From the looks of the prototype they showed, it doesn’t look like a big sacrifice.
I would imagine the outward-bent flange is to define their FRAME PERIMETER and provide a mount for the box, since their hard parts can’t extend more than an inch beyond the FRAME PERIMETER (under 2013 rules, mind).
Considering the AndyMark C-Base is 1.13" wide (and you can’t really mount things on the outer face with the present frame perimeter rules), I doubt it’s much of a loss of usable space. If you needed to mount something on the outer flange, I believe you could still hog out part of the box tubing on the upper face to provide room for a bolt or rivet. How much strength you give for that I’ll leave to the pros.
Thanks, this is actually the first year we’ve done something like this. The prototype was designed in the fall and built mostly over winter. The actual bumper box frame is comparable in strength and weight to a west coast frame like 254 makes every year (before we add the plywood for the bumpers.) Because we only have one set of bumpers and use Snap-On covers we didn’t have a weight problem. A lot of our ability to make weight for the last 10 years was dependent on using thinner materials then most teams do. We make up for this by using stronger/harder-to-bend aluminum then most teams/shops use and bend it ourselves. This has its pros and cons.
The 2x1 aluminum box frame fits within the frame perimeter, however, because we have an outward facing flange we can still mount stuff over the box beam. We can’t mount stuff underneath it because the one piece bumper is removed via bottom of the robot.
Yes, the flange is important in order to bolt the box bumper frame to the robot frame in two planes (basically making them one.)
Actually, instead of drilling the box beam out to mount stuff we just mount stuff to it via rivnut. Our entire arm and arm structure was basically bolted through the outboard 0.05" thick flange into the 1/8 box frame. It was also attached to the actual frame via 4 small rivets to maintain legality. This was both the strongest way to mount it and made it easy to remove the entire top of the robot if need be (there was never a need.)
The 2013 robot does have a outboard flange. Simply attaching a box frame to the outside of your frame would be illegal. If anyone attempts a drivetrain like this I strongly encourage them to go over the 2011, 2012, 2013 bumper rules with a fine tooth comb.
Thank you, I attached a paper I created last year around this time basically detailing my “drivetrain philosophy” but never published it. I’m not sure its awesome but is relevant.
All of this is pretty off topic from the thread except to say that if you want to design a new chassis make sure you understand why you are doing what you are doing. Always design with a purpose/problem in mind and revisit that problem frequently as you go. If you do this at the end of it all you can’t help but to have solved the problem you set out with (then iterate to more elegantly solve the problem).
I’m sure Jim will post the 2013 CAD sometime in the near future. Perhaps it would be better to hold questions until that thread, create a new one (I can talk about design decisions/implementations for hours), or PM me if you’re still curious about the WASPdrive.