I'm happy to see you all got this built. Prototyping in the off-season is an invaluable experience for new and experienced team members, allows you a chance to safely try new ideas, and helps you to work out the kinks in your manufacturing processes. Even if, on the day of kick-off, you have to throw this design out (...and I hope that you won't...) or rebuild all of your modeling and design work from the ground up, it's worth the effort.
55 lbs. is respectable -- especially with a pneumatics system on board and two of those large CIM motors. That alone probably represents ~15 lbs. of your total weight. The 1x2" extruded profile is a bit heavier than rectangular tubing, yes, but that penalty may be worth the time saved in labor. We finished our prototype chassis, for the most part, back in early November. It's 30 lbs. -- but that's with two motors and no pneumatics system -- and it required considerably more manufacturing effort. The most recent iteration incorporates a lot of the features y'all have here and, though it's a few pounds heavier, involves far, far less work. It's a worthwhile compromise.
If you don't mind answering a few questions:
-- From what are the bearing blocks made? They look like they're 1/4" thick, overall dimensions of 2.25 x 1.5. McMaster-Carr, nor onlinemetals.com, seem to carry stock of these or similar dimension. Are they custom made?
-- What machining work was done to the 1x2 extrusion to accomodate the axles?
-- Where'd you find 1/2" bore, keyed sprockets for #25 chain?
What were lead times and cost like?
Thanks for sharing this.