Projectile Throwing Engines
Sir Ralph Payne-Gallwey
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This engine was of much more recent invention than the catapult or the ballista of the Greeks and Romans. It is said to have been introduced into siege operations by the French in the twelfth century. On the other hand, the catapult and the ballista were in use several centuries before the Christian Era. Egidio Colonna gives a fairly accurate description of the trebuchet, and writes of it, about 1280, as though it were the most effective siege weapon of his time.

The projectile force of this weapon was obtained from the gravitation of a heavy weight, and not from twisted cordage as in the catapult and ballista. From about the middle of the twelfth century, the trebuchet in great measure superseded the catapult. This preference for the trebuchet was probably due to the fact that it was able to cast stones of about 300 lbs. in weight, or five or six times as heavy as those which the largest catapults could project.1

The stones thrown by the siege catapults of the time of Josephus would no doubt destroy towers and battlements, as the result of the constant and concentrated bombardment of many engines. One huge stone of from 200 to 300 lbs., as slung from a trebuchet, would, however, shake the strongest defensive masonry.

The trebuchet was essentially an engine for destroying the upper part of the walls of a fortress, so that it might be entered by means of scaling ladders or in other ways. The catapult, by reason of its longer range, was of more service in causing havoc to the people and dwelling inside the defenses of a town.

From experiments with models of good size and from other sources, I find that the largest trebuchets--those with arms of about 50 ft. in length and counterpoises about 20,000 lbs.--were capable of slinging a stone from 200 to 300 lbs. in weight to a distance of 300 yards, a range of 350 yards being, in my opinion, more than these engines were able to attain.2

1 The catapult had, besides, become an inferior engine to what it was some centuries before the trebuchet was introduced, the art of its construction having been neglected.

2 Egidio Colonna tells us that the trebuchet was sometimes made without a counterpoise, and that in such a case the arm of the engine was worked by a number of men pulling together instead of by a heavy weight. I cannot believe this, as however many men pulled at the arm of a trebuchet they could not apply nearly the force that would be conveyed by the gravitation of a heavy weight.



FIG.18. THE TREBUCHET. The arm is fully wound down and the tackle of the windlass is detached from it. The stone is in the sling and the engine is about to be discharged by pulling the slip-hook off the end of the arm. The slip-hook is similar to the one shown in fig.10. N.B.--A Roman soldier is anachronistically shown in this picture. The trebuchet was invented after the time of the Romans.


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