I've been experimenting with the rack and pinion driven flip face mechanism. I had originally used a gear from the rack and pinion project but found that it was very intolerant to changes in dimensions. I'd make a copy and it would work just fine but the next one I made, with slight variations in alignments and it would jam up. I reckon that it has something to do with the teeth of the pinion catching on the sides of the rack. When I  tried the same mechanism but with teeth with flat tops it seemed to work better. The problem with this design is that the teeth can easily distort.

To get over that problem I've glued a disk, top and bottom to hold the teeth in shape.

The next step will be to try this design of gear in place in the flip face model. I'll be leaving that until tomorrow though as I have man flu and will be spending the rest of the evening under a blanket watching old episodes of Star Trek. Bleugh.