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A crossbow is a type of weapon based on the bow and consisting of a horizontal bow-like assembly mounted on a stock. It shoots projectiles called bolts or quarrels. The medieval crossbow was called by many names, most of which were derived from the word ballista, a torsion siege engine resembling a crossbow. Historically, crossbows played a significant role in the warfare of East Asia, Europe, and the Mediterranean. The invention of the crossbow in ancient China caused a major shift in the role of projectile weaponry. The traditional bow and arrow had long been a specialized weapons system which required a considerable degree of lifetime training, physical strength, and expertise to operate with any degree of efficiency. In many cultures, bowmen were considered a separate and superior caste, despite being usually drawn from the common class, as their archery skill-set was essentially developed from birth (similar to many horseman cultures) and was impossible to reproduce outside a pre-established cultural tradition, which many nations lacked. In contrast, the crossbow was the first projectile weapon to be simple, cheap, and physically undemanding enough to be operated by large numbers of conscript soldiers, thus enabling virtually any nation to field a potent force of ranged crossbowmen with little expense beyond the cost of the weapons themselves.〔(【引用サイトリンク】url=http://www.medieval-life-and-times.info/medieval-weapons/crossbow.htm )〕 In Europe, crossbows became widely used in the early medieval period, and this led to the ascendancy of large mercenary armies of crossbowmen (best exemplified by the Genoese crossbowmen), and the eventual death of the heavily armored aristocratic knight, as armies became progressively dominated by conscripts equipped with increasingly powerful ranged projectile weapons. In modern times, crossbows have been largely supplanted by firearms in most roles but are still widely used for shooting sports, hunting, and when shooting in relative silence is an important consideration. ==Construction== A crossbow is a bow mounted on a stick (called a tiller or stock) with a mechanism in it which holds the drawn bow string. The earliest designs featured a slot in the stock, down into which the string was placed. To shoot this design, a vertical rod is thrust up through a hole in the bottom of the notch, forcing the string out. This rod is usually attached perpendicular to a rear-facing lever called a trigger or "tickler". A later design implemented a rolling cylindrical pawl called a "nut" to retain the string. This nut has a perpendicular center slot for the bolt, and an intersecting axial slot for the string, along with a lower face or slot against which the internal trigger sits. They often also have some form of strengthening internal "sear" or trigger face, usually of metal. These "roller nuts" were either free-floating in their close-fitting hole across the stock, tied in with a binding of sinew or other strong cording; or mounted on a metal axle or pins. Removable or integral plates of wood, ivory, or metal on the sides of the stock kept the nut in place laterally. Nuts were made of antler, bone, or metal. Bows could be kept taut and ready to shoot for some time with little effort, allowing crossbowmen to aim better.〔Hanafi et al. 2011: 23〕 The bow (called the "prod" or "lath" on a crossbow) of early crossbows was made of a single piece of wood, usually ash or yew. Composite bows are made from layers of different material, often wood, horn, and sinew glued together and bound with animal tendon. These composite bows made of several layers are much stronger and more efficient in releasing energy than simple wooden bows. As steel became more widely available in Europe around the 14th century, steel prods came into use. The crossbow prod is very short compared to ordinary bows, resulting in a short draw length. This leads to a higher draw weight in order to store the same amount of energy. Furthermore, the thick prods are a bit less efficient at releasing energy, but more energy can be stored by a crossbow. Traditionally the prod was often lashed to the stock with rope, whipcord, or other strong cording. This cording is called the ''bridle''. The strings for a crossbow are typically made of strong fibers that would not tend to fray. Whipcord was very common; however linen, hemp, and sinew were used as well. In wet conditions, twisted mulberry root was occasionally used. Very light crossbows can be drawn by hand, but heavier types need the help of mechanical devices. The simplest version of mechanical cocking device is a hook attached to a belt, drawing the bow by straightening the legs. Other devices are hinged levers which either pulled or pushed the string into place, cranked rack-and-pinion devices called "cranequins"〔(Cranequin )〕 and multiple cord-and-pulley cranked devices called windlasses. File:The Martyrdom of St Sebastian (detail).jpg|Stirrup File:Armborst 1, Nordisk familjebok.png|Pull lever File:Armborst 2, Nordisk familjebok.png|Push lever File:Armborst 3, Nordisk familjebok.png|Cranequin (Rack & Pinion) File:Altarpiece of St Sebastian (detail).jpg|Cranequin (Rack & Pinion) File:Armborst 4, Nordisk familjebok.png|Windlass File:HJRK A 2269 - Crossbow windlass, late 15th century.jpg|Iron cranequin, South German, late 15th century File:Småland vapen.svg|A lion holding a crossbow on the coat of arms of Småland, Sweden. The province's original coat of arms (1560) was of a crossbow alone, the lion being added later. 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「crossbow」の詳細全文を読む スポンサード リンク
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