Water-wheel driven by a river to grind mills
Sizing the wheel, its fall and channel in braccia to reckon the mills it can power
The page works out how to power a set of grinding mills from a river using a large wheel roughly 10 braccia high. Leonardo describes damming the flow with a board so the water gains one braccio of fall, then reckons how many mills each square braccio of water can grind. A note between two drawings of a three-part wheel explains that its middle section takes the water while the two outer parts drive the whole. The upper diagram carries the measures 4-2-4-3, and lower sketches show a drum-like device and a paddle wheel on its base.
On this page
Damming a river to give the wheel one braccio of fall
If the wheel is 10 braccia high, one braccio stands underwater and one is lost through the hole at the axle. Setting a board across an 8-braccio river that rises one braccio above the surface brings the water level with the board and yields a braccio of fall to drive the wheel.
Reckoning how many mills the water can grind
Every square braccio of water grinds 4 mills at 3 once per mill, given the 3 braccia of fall the wheel ordinarily needs. Thus 8 square braccia of water would grind 32 mills on one line — though Leonardo prefers to say 16, for greater certainty.
Three-part wheel: centre takes the water, sides drive
A short note set between two figures of a tripartite wheel gives the correct arrangement: the middle section receives the water while the two outer sections impart motion to the whole assembly.