Roberval Balance

Fooling Physicists since 1669. All instincts (mine too) tell us to treat this like a simple see-saw, but we quickly realize that no matter how far out we slide the weight on the right we can not balance the weight on the left. Sliding the weight out does increase the reaction forces acting on the ends of the straight links, but does not increase torque acting on middle pivot points. For more info see www.Eckerd.edu/3d-physics.

Parts snap fit together so results may vary. I run a drill through the holes and oil before fingers before assembling.