I like http://507movements.com/mm_398.html http://507movements.com/mm_398.html which is a programmable drive system. Constant rotation input can give you a cyc

I like http://507movements.com/mm_398.html http://507movements.com/mm_398.html which is a programmable drive system. Constant rotation input can give you a cyclic but irregular and arbitrary output movement. Another good programmable mechanism is a spring made from sheet metal. Take a flat piece and cut a spiral with the width of the material proportional to the force you want at that part of the spring's travel. Stretch it out to form a little tower, with the base on a solid surface, and the load carried on the center of the spiral.