The Trebuchet

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Explanation and history of mangonels and trebuchets

Many wars were waged in the conflict ridden Middle Ages, which forced many cultures to interact who wouldn’t have otherwise. These interactions lead to the spread of siege weapon technology which became more effective and deadly producing more accurate and accurate results. Once introduced to society this siege technology affected the world in several different ways. It changed the way combat was fought, how fortifications were built and essentially created the position of the military technician. However, the observations of this technology, especially in the case of the trebuchet, allowed for development and implementation of scientific concepts especially for the field Physics.

Late Roman military technology had forms of stone-or-bolt throwing machines. This artillery was based upon the torsion principle of stored energy. These machines were designed to launch missiles with a flat-trajectory and to pick off foot soldiers rather than to damage enemy fortifications. These weapons were able to launch “incendiary materials” and were often directed at the enemy’s siege weapons.

The Roman technology survived the fall of the western half of the empire as evidenced by the re-emergence of “sophisticated siege technology” in the 6th and 7th centuries in regions that retained Roman-Latin culture and were unaffected by the German conquest, even in areas as remote the Celtic West and Northern Britain.  Siege technology in France was better developed in the South which had been Romanized.

It was also clear that the Byzantine Empire had contributed to Western Europe’s development of more modern siege technology. The Byzantines had gained their knowledge not only from remaining Late Roman technology but from interactions with the Islamic civilization. The Islamic civilization itself had had contacts with several different cultures as they conquered lands in the Middle East. In the early Islamic period, the early Arab caliphate depended heavily on siege technologies of conquered people, “mainly Arabised Syrians, Greek Byzantines, Iranians and Turks.”

The Islamic civilization also had contacts with China which had more advanced technology than the Graeco-Roman world.  For instance, the staff-sling was known to the Roman world but the Chinese were the ones who thought to enlarge it and mount it on a fixed pole or wooden frame, which created a means for throwing large rocks.  Thus “man-powered beam-sling” mangonel was invented.

The mangonel was invented between 5th and 3rd centuries BC and reached the Middle East “by at least” the 7th century AD.  How the mangonel arrived in Europe is still unclear. One explanation states that it may have been brought by the Avars, who had been driven from the “northern frontiers of China.”  The mangonel was specifically mentioned in the writings of Byzantine Archbishop John of Thessaloníki, who describes it being used by an Avar-Slav army in AD 597.  By the 9th century its use in Europe was widespread as evidenced by its use by Parisians against Viking attack in 885-886.  By the late 11th century a similar stone throwing weapon was being used by Christian armies in Spain.

It seems that the First Crusaders may have used a small mangonel inside Antioch in 1098.  They also mention of “rock throwers” used in the siege of Jerusalem that were used as “anti-personnel weapons” and to destroy the enemies artillery. They did not attempt to breach the walls with this artillery. This all suggests that these machines were mangonels.

After 1050 siege activity soared, as a response to combative activities and military problems in Latin Europe from 1060-1120. In the 12th century, there was significant growth which lead to the city development such as the construction of urban fortifications and castles built with stone instead of earth and wood. These changes created a need for more complex siege operations, which had to include more effective siege weapons.  By the time, the Crusaders in the 12th century headed on their mission, Islamic military technicians found them to be of interest and added their form of stone-throwing engine called Ifranji or 'Frankish' to existing Arab, Persian, Turkish, Rumi (Roma) or Byzantine machine.

During the 12th century, the Europeans had contact with the Islamic world due in part to the Crusades which improved European technology.  For example, by the mid-12th century there were striking similarities between siege weapons used by the northern Italians and those used by the Crusaders Stares, Syria and Egypt. Later 12th and 13th century references to Turkish mangonels in places such as France and England show that these devices had been adopted from the Islamic world.

Although a “revived Byzantine Europe” was developing siege technology 10th century and its military technicians may have contributed to the development of an improved form of mangonel which came to be known as the counterweight trebuchet, the counterweight trebuchet was actually invented in the eastern Mediterranean or the Middle East in the early 12th century.  Its invention is most likely due to a Muslim engineer who had thought of taking the man-power out of the mangonel by replacing the gang of puller with a heavy weight. And a heavy weight could be easily assembled by filling a box with dirt, or any other heavy material available.

The mangonel and its ancient counterparts were limited in their destruction. They were used mostly as anti-personnel weapons and to destroy the enemy's artillery. The mangonel was further limited because of its use of man-power for both the sling and its gang of rope pullers, which among other things limited its size.  It had to use very specific stone of a structured weight and shape which required masons. The trebuchet could launch a variety of objects and could do so with a force that could knock down walls.

During a siege, trebuchets were usually grouped into batteries, as were mangonels. Trebuchets could also be placed on a ship to attack the walls of an enemy port, as was done by the Italians. 

By the start of the 13th century some Italian “trabucchi” or trebuchet which were light and easy to assemble, could be put on the tops of towers.  Depending on their size, the trebuchets could hurl everything from stones to corpses.

They were referred to as “engines.” And the people who designed made and used them were called “ingeniators.” Both terms come from the Latin term “igenium” which is defined as “an ingenious contrivance.”  These people were often commoners and were able to market their skills to give them a high position in society.

The ancient machines were powered by torsion. Mangonels were powered by traction which is why they are also referred to as traction trebuchets. The physics of the counterweight trebuchets was slightly different than both of these.

The trebuchet's premise and structure was simple. It consisted of a long beam pivoted on a fulcrum, the support on which the beam turns was much closer to one end than the other.  This axle divided the beam into two sections, one larger than the other. The long part of the arm had a cup or more commonly a sling at the end of it to hurl the missile. The shorter part had at its end an attachment for pulling ropes or a counterweight. When it was set up for launch, the entire beam is vertically slanted with the short arm in the air and the long end facing the ground.  This was achieved by pulling down the long end of the beam, most likely with a winch, which is a drum that has been wound with a rope of cable for hauling or hoisting.  Then a missile would be placed in the cup or sling and the beam was locked into place, which in turn lifted and fixed the weight at the short end.  To launch the missile, one would release the long end, and the short end, the counterweight, would plunge, forcing the long end to swing upward. The sling would then unravel which would increase the speed of the missile greatly and it flew through the air to reach its target.

The box that served as a counterweight on the short end could “be the size of a peasants hut and contain “tens of thousands of kilograms.” The missile contained by the sling or cup on the long end of the beam could weigh between 200 and 300 kilograms. It is said that some bigger trebuchets could launch projectiles weighing between 900 and 1360 kilograms. Such large capacity allowed objects as big as dead horses or bundled human corpses to be flung onto the enemy. In modern times, hobbyists can throw things as big as cars or baby grand pianos.

The trebuchet did allow for more regular and accurate targeting than the mangonel, because of the elimination of manpower and the use of a large quantity of various sized ropes.  But the dynamics of the trebuchet were so complex that it was very difficult to adjust the range and direction of a shot. The modern reconstructions show the weight of a projectile decreases the amount of time it takes the sling to open. Therefore if a projectile is not heavy enough the sling will open too late which results in a short distance launch not too far from the trebuchet itself.

Engineers worked hard to modify the earlier trebuchet designs in order to increase its range by “extracting the most possible energy from the falling counterweight” and “to increase accuracy by minimizing recoil.”  Unlike traction trebuchets (mangonels), the counterweight trebuchet had a long sling because they are not limited by issues of man powered operations.  Due to the removal of the rope pullers, a trough could now be placed underneath the beam to hold the sling.  This change “increases the effective length of the throwing arm” which in turn effects its performance.  This is based opon the torque to do a force. By increasing the length between the pivot at which the force is applied they created a greater effect on the rotation.  This change also permits the engineers to make more improvements by making the angle at which the missile is released more independent of the angle of the arm.

Through trail and error, the engineers varied the length of the sling ropes to increase the trajectory and to maximize the amount of potential energy that is converted into kinetic energy, energy that is transferred to the missile.  They found that to achieve the largest the trajectory the shot must leave the machine at an angle of approximately 45 degrees perpendicular to the ground.  The arm should be as high off the ground as possible, which is when potential energy is the greatest.  And that the sling must open to launch the target only when the arm has closely approached a vertical position with the counterweight at the bottom of its trajectory.

The observations that were used to improve the trebuchet may have also influenced important physical concepts and helped develop “medieval insights into the forces associated with moving bodies.” 

Large trebuchets created sudden stresses when shot and could not be placed on walls due to risk of destabilizing the wall and having it come tumbling down. These trebuchets were placed on roofs and larger towers. Eventually, trebuchets were used as a defensive measure for cities and 13th century fortifications were built with more large projecting towers then they were in the 12th century.  The first use in battle for the counterweight trebuchet in the Islamic world was atop fortified towers.

Although these siege weapons were discussed as part of the history of particular sieges, they were referred to as how successful they were in getting the mission accomplished. The way they worked and pictorial depictions were usually inaccurate, based on the accounts of ancient writers which varied widely in their terminology.

There were a wide array of variations on the basic trebuchets mentioned in the medieval sources. In one account by Phillippe Mausket around 1260 he mentions a tumerel, which is rumored to be a form of trebuchet, however the word was also used to mean a “a deadfall trap” so it most likely was meant as a descriptive poetic term.  The Arabic and Greek texts were more specific in their terminology than European texts.  The variation in terminology makes it difficult to trace the spread of the trebuchet form the Middle East to Europe.

The first time a trebuchet was specifically mentioned in a historical chronicle was in 1199, in a description by Codnellus of the Siege of Castle nuovo Bocca’d Adda near Cremona in Italy.  According to Egidio Colonna’s fanciful Regime Principum, written around 1280, they were four types of trebuchet. The first was a man powered trebuchet which is actually a mangonel or derrière, the second was the counterweight trebuchet, with a fixed counterweight, the third was also a counterweight trebuchet, with a swinging or movable counterweight, which increased the trebuchet’s range, and which was referred to as a biffa. And the fourth trebuchet also had a counterweight which supposedly combined both a fixed and a swinging counterweight.

There was a similar weapon called a bricola was mentioned in early 13th century Genoa. It could be used to throw incendiary missiles and be mounted on a cart and basically became a form of field artillery. Evidence points it possibly being a light weight form of a trebuchet with a counterweight that was fixed in a way it was almost an integral part of the beam-sling. 

At one point a hinged counterweight was developed, which may have been the third type of trebuchet referenced to earlier. During the “cocking process” the boxes of hinged counterweight machines hung directly below the hinge.  This increased the range further by increasing the effectiveness of trebuchets conversion of potential or gravitational energy to projectile motion or kinetic energy. This process relied on gravity to work properly. The center of gravity of the weight fell straight down during the first phase of acceleration as the hinge straightened, the rotation of weight around its center of gravity increased the amount of potential energy that could be converted into kinetic energy. 

Medieval engineers saw that “hinged counterweight machines, all else being equal, would throw their projectiles farther they would fixed weight ones.” The addition of a hinge to the counterweight trebuchet greatly “increased the amount of energy that can be delivered through the beam to the projectile.” According to computer simulations, these machines apply seventy percent of their energy into the projectile. Since some energy was lost after the hinge has opened fully when the beam began to pull the counterweight sideways, the swinging counterweight had a significant braking effect on the rotating beam, and the rotation of the beam slowed as the projectile was released. The deceleration eased the strain on the machines framework just as the missile departs, which decreased the recoil so the frame was less likely to slide or bounce The much gentler release of the trebuchet meant engineers didn't have to reposition the frame after every shot and could accurately and rapidly launch a target into a particular spot. For instance, a median size trebuchet built in Denmark by the Museum of Falsters Minder can group its shots, at a 180 meter range, within a 6m square. There was also a trebuchet which propped the counterweight to make it even more effective. This may be the fourth type of trebuchet Egidis Colonna was referencing to.

The trebuchet was a devastating machine that still holds an air of wonder. The trebuchet is still reconstructed for demonstrations to this day. There are several modern day examples. From the “Highland Fling Project” where a group of people from both Europe and the United States gathered at Urquhart Castle at Inverness Scotland in 1998 to test the trebuchet's effectiveness and discovered it could hurl objects as big as 136 kilograms as well as knock down castle walls, to a BMW commercial where they use a trebuchet to “unpimp” a car by placing it on the trebuchet sling to so that the car will be launched into the ground. 

There is even a hobbiest on that launches objects from his Trebuchet which he refers to as Mongo.

Trebuchets were an amazingly effective and popular weapon in the Middle ages. There was a prince who was given a toy trebuchet, and a count who used a model to do demonstrations by breaking glasses on his dinner table.

Although trebuchets are simple in principal they can be dangerous if not operated properly. They are siege weapons and require a specific structure to function correctly. The last known use of the trebuchet as a weapon was by Cortés in the siege of Tenochtitlán.  During the course of

the battle he was running low on gunpowder and resorted to building a trebuchet.  Its construction took many days, and its premier launch failed. The stone went straight into the air and crashed back to smash it.  (Also based on a simple principal of what goes up must come down!) What remained of the machine was promptly dismantled.  More recently, a trebuchet was built on the popular television series, “Little People, Big World.” Although this trebuchet functioned properly a mishap occurred during its operation. The sling snapped and one of the children and an adult on the show were seriously injured when they were thrown back and trashed around by the force which was suppost to be exerted by the sling on the pumpkin-projectile. They were hospitalized and recovered but it is a pertinent reminder that a trebuchet is not a toy but instead a deadly weapon,  which held its own for several centuries until it was replaced by the use of gunpowder in cannons.

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Works Cited

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Counterweight Trebuchets

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