Can this design work? Try this small experiment before building the design. (See drawing below) Acquire a foot of string, a weight and a coke can. Tie the weight to one end of the string. Hold the coke can by hand in a horizontal position. Place the string in parallel (in line) with can at one end. Hold the string against coke can with your fingers with the weight hanging down. Perform a half hitch around the coke can with the weighted end now hanging. Coke can will be in line with 3 o'clock position. Allow the can to rotate to 4 o'clock. The weight will spiral and slide the string down and outwards moving the center of gravity from where the weight was originally. Rotate the coke can back to the 2 o'clock position. The string and weight will spiral back to the original position. Rotate the coke can to the 6 o'clock position and the pendulum will be released from can transfering the weight back to your fingers.