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!