On simple impetus; the drawplate's tempered edge
Simple versus composite impetus and air resistance; the acute steel angle that shapes the plate
The page joins a note on the physics of impetus to further wire-drawing (trafila) design. Leonardo defines simple impetus as that which moves an arrow or dart through the air, and composite impetus as that of a stone released from a sling, which is short-lived because the whirling motion's noise shows the body meeting resistance in the air it penetrates. Turning to the drawplate, he specifies opposing iron cones of great obliquity made powerful by percussion, and requires the die's internal angle b c (and the acute angle o c) to be acute and of tempered steel to shape the ribs and faces of the plate. A large staved cylinder, an inclined device and a radiating angle diagram are drawn at right.
On this page
Simple versus composite impetus and air resistance
Simple impetus moves the arrow or dart through the air; composite impetus moves the stone released from a sling. This composite impetus does not last long, because the noise generated by the whirling motion of the moving body shows that the body meets resistance in the air it penetrates.
Opposing iron cones made powerful by percussion
These opposing cones (coni contrari), being of iron stirrups and of great obliquity in themselves, become of the greatest power by means of percussion.
The die's acute, tempered-steel shaping angle
The internal angle b c of the iron stirrup should be acute and well tempered, being one of the shapers of the plate, with the drawplate's edge below the line a b to make the plate's faces. This third demonstration of the acute angle o c generates the ribs of the plate; it suffices that the angle be tempered steel for the space of one finger.