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For the font, see Trebuchet MS.

Trebuchet1.png A trebuchet (, or ), also sometimes called a trebucket () is a medieval siege engine, a weapon employed either to batter masonry or to throw projectiles over walls.

The trebuchet is thought to have been invented in China between the 5th and 3rd centuries BC. The counterweight trebuchet evolved from the simpler Chinese traction trebuchet. The device reached Europe around 500 AD. It was used during the middle ages to throw the bodies of people who had died from the black plague over castle walls, in an attempt to infect the people under siege. Trebuchets were incredibly accurate compared to other forms of medieval artillery, and were often used to destroy specific sections of wall, unlike catapults, which were used to instill fear rather than being used for any accuracy.

Action of the trebuchet

A traction trebuchet functions in the same way as a counterweight trebuchet, except that instead of a hoisted weight, the hurling arm is powered by a crew of men, pulling on ropes attached to the short lever arm. A counterweight trebuchet is powered by a very heavy counterweight, acting on a lever arm. The fulcrum of the lever (usually an axle) is supported by a high frame, and the counterweight is suspended from the short arm of the lever. The sling is attached to the end of the long arm of the lever. One end of the sling is captive, while the other end is hooked to the long arm in such a way as to release when the arm and sling reach the optimal hurling angles. The trebuchet is energized by lowering the long arm and raising the weighted short arm, usually with a winch, and is locked into the charged state by a trigger mechanism (cocked). With the long arm lowered near ground level, the sling is loaded with the projectile, and laid out on the ground, with the captive and hooked ends away from the target, and the load and pouch laid on the ground toward the target. When the trigger is released, the weighted short arm is driven by gravity into an accelerating pendulum motion, causing the lighter, long arm of the lever to revolve around the fulcrum at the opposite arc, which in turn, pulls the sling and its contents into a whipping motion at the end of the long arm. As the arm continues to swing past the vertical position, the counterweight is now rising causing the lever motion to begin to slow, while the sling continues to whip forward around the end of the long arm. When the sling reaches its launch angle, one end slips from its hook, releasing the projectile toward the target.

Each of the components of the trebuchet affect its performance. The lever is critical. It must be as light as possible, for maximum acceleration, yet strong enough not to break under the stresses. The ratio of the length of the long to the short arms of the lever, and to the sling length, are important factors in determining the range of the projectile. The object of a good design is to transfer as much of the potential energy of the hanging counterweight into kinetic energy of the projectile. The maximum range for a hypothetical 100% energy transfer, R_\textrm{max}, of the projectile can be shown to be R_\textrm{max} = 2 h m_\textrm{c} / m_\textrm{p}, where h is the distance the counterweight falls, and m_\textrm{c} and m_\textrm{p} are the mass of the counterweight and projectile, respectively. The efficiency of a real trebuchet is then easily determined as the ratio of the actual range achieved to the calculated maximum range.

Medieval designs were probably carried out by making variations on a scale model and determined empirically. There are no really detailed descriptions of medieval or earlier trebuchets that give, for example, the dimensions or shape of the beam, the ratio of its long arm to its short arm, and so on. No specimens or models from medieval times survive. The few extant contemporary drawings of them are highly schematic and even sometimes show physically impossible proportions. Methods used for optimizing their performance and design were apparently closely held military secrets, and are not available to present-day reconstructors.

Emplacing and aiming the trebuchet was also, no doubt, done by empirical trials. Small adjustments can be made by changing the angle of the hook holding the free end of the sling, a process which requires a heated forge on a full-scale engine. For larger, quicker adjustments, the length of the sling can be altered. Small adjustments from side-to-side can also be made by moving the channel in which the missile and sling slide in the base of the frame. The trebuchet itself could be moved as well, but with larger trebuchets, this would have been difficult; the largest trebuchets could weigh many tons.

Because of the time required to load the sling and to raise the counterweight, a large trebuchet's rate of fire is slow, often not more than a couple of shots an hour. This was due both to their sheer size and the massive weight of their counterweights. Smaller trebuchets can fire a couple of times a minute. The payload of a trebuchet was usually a large rounded stone, although other projectiles were occasionally used: dead animals, beehives, the severed heads of captured enemies, small stones burned into clay balls which would explode on impact like grapeshot, barrels of burning tar or oil, Greek fire, or even unsuccessful negotiators, prisoners of war, and spies catapulted alive.

Trebuchets were formidably powerful weapons, with a range of up to about 300 yards. Castle designers often built their fortifications with trebuchets in mind; for instance, Caerphilly Castle in Wales was surrounded by artificial lakes to keep besiegers and their siege weapons at a distance. The range of many trebuchets was in fact shorter than that of an English longbow in skilled hands, making it somewhat dangerous to be a trebuchet operator during a siege. This meant that sieges could be long drawn-out affairs, sometimes lasting for years at a time.

A trebuchet can increase its efficiency (and hence either range or payload) by allowing the counterweight to take the straightest possible downward path. This maximises the transfer of the counterweight's potential energy to the projectile rather than to stressing the frame. Mounting the counterweight on a pivot straightens the path of its fall, increasing its effectiveness. A fixed counterweight trebuchet in particular can therefore be made more efficient by the addition of wheels to allow the frame to move freely back and forth. This also allowed the trebuchet to fire farther.

The addition of wheels also makes the trebuchet more stable as part of the forward momentum of the falling counterweight is transferred to the forward motion of the trebuchet instead of a tilting action of the vertical frame, possibly tipping over of the machine or severely damaging the structure. The velocity of the trebuchet frame is added to that of the item being thrown, increasing its velocity and range by up to 33 percent. The wheeled trebuchet can effectively employ a fixed counterweight, mounted to the short end of the throwing arm, rather than the pendulum weight described above. Such weights are believed to have been made from lead, evidenced in at least one case by requisitions for the lead used as roofing material in churches.

History and first uses

The invention of the trebuchet derives, no doubt, from the ancient sling. A variant of it, the staff sling, involved using a short piece of wood to extend the arm and provide greater leverage. This was evolved into the traction trebuchet by the Chinese, in which a number of people pull on ropes attached to the short arm of a lever that has a sling on the long arm. This type of trebuchet is smaller, has a shorter range and is a more portable machine, but has a faster rate of fire than a larger counterweight powered one. The smallest traction trebuchets could be powered by the weight and pulling strength of one person using a single rope; but most were designed and sized to utilize from 20 to 100 men, generally two per rope. These teams would sometimes be local citizens assisting in the siege or in the defense of their town. Traction trebuchets had a range of from 200 to well over 300 feet (60 to 100+ meters) when casting weights up to 130 pounds (60kg).

It is believed that the first traction trebuchets were used in China as early as in the 5th century BC, descriptions of which can be found in the 5th century B.C. Mozi. Chinese counterweight trebuchets were called the Huihui Pao (回回砲) or Xiangyang Pao (襄陽砲). ("huihui" means Muslim) because they were first encountered in China at the siege cities of Fancheng and Xiangyang when the Mongol army, unable to capture the cities despite besieging the Song defenders for years, brought in two Persian engineers who built hinged counterweight trebuchets and soon reduced the cities to rubble and forcing the surrender of the garrison.

The trebuchet spread westwards and reached the Arab countries through Persia and Byzantium. The first trebuchets - or the art of building trebuchets - arrived in the Nordic countries by way of Northern Germany, where engines of war are regularly mentioned in the books of the Hanseatic League. There is some doubt as to the exact period in which these devices or knowledge of them reached Scandinavia. The Vikings may have known them at a very early stage, as the monk Abbo de St. Germain reports on the siege of Paris in his epic "De belle Parisiato" dated about 890 A.D. that engines of war were used. Another source mentions that Nordic people or "the Norsemen" used engines of war at the siege of Angers as early as 873 A.D.

Trebuchets were first used in Italy at the end of the 12th century, and were introduced to England in 1216 during the Siege of Dover. The forces of Simon de Montfort built a massive trebuchet nicknamed La Malvoisine ("Bad Neighbour") for their siege of the pro-heretic town of Minerve during the Albigensian Crusade (1210).(During the siege of Stirling Castle in 1304, Edward Longshanks ordered his engineers to make a giant trebuchet for the English army, named "Warwolf." No details of its design survive.

With the introduction of gunpowder, the trebuchet lost its place as the siege engine of choice to the cannon. The last recorded military use was by Hernán Cortés, at the 1521 siege of the Aztec capital Tenochtitlán. Accounts of the attack note that its use was motivated by the limited supply of gunpowder. The attempt was reportedly unsuccessful: the first projectile landed on the trebuchet itself, destroying it.

In 1779 British forces defending Gibraltar, finding that their cannon were unable to fire far enough for some purposes, constructed a trebuchet. It is unknown how successful this was: the Spanish attackers were eventually defeated, but this was largely due to a sortie.

Trebuchets today

Today, many hobbyists build and experiment with trebuchets and it is used in classrooms to illustrate mechanical and physical principles. The trebuchets range in size from table-top to huge machines weighing many tons.

Recent modern developments include: the floating arm trebuchetwhere the counterweight is constrained to drop down vertically, while the fixed axle is replaced by rollers; a variation is the F2K trebuchet. Other variations are the "scissor-jack" *. Modern hobbyist trebuchets sometimes replace the counterweight with banks of springs.

Another notable variation on the classical trebuchet involves one that props the counterweight in its initial configuration. Since the center of mass is higher than the conventional one in which the counterweight hangs from the end of the short end of the beam, more energy is available for throwing the projectile. This is a little more complex, though, and few have been built. King Arthur, a propped counterweight trebuchet built by the team led by Christopher Gerow, was a Punkin Chunkin champion for four years running. Its reign was ended in 2004 by the huge Yankee Siege*, with a record throw of 1394 feet.

Another trebuchet is a MRT, or multi-rotational trebuchet. It is less efficient than a floating arm trebuchet, but more efficient than a traditional trebuchet. Its arm makes one or more full rotations before launching the projectile.

A United States organization, Science Olympiad, hosts a "Storm the Castle" event for middle and high school students involving the trebuchet. The competitors build a small trebuchet (maximum one meter long, 75 cm wide, 75 cm high) and fire projectiles at targets of varying distances.

Etymology

Trebuchet is Old French, from trebucher "to throw over" < tres "over, beyond" and buc "torso" < Latin trans and a Germanic word.

Trebuchets are often referred to as a variety of catapult, though this word is today generally reserved for a device powered by elastic energy.

Other names for counterweight (or counterpoise) trebuchets include bricole or brigola, which translates as two-testicle and refers to trebuchets with a split counterweight, and couillard, which translates as testicle and refers to a trebuchet with a single counterweight.

Descriptive terms, such as a "witch with ropes for hair" were used by some sources to describe how a traction trebuchet looks.

The "HollyWood catapult" is a trebuchet without a sling--the projectile is placed in a cup at the end of the long arm of a beam . It is a very poorly performing trebuchet. There is no evidence that it was actually used in warfare.

Pop culture trivia

Recent depictions of trebuchets in pop culture include:

  • In the television series Northern Exposure, two 1992 episodes ("Burning Down the House" and "Heroes") featured a trebuchet, used to fling a piano and a coffin, respectively.
  • In the 1999 computer game The Age of Kings, a trebuchet is the ultimate siege unit, which is produced only from castles.
  • The 1999 film The Story of Joan of Arc by Luc Besson, a trebuchet was built and put into action for several war scenes, related to the siege of the city of Orléans by English invaders during the Hundred Years' War.
  • The trebuchet is featured prominently (along with the catapult, ballista and mangonel) in the Stronghold series of video games by FireFly Studios (2001-2005). The game centers on building, maintaining and defending a castle while raising an army to storm your opponent's castle. In the game, the trebuchet has a longer range than the catapult (q.v.), and is useful, due to its higher trajectory, for battering towers and launching projectiles (and cows!) over castle walls.
  • In the 2003 film The Return of the King (film), the defenders of Minas Tirith fired their trebuchets from the top of the city's walls, using the debris of their city made by the catapults of Mordor's army. Trebuchets were in fact used in this way as their recoil is less than that of a comparably sized torsion weapon.
  • In the official game for the 2003 film The Return of the King (film), you have to launch one fireball from two separate trebuchets to progress through the level "The Southern Gate" .
  • In the 2003 film Timeline, during the battle of Castlegard, the French army used trebuchets to launch fire at the English castle.
  • In a 2004 episode of the television series MythBusters, the team converted a boom lift into a trebuchet in an attempt to duplicate the results of a myth. The lift threw Buster the crash test dummy a short distance, then promptly collapsed.
  • In the 2004 computer game, Civilization III Conquests, trebuchet appeared as the ultimate siege weapon before the advent of cannon. The player was able to built it only after discovering engineering technology. And apparently again in the incoming expansion of the game Warlords
  • In the 2005 film Kingdom of Heaven, both armies use trebuchets to launch fireballs and stones at each other.
  • In the television series Lost, the first-season episode "Deus Ex Machina" features a lesson about the construction and use of the trebuchet, as the survivors build one in an attempt to gain entry into a mysterious hatch on the island. The trebuchet used in this scene had no sling or projectile but instead had a striking blade at the end of the arm, designed to hit the hatch door on the ground with the full force of the counterweight. The device shown was structurally flawed and would not have worked as shown.
  • In 2006, Volkswagen aired a series of commercials around the theme, "Un-pimp your ride." In one of them, a trebuchet was used to fling (and destroy) a customized car.
  • A commercial for Tooheys beer that aired in 2006 in Australia features several trebuchets being used to hurl ingredients into the clouds to make it rain beer. *
  • The 2006 TLC show, "Little People, Big World" featured star Matt Roloff, a little person, constructing a trebuchet to launch pumpkins.
  • Punkin' Chunkin' is an annual event in Delaware where people use trebuchets and other mechanical devices to hurl pumpkins great distances.
  • In the movie The Last Castle the prisoners build a trebuchet out of weight equipment and other items from the prison.
  • A historical flashback in the 2006 film The Da Vinci Code depicts several Crusader-era trebuchets in action, laying siege to the Muslim-held city of Jerusalem.
  • The children's TV series Tiny Planets stars a pair of fluffy, friendly CGI aliens named Bing and Bong who travel through space on a bungee-tethered sofa propelled by a huge brass trebuchet.
  • In the movie King Arthur, Merlin uses trebuchets to stall the advancing Saxon army.

References

  • Chevedden, Paul E., et al., The Trebuchet in Scientific American, July 1995 p66-71.*

  • Chinese Siege Warfare: Mechanical Artillery & Siege Weapons of Antiquity- An Illustrated History *

  • Hansen, Peter Vemming Medieval Siege Engines Reconstructed: The Witch with Ropes for Hair in Military Illustrated, No. 47 (April 1992) pp15-20.

  • Hansen, Peter Vemming Experimental Reconstruction of the Medieval Trebuchet Acta Archelologica 63 (1992) pp189-208. *

External links

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