If you've been following along on Instagram you'll have seen this gear mechanism as I've been working on it. Check it out in animated action here.
This is a two stage reduction gear. Both stages use the same pair of gears. A nine tooth gear meshing with a nineteen tooth gear giving a reduction of 19 : 8 or 2.375 : 1
The two gear sets are chained together. To work out the final output speed you simply multiply the two ratios together. 2.375 x 2.375 = 5.640625 So the output crank turns at just about 5.6th the speed of the input handle. (Not 5.3 as I incorrectly wrote on my Instagram comment. Grrr!)
You can see the input gear more clearly on this picture.
And here is the finished thing.
I'm away for a few days now but as soon as I'm back I'll be adding this as a project. I'm really pleased with how these mesh gear mechanisms are working out, I feel like I finally really have a grip on paper gears!