Wednesday, March 12, 2003

Catapults in Greek and Roman Antiquity

Catapults were invented about 400 BC in the powerful Greek town Syracus under Dionysios I (ca. 430-367 BC). The Greek engineers first constructed a comparatively small machine, the gastraphetes, sort of a crossbow. The gastraphetes was powered by a specially large composite bow. The military effect of the new weapon during the siege of Motya (Sicily) 397 BC encouraged the Greek engineers to enlarge the machine further. They put a larger gastraphetes on a carriage and added a windlass to cock the heavier machine. Certain physical barriers prevented further enlargement of the composite bow. Therefore in mid-fourth century BC torsion springs were introduced instead of the composite bow. The torsion spring consisted of a bundle of rope made from horse-hair or sinew. Such a spring could be enlarged indefinitely. The new catapults were equiped now with two torsion springs powering the two arms of the catapult. Very soon the new design superseded the old gastraphetes machines. Alexander the Great already employed torsion spring catapults on his campaigns. All Hellenistic armies and all powerful Greek cities soon owned a park of torsion artillery. Inscriptions from the Chalkothek on the Acropolis of Athens first mention torsion spring catapults there about 330 BC. In the 3rd century BC the two main types of catapults were standardized: the euthytonon for shooting arrows and the palintonon for throwing stone balls. They now could be built after the standard calibration formulae layed down in contemporary technical treatises. In this form Carthage and Rome also adopted the heavy weapons. This type of Hellenistic torsion artillery still was employed under Augustus, when Vitruvius wrote his work. About 100 AD the Romans redesigned the torsion artillery, developing quite different new arrow-shooting machines.
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