Design for an articulated 'unjointed' mechanical wing
A jointed cane rod with matched springs and a greased leather cord for a flapping wing
The upper drawing shows a long, articulated ('unjointed') wing-rod fixed at points c and b, its cane spars linked along their length by springs r and S and a leather cord. Leonardo explains that when the tip a drops to m the cord section c–a doubles in length, drawing the bindings a and g together so the rod flexes strongly, and insists the two springs be of equal strength so neither yields before the other. He then specifies the materials: a well-greased ox-leather cord, spars of thick cane made in jointed pieces, and springs built from bundles of equal iron wires (or of ox-horn). A small joint detail is drawn at the foot of the sheet.
On this page
Articulated wing-rod and its flexing motion
When the tip a of the unjointed rod lowers to m, the cord section c–a doubles in length, so that at a–g the two bindings draw together and the rod bends strongly. The wing is fixed at c and b, with springs r and S set along its length.
Construction: cane spars, leather cord and iron-wire springs
The cord is to be of well-greased ox-leather, soaped with soft soap where it plays over the bindings. The spars are of thick cane, made in jointed pieces and as long as desired. Each spring is built of many iron wires of equal thickness, number and length between its bindings (or of ox-horn) so that all flex together at one moment.
Matching the two springs
The two springs r and S must be of equal strength so that neither flexes before the other. If spring r should yield first, the cord's bindings n and o are tightened, since the closer these bindings lie the stiffer the spring becomes; the same holds for spring S.