I know that I am using springs here, but I also used wheels (they just clipped inside of each other), and normal blocks. They came back with more or less the same result. If only the game code allowed for the equal and opposite reactions that take place every day on someone's desk. COLNTROLS - AC 1-5 (activates each pilon on hinge) and VTOL to start Newton's cradle.
This could possibly be a good platform for comparing other things (maybe engine hp test comparison or other things) so feel free to use it