Let’s say you have two boards end to end, each on fulcrums, angled up like an A. Leading to the apex of the two boards, you have a platform at about the height

Let’s say you have two boards end to end, each on fulcrums, angled up like an A. Leading to the apex of the two boards, you have a platform at about the height of the apex. Now let’s say you to take a step forward off that platform onto the apex of those two boards at the same time, pushing them down and lifting their ends. Do you have to expend any additional _forward momentum_ energy to take that step? Now let’s say there was a big spring between the opposite ends of those two boards, and that spring just happened to compress at a weight a bit lower than force generated by you stepping onto the apex. Now, imagine stepping off the apex. As you do, you feel the apex rise and push your leg off. Now apply that mechanic around an axle, and use mechanics to ensure only the springs nearing the top of the axle (as it rotates) compress when downward force is applied to the axle itself. That’s as good as I can describe how I understand it, and I can’t see how it violates any physical laws. It’s just a clever use of springs.