Mostly aluminum. Our chassis is typically c-channel, and the superstructure is a lot of 8020. If anyone is using 8020, I highly recommend that you use their " end fasteners." Very lightweight and strong way to make right angle joints in 8020. Ok, so you have to do a little work and tap the ends of the extrusions. Nearly everyone on our team knows how to tap metal now! Oh, and in order to get good 90 degree joints, you really need to have a very good miter saw with a non-ferrous metal blade to cut the 1010 extrusions very cleanly, very accurately. A band saw or hack saw, in my experience, will not do.
We also use a fair amount of polycarbonate. We either use the AM perforated sheets (to mount electrical components) or multi-wall polycarbonate, which is exceptionally strong and light, useful for mounting very light components, or as a modest armor plating, to prevent incidental intrusions of other robots/game pieces to interfere with our robot's internal wiring. We will typically buy a
sheet, and have it cut to 2'x4' to ship it cheaply.
Steel pillowblocks, various components from AndyMark, VexPRO, and/or McMaster Carr typically comprise the rest of our robots.
For us, with very modest machining capabilities, simplicity of fabrication is paramount.
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Jim Grove, Mentor
firebirds1915.blogspot.com
(2007-2017) 1915, McKinley Tech HS, Washington, DC
(2009) 2932, Mid-Pac Institute, Honolulu, HI (Rookie Season)
(2011) 2425, Hillsborough HS, Tampa, FL
(2013-2015) 4464, College Park, MD, 2013 Rookie All Star Winner and 2014 Regional Champions, Washington, DC
FIRST is not rocket science. But it is like drinking from a fire hose.