Flight of the swallow and the mechanical wing
Beating flight analysed as jointed levers with weights along the wing
A dense flight sheet in which Leonardo compares a mechanical wing to the wing of a swallow and analyses the forces of beating flight. Diagrams lay out a jointed wing as a chain of levers (shoulder, a b c d e) marked with successive degrees of motion, and a long passage works out how a bird's weight is distributed and resisted along arm, hand and fingers. A note contrasts the swallow's short-armed, long-handed wing with the kite's, describing how the hand rows toward the tail while the arm drives downward. Reminders to 'attend to the centre of gravity' and to weigh the body, arms and wing-membranes recur.
On this page
Mechanical wing built as jointed levers
The upper diagram sets out an artificial wing as a series of levers from the shoulder through points e d c b a, labelled by increasing degrees of motion and of air density. Leonardo gives the segment lengths (a b 2 braccia, b c 6, c d 3, d e 3, e f 3), totalling 16 braccia to f and 32 across the pair.
The swallow's wing compared with the kite's
The swallow's wing is very short in the arm and long in the hand, unlike the kite's. Its beat works two ways at once — the hand rows toward the tail and the arm toward the ground — so that one motion drives the bird forward while the other keeps it aloft.
Weight and resistance distributed along the wing
Leonardo halves the load at each joint: of a 300-pound whole, 150 rests at the centre of gravity to the arm's root, the elbow bears 150, the hand 75, the half-hand 37.5, and the fingers' end 17.75 pounds. He reasons that with 100 pounds spread over 100 square braccia of air, each square braccio sustains one pound.
Weighing the parts to find the centre of gravity
A feather is sketched with the instruction to weigh the body, the arms and the membranes separately and to take the centre of gravity. A companion note on the jointed-arm figure calls for attention to the centre of gravity across the three depicted joints.