Ancient Artillery and Siege Engines - Historum

**Salah** · April 26th, 2012, 10:22 AM

I thought it would be interesting to start a thread for the general discussion of artillery and siege engines used in the pre-modern world, with emphasis on Classical Greece and Rome.

Siege towers and elaborate battering rams - some mounted on wheels - were used by the Assyrians, who were very proficient at siege warfare. The Hittites were less so, and supposedly waiting until nightfall to launch surprise attacks on enemy fortifications.

The Hellenistic world witnessed several monstrous contraptions during the era of the Diadokhi.

The Romans were known especially for their ballistae, sort of giant crossbows used as anti-personnel weapons, but they also used catapults and scaling ladders.

Shapur · April 26th, 2012, 11:11 AM

building the impossible: the roman war machine. part 1 - YouTube

This is a pretty interesting video of some people trying to build a replica of a large Roman siege engine. I don't know how accurate the reconstruction was but it does give you some idea of the huge size of these machines.

**Guaporense** · April 26th, 2012, 05:26 PM

I recommend:

Amazon.com: Greek and Roman Artillery 399 BC-AD 363 (New Vanguard) (9781841766348): Duncan Campbell, Brian Delf: Books

Amazon.com: Greek and Roman Siege Machinery 399 BC-AD 363 (New Vanguard) (9781841766058): Duncan Campbell, Brian Delf: Books

**Guaporense** · April 26th, 2012, 05:35 PM

The first catapults in the Classical World were invented around 400 BC, in Syracuse. It is said that they were developed by the Syracusans in their war against Carthage. The first Greek catapults were simple tension based engines based on the Gastraphetes, a crossbow type weapon, invented around 420 BC:

The early catapults, it was basically a bigger Gastraphetes:

The next big development in catapult technology were made in the mid 4th century BC, by the Macedonians, who developed the revolutionary torsion based catapult technology. Allowing greater range and power:

By the time of Alexander the basic design of the catapult was already established. Though optimization of the catapult dimensions in order to maximize range and power would only occur during the early hellenistic period (323 BC to 170 BC).

A good text on ancient catapults:

http://www.mlahanas.de/Greeks/war/Catapults.htm

Quote:

The effectiveness of the catapult led to efforts to improve its performance even beyond the introduction of the torsion bow. The engineer Ctesibius, for example, working in Alexandria in the middle of the third century B.C., attempted to supplant hair and sinew ropes, which were susceptible to breakage, rotting and changes in tension due to humidity or stretching. Both of his two alternative designs incorporated rigid arms pivoted close to their inner ends, which were bent in such a way that they pressed, when the bow was drawn, either on hammered bronze springs or pistons sliding in airtight cylinders [see illustrations]. Neither the compression of the bronze springs (which are of course inferior to steel springs for most purposes) nor the compression of the small amount of air the cylinders could contain, however, could provide a force comparable to that of a torsion bow. (In the process of researching his ideas Ctesibius discovered that “fire” would fly from the cylinder together with the piston he had forced into it with a hammer. The flame or smoke came perhaps from the ignition of the carpenter’s glue he used as a sealant. If the ignition was caused by the compression heating of the air, he can be viewed as the discoverer of the diesel effect.)

At about the same time Dionysius of Alexandria developed what was perhaps the most remarkable machine of its kind: a repeating catapult. [see illustration]. Arrows were loaded into it a vertical, gravity-fed magazine and then transferred one at a time into the firing groove by a rotating tray whose motion was controlled by a cam follower system actuated by the slider. In this system the follower reciprocated alongside the cam, which turned in response. No earlier instance of such a cam in known, and none as complex is known until the 16th century. A single windlass motion controlled the tray, the slider, the claw and the trigger, so that simply winding the windlass back and forth would automatically fire the machine until its magazine was empty. It is here that the flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance. The chain links presumably had extensions that meshed with an inverted gear: in other words, the teeth were internal, not external, much like those of a modern cam saw. (This interpretation rests in part on details in the surviving text and in part on the mechanical necessities of the situation.) The repeating catapult failed to replace the standard one. It paid for its ease and speed of operation by having too short a range. Furthermore, its accuracy paradoxically worked against it. The device concentrated its shots so closely at its maximum range (about 200 meters) that it did not pay to open fire on even a small group of troops at that distance. (It was a model of one of these repeaters that split an arrow in Schramm’s shooting exhibition for the Kaiser.) Commanders also feared that it would waste ammunition, a complaint that was raised again with the invention of repeating rifles two milleniums later. Another reason for the failure of these interesting variations can be seen in the sophistication of the engineering efforts applied in the meantime to the common catapult. Its success made it imperative to achieve ranges at least as long as those of the enemy. This made it necessary to adjust the quantity of elastic fiber to the weight of the missile. Probably the designers were pushed not to the point of attaining absolute maximum range but only to the point where escalating costs, declining convenience in handling or diminished accuracy due to downrange ballistic factors supervened. One of the crucial steps in designing the torsion springs was establishing a ratio between the diameter and the length of the cylindrical bundle of elastic cords. If the cords were too short, they would develop high internal friction and might not have allowable elastic elongation to avoid breaking when the arms were pulled all the way back. If they were too long, some of the elasticity would remain unused as the arms were pulled to the limits imposed by the framework. All the surviving catapult specifications imply that an optimum cylindrical configuration was indeed reached, and it could not be departed from except in special circumstances, such as the exclusively short range machines Archimedes built at Syracuse.

This optimization of the cord bundle was completed by roughly 270 B.C., perhaps by the group of Greek engineers working for the Ptolemaic dynasty in Egypt. There and at Rhodes the experiments of the catapult researchers were, according to Philo, “heavily subsidized because they had ambitious kings who fostered craftsmanship.” This phase of the investigations culminated in quantified results of a distinctly modern kind. The results were summarized in two formulas. For the arrow shooter the diameter of the cord bundle was set simply as 1/9 of the arrow length. The more complex stone thrower formula stated, in modern terms, that the diameter of the cord bundle in dactyls (about 19.8 millimeters) is equal to 1.1 times the cube root of 100 times the weight of the ball in minas (about 437 grams). d = 1.13√100m The stone-thrower formula has two remarkable features. First, it gives a true and accurate solution for optimal design. To see why, first assume (as is indeed reasonable) that the catapult engineers wanted to maximize the performance of their machines. Accordingly they had to maximize the kinetic energy of their projectiles. To do this they had to maximize the potential energy stored in the torsion springs. Modern elasticity theory applied to the design of these springs tells us that the stored energy available will be proportional to the amount of initial tension give the bundle in string it through the frame, the additional tension caused by the pre-twisting of the bundle, the square of the angle indicating the amount of additional twisting by the pulling back of the bow arm, and the cube of the bundle’s diameter. The cubing of the bundle’s diameter means that to express the diameter in terms of the mass of the projectile one would have to extract a cube-root.

Note that to arrive at this result one must employ the concepts of kinetic and potential energy, which were not brought into meaningful relation until the 18th century and the work of Leonhard Euler and Daniel Bernoulli. Also needed is elasticity theory, which had been begun by Hooke and Robert Boyle about a half a century earlier. Finally, one must employ the principles of ballistics, which were not clarified until the work of Francesco Cavalieri and Galileo Galilei in about 1630. That the ancient catapult engineers were able to arrive at a formula that stands up in the light of these much later developments is truly impressive.

Quote:

It would appear, therefore, that the catapult engineers conducted experiments that forced them into a domain that traditional mathematical procedures had not yet penetrated. It is fairly easy even today to fit third-degree data to a second-degree curve if the data are bad or the investigator in unscrupulous. Hence one must feel a good deal of respect for these ancient investigators. They must have repeated their catapult-firing tests many times, kept very accurate records and interpreted their results with a high degree of precision. The introductory passages of Philo’s Belopoeica lay great stress on the experimental procedures and achievements of the early catapult engineers, and from the vantage of modern engineering theory the accuracy of this account seems to be fully borne out.

Having arrived at an optimal volume and configuration for the torsion-spring bundle, the catapult engineers continued their experiments until they had optimized the dimensions for the remaining pieces of the machine. If the arms were too short, the cocking force required would be excessive, the travel of the bowstring would be limited and its energy-transfer capabilities would be curtailed. If the bow arms were too long, they would retard the action of the springs by their increased mass or make the weapons too bulky. Once the length of the bow arms was determined, the length of the slider and the stock could be determined by the travel of the bowstring, and so on for the rest of the machine.

Eventually the catapult engineers wrote their text in such a way that the dimensions of the major parts were given as multiples of the diameter of the spring. Once this diameter had been calculated for the size of the projectile desired the rest of the machine was automatically brought to the proper scale. The surviving texts that contain this information testify to a level of engineering rationality that was not achieved again until the time of the Industrial Revolution.

The last major improvement in catapult design came in later Roman times, when the basic material of the frame was changed from wood to iron. This innovation made possible a reduction in size, an increase in stress levels and a greater freedom of travel for the bow arms. The new open frame also simplified aiming, which with the wood construction of the earlier machines had been limited, particularly for close moving targets.

The advanced catapult design came too late for the expansive period of the Roman civilization, but it played a role in stabilizing the boundaries of the Empire and in helping to prevent their erosion. As the decline of the Empire proceeded, however, the technical skills necessary to build and maintain such sophisticated machines appear to have become scarcer. A new, simpler machine called the onager, with only one spring and one arm, which terminated in a spoon and was used for throwing stones now came increasingly into prominence. [Actually, a spoon would rarely be used, since the use of a short sling at the end of the arm instead, as described by Ammianus Marcinellus, is far more efficient in hurling the stone and yields much greater force of impact. – Darius Architectus] It would be provide the heavy artillery of the Middle Ages until the appearance of the trebuchet, whose even simpler construction was gravity-powered.

The scientific design of complex machines, with deliberate experimental adjustment of the dimensions of the components, did not appear again in Western civilization until the 18th century. During the ancient period the changes in which the catapult played a key part prefigured in striking ways issues that would appear again in the relations between science and technology on one hand and warfare and society on the other.

**Guaporense** · April 26th, 2012, 05:55 PM

From 420 BC to about 270 BC the ancient catapult evolved from the primitive gastraphetes into it's definitive form, with optimized design. Catapults never got better afterwards.

**Guaporense** · April 26th, 2012, 05:59 PM

The Gastraphetes in action:

The Greek Gastraphetes - YouTube

**Guaporense** · April 26th, 2012, 06:03 PM

Quote:

Originally Posted by Shapur

This is a pretty interesting video of some people trying to build a replica of a large Roman siege engine. I don't know how accurate the reconstruction was but it does give you some idea of the huge size of these machines.

Actually, the 1 talent stone catapult weren't the biggest. The diadochi build some catapults of 3-4 talents stones (i.e. 80 to 100 kg, about the same size as the stones thrown by trebuchet). Much larger than this one, which was actually the typical large catapult for the Romans.

Bart Dale · April 26th, 2012, 07:31 PM

Quote:

Originally Posted by Guaporense

Actually, the 1 talent stone catapult weren't the biggest. The diadochi build some catapults of 3-4 talents stones (i.e. 80 to 100 kg, about the same size as the stones trow by trebuchet). Much larger than this one, which was actually the typical large catapult for the Romans.

80 kg to 100 kg was the size of stones thrown by traction trebuchets and the average counterweight trebuchet. The largest counterweight counterweight trebuchets, however, could throw much, much, larger stones, up to 1000 kg. (Modern recreations have thrown cars, so the 1000kg is not an exageration)

"During the

Crusades

,

Philip_II_of_France

named two of the trebuchets he used in the Siege of Acre in 1191 "God's Stone-Thrower" and "Bad Neighbor."[12] During a siege of

Stirling_Castle

in 1304,

Edward_I_of_England

ordered his engineers to make a giant trebuchet for the English army, named "

Warwolf

". Range and size of the weapons varied. In 1421 the future

Charles_VII_of_France

commissioned a trebuchet (coyllar) that could shoot a stone of 800 kg, while in 1188 at Ashyun, rocks up to 1,500 kg were used"
Trebuchet - Wikipedia, the free encyclopedia

Trebuchet

**Guaporense** · April 26th, 2012, 07:41 PM

I mean't typical. The trebuchets trowing 1,000 kg stones were clearly not practical.

Though the general design of trebuchtets allow greater weights overall than catapults, while being of simpler construction, ideal for the limited technical resources of the middle ages. The main problem of the trebuchet is that it's aiming is terrible. It was not useful for battlefield use, only for sieging castles. Unlike the ancient catapults that were almost substituting the archer during Roman times:

**Guaporense** · April 26th, 2012, 07:45 PM

Archaeological evidence:

Reconstruction:

The 80 kg stone thrower: