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Originally Posted by Kevin Sevcik
I think your hands down favorite/best material to construct a robot out of is waterjetted and bent aluminum sheet metal, since you can design it to the exact requirements you need, given you an optimum strength to weight ratio.
Lacking the fabrication support necessary for the above, 57 has settled on the kit frame with a chassis of 1"x1"x1/16" wall square aluminum tube, mostly held together with more 1/16" sheet plates riveted with 3/16" aluminum structural rivets. It's pretty lightweight, plenty strong if you're not dropping your robot off a cliff, and we can get 20' sticks of the stuff for $6 from a local supplier, even on a Saturday. Which is harder to say about AM channel or 80/20 or another T-slot extruded aluminum.
Thick wall AM style channel is heavier and tougher than we need for any framing purposes. Thin wall channel would be flimsier than tube, if lighter. Either of the u-channel options means you have an entire side that can be a pain to attach things to.
80/20 style extruded aluminum is good for prototyping and quickly adjusting parts, etc. Only problem is that it's heavier than the 1/16" wall tubing that we use, for no more benefit than the quick propotyping.
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I was about to write about 2815's construction methods of recent years, but this really is what we use--the last two robots (with three blue banners between them) have been constructed of 1"x1" square tubing acquired from the Lowe's near where I work (which is not as cheap as Kevin's aluminum--I want your source!), attached with gussets of various sizes and shapes (we use some angle as well) with rivets and attached to the AndyMark C-Base kit frame. For all the nail-biter moments these two robots have given us, the structure has been rock solid.
It's been many years since I worked with 80/20 (and then as part of an elevator rather than a frame); the stuff can definitely get heavy. If I were building a sliding mechanism, or a part that I knew would require a lot of quick adjustments, I would consider it...but I doubt I'd want to build a whole robot out of it.
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Originally Posted by Siri
Do you have any advice or books/white papers/etc to recommend concerning designing for 1/16" tube? We're pretty much all 1/8" tube or angle for everything on our bots. I've heard great things about 1/16", but we've warped welded 1/8" chassis occasionally so there's some hesitancy.
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We build our structures so the 1/16" tubing is inboard--the only exception was our original roller claw in 2011 (which broke when our drivers smacked it into the player station glass at speed). From there, it's just been judicious application of 1/8" rivets (sometimes by overzealous freshmen) to hold it together. If you get to St. Louis, look us up--there's no secret sauce to our framing setup, and we'd be happy to show it.
We haven't tried welding any of our parts--call it a bit of paranoia about breaking parts in the heat of competition. Granted, we could duct tape it these days...but the idea of just throwing rivets into a new piece of metal has its appeal.