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 turns its wheels. The countdown timer uses a more complex system of springs, gears, ratchets, and linkages to slowly tick down the seconds as it discharges for a countdown of up to six minutes. As you assemble these models one at a time from over 130 pieces, you will learn about the inner workings of spring-powered devices like wind-up toys and ticking mechanical clocks.Discover the physics concepts of potential and kinetic energy as you experiment with your spring-powered machines. Easy, snap-together assembly requires no glue. The kit includes step-by-step illustrated instructions. For Ages 6 and up. WARNING: CHOKING HAZARD – Small Parts. Not for children under 3yrs.