Backgear

[sanddrag]

I've recently been studying the lovely little Atlas model 618 lathe and discovered a quite clever device it has called a backgear. Does anyone else know what a backgear does? It is pretty neat. It allows for more reduction in a smaller amount of space. Take a look at this link http://www.lathes.co.uk/latheparts/page4.html

The 4 step pulley and small gear SG are permanently connected and ride freely on their shaft. All the other gears are affixed to their shaft.

I wouldn't use engage and disengae this setup for shifting, but it (engaged) seems like a good idea for a high reduction yet space saving gearbox for FRC applications.

In case it isn't clear, the 4 step pulley is the input and the threaded shaft is the output in this particular picture.