Weston Middle School

Massachusetts Grade 8

Technology/Engineering MCAS Review

Tension and Compression in Drawings of Leonardo da Vinci

In the Italian Renaissance, there was no line drawn between the so-called 'fine arts' of painting and sculpture and applied arts such as engineering. This drawing by Leonardo da Vinci illustrates how he considered the forces of tension and compression exerted on the muscles in planning a drawing.

The giant crossbow

From Heretic, by Bernard Cornwell:

. . .Thomas had a new bow. Most archers, when their old bows wore out, simply purchased a new one from supplies that were shipped from England, but there were no such supplies in Castillon d' Arbizon and besides, Thomas knew how to make the weapon and loved doing it. He had found a good yew branch in Galat Lorret's garden and he had sawed and slashed away the bark and outer wood until he had a straight staff that was dark as blood on one half and pale as honey on the other. The dark side was the yew's heartwood that resisted compression while the golden half was the-springy sapwood; when the bow was finished the heartwood would fight against the cord's pull and the sapwood would he1p snap the bow straight so the arrow would fly like a winged demon.

The new weapon was even bigger than his old bow and sometimes he wondered if he was making it too big, but he persisted, shaping the wood with a knife until it had a thick belly and gently tapering ends. He smoothed, polished and then painted the bow, for the wood's moisture had to be trapped in the timber if the bow was not to break, and then he took the horn nocks from his old bow and put them on the new. He also took the silver plate from the old bow, the piece of Mass cup that bore his father's badge of a yale holding a grail, and he pinned it to the outer belly of the new bow that he had rubbed with beeswax and soot to darken the wood. The first time he strong it, bending the new staff to take the cord; he marveled at the strength he needed and the first time he shot it he watched astonished as the arrow soared out from the castle battlements . . .