The folding flap shafts are driven by a pair of stepper motors salvaged from old dot-matrix printers. The two green plastic gears were obtained from Dick Smith Electronics, and by an amazing stroke of luck happened to be exactly the right pitch to mesh with the gears on the steppers. With the centres verycarefully drilled out to 4.1mm, they fit snugly onto a Meccano shaft. I wasn't quite careful enough with the lower one, which is why it looks a bit wobbly, but it works!