I've ported the Antikythera Mechanism to Python: antikythera.py The Antikythera Mechanism is an ancient Greek astronomical calculator made from a gaggle of gears, so it's a kind of digital ratioing machine. I just modelled the gears in Python then bound it all together per some schematics of the mechanism. Here's an example of how to use the script:
$ ./antikythera.py 20 Sun: 20.0° Moon: 267.36842° 4 Year Dial: -5.0° Synodic Month: -247.36842° Lunar Year: -20.61404°
The input argument is the number of degrees clockwise through which to turn the drive wheel. The outputs are the number of degrees through which the respective output gears have been moved. The latter three go anticlockwise because you look at them from the other side of the mechanism, behind the base plate.