This car weighs almost a full 1 pound, but is purely gravity powered so met the rules of our “unlimited” class. It takes a little work to prepare it for launch, but then boy does it GO. This car has a 21″, 1/8″ diameter piano-wire rod attached to the car leaning 15 degrees rearward of perpendicular to the ground. The rod has a 1/2 inch washer welded to the bottom end, is embedded into a hole in the car and glued in place with PL Premium construction adhesive (available at home depot, but only in chalking tube amounts). The 8 ounce ball weight (standard fishing gear) has a hole drilled in it and slides freely along the rod. It is raised to the top of rod to prepare for launch. The angle of the rod is really important and matched to the track I was racing on, so that the rod is vertical while in the starting gate. Otherwise, the car would fall over with all that weight up so high. A strong thread, attached to the ball weight – the attached thread goes around the top pulley and back down to the rear axle. The thread is wound around the “gear” on the rear axle.