Caesar\'s Self-Propelled Siege Tower

[Koyuncu]

Recently while reading the book, The Genius of Archimedes – 23 Centuries ofInfluence on Mathematics, Science and Engineering I met an interesting claim. An article in the book mentions Caesar's usage of siege towers that are moved with no apparent power source. Writers' claim is that it is certain some kind of mechanism used for powering wheels from inside of tower. Yet, I think it is also quite possible to push siege towers within by placing enough human power.

Here the related part of article;

Nevertheless it seems quite certain that the siege towers were self propelled; as for this aspect is concerned, it is also interesting to report the following piece from Julius Caesar (the De Bello Gallico, liber II, par.XXX and XXXI [3]), in which describes the siege at a town of the
Atuatuci Gauls:

XXX – …Ubi vineis actis aggere exstructo turrim procul constitui viderunt,
primum inridere ex muro atque increpitare vocibus, quod tanta machinatio a tanto
spatio instrueretur: quibusnam manibus aut quibus viribus praesertim homines
tantulae staturae - nam plerumque omnibus Gallis prae magnitudine corporum
suorum brevitas nostra contemptui est - tanti oneris turrim in muro posse conlocare
confiderent?

XXXI – Ubi vero moveri et adpropinquare moenibus viderunt, nova atque
inusitata specie commoti legatos ad Caesarem de pace miserunt, qui ad hunc
modum locuti: non se existimare Romanos sine ope divina bellum gerere, qui
tantae altitudinis machinationes tanta celeritate promovere et ex propinquitate
pugnare possent, se suaque omnia eorum potestati permittere dixerunt.

XXX – … As soon as (the Gauls) saw that, having we pushed on the vinea
(mobile roofs) and built an embankment, we started to built a tower, at first they
derided and insulted us because a so big device was built so far (the walls): on
what hands and on what force could ever the Romans rely, small as they were, in
order to bring near the walls a so heavy tower? All the Gauls, in fact, scorn our
height if compared with their large bodies.

XXXI – As they saw that the tower was moved and was approaching their
walls, frightened by the unusual sight, (the Gauls) sent ambassadors to Caesar to
negotiate the peace; they said that they think the Roman make war with the help of
the gods since they can move such big machines so fast, (hence) the put
themselves and all their wealth under the power of Caesar.

So what do you think of this? Is there any other instance or any evidence of such mechanisms for powering siege engines?

[Flavivs Aetivs]

Didn't Nero or someone have a Boat on a lake in Italy powered by Oxen rotating a turn-thingy (they did the same thing with a windmill or oxen to grind flower)?

Could that have been it?

[Prasutagus]

Didn't Nero or someone have a Boat on a lake in Italy powered by Oxen rotating a turn-thingy (they did the same thing with a windmill or oxen to grind flower)?

Could that have been it?

Is this what you're looking for? http://en.wikipedia.org/wiki/Nemi_ships

[Flavivs Aetivs]

Yeah I think that's it.

[Prasutagus]

That was Caligula, then. glad I could help :grin:

[Eleatic Guest]

Caesar does not explictly mention that the tower was moved by some hidden source from within. The Romans could have simply pushed it towards the walls and the Celts were surprised that such a large tower can be moved at all.

I think some authors have proposed a kind of belt-drive for siege towers, but others believe that it would not provide enough propulsive power by far to move such a beast around the park.

[D B Campbell]

An article in the book mentions Caesar's usage of siege towers that are moved with no apparent power source. Writers' claim is that it is certain some kind of mechanism used for powering wheels from inside of tower.

This is a 2010 article entitled "Ancient motors for siege towers" by C. Rossi, F. Russo & S. Pagano. The first of these three names automatically rings alarm bells in my mind. In the past, he has been responsible for some claims that I find surprising and sensationalist (e.g. that Archimedes used steam-driven cannons). He rarely cites sources and seems to rely chiefly upon his imagination (I should add "in my opinion", so as not to offend anyone).

It is a pity that the three authors do not cite any previous scholars who have addressed the problem of moving a siege tower. It is clear that they have read some of them, because their first two schemes are lifted (without acknowledgement) from Marsden and Schramm. Yet, rather than credit these scholars, they pass the designs off as their own (e.g. "Fig. 3. Authors' pictorial reconstruction of the propulsion by capstans" is a coloured-in version of Marsden 1971, p. 87 fig. 3; "Fig. 5 Pictorial reconstruction of tread wheels" is an obvious borrowing from Schramm & Rehm's edition of Biton).

In fact, if they had consulted the excellent 1983 book by Otto Lendle (Texte und Untersuchungen zum technischen Bereich der antiken Poliorketik -- this is basic required reading for anyone interested in siege machinery), they would have seen that both methods have been critiqued and found to be unlikely.

Yet, I think it is also quite possible to push siege towers within by placing enough human power.

You are quite right. Lendle drew attention to the design of the undercarriage of these machines -- unfortunately, our Italian colleagues do not get into this degree of analysis. In fact, they don't analyse the design of the siege tower at all! The bases of the larger siege machines all incorporated rows of closely spaced crossbeams, between which dozens of men could be deployed as a human source of propulsion.

In my 2003 book Greek and Roman Siege Machinery, pp. 12-13, I discussed another possible method of propulsion. For the truly gigantic helepoleis, I suggested adapting a method first illustrated (afaik) by Chevalier de Folard, whereby the power source (whether animal or mechanical) is situation some way behind the helepolis, and propels it forwards by means of pulleys acting on anchor points concealed beneath the front of the helepolis; as the helepolis advances, the anchor points are periodically moved forwards, but always concealed beneath the gigantic frame of the vehicle so as to be protected from sabotage.

Russo and his colleagues state that "Some possible reconstructions of motors that could have been used for the helepolis’ motion were examined", before concluding that "Among these, the one that seems more suitable and effective is the counterweight motor." They are mistaken. (In my opinion, of course.)

I am wryly amused by their final statement, that "this also is an example that shows how, in order to correctly understand the past, it is necessary a wider cooperation between scholars having humanistic knowledge and scholars having technical knowledge." Or maybe just read the relevant literature? :wink: