Orsova ballista field trials to start.

[samuli seppanen]

Your ballista is simply awesome. It's very nice that you've provided chronograph readings for your shots - they are _very_ impressive but I think you can improve them further - even after going from 2/3 draw to full draw. I've been designing, making and tuning crossbows for years and I think you could do a couple of optimizations all aimed at minimizing _moving_ dead weight. By dead weight I mean arms and the bowstring: their only purpose is to transfer energy from the cord bundles to the bolt. So the less mass they have the better. It's also important to keep as much mass away from the arms' tips as possible. I suggest the following optimizations:

1. Make the arms of equal thickness and taper them aggressively from the sides towards the tips

This way the whole arm is strained (somewhat) equally during operation (draw and release), lessening the risk of fracture at highly strained parts and reducing mass - especially at the tips where it matters most. So, for example, you could have arms that are 3 units wide (at the bundles) tapering down to 1 unit at the tips. The arms could be, say, 1 unit thick all the way.

For more information take a look here:

• [url:o0sikxco]http://users.utu.fi/sjsepp/paja/designing_crossbows/designing_crossbows.html#DesignPrinciples[/url]
  
• [url:o0sikxco]http://users.utu.fi/sjsepp/paja/designing_crossbows/designing_crossbows.html#Tillering[/url]

When you think of the arms as rigid bow limbs it (should) all make sense.

2. Make the arms as thin and as narrow as safely possible

This seems obvious, but again, reducing arm mass makes all the difference. I'd use "remote control" both during cocking and release. I'd hate to see what happens if/when the arms break.

3. Make a good bowstring which has minimal mass for it's weight

Again, the bowstring is nothing but dead mass, so making it as light as possible increases the bolt velocity significantly. If you add, say, one ounce to bowstring weight, the bolt velocity is reduced as much as if you had originally used a bolt that was 1/3 ounce heavier. Also make the bowstring from material which has minimal stretch. Linen is probably the only "period" high-quality string material easily obtainable. Dynema is probably the best synthentic material - it's at least 3 times as strong as Dacron and/or best quality linen.

EDIT: forgot the link to my bowstring making article: [url:o0sikxco]http://users.utu.fi/sjsepp/paja/making_bowstrings/making_bowstrings.html[/url]

These optimization will increase the dry-fire speed and overall efficiency of the ballista considerably. I can't promise anything, but I'd expect 5-15% increase in velocity depending on bolt weight. The closer to zero bolt weight you go, the bigger the relative improvement. Let me know if you need any help with this - my own inswinger project has been slowly gathering speed. I'm starting with a light, manually cocked manuballista, trying to make it as "period" as possible in all aspects.

All the best,

Samuli

[Crispvs]

"I'd hate to see what happens if/when the arms break."

A few years ago I was acting as number two on our cheirobalistra, in the loader's position, when an arm broke. The arms were drawn back and then, when they were fully drawn back the right arm broke. This happened so fast that I did not see it happen, despite the fact that I was looking at the arm at the time. I immediately looked towards the crowd of onlookers, fully expecting to see one of them falling with a serious injury, but there was no sign that the broken portion of the arm had flown that way. I then saw that the broken part of the arm was still attached to the bowstring and was swinging from it, which made sense considering that the bowstring is securely attached to the arms to prevent it from shifting when it is not under tension. A moment later I noticed a scratch on my armour, demonstrating that the broken arm had travelled in an arc until it had hit me and presumably some of the force was dissipated on the armour, as well as deflecting it so that it passed under the stock of the machine, where its journey was arrested by the string catching on the stock. If I had not been there it might have continued round and passed over the top of the stock, although it might have caught the number one man as well. As it hit me we cannot know. It did prove a good lesson though in the value of wearing armour whilst operating artillery.

Crispvs

[Crispvs]

"I'm starting with a light, manually cocked manuballista,"

What do you mean, when you talk of manually cocking your artillery piece? Bear in mind that torsion artillery is a very different beast to a crossbow. Bear also in mind that torsion artillery effectively replaced the belly bow / gastrophetes method of cocking. Regarding the reconstruction of torsion artillery pieces as gastrophetes type machines, Alan Wlkins points out in his article in JRMES 11 (2000):
" All these interpretations appear to have been arrived at by an exercise in vaccuo, with little, if any, consideration of either the historical development of Graeco-Roman torsion arrow shooters, or the performance required of them. In particular the interpretation of the cheirobalistra as a weapon lacking a winch, sparked off by Baatz's 1978 article in 'Britannia', flatly contradicts Heron's authoritative statement that torsion catapults developed so much power that the stomach-bow's withdrawal-rest had to be replaced with a winch, with a pulley system added for the larger machines*."

* Bel. 84-5.


Crispvs

[P. Clodius Secundus]

What do you mean, when you talk of manually cocking your artillery piece? Bear in mind that torsion artillery is a very different beast to a crossbow. Bear also in mind that torsion artillery effectively replaced the belly bow / gastrophetes method of cocking. Crispvs

Actually, as your later quote indicates, it was a matter of scale and power not the means of storing energy (tension vs torsion) that replaced the gastraphetes cocking system with a winch "for the larger machines". This is supported by Biton's large bow powered machines which also needed winches.
It's simple... Big = winch and stand. Small = belly-cocked and no stand. There is no evidence that Heron's cheiroballistra ever had a winch or stand. It does, however, have the three features needed to operate as a belly-cocker. Namely, a slider, dovetails, and crescent shaped fitting at the rear of the case. As Aitor has demonstrated it can be interpreted this way and produce a workable, though not necessarily practical weapon. Nor, is there any evidence that it was ever fielded. That is often not the point of the execise. Many of Philon's weapons can be written off as mere novelties, but they document attempts at progress. The first automobiles were impractical toys, but they showed the path forward. If someone were to take Heron's novel metal frames and scale them up into the engines seen on Trajan's Column they would certainly need winches and stands, but then they would probably be transported in mule carts and called carroballistas.

[samuli seppanen]

"I'm starting with a light, manually cocked manuballista,"

What do you mean, when you talk of manually cocking your artillery piece? Bear in mind that torsion artillery is a very different beast to a crossbow. Bear also in mind that torsion artillery effectively replaced the belly bow / gastrophetes method of cocking. Regarding the reconstruction of torsion artillery pieces as gastrophetes type machines, Alan Wlkins points out in his article in JRMES 11 (2000):
" All these interpretations appear to have been arrived at by an exercise in vaccuo, with little, if any, consideration of either the historical development of Graeco-Roman torsion arrow shooters, or the performance required of them. In particular the interpretation of the cheirobalistra as a weapon lacking a winch, sparked off by Baatz's 1978 article in 'Britannia', flatly contradicts Heron's authoritative statement that torsion catapults developed so much power that the stomach-bow's withdrawal-rest had to be replaced with a winch, with a pulley system added for the larger machines*."

* Bel. 84-5.
Crispvs

First of all, I'm very familiar with torsion artillery and have read thoroughly almost everything that has been published of the subject. And yes, I'm planning to make a manually cocked weapon for starters. Now, Aitor (2003) makes a very convincing case for the manuballista being cocked similarly to the gastraphetes. If you change the inner diameter of the washers in "Cheiroballistra" like Wilkins (2000) and Marsden (1971) did, you'll soon have to fix other textual "corruptions", too. Aitor's article (2003) is freely available here:

[url:3e09oq1h]http://gladius.revistas.csic.es/index.php/gladius/issue/view/5[/url]

Although I haven't been able to obtain Wilkins' JRMES articles I strongly disagree with the idea that "torsion artillery _has_ to be very strong" (=require a winch) to be useful. After all, the cord bundles are just a source of power like a bow used by a crossbow. In that light I'd be very careful in interpreting Heron's statement about "torsion catapults developing too much power to be cocked manually" as _proof_ that ballistas without a winch did not exist. There may have been other reasons, but the power source is definitely not one of them.

Anyways, if you take a look at Nick's latest chronograph readings (401.8fps), you'll start to realize what potential torsion artillery really had (unless sinew had markedly less performance). Also, I don't think Nick's ballista has even reached it full potential yet (see my earlier comments). As a comparison, you'll be lucky if you get 250 fps from a warbow or a crossbow with hunting/war weight arrows - regardless of the construction method and materials you use. Although Nick's ballista has 4500 poind draw weight, similar velocities are almost certainly possible with a manuballista, given that components are scaled down and optimized accordingly.

Nick's data leads me to believe that _if_ manuballista was used on the field, it's usefulness was due to it's high dry-fire speed. It may also have had a very high efficiency (bolt energy/energy put into the springs) compared to a typical bow/crossbow (50-75%). By dry-fire speed I mean the speed at which a theoretical 0 grain bolt would travel. High dry-fire speed means that you can reduce the bolt weight a lot before it's kinetic energy starts dropping sharply. This means that you can use light bolts and achieve high velocities (e.g. ~400 fps) while maintaining enough "punch". So while you can't put lots of energy into a gastraphetes-style manuballista due to human limitations, you may be able to shoot small bolts at very high speed compared to the bow or crossbow. This of course means a long effective range.

The only way to be sure if a manuballista without a winch was of any use is to make one and go through all possible optimization steps to see what it can do. This is what I intend to do (and document), starting this May. I refuse to let this Wilkins guy tell me such things did not exist or if they did, that they at least could not have been inswingers .

[P. Clodius Secundus]

The only way to be sure if a manuballista without a winch was of any use is to make one and go through all possible optimization steps to see what it can do. This is what I intend to do (and document), starting this May. I refuse to let this Wilkins guy tell me such things did not exist or if they did, that they at least could not have been inswingers .

I commend your independence of thought and look forward to hearing your results. Aitor's efforts in this vein have been highly informative. I too, often find myself at odds with Mr. Wilkins' theories and conclusions. I this instance though, I partially agree with him. Here's where and why...
Throughout the Republican and Early Imperial periods archaeologists have found washers in the 35-40mm range. These presumably are all from wooden-framed weapons. IIRC There is no definitive proof which type of frame the washers found at Volubilis belonged to. Therefore, all the washers directly connected to metal-frames are large enough that they would almost certainly require the use of a winch and stand. To my mind it is entirely possible that Heron's cheiroballistra was never widely adopted in the field in it's hand-held configuration.
One thing that I find odd is that when most build a large metal-framed inswinger they continue to follow Heron's case and slider layout, including the crescent shaped fitting. As John Anstee pointed out this is unnecessary. Using a sliding block for the claw and trigger only the canalis fundus needs to extend beyond the ladder. That is supported by the images on Trajan's Column.

[Dan Howard]

Riveted iron maile would be necessary.

There is no commercially available riveted mail that has anything in common with Roman mail (or any other kind of historical mail). I have already given a long list of reasons why commercial mail is unsuitable. Before testing mail one would need to analyse some extant examples of Roman mail and find someone like Erik Schmid to make a replica based on the results of that investigation. Then you would need to make several reconstructions of various kinds of underpadding based on the available theories and see if they make any difference to penetration. There is a reason why these tests have not been done before. They are expensive and difficult to do properly.

[D B Campbell]

Throughout the Republican and Early Imperial periods archaeologists have found washers in the 35-40mm range. These presumably are all from wooden-framed weapons. IIRC There is no definitive proof which type of frame the washers found at Volubilis belonged to. Therefore, all the washers directly connected to metal-frames are large enough that they would almost certainly require the use of a winch and stand. To my mind it is entirely possible that Heron's cheiroballistra was never widely adopted in the field in it's hand-held configuration.

I'm not sure I follow your logic, Randi. Are you saying that small metal-framed machines did not exist, because there are no definite finds of small washers from the later period? (As far as I recall -- I don't have the archaeological report here -- the Bath washer is undated, so it could come from a late context.)

In 1986, when I stumbled upon the passage of Arrian describing one of the customary exercises of the cavalry as shooting missiles "not from a bow but from a machine" (Takt. 43.1), I immediately assumed that this was a hand-held arrow-shooter like the cheiroballistra. (Arrian was writing during the reign of Hadrian.) I suppose there might be another explanation, ... but I like mine. :wink:

[Paullus Scipio]

Arrian (43) wrote:

In addition to this ( throwing the lancea and javelins/darts) there are performed shooting exercises of various types, with light darts or bolts, these being shot not from the bow, but from a 'machine', or with stones slung or thrown by hand, at a target placed mid-way between the two I have mentioned previously. Here, again, they do well if they demolish the target with their stones - not an easy task as it happens.....

The cavalry in question are the armoured heavy cavalry, not a 'missile' unit such as light horse archers, and the words used for the missiles - 'light darts and bolts' are the same as those used for the ammunition of the stand mounted 'scorpiones'/arrow-shooters of the Legions, described by Arrian and Josephus, who have the artillery (and siege train) carried by mule ( e.g. III.123).

That being so, what reason would you assume 'cross-bow' like hand held 'cheiroballistra', rather than, say, the usual arrow-shooters, or perhaps carro-ballista, issued to a cavalry unit ? - see for example Arrian's "Order of Battle against the Alans", where artillery is deployed on the extreme flanks with the cavalry.

The first mention of hand-held weapons is the 4 C AD Vegetius' 'manuballistae' (torsion arrow-shooters) and 'arcuballistae' (non-torsion - crossbows? ) - though it is well known that he drew on earlier material. Certainly Heron's 'Cheiroballistra' (manuballista in latin), if the interpretation as a type of 'belly-bow' is correct, may be such a machine, but we don't know the date of his (incomplete) manuscript. On the basis of the similarity to machines on Trajan's column ( definitely not hand-held !), and Heron's reference in his 'Dioptra' to an eclipse of the moon to calculate the distance from Alexandria, where he lived, to Rome, it is assumed he flourished in the late 1 C AD, but his work could well be much later........

However, there is one overwhelming objection to cavalry being equipped with 'cheiroballistra/manuballista/belly-bows' and that is that one can't reload on horseback - they are too powerful - and a mounted man could not therefore use such a 'machine' without dismounting to reload, which would be pointless and militarily useless.

All of these reasons militate strongly against Arrian's 'machines' being a hand-held arrow-shooter, but rather supporting artillery, possibly 'carroballista'.

[Crispvs]

"I refuse to let this Wilkins guy tell me such things did not exist or if they did, that they at least could not have been inswingers"

With respect, "this Wilkins guy" (as you have referred to him) has been studying artillery for a very long time and was a personal friend of Eric Marsden. He has also taught university level Latin and Classical Greek for many years and is fluent in both languages. Therefore, this puts him in an almost uniquely good position to tell us what is written in ancient artillery treatises. If he says that a particular word or measurement in the published text has been corrupted, there is probably no-one on Earth better qualified to say so. He is, after all, reading the texts in their original languages rather than in possibly corrupt translations.

Thanks for posting the link to Aitor's article. I have read it before of course (as well as reading his article in JRMES 11, and hearing him present that same paper at the RoMEC conference [supported by an admirable number of slides] in 1999) but it was some years ago and so it was good to read it again and confirm that I had not forgotten his main points. Although Aitor puts a lot of effort into his articles and is always to be commended for his inclusion of so many illustrations and diagrams, I cannot avoid the feeling that both in his 2000 paper and the 2003 paper you have provided a link to, he has written it on the assumption that the inswinger theory is the natural order of things. Thus he states that certain arrangements suit inswinger configurations but I feel that at times he does little to justify this view. Also, in the 2003 article his actually quotes Heron's statement which seems to conflict with the inswinger theory:

"Heron is at pains to explain that: ‘Thus, when the half-springs are strung and the arm recoils outwards —the one in ???? towards ? as ?

(continues in the following post)

[Crispvs]

(RAT has been refusing to let me post up my entire posting for some reason despite trying several times. The rest of the post starts below and continues straight from where the post was inexplicably cut off)

???? towards ? as ?ç—, you must pull back the bowstring as described, load the missile, and squeeze the trigger.’

Even if Y and O (sorry I cannot type the correct character) are the ends of the connecting ladder, this does not necessarily preclude an outswinging configuration, which would seem to be supported by the statement that the arms recoil outwards.

Much of Aitor's argument rests on the assumed positions of the missing stanchions of the Hatra frame. He seems to assume that these must have been in particular positions and that these positions preclude the effective use of the outswinging configuration. However, Wilkins (2003) shows that other arrangements of the stanchions are possible and that it would indeed have been possible for the Hatra catapult to have been of outswinger configuration. When I asked him about the cuspings on the internal sides of the frame, he pointed out that longer arms would allow more leverage on the bowstring to produce more power. Such longer arms would need larger 'heels' to give stability to the arms themselves and the cuspings would therefore be ideally positioned to allow the arms to be drawn further back without the heels being obscured by the frame, with the heels moving into the cuspings as the arms were drawn back.

At this point I should say that Alan Wilkins has been criticised more than once here on RAT for adding parts to his reconstructions which have not been found in the archaeological record. However, none of the surviving frames constitute the complete head units of the catapults they came from and it is debatable whether any of the surviving frames retain even all of their original metallic parts. Simply joining up the surviving parts and assuming that they constitute the entire frame ignores the fact that significant potions may be missing. After all, have any ratchets or other windlass gear been found in association with any of the known frames? We can be fairly sure that winches would have contained or been associated with at least some metal parts, as would the trigger. If these essential items are missing, why assume that what we actually have is complete? It is obvious that although the surviving treatises contain much minutiae on certain parts of their respective machines, other parts are less carefully described and some parts may well not have been mentioned. How often are the bars which rest atop the washers mentioned? Yet without these essential pieces the whole machine would be useless. We are lucky to have the evidence for them from the archaeological record, what what if we didn't? Also, how do we know that we are arranging the surviving elements of the frames the correct way up? Aitor on more than one occasion has stated that inswinger configurations are obvious from the positions of the side stanchions on the surviving spring frames but those same spring frames need simply to be placed the opposite way up to make an outswinging configuration equally obvious. Wilkins has also pointed out that the inswinger configuration also suffers from the flaw that as the ends of the arms draw close to each other before progressing forwards, much of the tension the bowstring has initially picked up is lost as the string goes momentarily slack, meaning that the net gain in power from the arms increased arc of travel is significantly less than it might otherwise be.

Anyway, it is high time now that I retired to bed for the day so I will end here.

Crispvs

[Dan Howard]

However, there is one overwhelming objection to cavalry being equipped with 'cheiroballistra/manuballista/belly-bows' and that is that one can't reload on horseback - they are too powerful - and a mounted man could not therefore use such a 'machine' without dismounting to reload, which would be pointless and militarily useless.

German reiters used various tactics, such as the caracole, that involved a single shot from a pistol before charging into combat. The pistol was discarded after that shot - no reloading involved. I don't see much difference between shooting a crossbow once from horseback and a legionaire throwing a pilum before charging the enemy. The point is to break up the formation before engaging.

[D B Campbell]

However, Wilkins (2003) shows that other arrangements of the stanchions are possible and that it would indeed have been possible for the Hatra catapult to have been of outswinger configuration.

In fact, it would be true to say that Aitor has shown that the Hatra ballista could have been of inswinging configuration, and Alan has shown that it could have been out outswinging configuration. You pays your money ...

It is just worth noting that most people take the eight corner pieces of the Hatra frame to imply four full-length stanchions. However, Alan has removed the two rear stanchions -- I don't think he explains this in his book, but it is clear from his sketch (fig. 55 p. 70) -- in order to make his outswinger work. (For a proper study of the Hatra find, Dietwulf Baatz's 1978 paper is essential, as you probably know.)

However, none of the surviving frames constitute the complete head units of the catapults they came from and it is debatable whether any of the surviving frames retain even all of their original metallic parts. Simply joining up the surviving parts and assuming that they constitute the entire frame ignores the fact that significant potions may be missing.

I think everyone realises this. However, the beauty of the Hatra find is that the springframe was discovered, face down in the sand where it had presumably fallen during use. So we are entitled to believe that we have the complete front end of the machine, with the components lying in their original positions. (See Greek and Roman Artillery p. 41-2.) The trigger mechanism along with the winches and ratchets would have been at the back end, which wasn't preserved. (Pity the whole thing hadn't fallen down a well.)

Also, how do we know that we are arranging the surviving elements of the frames the correct way up? Aitor on more than one occasion has stated that inswinger configurations are obvious from the positions of the side stanchions on the surviving spring frames but those same spring frames need simply to be placed the opposite way up to make an outswinging configuration equally obvious.

In the case of the iron kambestria, this has always been conceded. (See, e.g., Greek and Roman Artillery p. 39-41, where the cheiroballistra is shown as an outswinger.) But the beauty of the Hatra find is that it shows us where the cut-outs should be -- on that machine, at any rate. Aitor has extrapolated to encompass all iron-framed catapults.

[P. Clodius Secundus]

I'm not sure I follow your logic, Randi. Are you saying that small metal-framed machines did not exist, because there are no definite finds of small washers from the later period? (As far as I recall -- I don't have the archaeological report here -- the Bath washer is undated, so it could come from a late context.)

In 1986, when I stumbled upon the passage of Arrian describing one of the customary exercises of the cavalry as shooting missiles "not from a bow but from a machine" (Takt. 43.1), I immediately assumed that this was a hand-held arrow-shooter like the cheiroballistra. (Arrian was writing during the reign of Hadrian.) I suppose there might be another explanation, ... but I like mine. :wink:

Duncan,
I’m not saying they didn’t exist, just that there is no direct evidence linking them to iron-framed machines.
My :wink: explanation/timeline is…

Mid 60s AD The Heron of Alexandria, the Edison of his day, writes the cheiroballistra text describing a hand-held belly-cocked weapon featuring a new type of iron frame. As Aitor’s work demonstrates, his treatise produces a workable machine, but it may have been underpowered or not considered a significant enough improvement to warrant replacing the Xanten type weapons. Unless direct evidence is found, their existence as anything other than a theoretical exercise is assumption rather than fact. As preceedent I would cite Philon's wedge, bronze spring, pneumatic, and repeating catapults. None of these "improvements" seem to have been adopted.

69 AD Large wooden euthyones still in use at Cremona. The last evidence of this type of weapon in the arsenal.

70s AD Heron’s design is scaled up and given a base and winch turning it into a practical weapon Large wood framers are phased out.

87 AD the Dacians demand the transfer of the latest technology as part of a peace treaty. This might have included the new metal-framers.

98 AD A hand-held Xanten type weapon is shown on Vedinnius’s tomb. This may indicate that they remained in use longer than their larger cousins. In any case, none of the small washers @ 40mm (Elginhaugh, Bath, Volubilis) can be connected with iron-framer components. Most of the larger washers can. Thanks to Xanten we do have proof that they were used with wooden frames. The passage you quote from Arrian doesn't specify what type of machine the cavalry used, so unfortunately it adds little to the debate. Thus there is no substantive evidence that Heron's design was fielded at that scale. It's true that "Absence of evidence isn't evidence of absence", but it sure ain't evidence of presence either. :wink:

101 AD Trajan’s troops bring their latest and most powerful iron-framers on campaign. They look slightly different than those of the Dacians.

[D B Campbell]

The passage you quote from Arrian doesn't specify what type of machine the cavalry used, so unfortunately it adds little to the debate.

Adds little ... other than the fact that it kicked off the whole hand-held torsion weapon discussion! //scholar.google.co.uk/scholar?hl=en&q=Auxiliary+Artillery+Revisited+Bonner+Jahrbucher&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0:3j18vxuc]Unfortunately, BJ 186 not available electronically.[/url])

Arrian's Tactica is an interesting document, in (the latter half of) which he describes the type of cavalry manoeuvres that Hadrian would have witnessed during his inspections. It's fairly clear that the horsemen are shooting from horseback -- critics may carp that Arrian is not explicit on this point but, as you yourself will appreciate, envisaging the horsemen dismounting and wheeling out a carroballista surely isn't in keeping with the general context of cavalry manoeuvres!

That leaves us wondering what kind of "machine" could be used on horseback. (My 1986 paper included an exhaustive analysis of Arrian's use of the word, and I concluded that it must be a miniature catapult of some kind; a Hadrianic date suggests either the cheiroballistra itself, or the much less-well-known arcuballista, which I proposed might have been more like a standard crossbow.)

As I said, you pays your money ...