Orsova kamirion upgrade

[Nick Watts]

I was wondering if anyone has any information about the metallurgical condition of the original Orsova kamirion. Specifically, it would be helpful to know if the steel used had been hardened and taken to a spring temper. My current reconstruction uses a mild steel kamirion and is starting to take a set now that the draw weight has hit 5000 lbs. More info is available on all the performance specs at my blog: http://www.wattsunique.com/blog/

The intent here has been to maximize (ie. push the limit until something breaks) to see what the possible performance envelope would have been for the original machine. My reproductions of the artifacts are as close to the originals dimensionally as I could make them. If the artifacts were made from a higher grade of steel than simple wrought iron, that might suggest the power of the original machine was equal to or in excess of the 2000 plus foot lbs. my reproduction is currently generating before things starts to break down. Sure would appreciate any insight you guys have on this. Nick.

[Gaius Julius Caesar]

I can't help here, but am impressed with the link.
A nine mm lead slug, is , to be totally fair, no real comparison to a Roman ballista.
But does give an impressive show of the devastating potential of these ancient machines.
I would rather face someone shooting 9mm lead at me, wearing good armour, than a ballista or catapult.(rather neither, but if forced to chose)

[Paullus Scipio]

Can't help with the specifics of the Orsova kamarion, but I can supply some general information.

It was long known that juxtaposition of wrought iron to charcoal increased the hardness of the wrought iron. Two steel making processes were known and practiced in antiquity; the cementation process and the crucible process. The cementation process involved heating wrought iron in contact with a carbon source (usually charcoal) in such a way as to exclude exposure to air. In the crucible process wrought iron bars were melted in crucibles in which charcoal had been placed.
Steel tools made by the cementation process of Roman origin were found in Britain dating to the second century AD. Carbon content varied irregularly throughout from 0% to 1.3%.(mild steel is 0.15-0.25%; medium carbon steel is 0.25-0.5%; high carbon steel 0.5-1.6% - the hardest and strongest, and used today for cutting tools) It was this irregular distribution of carbon that made the cementation process, or "home-made" Roman steel a bit "hit-and-miss". But clearly high-carbon steel was known and used.

In addition, true steel in the form of "Wootz" steel had been known in India from around 500BC, using the crucible method (and after Alexander's time was known to the mediterranean world.) From after 330 BC, the crucible process was also used to produce 'springy' Damascus steel. However the techniques used were kept secret and did not become widespread.

While steel and the processes to produce it were not understood in the Roman world, medium and high carbon steels were certainly in use, often a mixture of both! ("If it works, use it!")

[lyuv]

Some points:
1) Carbon content is important, but great deal of the steel's properties lies in the heat treatment. Same steel will be soft, hard, springy or brittle, depending on the treatment. So I think there is no choice but have an analyses of the original (hoping it was not present in a fire).

2) In engineering we always (now and then) use safety margins. For variations in manufacturing, to compensate for corrosion, erosion and fatigue, and to make sure our troops and war machines will be safe. Doubling is the minimum margin. So whatever the breakage point of your machine is, I would suggest the operation force/energy is no more than half that.

3) It is wrong to compare arrows to bullets. Not because "its not fair", but because it's just incorrect. For example, a 0.22lr bullet, that would penetrate few inches, has more energy than a crossbow's bolt, with 1" point diameter, that would pass a deer. It's mainly a matter of momentum. While this may make the balista look even better, considering fire rate, weight and manuverability ect, isn't good for the balista's marketing...

[P. Clodius Secundus]

Nick,
I love the stuff you're posting on your blog. I'm still focused more on the carroballista base and it's interaction with the cart and other distractions. It's nice to know that you are out there experimenting working on the design and function of the weapon itself. I like that you've made the forked ends of your kimarion even. A lot of folks have made their front fork significantly longer than the rear (or is it vice-versa?). The original is greatly corroded but from what I can see, if they were uneven, the long forks would have to have been diagonally opposed to each other. That assymetry doesn't make sense. Given the physical artifact they could have been slightly longer in the front or rear but not as much as some recontructions. Keep up the good work. Just be careful. Firefly is getting scary powerful.

[Nick Watts]

Thank you all for your kind comments about my labors here in the "little catapult factory". Probably we will never know what condition the steel from the original kamirion was in. For my part I am upgrading my reconstruction to include a spring steel kamirion that is 1/3 heavier than the mild steel one in use now. That should provide plenty of safety margin for that part of the machine. The mild steel field frames appear to be plenty strong enough to handle the loads so long as the kamirion doesn't slouch on the job. When that happens the top half of the field frame can take a slight twist inwards and that bends the stanchions. After the current upgrades are completed I intend to hold to a firm rule of no more than 5000 lbs on the draw weight. At that point any new increases in performance will have to come from making the design more efficient. With lots of perfectly inauthentic kevlar in the limbs, I hope to be able to survive the experience of some more extended shooting with this contraption.

Some of you had mentioned that making comparisons between the penetrative qualities of a 9mm round and a steel tipped ballista bolt, is not really valid. Well of course, you are perfectly correct. Hence the title of that particular posting "Apples and oranges. Again." If I didn't consider all this work to be a bit of a lark you may be well assured nothing at all would get done. (I have never used one of those smiley things in my life before, so here goes....... : D D D D D D D D D D D )

Thanks for reading my blog. Hope to keep you all somewhat entertained as I submerge back into my work. Nick.

[D B Campbell]

Like you guys, I've been following Nick's blog, on and off, for a while, and marvelling at his achievement.

I like that you've made the forked ends of your kimarion even. A lot of folks have made their front fork significantly longer than the rear (or is it vice-versa?).

Interestingly, this asymmetry is one of the features of the original cheiroballistra, as described in the Greek text of that name. Whether this feature was carried over into the larger versions of the machine is unknown. Frustratingly, as so often in archaeology, the one piece that might have helped here, the Orsova kamarion, is broken at the critical areas. (The reason for the asymmetry has not been adequately explained, so we do not know its significance. Yet.)

[lyuv]

Just a point to consider:

I take great interest in the construction of crossbows (modern), the principals of which are not different from you balista, except for scale. One of the major parameters that affect efficiency is the weight of the limbs and string. At the moment of shooting, you accelerate not only the bolt, but also the limbs and string. Each part of these to a different degree, but given their great mass (much greater than the bolt), you lose a LOT of energy.

I dont know the geometry of the original limbs, but if efficiency is the goal, I"d start there. Lower mass for the same horizonal bending resistance spells lower and wider cross section. Perhaps even a truss composed of beams and ropes. This may be more authentic than carbon...

[P. Clodius Secundus]

Like you guys, I've been following Nick's blog, on and off, for a while, and marvelling at his achievement.

I like that you've made the forked ends of your kimarion even. A lot of folks have made their front fork significantly longer than the rear (or is it vice-versa?).

Interestingly, this asymmetry is one of the features of the original cheiroballistra, as described in the Greek text of that name. Whether this feature was carried over into the larger versions of the machine is unknown. Frustratingly, as so often in archaeology, the one piece that might have helped here, the Orsova kamarion, is broken at the critical areas. (The reason for the asymmetry has not been adequately explained, so we do not know its significance. Yet.)

Duncan, as you have noted Heron's cheiroballistra text does indicate symmetrically opposed forks of greatly different length. They are also curved while the Orsova's appear to have been straight. Little differences like this as well as major incongruities such as the washer diameter, spring height, and omission of components (winch & base) are the reason why I feel it is a mistake to rely too slavishly upon Heron's text when reconstructing a larger and much later machine. It is akin to using the assembly manual for a rifle to reconstruct a cannon. While there will certainly be commonalities of function which may serve as a guide, the parts you've found will not likely be simply scaled up versions of the ones in the manual. Factor in three hundred years between the two and the margin of error only increases. This is one case where I feel it is better to "listen" to the artifacts and follow general principles for machines filling that role in the arsenal than to try to make them conform to an out-of-date text. Especially when there is no evidence that the cheiroballistra as origially described ever ammounted to anything more than an experiment or theoretical exercise.

Heron's only other foray into artillery Belopoeica was a rehash of Ctesibius' original work, while many of the other inventions credited to him (vending machines, automatic theaters, thunder boxes, etc..) were little more than theatrical gimmics or parlor tricks. Harnessing wind to power a pipe organ (windmill) and steam to spin a ball (the first steam engine) are the two most prominent examples of technologial breakthroughs he never seems to have fully exploited. Why is it then inconceiveable that this happened with his weapon as well? The only difference in this case appears to be that someone may have recognized the value in his design and developed into the weapons later seen on Trajan's Column. Apparently beasts and slaves were abundant enough that potential sources of motive power could be left on the table, but improvements in weaponry were always valued by the state. That's a lesson Hiram Maxim learned when he perfected his machinegun.

[D B Campbell]

Duncan, as you have noted Heron's cheiroballistra text does indicate symmetrically opposed forks of greatly different length. They are also curved while the Orsova's appear to have been straight.

I'm afraid this curvature was another of Marsden's "improvements". If he had published the manuscript illustrations, he might have realised his error. (But the manuscript illustrations are by no means perfect -- they show the forks as being the same length, although the text clearly states that they weren't.)

It is akin to using the assembly manual for a rifle to reconstruct a cannon.

I don't think the difference was as great as that, Randi -- that's my humble opinion, at any rate. The ancients were used to scaling their catapults up and down. But I totally agree that, scaling a machine up, new problems will appear that require to be addressed -- the winch and the stand are just two of the most obvious ones, but stresses and strains will multiply, too.