[EricH]

Originally Posted by Mk.32

Look into using 1/16 a lot of team use it and it is lighter and should be adequate. Also I assume the center wheel is dropped?

It's only adequate because bumpers are required. [Insert "back in my day" comments about frames, metal-on-metal contact, and lack of bumpers here.] I'd keep the 1/8" wall; if your bumpers come off somehow, it'll give better structure. Also, 1/16" can be tougher to weld, or so I understand.

Remember, your drive frame also has to take the loads put on it by the superstructure. I actually designed a drive frame for a non-FIRST application recently, and I went with 1"x1"x1/8" for a 80-kg, 1.5m x 0.75m x 0.75m robot that is not going to have any contact with another robot, but traverses difficult terrain, for the entire drive frame and superstructure support. The entire robot, in CAD, is rather under the 80-kg mass (though this does not include payload). Last I checked, FEA had yet to be done, so I'm not certain whether I can reduce the size and/or thickness or not.

However, there is a way to make the frame lighter--those inside upper rails can come off. Brace the gearboxes using rods run between them crosswise, instead of a welded piece running lengthwise. (This is also the one place that I'd say that 1/16" would be adequate; you could also use angle aluminum.)