I think one way to do this uses a differential (URL) and a pole reverser (URL). I don't have a picture to hand but the idea is simple. One side of the differential is connected to the low torque "input axle". The differential housing is connected to (...) (18 years ago, 21-Mar-07, to lugnet.technic, lugnet.robotics)
Alexander, Thanks for the differential/pole-reverser idea. Based on your description, I was able to get a prototype running very rapidly! I'm still seeking a clean more mechanical version, but this certainly will work for now. Along the lines of a (...) (18 years ago, 23-Mar-07, to lugnet.technic, lugnet.robotics)