I cannot seem to find a robert rock. It would be great to see a picture of his articulating machine. I like his custom cad machine but fear that 3.5 mph would be a little slow. Very neat. Red Square site has a very neat belt drive C-101 4x4. I am working on a hybrid articulator design that has a gear shift rear with hydraulic assist front. I have to complete some diagrams and I will share them. All parts should be readily available and reasonably priced. I cannot seem to come up with a fulltime 4wd machine that would not require some kind of extreme machining.
http://www.wheelhorseforum.com/galle...576-c-101-4x4/
https://www.youtube.com/watch?v=_-61aaKItAE