of months ago someone pointed me to this fascinating video from Disney Research – Computational Design of Mechanical Characters. It’s full of some amazing character models featuring realistic motion, all achieved using mechanical links and gears. Of course I was immediately inspired to build my own version of the Sisyphus model out of LEGO parts. I definitely wanted to add my own touch to it though and, in addition to tweaking the geometry a little, I decided to add a boulder and extend the motion to it as well.
You can see the results in the video below, where I also discuss the details of the mechanics.
I have put together building instructions for both the full model and just the core, if you are only interested in building the main mechanism.
Depending on the relative orientation of the two crank shafts when you connect the chain, the motion of the legs and the body/boulder may not be in sync. It’s quite easy to adjust this after the fact – just slide the 12 tooth double bevel gear (the black one on the main drive shaft) to disengage the leg crank shaft, orient the two crank shafts as they are depicted in the instructions, then reengage the gear.