Odometer - Codex Atlanticus Folio 1r

The Odometer was designed to measure the distance travelled by the small cart. It was done through a series of gears which turned a wheel holding pebbles, these being released into a bucket beneath the carts framework. Counting the pebbles at the end of the journey allowed the distance travelled to be calculated.
The history of the odometer is a long one stretching back to Alexander the Great when he used an unknown device to measure the distance of his travels with great accuracy. Following that, a Roman device that used the principle later picked up by Leonardo was described by Vitruvius as using a Roman Chariot wheel 4 feet diameter at the heart of the system that counted pebbles dropped into a bin after so many wheel rotation.
It would seem that Leonardo’s design using square toothed gears failed to work.
I have used the alternative worm gear on Leonardo’s alternative design to produce a model that will work.