Built this about 10 years ago. It came back a few years after that
for new rubber bands and shrink wrap tubing :) when I took
this video of it in operation.
I only recently found it (this morning).. was a fun project, thought I'd share it.
All pneumatic, no electronics -- and pretty low-budget!
Uses 3 air cylinders, one valve (5/2?), and air limit switches.
And rubber bands, of course!