Having put the model together at the end of yesterday I really wasn't happy with the way the paper leaf springs worked. They were stiff had a limited range of movement. Back to good old gravity then. To add a bit of friction to the main wheel shaft I have a loop of card curved over the top of the shaft. At the bottom of the shaft are a couple of coins. The whole assembly slips into a tube so that its not flapping around.

I've stuck with the pawl being at the bottom of the wheel. With it at the bottom its movement is easily restricted, if it was over the top of the wheel it would be free to lift right off and over. I'd have to add a cover to keep the pawl in place.

So there it is complete. It works great! Turn the handle either direction and the main wheel advance one tooth at a time, always in the same direction which is weird. I need to add some box sections to the box to stop it twisting then that'll be it done. Excellent.