Hey, do you have a closeup of the wheels? They look pretty light.
(…They involve lots of milling and enormous piles of aluminum chips again, don’t they.)
does one sprocket there control steering and the other ( the top one I’m going to guess) drive it? if thats the case I seem to be on the right track with my design!! it is very much similar 
Yeah, they’re a two inch wheel. I’ll email you a picture of the wheel, or even the file itself if you want. They’re about half a pound, a 4 inch wheel, 2 inches wide.
Yeah, this is a coaxial crab, so the top sprocket drives the wheel, and the second one steers it.
whats the weight of the full pictured module?
About 4 pounds.