Trebuchet

From Academic Kids

Trebuchet at Chⴥau des Baux,
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Trebuchet at Chⴥau des Baux, France

A trebuchet is a weapon, a medieval siege engine, employed either to batter masonry or to throw projectiles over walls. The name engine was derived from the Latin word ingenium meaning ingenious device.

The trebuchet was a development of the Chinese traction trebuchet. In the traction trebuchet a large crew of men pulled down on ropes to propel the missile. In the European trebuchet these men were replaced with a large fixed or pivoting counterbalance weight.

Trebuchets are often referred to as a variety of catapult, though it would be more correct to describe them as a scaled-up sling.

Contents

Action of the trebuchet

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Three-quarter view of a trebuchet

A trebuchet is moved by a counterweight. The axle of the arm is near the top of a high strutted vertical frame. The shorter arm of the balance carries the counterweight and the longer arm the sling that carries the shot. The sling is usually braided from rope, and has a captive end attached to the arm, and a free end whose loop slips from a hook. A trigger, usually a toggle in a chain, holds the arm down after the trebuchet is cocked. Cocking is often performed with windlasses. Because of the long winding time, a trebuchet's rate of fire was extremely slow, often not more than a couple of shots an hour. Yet some of the smaller types of trebuchets could fire a couple times a minute.

In operation the long, nonweighted end is pulled toward the ground, and held by a trigger. When the trigger is released, the arm pulls the sling out of a channel in the base of the frame. When the ball moves close to the top of its arc, the free end of the sling slips from the hook, and the missile flies free. The trebuchet's arm and frame then oscillate for several cycles.

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Side view of a trebuchet

The efficiency of a trebuchet can be improved by helping the weight to fall more nearly straight down. One method is to place the weight in a swinging or jointed bucket. The sand or stones in the bucket can also be less expensive than fixed metal weights, as well as being easier to gain access to on site. Another trick is to place the supporting frame of the trebuchet on wheels. These improvements may improve overall throwing distance.

Aiming a trebuchet is best practiced with a scale model. Usually small adjustments in elevation 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. The perfect release angle is when the missile will fly at roughly 45 degrees, because this optimizes range. After the desired range is achieved, the trebuchet can be moved toward or away from the target. Small adjustments from side-to-side can be made by moving the channel in which the missile and sling slide in the base of the frame.

Trebuchets were formidably powerful weapons, but relatively short-ranged compared to later gunpowder artillery, with a range of up to about 200 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 most trebuchets was in fact shorter than that of a 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.

The payload of a trebuchet was usually a large rounded stone, although other projectiles were occasionally used: dead animals, the severed heads of captured enemies, barrels of burning tar or oil, or even unsuccessful negotiators catapulted alive.

The largest trebuchets could weigh dozens of tons. Not surprisingly, they were not readily transportable and instead had to be built on the spot where they were to be used.

Usage of the trebuchet

The trebuchet is thought to have been invented in China between the 5th and 3rd centuries BC, and reached Europe around 500 AD .

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.

Due to the increasing popularity of gunpowder, the last historically recorded military use was by [[HernᮠCort鳝], whose gunpowder was in short supply, at the siege of the Aztec capital, [[Tenochtitlᮝ], in 1521. This trebuchet was shot once. Due to a miscalculation the trebuchet fired up into the air, and came right down. According to popular myth, its projectile landed right on the device, destroying it. It is also somewhat unclear from the sources as to what kind of contraption that was actually built. Whether it was an actual trebuchet or merely a catapult is unclear.

A simulation of trebuchets in action can be seen in the 2003 movie The Lord of the Rings: The Return of the King. The defenders of Minas Tirith fired their trebuchets from the top of the city's battlements. Although this appears very effective, it was never historically used, as castle walls were not big enough to hold a good trebuchet, and the forces exerted by such a siege engine on the walls would destroy them.

Today, people still build and use trebuchets as a hobby. For example, the Punkin Chunkin competition, an annual competition to throw pumpkins for distance, has a trebuchet category. Modern hobbyist trebuchets sometimes replace the counterweight with banks of springs.

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

Variants

A manual trebuchet is called a "stave sling". Basically, it is a sling on the end of a staff. These were the most important form of military sling. They usually shot small lead projectiles called "glans" (Latin for acorn).

If instead of using a counterweight, the spoke is pulled by 2 or more people, the trebuchet is called a traction trebuchet or perrier.

A very recent development is the floating arm trebuchet, where the counterweight drops down vertically.
Another is the so-called F2K trebuchet, in which the counterweight drops vertically and the arm has an extra set of rollers for smoother transition of energy from the counterweight to the arm. Both of these types of trebuchet are more efficient than the standard Fixed-Axle trebuchet.

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