I started with cleaning off my rather cluttered workbench, and laid out the parts for the S2. 

The S2's assembly starts with the V-Wheels and smooth idlers. Each one has two bearings, a spacer or washer, and a Delrin shell. Everything presses together, but you really need to have a screw in in the center to hold that center washer in place. 

There are a lot of these. 20 V-wheels, and 6 smooth idlers.