A bucking bar is used, as you all know, to supply holding power to the head of the rivet while the other end is being bucked. Confusing, right? Not really. The videos are extra informative because they show 3 different ways to hold the head. Video 1: A pneumatic or hydraulic "jack". Video 2: A pneumatic hammer. Video 3: Totally hand held big round bar pushed up against the head with human power. All seem to use a pneumatic hammer to upset the rivet. None of it is high tech. All if it is basic common sense. Looks like a lot of fun. I would highly recommend to some of those guys in the videos to wear eye protection.
I can envision an over-center, adjustable (pinned, jack screw or sliding ratchet) clamp that goes from one side of the frame to the other (like the "jack"). This would meet the requirement for fast acting and could be home made. No extra air tool required for that bucker! Example of "over center": Truckers chain tensioner, but in reverse.
