Ballista
 Reenactor with manuballista, Retrieved 6 February 2008 |
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Trigger of the polybolos, retrieved 6 February 2008 |
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Side elevation of the polybolos, retrieved 6 February 2008 |
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From above with magazin removed, retrieved 6 February 2008 |
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Another view of the trigger, retrieved 6 February 2008 |
The ballista (Latin, from Greek βαλλίστρα ballistra and that from βάλλω ballō, "throw"), plural ballistae, sometimes called bolt thrower, was an ancient missile weapon that launched a large projectile at a distant target.
Possibly the earliest mention of ballistae occurs in a description of weapons made by King Uzziah, who reigned over the Kingdom of Judah in the eighth century BC: "And he made in Jerusalem engines, invented by cunning men, to be on the towers and upon the bulwarks, to shoot arrows and great stones withal. And his name spread far abroad; for he was marvellously helped, till he was strong."
Developed from earlier Greek weapons, it relied upon different mechanics, using two levers with torsion springs instead of a prod (the bow part of a modern crossbow), the springs consisting of several loops of twisted skeins. Early versions projected heavy darts or spherical stone projectiles of various sizes for siege warfare. It developed into a smaller precision weapon, the scorpio, and possibly the polybolos.
The early ballista in Ancient Greece was developed from two weapons called oxybeles and gastraphetes. The gastraphetes ('belly-bow') was a hand held crossbow. It had a composite prod and was spanned by bracing the front end of the weapon against the ground while placing the end of a slider mechanism against the stomach. The operator would then walk forward to arm the weapon while a ratchet prevented it from shooting during loading. This produced a weapon which, it was claimed, could be operated by a person of average strength but which had a power that allowed it to be successfully used against armoured troops. The oxybeles was a bigger and heavier construction employing a winch, and was mounted on a tripod. It had a lower rate of fire and was used as a siege engine. With the invention of torsion spring bundle technology, the first ballista was built. The advantage of this new technology was the fast relaxation time of this system. Thus it was possible to shoot lighter projectiles with higher velocities over a longer distance.
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