Trebuchet Research Paper

The trebuchet is a type of siege engine originating in China sometime before the fourth century and used primarily during battle throughout the middle ages. This large artillery weapon worked by launching projectiles great distances to destroy walls to rubble or to throw diseased corpses over castle wall. One of the first documented use of a trebuchet was a traction trebuchet used at the Battle of Caishi in 1161, where trebuchets operated by the Song Dynasty fired bombs composed of lime and sulfur at the ships belonging to the Jin Dynasty navy during the Jin- Song wars. The traction trebuchets were also frequently used by the Islamic armies during the Muslim conquests in the seventh century.

In around 965, the hand trebuchet was used by emperor Nikephoros
II Phokas of the Byzantine empire to disrupt enemy formations in the open field. In the twelfth century, the trebuchet was innovated into a counterweight design and was first used while taking conquest of Saladin. The next record of the counterweight trebuchet is found in the work of the 12th century Byzantine historian Niketas Choniates who describes that it was used by Andronikos I Komenos at the siege of Zevgminon in 1165 which was equipped with a windlass, a device that was required neither for traction nor hybrid trebuchets to launch missiles. During the second siege of Tyre in 1124, it was reported that the crusaders made use od “great trebuchets.”
The use of the new counterweight trebuchets was at it’s highest development during the 12th century during the Siege of Acre where kings Richard I of England and Philip II of France fought for control of the city. In 1421, Charles VII of France commissioned a trebuchet that could launch a stone weighing 800kg, while in 1188 rocks weighing up to 1500 kg were used. At the siege of Lisbon in 1147, the cycle rate was noteworthy, in which two trebuchets were capable of launching a stone every fifteen seconds. However, stones were not the only type of ammo used. In 1422 Prince Korybut of Lithuania fired men and manure past enemy walls, spreading

diseases to the opposing army. In 1268 China, Mongols sieged Facnheng and Xiangyang. Despite battling the Song dynasty for years, the mongol army was unable to capture the cities until, with the assistance of two Persian engineers, they built hinged counterweight trebuchets. Due to the introduction of gunpowder in the ninth century, the trebuchet lost its popularity and the siege engine of choice became the cannon. The last recorded uses of a trebuchet in battle was in 1521 at the seize of the Aztec capital Tenochtitlan. Hernan Cortes, the governor of Spain at the time, was motivated to use the trebuchet because of the limited supply of gunpowder. The attempt however proved unsuccessful with the first projectile landing on the trebuchet itself and destroying it. In 1779, during the defence of Gibraltar, British forces found that their cannons were unable to reach the distances they wanted to cover. The forces decided to construct a trebuchet in its place however it is unknown how successful this feat was.

While rarely used as a military device in the 21th century, there are two incidents in which trebuchets were used as an artillery weapon. During the Syrian civil war in 2013, rebels used a trebuchet in the Battle of Aleppo to dire explosives at government troops. A year after this incident, during the Hrushevskoho street riots in Ukraine, rioters used an improvised trebuchet to launch Molotov cocktails (petrol bombs) and bricks at the Berkut (special police force). Despite these two incidents, trebuchets are no longer commonly used in battle but are instead utilized for recreational or educational purposes.

Part B

Traction Trebuchets
Developed as a siege engine, the trebuchet was made three different ways. The very first trebuchet originated in China and was called the Traction Trebuchet. The design of this siege engine was derived from the ancient sling which contained a short piece of wood to extend the arm thus providing more leverage. Inspired by this design, the Traction Trebuchet requires a number of people to pull on ropes attached to the short arm of a lever that has a sling on the long arm. The smaller traction trebuchets could be powered by one person and one single rope, however many were intended to be used by roughly fifteen to fourth five men, each holding two ropes. Traction trebuchets had a range of thirty to sixty-one meters when firing weights up to two hundred and fifty pounds. Because of its small size and short range, this type of Trebuchet was more portable and had a shorter cycle time than the larger types that came after it, however because it utilized the power of the human body to operate it, this method was deemed inefficient for warfare, leading to its innovation by ancient engineers.

Hand Trebuchet
The hand trebuchet consists of a staff with a short sling at one end mounted on a pole using a lever like mechanism to fire projectiles. This type of trebuchet only requires one person to operate it.

Fixed Counterweight Trebuchet
Innovating the previous models, engineers created a trebuchet that utilized the force of gravity rather than that of humans. A counter weight trebuchet works by using the energy of a falling counterweight to launch a projectile. In order for the launch speed to reach it’s maximum, the counterweight must be heavier than the projectile that is being launched. The key to a counterweight trebuchet’s power is the use of the throwing arm as a lever. By keeping the pivot point of the arm close to the counterweight, the power and speed delivered to the projectile at the end of the long throwing arm can be magnified by the builder. This design is what allows a counterweight trebuchet to fire projectiles much heavier than those previously used in earlier trebuchet and even catapults design, and to throw those projectiles with a much greater force.

As society advanced, so did the design of the trebuchets.
The counterweight trebuchet was extremely effective however it was subject to a great deal of stress during operation leading to a shortened life cycle. In order to resolve this problem, the counterweight was placed upon a hinge. This allowed it to swing as it reached the bottom of its fall, consequently reducing the stress placed upon the frame and throwing arm. This redesign not only improved the life span of the device, but also increased the total distance traveled. By increasing the distance covered, engineers were able to also increase the rotational speed of the lever arm, thus increasing the launch speed and force of the projectile.

Our Trebuchet
The trebuchet we made is a fixed counterweight trebuchet. We chose to create this type because it was the newest and thus the most innovative type. Its style and build is simple while still being more effective then the types of trebuchets that came before it. We also chose it because it was the most common type used throughout history because of its optimal design which launches the projectile the farthest horizontal distance, and allows us as builders to magnify our trebuchets power and
speed.