pic: Side view of third try drive.

[Mr_I]

Thanks to all for the explanation. No, I did not realize the ball differential was in use (or even existed!). Very cool, but I honestly hope you won't need this in competition this year, because there are few teams that would be able to do this!

(Note: I don't mind being educated -- I figure it's part of my job in life to ask the questions that bunches of other people might have but are too shy to pose.)