We use 1/8" rivets EVERYWHERE.
See how to link here:
http://www.huntingtonrobotics.org/in...d=1&Itemid =2
Or Video here:
http://www.huntingtonrobotics.org/in...=1&key=1&hit=1
The whole frame is "ribbed" and "skinned". Just like an airplane is made. No need for welded steel. It does get "dented", but it never has "failed" on us yet. Even the wheels are riveted with bulkheads and quite strong.