After a year of daily work and more than 1000 Km the hinge was wearing out making steering unprecise. So I decided to rebuilt the mechanism and try to make it even stronger.
Many people watched the original instructable last year but nobody told me about doing something similar. I hope this one helps somebody to try it. The bicycle is really fun and many interested people ask me about it in the street.
Hub diameters are not standard.
The diameter of the hub should be similar to the diameter of the handlebar stem.
Of course you would not do that with an aluminum stem!
Aluminum stems have usually a two pieces clamp, this step would not be needed. However, matching the diameter of the hub would be more difficult.
You may also find a way to fix a spare crank to the fork instead.