I just made a 2-MOTE (MOT electromagnet) brake as an evaluation of the idea:
I made it small to keep the time, effort, and materials small. But it has an 8-1/2" capacity, which would be enough for a lot of the stuff I do (e.g. electronics project boxes).
Unfortunately the results are very disappointing. I ran the MOTE's on250v (AC into the bridge) and could not quite finish the bend on .040 (about 20 ga) steel. 18ga (.050) started, but only got to about 45 degrees before the clamping bar started sliding back. .030 bent very nicely and although too light for a lot of stuff, boxes in that guage would be useful.
So I have definitely ruled out MOTE's for the 24 inch brake that I'd like to make. I'll be thinking about what it would take to wind the coil for that. I expect that it would be painful, but the challenge would be interesting.