My semester project is to create a device that will make a sound at 5,10 15, and 20 seconds exactly using only gravitational energy. -My initial design used two rotating axles with two gears through them and a chain. It would begin by me dropping a weight attached to one of the axles making it rotate exactly five times and hitting something to make a sound. I would also use the inside mechanism of a tape measurer to somehow make the axle retract back into place at exactly five turns and make another sound and so forth.... However this is a lot easier said than done. Any suggestions to this idea would be helpful or something totally new would also be great.