The trebuchet is said to have revolutionized warfare around 1200 A.D. With it’s roots extending from 5th century China, the trebuchet was used in both Islamic and Mongol conquests by defenders and attackers alike. Trebuchets are large throwing devices capable not only of throwing a 400 pound ptojectile 350 meters, but also with surprising accuracy. The projectile was rolled into place along a plank that lay underneath and parallel to the throwing arm. The rope sling that cradles the object to be thrown hooked over a metal or wooden prong attached to the throwing arm. The end of the arm opposite the projectile, which was later weighted to add force to the throw, is hoisted and locked into place until the trebuchet is ready to fire.
At the moment of firing, the beam is released and the weighted end of the arm swings earthward, sending the sling skyward. At the same time, the ball is pulled down the plank and, due to the force of the cradling sling, is drawn upward in an arc. When the projectile reaches a certain angle, one end of the sling slips off its prong to release the ball in a curving arc toward its target.
The earliest trebuchets used human power to haul downward on the hoisted beam and fire relatively small projectiles over a distance. They survived during Greek and Roman times as onagers, mangonels and other machines designed to hurl javelin. During the Crusades, human-powered trebuchets were rediscovered and used by both Crusaders and Saracens, where the development of the counterweight trebuchet began.
During the Crusades of the late 12th century, weights were added to the end of the throwing arm opposite the sling, allowing for a larger trebuchet size, range and projectile weight. This advancement produced a higher curving arc that could not only breach walls but sail over them.
|
Drawings from the 13th century show another advancement in trebuchet technology: wheels added to the base. These wheels not only allowed for maneuverability and aim of the trebuchet, but reduced the impulse opposing the firing motion (as seen in the as-yet-undiscovered Newton’s Second Law) that could potentially cause the trebuchet to rock and fall or even shake apart.
An added bonus of the addition of wheels is that the trebuchet can roll forward. This forward motion is a result of gravity acting on the weight as it swings downward, allowing the weight a straighter downward path. The motion also puts more energy behind the ball—energy that would have been lost in changing the weight’s trajectory—and allows the ball to sail farther .
Another, even later development was a change in the counterweight from a weight in fixed position to the hinged basket often seen in manuscripts. The basket rotated around the end of the beam rather than being fixed to the throwing arm. This basket was filled with sand, rocks, lead or any other easily-available heavy material. These hinged-basket counterweight trebuchets eventually replaced the fixed-weight trebuchet. According to the 13th century writer Aegidio Colonna, trebuchets with hinged baskets shot farther, though less accurately than fixed-weight trebuchets.
By the 13th century, trebuchets were widespread through Europe, the Holy Land and Asia Minor. It has been suggested that the Franks used a trebuchet against the Vikings at the battle for Brissarthe during the reign of Charlemagne, but evidence for this is scanty, says Bradbury’s book (p. 36, 1992). The earliest clear mention of the use of a trebuchet in battle is of King William the Lion of Scotland at the battle of Wark in the mid-1100s. The engine was hardly efficient, as the only shots fired fell upon the Scottish knights, but on the whole, trebuchets were more effective than was demonstrated at this particular siege.
Back to top |
