Rubber band car designs range from the ultra-simple to complex designs that use a rubber band as a drive belt rather than a kinetic energy battery. They all begin with a similar basic design consisting of a flat frame, two loosely connected axles, a rubber band and wheels. Feel free to modify a basic design to make it more functional or exciting.
The Basic Rubber Band Car
Find a cardboard box that is 1/2-inch or more shorter than a pencil. Carefully punch holes at each end of the box that are 1-inch up from the bottom and 1-inch in from the front and back, respectively. Place a new, unsharpened pencil through each set of holes to form the axles. Loop a rubber band over the shaft of a thumbtack and press the tack carefully into the pencil at the middle point. Affix CDs or large plastic caps to the end of the pencils for wheels. Punch one more hole in the front centre of the box and insert the loose end of the rubber band through the hole. Slide a pencil between the extruding band and the side of the box. Roll the car backward to wind the rubber band and give it a small push to get it started rolling.
Wooden Rubber Band-Powered Car
A wooden rubber band car uses a single flat piece of wood as the frame of the car. Install one small eye hook at each corner and extend wooden rods through the eye hooks as your axles. Cut the wheels out of a piece of lumber using a hole saw. Cut the front wheels a little smaller than the rear wheels to give it a sporty appearance. Drill holes in the centre of the wheels and attach them to the axles with wood glue. Loop a rubber band over the front axle and attach it tightly with a thumbtack. Affix the opposite end of the rubber band to the rear edge of the car with a thumbtack. Pull backward to "charge" and release it to "drive." For more power, use one rubber band on each side of the car instead of a central band. Make the car body out of cardboard or carved balsa wood and attach it with glue.
Belt Drive Designs
Small cars are sometimes powered by electric motors which turn a band around the axle. The basic wooden car design is used except that the rubber band is looped around the back axle instead of attached to the front. Cut a slot in the frame of the car for the rubber band to extend through and loop it over the driveshaft of a small battery-powered motor. Lift the motor upward until the rubber band is pulled taut and mount it at that level using a small block of wood. For better performance, paint the drive portion of the axle with a rubberised coating to increase traction with the spinning rubber band.