Centre of gravity, the windlass lever, and swifter wheels
The central line to the world's centre, the three kinds of motion, and why a hub-thin wheel turns faster
Folio 190r sets out several 'Regola' (rules) of mechanics illustrated by fan-shaped cord diagrams and a wheel. Leonardo defines the 'central line' as the line running from a body's centre of gravity to the universal centre of gravity of the world, and states that a suspended body gives more of its weight to whichever support is nearer the weight's axis. He classes all motion as natural, violent, or mixed, notes that light bodies which do not push aside the air fall in varied paths like a sheet of paper, and defines the lever-arm of a windlass. A closing rule holds that a wheel thin at the hub and thick at the rim turns more swiftly than one of opposite shape.
On this page
The central line to the world's centre of gravity
Leonardo defines the 'central line' as that which stretches from the centre of gravity of a suspended or resting body to the universal centre of gravity of the world.
Unequal supports of a hung body
A body held in the air by cords or beams gives more of its weight to whichever fastening is nearer the axis of the weight. The fan-shaped cord diagrams show the load shared among the lines.
Three kinds of motion: natural, violent, mixed
Every motion is natural, or violent, or violent-natural, that is mixed, like a balance that falls downward.
A falling sheet of paper makes varied motions
Light bodies that do not drive the air before them gain no impetus but move in varied paths, as is seen in the fall of a large sheet of paper.
The lever-arm of the windlass
The length of the windlass's lever runs from the centre of the moving force to the middle of the windlass (argano) it turns.
A wheel thin at the hub turns faster
A wheel thin in the middle and thick at the rim moves more swiftly than one shaped the opposite way. A body descends more nearly along the perpendicular when its centre of gravity is more evenly distant from its surface.