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[DampRobot]

It appears like most teams use welded aluminum extrusion, if not using the kitbot frame. The most common sizes appear to be 2x1x1/8 on the base, and 1x1x1/16 on the superstructure.

My team has took the rather unusual step of using rivets last year to assemble the frame. We used almost exclusively 1/16" aluminium tubing, with 1/8" gusset plates that riveted the whole thing together. A variety of sizes of rivets were used, from 1/8" aluminium to the huge 1/4" steel. The rivets were a weight saving measure after trying to use steel bolts.

I would recommend rivets to a team with an accurate mill and a desire to save weight. With an accurate mill, the gussets and the frame members can be made so the frame is perfectly straight (we have had some problems with crooked welded frames in the past). Also, rivets allowed us to use almost exclusively 1/16" tubing, which saves weight, but is near impossible to weld. I estimated that this saved us 5-8lbs.

If you do decide to rivet (or to bolt and then are forced to go to rivets), keep in mind that you have to size the rivet for how much material it is gripping. Not just any size will do. Also, 3/16" rivets work in #10 holes.