Wow. Years ago, only Pine was allowed, and only in certain thicknesses. Plywood might have been 1/2" limit, I don't recall. But solid pine could only be a max of a nominal 1 x 4, so if you wanted bigger, you had to laminate it yourself. None of that designer stuff like Baltic Birch or bamboo or Bocote. We glued up our drive wheels from 1 x 4's (large aluminum sections were forbidden).
In our first year, we used wood because it was easier to saw in a wood shop, easier to glue and a whole lot cheaper than aluminum. And you could burn last year's 'bot in a wood stove to heat the shop for this year' build.
