Nice project. I have planned to make my own too. But im trying to find out how to make drive wheels etc. Without a metal lathe. Drill and angle grinder has been my solution so far. But its difficult to get balanced result.. I tried to make frame from the pipe and plate by welding them together, then machined with drill and angle grinder.

Works.. but result vibrates too much. Needs another try, but i think it might work.

Thanks for the pictures, got some usefull information from them.