[catacon]

Team 1444 has done 6WD a few different ways. First was to drive the center wheels directly from the transmission (both one and two speeds) and then have one chain to the rear and one to the front; similar to what is posted above. I believe one year, you also drove the rear wheels directly then used a single chain to connect the front two wheels (one each side). This worked fine, but it was move difficult to manage and tensions, but really I so no difference in performance between the two methods.

We have also used gears to connect all six wheels. We drove the rear wheels directly, then used gears all the way up the sides to connect to the front wheels. The advantage of this is that it is easy to get another stage of gear reduction and you get instant engagement; you don't have to wait for the chain to tighten up. It is also much quieter. However, there were a TON of gears and a lot of precise machining.

For simplicity's sake, I would go with the double chain drive described above. As mentioned before, it is always good to drive one set of wheels directly. The middle is usually the best choice is you are using proper tank/skid steering with the center wheel lowered.