Have some fun with a rubber-band-powered toy car. This car moves without electricity (batteries) and can help you teach children about momentum and energy. Plus, they'll learn about making their own toys. If you build more than one of these, they can have speed and distance contests.
Cut four sections of dowel rod 1 inch in diameter and 1/2 inch wide. Use a mitre box to make sure the cuts are perpendicular. Sand the cut sides smooth. These sections are the wheels.
Clamp a wheel into a vice. Use a strip of cardboard to protect the wood so that the vice does not scratch the wood. Do not make the vice too tight, or it will dent the wood (especially soft woods like pine).
Find the centre of the wheel by finding the intersection of two perpendicular lines drawn across the widest point of the cross section.
Drill a hole into the centre of the wheel. Take frequent, short breaks while drilling to keep the wood from overheating and burning from the friction of the drill bit. Repeat this process to with the remaining three wheels.
Cut a 4-inch-long block of wood from the 2- by 4-inch board to form the body of the car. Sand the rough edges smooth.
Pre-drill the pilot holes for the eye screws into the corners of the block 1/2 inch in from both adjacent sides to a depth of 1 inch. Screw the eye screws into each hole until the threads are no longer visible. Twist the eye screws so that they are all facing the same way and can hold an axle through the centre of each parallel pair of eye screw eyes.
Cut the 1/4-inch-diameter dowel rod into two sections that are 1 1/2 inches wider than the body of the car. Slip these newly cut axles through the eyes of the eye screws so that a pair of eye screws holds on each axle. Use wood glue to glue the wheels on either end of each axle.
Pre-drill another hole in the centre of the underside of the car's body to a depth of 1 inch. Screw a 1/2-inch-long wood screw into the hole until the threads no longer show but the head protrudes. Drill a 1/16-inch hole through the axle.
Slip the rubber band halfway through the hole, and slip one end through the other. Pull the end that was slipped inside the other until the end holding it tightens around it at the axle. Slip the loop that was enlarged by this action around the screw sticking out under the car.
Wind the axle with the rubber band in the opposite direction that you want it to go. Place the car's wheels on the ground and release.
If the wheels "peel out," add rubber bands around the wheels for traction. If the rubber band does not drop off the screw as soon as it is unwound, the car will momentarily change direction when the force stored in the rubber band overcomes momentum. Paint the car with non-toxic paint if desired.
Allow only children who are mature enough to be responsible with rubber bands, heavy toys, sharp objects and things that unscrew to use the car. Do not release the car where people may walk, where it may fall or where it may otherwise hurt people. Wear safety goggles when making this toy and when using rubber bands. Read and follow all safety instructions for your power equipment. Clamp pieces before drilling. Do not use toxic paints or materials. Make this project in a well ventilated environment.