There is a newer version in http://www.thingiverse.com/thing:2320002
Parametric gearbox module used to construct gearboxes in toys.
Gears with simple support to be cut off.
Example of two stage gearbox build using the module.
Small gear to be driven by motor with 2mm axis.
Output set on hexagonal 4mm shaft.
Print elements, remove support from gears, insert gears, click-in cover.