Our frame without electronics or the arm
What are the benefits of the concaves in the side of the frame? Other than that question its very impressive. I like the mecanums.
Seeing how they do have a mecanum drive, I would think it would be for herding/pushing tubes or for having the tubes “self-align” for an arm and/or manipulator to pick them up. The bend radaii on those curves looks like it would match a tube quite well. 
I would be guessing that they are there to line up the tubes when they run into it.
From our mechanical guy not me: its ergonmically designed for one person to carry by bending around your waist and grabing the other two sides with your hands. Oh it also looks pretty cool. From me: I asked the same question about the bends but im not incharge of the design. Plus what you guys kinda said in the two post before this one.
Reminds me of those new laundry baskets with one ergonomically designed side for that very reason. 
lol:D