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A trebuchet (French ''trébuchet'') is a type of catapult that was used as a siege engine in the Middle Ages. It is sometimes called a counterweight trebuchet or counterpoise trebuchet, to distinguish it from an earlier weapon called the traction trebuchet, where men pulling ropes provided the power. The counterweight trebuchet appeared in both Christian and Muslim lands around the Mediterranean in the 12th century. It could fling projectiles weighing up to at or into enemy fortifications. Its use continued into the 15th century, well after the introduction of gunpowder. == Basic design == The three distinguishing characteristics of a trebuchet are: # The trebuchet is a compound machine—a combination of simple machines. The trebuchet makes use of the mechanical advantage of a lever. Most trebuchets are powered exclusively by the force of gravity. Potential energy is stored by means of an extremely heavy weight box attached (by a hinged connection) to the counterweight portion of the throwing arm. Some earlier trebuchets stored potential energy as traction force (traction trebuchets). # When the trebuchet is fired, the weight box is permitted to fall and the force of gravity causes rotational acceleration of the attached throwing arm around the axle (the fulcrum of the lever). The throwing arm is usually four to six times the length of the counterweight portion. These factors multiply the acceleration transmitted to the throwing portion of the arm and its attached sling. # The sling is affixed to the end of the throwing portion of the throwing arm (opposite the counter weight portion). The sling contains the projectile and transmits the forces generated at the end of the throwing arm to the projectile. The sling also changes the trajectory, so that, at the time of release from the sling, the projectile is traveling in the desired speed and angle to give it the range to reach the target. The Couillard is a smaller version with a single stem or platform instead of the usual double "A" frames. The counterweight is split into two halves to avoid hitting the center stem. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「trebuchet」の詳細全文を読む スポンサード リンク
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