[EricH]

Originally Posted by T^2

368 did it this year with a pipe bender (I think) and 6063 alloy. 6061 will probably crack.

I've seen the effects of bending 6061 plate with a mandrel/vice setup. I'm not sure of the hardness, but one bend attempt--as I understand it, at the recommended minimum radius--did in fact crack, rather badly. (A slightly more processed plate--we think it was partially annealed--bent easily at a much smaller radius.)

The trick with a closed loop like what you seem to describe is that you have to have a way to get it out of whatever you're bending with after the last bend. Also, you'll probably want to weld/bolt/rivet/otherwise fasten the ends together. Oh... and heat can help you, but you need to be cautious using it, both from the standpoint of "this can set stuff on fire" and that of "this is changing the properties of this metal, do I really want to do that?"