cut out sides of car you want and a 6 by 6 bottom
cut out a circle hole in middle and a square hole in front for front wheel
put circuit together starting with power then sound trigger , fan , wire, dc motor and put all bits on top of car with double sided tape but dc motor put that next to square hole in front.
slip wire through the circle hole in car and connect to the dc motor.
put wheel on dc motor in the front and cut 2 2 inch pieces of square balsa wood and put the 2 back derby wheels in and glue to back of car and you are ready to go.