[IKE]

We on 33 have been doing a folded sheet metal chassis for the last few years. Once you learn how to work with sheet, it is pretty easy, very light and very effective. You do need to learn rivet techniques and how to bend metal accurately an effectivele. We use heat treated 6061 T6. Before everyone tells me you can't bend it, that is not true. Heat treated (T6) means you need to be very careful bending it and use an ample radius.

For the big structures we have generally been going with space frame welded aluminum tubing both square and round. I have a lot of race car chassis construction experience so it helps. One of our students did most of the welding this year. While she is not a pro, she gets the job done.

What material you decide to use depends on budget, equipment, and skill sets. 80/20 or Star bar is very easy to use but extremely heavy (from a KB33 perspective). 1/16" is the beefy stuff on our machine and we often go down to 0.035" wall round tube.

If you do not have a skilled welder, I would recommend visiting the Team 1216's website and check out their chassis. The pre-drill 1x1x1/16 box with a very specific hole pattern. This technique gives 90% of the strength of 1x1 box with the flexibility of Star-bar or the kit rails with a TON less weight. These guy are pretty modest and only went to 1 regional so you won't see a lot of buzz about them. As a structures guy, I have a lot of repect for this technique as it has the 4-way threat of strong, lightweight, flexible design, and easy to use/manufacture.

Another good source are the 2 "Behind the Design" books. You can almost tell what line of work the sponsors are in by the construction of the robot. With aircraft companies you will see a lot of sheet metal. Nasa and Robotics related sponsor teams seem to have a lot of CNC. Big 3 teams seem to have a lot of welding.

As far as material sponsors to order from Aircraft Spruce has an awesome selection but can be a bit slow to certain areas. They have some truly amazing materials line a strut material that is 11oz. for 8 feet. Online metals is a good plae to order small quantities, but were extremely slow on their delivery for us (I did find a way to expedite future orders). Mcmaster Carr is fast but expensive.