SpringBots: 3-in-1 Spring-Powered Machines

Build a motorized robot, race car, and countdown timer - all that run without any batteries or electrical power! The secret behind these fascinating machines is a power source called a mainspring - a spiral-shaped spring that stores up energy when wound up by hand, and then converts that stored energy back into motion when it discharges. The mainspring inside the robot turns gears which enable it to march forward on two legs. The race car zooms across the floor as its mainspring uncoils and...