Download
1 / 8
E N D
What is a Crossbow? A crossbow is powerful projectile weapon made of a prod mounted on a stock. The prod somewhat resembles a traditional bow and like the stock is traditionally made of wood.The prod was often attached to shaft by a strong cording known as a bridle. Unlike traditional bows, crossbows do not shoot arrows they shoot bolts (also called quarrels),which are not dependent upon lift. However, the bolts must be made very uniform (size and weigh were ensured by sealing the bolts with varnish) because the mechanical process of shooting demands regularity.A cross bow bolt is lighter than an arrow and has only two fletches/fins per bolt ( traditional arrows have three). The stock has a groove on which the bolt rests and travels along. To shoot a crossbow, the string on the prod must be pulled back until it is engaged by a nut ( this is called full cock).Some crossbows were wound with mechanical aid ( this allowed up to 400lbs of draw tension). Most crossbows were made from good hardwood such as oak or hard maple. The strings were made from almost any strong fiber but the most common was whipcord. All of the strings used were affected by humidity and not entirely reliable. Some of the prods were actually made of composite materials: horn, sinew and wood ( this allowed for greater draw tension).
The History of Crossbows The crossbow has been around for a long time. It was in use in China the 6th century BC and by the 2nd century BC the Chinese had developed a self-resetting lock mechanism. Romans used very ornate/well built crossbows and between 800-1650 Western Europeans also harnessed the power of the crossbow. Although the prod was originally made of wood of composite by the late 1400’s, advances in steel manufacturing allowed for steel prods( whose firing power was very uniform) to become more common. The crossbow does not have the range of a longbow, and usually takes longer to fire ( the cranking takes longer than setting an arrow). However, the crossbow allows for the user to carry the weapon cocked and loaded and requires almost no skill to shoot.
Leonardo’s Big Bow Leonardo Da Vinci, among countless other things, was an engineer , and one of the types of machines he designed were war machines. Moreover, Leonardo did not overlook the classic crossbow when designing and re-designing his machines. He drew up plans for a rapid firing wheel powered crossbow as well as a giant 24 meter wide cross bow. The giant Ballista was not designed for precession, it was supposed to shoot huge arrows into enemy ranks and cause general disarray. It was designed to be built on 6 carriage wheels for added mobility. ( The wheels were inclinable for extra stability). The shooting rope was stretched with a worm screw ( employing leverage and reducing the force needed to pull back the string). The string was then released with a hammer lever. The lever would strike a flexible (metal/wood) switch which would then drop down enough to allow the string to move. The potential energy in a crossbow is stored in the springs ( the crossbow arms) and then converted to kinetic energy as the switch is activated and the string released.
http://brunelleschi.imss.fi.it/genscheda.asp?appl=LIR&xsl=animazione&lingua=ENG&chiave=101761http://brunelleschi.imss.fi.it/genscheda.asp?appl=LIR&xsl=animazione&lingua=ENG&chiave=101761
