Here is my new gearbox with stepper motors. Base of the gearbox is from two scanners/printer canon pixma mp150 (metal frame, motor and three gears), Last gear with output shaft is added by me. First setup was made with belt, but as I expected traction was not good. So at last version I come up with fourth gear on output shaft.
here are more photos https://sites.google.com/site/mariusrdv/homemade-gearbox-with-stepper-motor
and video url: http://www.youtube.com/watch?feature=player_embedded&v=NZ9BloVlygI
Here is first try with toothed belt.
Here is final version with extra gear.
https://www.youtube.com/watch?v=NZ9BloVlygI?version=3