- For the font, see Trebuchet MS.
Trebuchet at Château des Baux, France.
A trebuchet (occasionally referred to as a trebucket) is Medival Catapults a medieval siege engine, Medeival Catapults a weapon employed either to smash masonry walls or to throw projectiles over them.
The trebuchet is thought Medeval Catapults to have been invented in China between the 5th and 3rd centuries Mediveal Catapults BC. The counterweight trebuchet evolved from the simpler Chinese traction Medieal Catapults trebuchet. The device reached Europe around 500 AD. It could fling three hundred pound projectiles at Meideval Catapults incredible speeds into an enemy fortification, quickly obliterating walls and defenses. Occasionally it was used to throw the bodies of people and animals who had died from various diseases including the black plague over castle walls, in an attempt to infect the people under siege. Trebuchets were far more accurate than other forms of medieval catapults.
- 1 Action of the trebuchet
- 2 History and first uses
- 3 Modern use
- 4 Etymology
- 5 Pop culture references
- 6 References
- 7 External links
Action of the trebuchet
19th century French three-quarter drawing of a medieval 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 rises causing the lever motion to begin to slow down, 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 stress. 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 energy as possible from the falling counterweight into the projectile. The maximum range for a hypothetical 100% energy transfer, Rmax, of the projectile can be shown to be Rmax = 2hmc / mp, where h is the distance the counterweight falls, and mc and mp 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, hostages, and captured spies.
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.
A trebuchet can increase its efficiency (and hence either range or payload) by allowing the counterweight to take the straightest possible downward path (below left). 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 (below right). 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. The weights were usually stones and rubble, since lead was far too expensive and could be used for better purposes in a siege.
History and first uses
A swinging-counterweight trebuchet
A wheeled-frame trebuchet
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 and has a shorter range but is a more portable machine and 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 BC 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 AD 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 AD.
At the Siege of Acre in 1191, Richard the Lionheart assembled two trebuchets which he named "God's Own Catapult" and "Bad Neighbour". During a siege of Stirling Castle in 1304, Edward Longshanks ordered his engineers to make a giant trebuchet for the English army, named "Warwolf". Range and size of the weapons varied. In 1421 the future Charles VII of France commissioned a trebuchet (coyllar) that could shoot a stone of 800 kg, while in 1188 at Ashyun balls up to 1,500 kg were used. Average weight of the projectiles was probably around 50-100 kg, with a range of c. 300 meters. Rate of fire could be noteworthy: at the siege of Lisbon (1147), two engines were capable of launching a stone every 15 seconds. Also human corpses could be used in special occasion: in 1422 Prince Coribut, for example, in the siege of Carolstein shot men and manure within the enemy walls, apparently managing to spread infection among the defenders.
The largest trebuchets needed exceptional quantities of timber: at the siege of Damietta, in 1249, Louis IX of France was able to build a stockade for the whole Crusade camp with the wood from 24 captured Egyptian trebuchets.
With the introduction of gunpowder, the trebuchet lost its place as the siege engine of choice to the cannon. Trebuchets were used both at the siege of Burgos (1475-1476) and siege of Rhodes (1480). 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.
Today, many hobbyists build and experiment with trebuchets. Trebuchets are also used in classrooms to illustrate mechanical and physical principles. Trebuchets range in size from table-top to huge machines weighing many tons.
The largest working trebuchet of medieval design today is at Warwick Castle, which is used as a tourist attraction and is fired by members of the public under professional supervision. It stands 19m tall and uses a 6 ton counterweight to fire 15kg stone balls distances exceeding several hundred feet. A modernly designed trebuchet, called T-Wrecks, can throw pianos weighing 500 lbs over 500 feet. In England a group of farmers threw a car close to 400 feet and a 55 gallon drum filled with gasoline over 1000 feet.
Recent modern developments include: the floating arm trebuchet, where 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" , "whipper" . 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, video, with a record throw of 1394 feet.
Another trebuchet type is the 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.
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.
Pop culture references
Recent depictions of trebuchets in pop culture include:
- The 1999 film The Messenger: 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 Orléans by Medieval English invaders during the Hundred Years' War.
- A makeshift trebuchet was used in the 2001 film The Last Castle starring Robert Redford
- 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.
- Punkin' Chunkin' is an annual event in Delaware where people use trebuchets and other mechanical devices to hurl pumpkins great distances.
- The NOVA episode "Secrets of Lost Empires II: Medieval Siege" featured the construction of two large trebuchets, one fixed- and one swinging-counterweight, which were built with medieval tools on the grounds of Urquhart Castle on the shore of Loch Ness in Scotland. The trebuchets were test-fired against a replica of a castle wall built on the site, and demonstrated the impressive accuracy, repeatability, and effectiveness of the weapon.
- The trebuchet features prominently in several of the battle scenes in the series A Song of Ice and Fire by George R. R. Martin along with various other medieval military tactics such as the flinging of dead bodies.
- The trebuchet appears several times during the Battle of the Pelennor Fields in the motion picture The Lord of the Rings: The Return of the King by Peter Jackson. The Gondorian defenders of Minas Tirith are shown with advanced trebuchet technology, whereas Mordor's army has only basic catapults for flinging burning objects and parts of dead bodies. However, the location of such large trebuchets atop stone towers as shown in the movie is unlikely, as the trebuchet recoil vibration would have damaged the structure itself.
- The trebuchet is featured in the the first season of the television series Lost in its 19th episode entitled "Deus Ex Machina."
- Trebuchet MS is a 1996 sans serif typeface with a hooped look to curves in letters, named after the medieval siege engine trebuchet.
- Chevedden; et al. (July 1995). “The Trebuchet”, Scientific American, 66-71. 
- Liang, Jieming (2006). Chinese Siege Warfare: Mechanical Artillery & Siege Weapons of Antiquity - An Illustrated History.
- Gravett, Peter (1990). Medieval Siege Warfare. Osprey Publishing.
- Hansen, Peter Vemming (April 1992). "Medieval Siege Engines Reconstructed: The Witch with Ropes for Hair". Military Illustrated (47): 15-20.
- Hansen, Peter Vemming (1992). "Experimental Reconstruction of the Medieval Trebuchet". Acta Archelologica (63): 189-208.
Wikimedia Commons has media related to:
- Secrets of Lost Empires: Medieval Siege (building of and history of trebuchets), from the NOVA website
- article on Trebuchet Mechanics (in PDF format)
- The Finnish Trebuchet
- Homemade Trebuchet
- Homemade Spring Trebuchet
- Medieval Trébuchet
- Animated Trebuchet
- Evolution of Sling Weapons
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