Construction
Mark and cut a 4 ½ inch wide and full length piece from the center of the 9 inch foam plate. Glue the 2 edge pieces together and mark the axle position by laying a 5 inch wide cardboard rectangle on the bottom. Mark the edges of the foam so the two axles are parallel and the car rolls straight. Glue a 4 1/2 inch piece of the large straws on the front and rear marks. Insert a 5 inch piece of the small straw thru the large straw for the rotating axles. Draw the 4 two inch diameter wheels on the remaining foam plate with a compass. Cut out carefully and push a pencil through the center. Mount and glue the wheels on the 5 inch straw ends so they roll without wobble. Cut, fold and fit a 5x1 piece of plate for the straw and balloon mount. Glue in place above the rear axle as shown in the photo. Cut a 3 inch long piece of the very large straw and make a 1 inch long cut in one end. Squeeze and glue or tape this end about 1/3 the original size. Cut a 5/8 inch diameter piece of plate or cardboard and punch or cut a center hole the size of the straw. Fit and glue on the other end of the straw. Stretch a 7 or 9 inch balloon over this circle. Glue the straw on top of the mount. Inflate and release on a smooth surface. Have fun and experiment by trying different exhaust hole sizes and baloon sizes for best speed or distance.