I was just at Smooth-On's main office getting some trial size resins.
I told the lady what I'd like to end up using the resin for (treads and maybe wheels and sprockets) and she told me that the resin (Task 4) works well for the wheels but some of them prefer to use a hard rubber for the treads rather than a resin due to slippage (no biggie there, just cast in some rubber pads if i intend to hit the streets). i plan to get further into that conversation with her via email (once I get a hold of here again).
Now when I get to the point of having my treads mastered for molding, I plan to have the thinnest part no less that 1/4" thick (i expect it to be up to 3/8" or there abouts in some spots).
now to figure out the design of the sprocket (can be bigger than 6" dia -- not including the sprocket teeth them selves).
ya, I know, I'm one of them thick headed people, but since it's what I work with all the time, I know something has got to work using this stuff (i just got to find it!).