Crossbow
A crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on a main frame called a tiller, which is hand-held in a similar fashion to the stock of a long gun. Crossbows shoot arrow-like projectiles called bolts or quarrels. A person who shoots crossbow is called a crossbowman, an arbalister or an arbalist.
Crossbows and bows use the same elastic launch principles, but differ in that an archer using a bow must draw-and-shoot in a quick and smooth motion with limited or no time for aiming, while a crossbow's design allows it to be spanned and cocked ready for use at a later time and thus affording the wielder unlimited time to aim. When shooting a bow, the archer must first fully perform the draw, holding the string and arrow while pulling them back with arm and back muscles, and then either immediately loose without a period of aiming, or hold that form while aiming. When using the heavy bows suitable for warfare, both actions demand some physical strength. As such, the accurate and sustained use of a bow in warfare takes much practice.
Crossbows avoid these potential problems by having trigger-released cocking mechanisms to maintain the tension on the string once it has been spanned – drawn – into its ready-to-shoot position, allowing a crossbow to be carried cocked and ready and affording its user time to aim it. This also allows for crossbows to be operated in succession by groups of people, with one person operating a cocked crossbow while others reload and ready them. Crossbows are spanned into their cocked positions using a number of techniques and devices, some of which are mechanical and employ gear and pulley arrangements – levers, belt hooks, pulleys, windlasses and cranequins – to overcome very high draw weight. These potentially achieve better precision and enable their effective use by less familiarised and trained personnel compared to the training and practice necessary to become proficient with the English longbow or the bows of steppe nomads.
These advantages for the crossbow are somewhat offset by the longer time needed to reload a crossbow for further shots. Crossbows with high draw weights require sophisticated systems of gears and pulleys to operate that are awkward and slow to employ on the battlefield. Medieval crossbows were also very inefficient, with short shot stroke lengths from the string lock to the release point of their bolts, along with the slower speeds of their steel prods and heavy strings, despite their massive draw weights compared to bows. Modern crossbow designs overcome these shortcomings.
The earliest known crossbows were invented in ancient China in the first millennium BCE and brought about a major shift in the role of projectile weaponry in wars, especially during Qin's unification wars and later the Han campaigns against northern nomads and western states. The medieval European crossbow was called by many names, including "crossbow" itself; most of these names derived from the word ballista, an ancient Greek torsion siege engine similar in appearance but different in design principle.
In modern times, firearms have largely supplanted bows and crossbows as weapons of war, but crossbows remain widely used for competitive shooting sports and hunting, and for relatively silent shooting.
Terminology
A crossbowman is sometimes called an arbalist, or historically an arbalister.Arrow, bolt and quarrel are all suitable terms for crossbow projectiles, as was vire historically.
The lath, also called the prod, is the bow of the crossbow. According to W. F. Peterson, prod came into usage in the 19th century as a result of mistranslating rodd in a 16th-century list of crossbow effects.
The stock is the wooden body on which the bow is mounted, although the medieval tiller is also used.
The lock refers to the release mechanism, including the string, sears, trigger lever, and housing.
Construction
A crossbow is essentially a bow mounted on an elongated frame with a built-in mechanism that holds the drawn bow string, as well as a trigger mechanism, which is used to release the string.Chinese vertical trigger lock
The Chinese trigger was a mechanism typically composed of three cast bronze pieces housed inside a hollow bronze enclosure. The entire mechanism is then dropped into a carved slot within the tiller and secured together by two bronze rods.The string catch is shaped like a "J" because it usually has a tall erect rear spine that protrudes above the housing, which serves the function of both a cocking lever and a primitive rear sight.
It is held stationary against tension by the second piece, which is shaped like a flattened "C" and acts as the sear. The sear cannot move as it is trapped by the third piece, i.e. the actual trigger blade, which hangs vertically below the enclosure and catches the sear via a notch.
The two bearing surfaces between the three trigger pieces each offers a mechanical advantage, which allow for handling significant draw weights with a much smaller pull weight.
During shooting, the user will hold the crossbow at eye level by a vertical handle and aim along the arrow using the sighting spine for elevation, similar to how a modern rifleman shoots with iron sights.
When the trigger blade is pulled, its notch disengages from the sear and allows the latter to drop downwards, which in turn frees up the nuts to pivot forward and release the bowstring.
European rolling nut lock
The earliest European designs featured a transverse slot in the top surface of the frame, 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 tickler. A later design implemented a rolling cylindrical pawl called a nut to retain the string. This nut has a perpendicular centre 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 physical straining, allowing crossbowmen to aim better without fatiguing.
Bow
Chinese crossbow prods were made of composite material from the start.European crossbows from the 10th to 12th centuries used wood for the bow, also called the prod or lath, which tended to be ash or yew.
Composite bows started appearing in Europe during the 13th century and could be 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.
Traditionally, the prod was often lashed to the stock with rope, whipcord, or other strong cording. This is called the bridle.
Spanning mechanism
The Chinese used winches for large crossbows mounted on fortifications or wagons, known as "bedded crossbows". Winches may have been used for handheld crossbows during the Han dynasty, but there is only one known depiction of it.The 11th century Chinese military text Wujing Zongyao mentions types of crossbows using winch mechanisms, but it is not known if these were actually handheld crossbows or mounted crossbows.
Another drawing method involved the shooters sitting on the ground, and using the combined strength of leg, waist, back and arm muscles to help span much heavier crossbows, which were aptly called "waist-spun crossbows".
During the medieval era, both Chinese and European crossbows used stirrups as well as belt hooks.
In the 13th century, European crossbows started using winches, and from the 14th century an assortment of spanning mechanisms such as winch pulleys, cord pulleys, gaffles, cranequins, and even screws.
Variants
The smallest crossbows are pistol crossbows. Others are simple long stocks with the crossbow mounted on them. These could be shot from under the arm.The next step in development was stocks of the shape that would later be used for firearms, which allowed better aiming. The arbalest was a heavy crossbow that required special systems for pulling the sinew via windlasses.
For siege warfare, the size of crossbows was further increased to hurl large projectiles, such as rocks, at fortifications. The required crossbows needed a massive base frame and powerful windlass devices.
Projectiles
The arrow-like projectiles of a crossbow are called bolts or quarrels. These are usually much shorter than arrows but can be several times heavier.There is an optimum weight for bolts to achieve maximum kinetic energy, which varies depending on the strength and characteristics of the crossbow, but most could pass through common mail.
Crossbow bolts can be fitted with a variety of heads, some with sickle-shaped heads to cut rope or rigging; but the most common today is a four-sided point called a quarrel. A highly specialized type of bolt is employed to collect blubber biopsy samples used in biology research.
Even relatively small differences in arrow weight can have a considerable impact on its flight trajectory and drop.
Bullet-shooting crossbows are modified crossbows that use bullets or stones as projectiles.