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Andrew Gill





Joined: 19 Feb 2015

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PostPosted: Wed 24 Mar, 2021 12:35 pm    Post subject: crossbow and arrow/prod dynamics         Reply with quote

Hi Everyone

Tod's videos and the recent discussion stirred up about the tiny so-called assasin's crossbow got me doing a lot of overdue research into crossbows. Being a mechanical engineer but lacking anything more interesting than a homemade hickory flatbow to test, I wanted to try my hand at some numerical modelling (disclaimer, I specialise in fluid dynamics and structural analysis is very much a second string to my lyre, so to speak). Sean Manning pointed out a very interesting thesis on using FEA methods to model a bow, which I'm trying to emulate in my spare time. These results I will also put up here if there is interest, when I'm fairly certain of them.

However, while reading Payne-Gallwey's Book of the crossbow, I realised that it was worth taking a look at the bolt as well.

I wrote a simple computer program to numerically calculate the flight path of an arrow, javelin or crossbow bolt, given its mass, "muzzle velocity", firing angle, approximate frontal area and drag coefficient (more on these two later). I can get various bits of information out - the velocity of the arrow at an arbitrary point in its flight, how far it will travel before hitting the ground (assuming level ground!) and how much energy it loses due to air resistance.

There's some uncertainty about the exact drag coefficent of an arrow in the published literature. A commonly accepted value is a little over 2, but have seen values as high as 4 and as low as about 1.5. The ugly truth is that drag-coefficients aren't actually constant, so its naive to assume that there is a single value to rule them all.

I checked it by looking at olympic javelin data, and got a range of about 85 m for the official test conditions (the actual range from both javelin gun and selected athletes was about 83m iirc).
Then I discovered Tod's video with the longbow arrow speeds at ranges of 25, 50, 75 and 100m. He discovered that an arrow loses 15-20% of its speed after 100m of flight.
I had to make a couple more assumptions, such as the angle that the arrow began its flight at, but my results were again fairly close for 100m - I got a value of between 20-24% decrease in speed, which I found pretty encoraging, given the uncertainty of the drag coefficient of the arrow, and the guesses that I had to make. So I have some confidence that I've done this as correctly as such a simple model can be done.

Now, having probably put a lot of people to sleep, the (hopefully) more exciting bit.
P-G's famous shot across the Strait of Menai is claimed to have been 440 or 450 yards, which is about 420m (google confirms this, by the way.)
My calculations suggest that for a drag coefficient of around 2 in still air, he would have had to shoot his arrow at nearly 100m/s (!) at 45 degrees (he was aware that this would give best range, as he comments on it later). Its initial kinetic energy would have had to be about 425 J, and it would have lost roughly two-thirds of that to air resistance by the time it landed.
On the face of it, these numbers are so far above what Tod is reporting that they cast his account in serious doubt in my mind unless there were some other factors at play here, or somehow renaissance crossbow makers really could somehow overcome the inherent limitations on steel prods; these numbers look a lot like those given by Andreas Bichler for his giant 1200lb horn crossbow, at least in terms of energy. Unless there is something else going on here...

Remember that I mentioned that the drag coefficient of arrows was quite difficult to pin down?
Well, another part of the problem is simply that some arrows simply have more air-resistance than others.
I have a suspicion (no more than a suspicion, mind you!) that this is part of what bit Tod with the long headed (type 7?) bodkin arrow which lost speed faster than the shorter headed one despite its greater mass. Contrary to popular belief, a long spike is actually more poorly streamlined for subsonic flight than a shorter, more rounded one (the reverse is true for supersonic flight, which is why rifle bullets are often pointy and subsonic pistol bullets rounded). We don't know what sort of bolt P-G was using, beyond that it probably weighed around 30z, or (80g for us metric types, I believe.) My little program suggests that a fairly small difference in drag coefficient can easily make a difference of 50m or more to an arrow's range in still air. We also know from Tod's experiments that head shape can have a noticeable aerodynamic effect on the arrows (the giant swallowtail on the crossbow effectively ruined the arrow's stability, for instance). People in the Renaissance had to use arrowheads that were effective at piercing their targets. But PG was trying to win a friendly bet with some friends, and had no such restrictions on head design (and also did a lot of trial-and-error experiments with different bolt designs).

Which brings me to my second point.
PG completely fails to mention the weather conditions at the time of his shot, though he mentions that it was in autumn.
Well, according to modern online average weather data, it seems that there is often a wind blowing from the south or east during the autumn months and it can be blowing quite strongly - 14 miles/hour is not uncommon, and 20 mi/h is by no means unknown. Conveniently, this would be at P-G's back when he made his shot. I made a small modification to my program to take into account the effect of a head- or tail-wind, to get best-case and worst-case scenarios. Again, it can make a fairly big difference to range - again more than 50 meters, if I've not botched the programming. I've attached a graph showing several trajectories for likely best and worst cases for

I also investigated the effect it would have had if he were standing on the 6m high battery when he fired his shot, but this seems to make less than 10m difference to the range either way, so is probably not relevant.

So, if P-G (who seems to have had a friendly bet on the matter) chose a particularly aerodynamic arrow design(he could have determined this by trial-and-error experimentation, which he seems to have done a lot of), and made his shots with a decently strong tailwind, the whole thing starts looking slightly more plausible than before. Using high-drag arrows in still air seems to give a maximum range of about 270m, while super-streamlined arrows with a strong but not unreasonable tailwind will just about do 420m. Given the amount of educated guesswork involved here, this is not even remotely conclusive, but it is suggestive...
And, if not totally convincing, it at least seems a little more plausible to me than that either Tod's magnificent bows are terrible, or that PG, who was apparently a noted professional ballistics expert of his time, was lying through his teeth.

And perhaps it shows that we should be cautious of ascribing some reputed performance to the superiority of one particular part of these quite complex weapons, such as the prod.

I don't know if this is of interest to anyone besides me, but if it is, I'll post whatever I find when my current investigation of the crossbow lath is complete (which will possibly take a bit longer). If any of this does interest anyone, or someone thinks I've bungled my modelling attempt (which would be embarrassing, but is certainly not impossible dispite my checks), please let me know.

Andrew

Edit: for some reason I can't upload the graph.
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Pieter B.





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PostPosted: Wed 24 Mar, 2021 1:13 pm    Post subject:         Reply with quote

Thanks for the write up!

What would your model say if you kept the same drag coefficient but raised the bolt weight to around 120-140 grams?
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Andrew Gill





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PostPosted: Wed 24 Mar, 2021 1:53 pm    Post subject:         Reply with quote

Hi Pieter

Thanks! That's a good question; I actually tested that but forgot to include it in my (already long) writeup. Increasing mass while keeping the drag coefficient constant makes the arrow fly quite a bit further (at least 40m), if you fire both light and heavy bolts at the same speed.

That's the problem, though, because the bolt's initial speed is also controlled to some extent by its mass (heavier bolts will accelerate more slowly from the force of the string, and thus attain a lower speed) and to some extent by the dynamic properties of the bow limbs. Once I do a finite-element model of the lath's behaviour, I'll be able to predict that with some accuracy, but it's pretty difficult to do with any certainty using simpler methods.

These numbers are for 80m/s, by the way, which is the speed I determined that P-G would probably have needed to shoot his bolt at if my hypothetical tailwind was blowing.

Andrew
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Pieter B.





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PostPosted: Wed 24 Mar, 2021 3:23 pm    Post subject:         Reply with quote

Quote:
That's the problem, though, because the bolt's initial speed is also controlled to some extent by its mass (heavier bolts will accelerate more slowly from the force of the string, and thus attain a lower speed


I think you are right on the first part but I think that might actually be why heavy projectiles are more efficient. The higher inertia and slower acceleration can allow heavy projectiles to translate more of the mechanical energy into kinetic energy yielding a similar velocity to a lighter projectile.

If fluid dynamics is your thing somethings like pistons or firearms might be illustrative.

For a given powder charge, given barrel length and given bullet weight you might get an initial velocity of 400 meter per seconds. If you then double the weight of the bullet but keep the powder charge and barrel length the same you would expect a drop in initial velocity matching the increased weight and thus keeping the muzzle energy similar. Only that doesn't have to be the case.

In a firearms the 'work' done by expanding gasses is equivalent to the area under a pressure-volume graph





If you increase the weight of the bullet the higher inertia of said bullet means the distance between the breech and the base of the bullet will be shorter when the powder finishes burning. This yields a higher chamber pressure because the same volume of gas is unleashed in a smaller space in the barrel, this increased pressure can be more effectively translated into kinetic energy. While it is certainly unlikely the heavier bullet will travel faster than the lighter one the heavy bullet might just be much more efficient in energy conversion so that the velocity matches that of the lighter bullet.

With crossbows we are looking at springs rather than gas but I suppose the inertia-energy efficiency factor holds true here also.

Quoting an old post by Tod himself: http://myArmoury.com/talk/viewtopic.php?t=199...;start=198

Quote:
The last bow I made a steel of 850lb at 175mm/6.5". I fitted it with a draw length of 150mm/6" and so was drawing to 780lb.

I shot an adjustable bolt ranging from 80grams to 125grams (1 oz =28.4 grams) and tested the speeds using an F1 Chrony.

The 80 grams bolt shot at 49m/s = 161fps

using 1/2MV squared = 96J

What comes next I found very, very surprising.

When I raised the weight of the bolts, the velocity reduced as you would expect, but only very slightly, until I reached 125g and then it started to drop off very rapidly. At 125g the velocity had reduced to 48.5 m/s which is a reduction in velocity of 0.5m/s or 1.6fps.

Using a 125g bolts at 48.5m/s the energy has increased to 147J

This is not the outcome I would have expected and would doubt the accuracy of it, however I know another person with a windlass bow of mine that is performing in a similar way.


Tod doubts the accuracy but I think we're actually looking at something that a physicist could explain. We're thinking in terms of static energy efficiencies whereas they are actually quite variable.

In crude approximation the spring which has a draw weight of 780 lbs at 6 inches has 264 joules of energy stored in it.

Propelling an 80 gram bolt to 49 meter per second yields 96 joules of kinetic energy or an energy conversion of 36.3%

Propelling a 125 gram bolt to 48.5 meter per second yields 147 joules of kinetic energy or an energy conversion of 55.6%

In other words increasing the mass of the projectile by 56% increased the energy conversion or efficiency of the spring by 19.3% yielding an initial velocity that is near enough the same and a projectile energy that is 53% higher than the lighter projectile.

I believe Payne-Gallwey was using a crossbow even heavier than the one above so I wouldn't be surprised if it could lob heavy projectiles even better.
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Duncan Hill




Location: Guelph, Ontario, Canada
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PostPosted: Wed 24 Mar, 2021 6:06 pm    Post subject:         Reply with quote

Bravo Andrew on you program and calculations, and to you both for working on these problems - I'm very interested to learn more!
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Jean Henri Chandler




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PostPosted: Wed 24 Mar, 2021 6:31 pm    Post subject:         Reply with quote

Andrew Gill wrote:
Hi Pieter

Thanks! That's a good question; I actually tested that but forgot to include it in my (already long) writeup. Increasing mass while keeping the drag coefficient constant makes the arrow fly quite a bit further (at least 40m), if you fire both light and heavy bolts at the same speed.

That's the problem, though, because the bolt's initial speed is also controlled to some extent by its mass (heavier bolts will accelerate more slowly from the force of the string, and thus attain a lower speed) and to some extent by the dynamic properties of the bow limbs. Once I do a finite-element model of the lath's behaviour, I'll be able to predict that with some accuracy, but it's pretty difficult to do with any certainty using simpler methods.

These numbers are for 80m/s, by the way, which is the speed I determined that P-G would probably have needed to shoot his bolt at if my hypothetical tailwind was blowing.

Andrew


I can't say anything about the effects of tides or tailwinds, but I don't find the distance particularly unthinkable for a late medieval crossbow.

Also more to the point - this particular number of 80m/s that you mentioned here is interesting, because in a video posted by Andreas Bichler or someone associated with him in 2016, he shoots an 81 gram bolt at an initial velocity of 69.3 m/s (at a replica of an almost equally interesting pavise shield based on an original in the Bayerischs Nationalmuseum München) and then a second 81 gram bolt at 69.85 m/s.

The 1200 lb draw crossbow replica he shot was also based on a specific original which he lists in the video.

Considering this test was from 2016 and (anecdotally) Bichlers weapons have continued to improve, I don't think it's beyond the pale that he may have a 13% improvement in efficiency, or if say, we had 100 more like him, that somebody could improve it that much just through trial and error. Or perhaps by taking an even closer look at the artifact with inventory number C 805, or several dozen others of similar design.

J

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Andrew Gill





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PostPosted: Wed 24 Mar, 2021 11:54 pm    Post subject:         Reply with quote

Hi everyone

Pieter, you make a very good point about heavier bolts being more efficient. If the bolt mass is above some value, the acceleration of the bolt will become the limiting factor in the combined lath-string-and-bolt system - ie. the bow is no longer fighting with itself more than it is fighting with the bolt to try to get the latter to move faster - which is of course a desirable situation that just gets better with heavier bolts, as long as the bolt still leaves the bow at a useful speed. (Tod illustrated this in one experiment by firing a very light modern bolt form a 960 lb crossbow - the speed gain is negligible because the lath's and string's response becomes the limiting factor) It's probably also why Andreas Bicher often fires much heavier bolts (200g or more iirc?) from his giant composite crossbows. And of course once it leaves the crossbow, the bolt is less susceptible to aerodynamic drag, assuming this stays roughly equal, so you get less of a range drop-off there as well.
And the bolt is less likely to outpace the bowstring at any point (I'm not convinced this can actually occur but if it did, it would certainly be more likely with a lighter bolt). And I'm sure there are other factors that I've neglected here. So heavier is definitely better!

Jean, I was hoping you'd join in here.
I've watched Andreas Bicher's videos and they are incredibly impressive. I would go so far as to say that if P-G had used a large composite crossbow rather than the steel one he mentioned, I don't think many would doubt his claims, or at least not to such a great degree.
The issue for me (and part of the reason why I'm investigating) is the apparently huge discrepancy between his (P-G's) claims for a steel bow, and the work of Tod, the french chap (Lebel?) and also my own rusty knowledge of the mechanics of leaf springs and cantilever beams and also the properties of steel (which I've devoted a decent effort to understanding because it is integral to my interest in medieval and renaissance weapons and armour, as well as being of some importance in my profession). I'm not at all convinced by the argument that there were lost methods either metallurgical of making such vastly superior steel crossbow laths, but I would love to prove myself wrong (even aside from the fascinating insights we'd gain into medieval technology, the benefits to making modern leaf springs alone would be worth the effort). A good scientist should never be sure of what he knows (and engineers are, or should be, applied scientists, after all).

By the way, on the subject of metallurgy:
I've examined the published properties of steels from modern maraging steel, high carbon steels and mild steel, to Japanese tamahagane and wootz and bulat (there's an excellent paper in which the researchers compare historical samples with "synthetic wootz" samples that they made themselves - so apparently making it is possible!) In all cases the modulus of elasticity was within a fairly narrow band of between 180 and 220 Gpa - there was one single old wootz sample which reached 250 GPa, but that's only a 13% "improvement" on the common value of 220, and this was unusual even among the historical samples investigated. (in fact, I think a higher modulus would actually probably make worse bows, though I'm aware you weren't arguing for using wootz specifically). The yield strength does vary quite a bit between alloys, which is relevant since this represents the limit to which a given bow can be loaded before it snaps or takes a permanent set, but in all the measured data I've seen, the better modern alloys always come out on top. If I've missed something I'd love to know, but based on published experimental data including old metal samples, I just don't see the answer being in the metallurgy.

If I were to look for a way to win a bit of extra performance from a steel bow lath, I'd look at fine-tuning the shape. As an engineer, my reaction to how to design a good crossbow would be to treat it like any other cantilever beam, and make sure that the stresses are within it are roughly constant along its length and slightly below the yield stress by some safety factor when drawn. From my rusty knowledge of structural mechanics, this results in a linear taper. But this is considering a bow or lath as a static system, and it is not - it is decidedly dynamic when it is doing its job. Iif one designs for efficiency, with the different speeds at which different points along the bow move when it is released, it might be possible to tune the profile and taper slightly differently, while still keeping yield stresses in reign. This is where the FEM model will come in.
It's a pretty obvious point, so I'm probably not the first to think of it (I'd be surprised if modern-style crossbow designers didn't do this as a matter of course), but it will be instructive to me and hopefully help me bows better. How much can we gain in this way? I've no idea! I share Tod's suspicion that there aren't huge improvements to be made, but until I crank the numbers, its no more than a suspicion.

There's another interesting point that I discovered: when you use a linen bowstring on a wooden bow, you have a bowstring material that has a modulus of elasticity about five times higher than the bow wood. When you use it on a steel crossbow lath or prod, it is about five times lower than the bow steel (these numbers are very rough; I need to check them). Now this is not as exciting as it may at first sound because the elasticity or stiffness of the bow string under tension is also dependent on the sectional area of the string, not just the modulus of elasticity, and crossbow strings are much thicker proportionally than longbow strings, so I don't think that the elasticity of the bowstring is actually a major factor. But its another thing to check.

So, to finish another marathon post: If anyone has data on the cross-sectional measurements and taper at several points along the length of an extant steel crossbow lath, that would be a huge help.

Also, Jean, if you can pass on any data from the range of shots, mass of bolts, etc during the schuzenfests in the mid to late 1400s (when steel crossbows were probably most common?) I'd be very much obliged. More data would help a lot!

Andrew

edited for clarity and spelling errors
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Michael Zimmermann





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PostPosted: Thu 25 Mar, 2021 2:21 am    Post subject:         Reply with quote

Dear Andrew,

since I am partially to blame for suggesting FEM modelling might be an interesting avenue to pursue here, let me offer a couple of suggestions as to people, who might be worthwhile contacting. Do keep in mind that crossbows are not at all part of my research, so...

There appears to be an equivalent to Andreas Bichler (who is Austrian?) in Germany, who has devoted himself to the historical (steel) crossbow since 1990; he is an engineer, like you, and renowned for his bowsmithing over here, I gather. His name is Jens Sensfelder and he built a crossbow for this exhibition in Berlin last year:

https://www.dhm.de/ausstellungen/archiv/2019/die-armbrust-schrecken-und-schoenheit/

He publishes a periodical, which occasionally has articles in English, called 'Jahrblatt der Interessengemeinschaft Historische Armbrust'.

Jens also supplies this workshop with bows:

https://www.armbrust-manufaktur.de/index.html

Their 'biggest' specimen is this guy:

https://www.armbrust-manufaktur.de/schwere_armbrust4.html

Sadly, no further data is supplied here, but might be available on request.

Best,

- Michael
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Andrew Gill





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PostPosted: Thu 25 Mar, 2021 3:13 am    Post subject:         Reply with quote

Hmm I said my structural mechanics were rusty, didn't I? I was right.
The taper on an end-loaded cantilever beam should not be linear (the internal shear-forces vary linearly, of course); the maximum stress is roughly proportional to one over the square of of the thickness of the beam in the bending direction, though they are linear to the width of the beam. So I think keep constant maximum stresses, you ideally want the thickness to vary in some way proprotionally to the square root of the distance from the bow tiller (assuming constant width in the other direction - varying the relationship between both tapers is one of the ways we can play with the bow's profile). I'll check this before going on.
Tod has mentioned that steel bows should taper down to roughly 60% of the center dimensions in both thickness and width. I get the impression that is based on both measurement of historical examples and some sort of structural calculation (I'd love to know more, if he reads this).

Just a small but important correction. Duh! Blush

Edit: this doesn't in any way affect the calculations I did on the projectile flight, luckily!


Last edited by Andrew Gill on Thu 25 Mar, 2021 3:35 am; edited 1 time in total
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Andrew Gill





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PostPosted: Thu 25 Mar, 2021 3:15 am    Post subject:         Reply with quote

Thanks Michael, that's a very good starting point!

Andrew
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Jean Henri Chandler




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PostPosted: Fri 26 Mar, 2021 3:31 am    Post subject:         Reply with quote

A couple of comments

Quote:
By the way, on the subject of metallurgy:
I've examined the published properties of steels from modern maraging steel, high carbon steels and mild steel, to Japanese tamahagane and wootz and bulat (there's an excellent paper in which the researchers compare historical samples with "synthetic wootz" samples that they made themselves - so apparently making it is possible!) In all cases the modulus of elasticity was within a fairly narrow band of between 180 and 220 Gpa - there was one single old wootz sample which reached 250 GPa, but that's only a 13% "improvement" on the common value of 220, and this was unusual even among the historical samples investigated. (in fact, I think a higher modulus would actually probably make worse bows, though I'm aware you weren't arguing for using wootz specifically). The yield strength does vary quite a bit between alloys, which is relevant since this represents the limit to which a given bow can be loaded before it snaps or takes a permanent set, but in all the measured data I've seen, the better modern alloys always come out on top. If I've missed something I'd love to know, but based on published experimental data including old metal samples, I just don't see the answer being in the metallurgy.


Admittedly, I haven't taken a serious look at 'wootz' type South Asian crucible steel in a while but I believe your "examination of metals" might need to go a little deeper or last a little longer. Despite claims to the contrary by the Russians, bulat is definitely not wootz, and I am highly dubious that 'synthetic wootz' is actually wootz either or shares the properties of an actual (pre-18th Century) wootz artifact like a sword. 'Synthetic wootz' could mean "mechanical wootz" i.e. pattern welded steel, which looks similar to wootz but doesn't share the same properties, or it could mean something else, but if they have actually managed to produce anything really close functionally to historical wootz steel that would definitely be news to me.

You also have to be cautious about what historical examples they are using (what kind of artifacts are they from and from precisely what period). Because nicer wootz artifacts like swords or daggers are rarely subjected to destructive testing (not to say never, but rarely).

The major characteristic of wootz that they are trying to emulate is the combination of ultra high carbon (up to 2%) with very high flexibility.

The last serious effort I heard of was by Lawrenche Livermore National Laboratory about ten years ago, and they apparently failed. However they did apparently manage to produce metals with a 5 fold increase in ductility, which to me proves there is a lot to learn still even in the field of metallurgy.. Again - I'm not even saying that the difference between modern replicas and period antiques comes down to metal, I really have no evidence that it does, the whole point of bringing up wootz was just to point out that we don't in fact know everything about pre-industrial metallurgy already.

I think your approach here is a bit backward.

So far as I understand, this is about an attempt to explain the relative performance of modern steel prod crossbows by two (?) modern replica producers, because their weapons don't perform as well as those made by one (known) maker of horn / composite prod replica weapons.

Bichler was as far as I know, the first to actually have some (still limited) success in even making functional composite prod crossbows. As I have pointed out, previous attempts sponsored by university studies failed as the prods rapidly lost power and de-laminated after just two or three shots.

In my opinion, the research should be driven by data from the antiques and from the world they existed in. The unique aspect of Bichlers replicas is not (to me) likely to be due to the inherent superiority of composite prods as it is to the fact that he is first and foremost a researcher who did extensive study of historical antiques and the methods of their fabrication.

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Andrew Gill





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PostPosted: Fri 26 Mar, 2021 10:11 am    Post subject:         Reply with quote

Hi Jean

The principle paper from which I got my info on wootz was "Nanoindentation behavior and microstructure of several wootz-type steels", by Paetzke et al of the technical university of Dresden. They used electron microscopes and some other rather specialised equipment to study five different samples, including an old indian one. It seemed pretty rigorous and was nicely written (I could understand most of it based on my engineering metallurgy courses). It is on researchgate, but I'm not sure if I'm allowed to post the link here - you can find it easily enough via google or I can PM the link. If you have a paper which refutes or qualifies their findings please send the details so I can read it. In fact, send me whatever literature you have on wootz. I disagree with some of your conclusions about it, but its a fascinating material whichever way you look at it.

As for whether I'm working backwards on the crossbow question: Yes I am, consciously. I want to see whether the claims of historical sources are plausible within the laws of physics. Can I independently design a steel bow lath that "on paper" matches these claims? But I also want to work forwards, by examining the historical data and artifacts to see what solution they arrived at. If the two converge, well, then we know! Otherwise I'll at least have a better inderstanding of the physics of bows.

In the previous thread, you spoke about faith. For me personally, faith is anaethma to research. I need to question everything, no matter how dearly I hold the belief, to arrive at the truth . I want to examine the historical records and modern experiments, but I will not decide beforehand which (if either) is correct. And I'm not even convinced that this is the right question to ask, honestly. This is my personal view, it shapes my approach to research, but I can't expect others to follow it.

So if you have data on renaissance crossbow performance, please share it with me. If we discover an ancient way to design excellent springs for crossbow laths, it will be incredibly exciting for everyone here. If we don't, we'll still learn a huge amount about the technology of this fascinating period, as well as how to at least make better modern steel crossbows. Which is also exciting.

Andrew
PS. The synthetic wootz was not pattern-welded. The account of its preparation is pretty fascinating.
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Jean Henri Chandler




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PostPosted: Fri 26 Mar, 2021 12:36 pm    Post subject:         Reply with quote

The only thing I question from that article (which i have not yet read though I might if I have time) is the notion that they have in fact created true synthetic wootz. I do know that there have been many attempts to create modern or synthetic wootz, (two examples are mentioned in the article I linked about Lawrence Livermore) and there have been some interesting results producing metals with unusual properties, but so far as I am aware nobody has yet succeeded in emulating the original, or even come very close to it.

As for faith - there is more than one type. Basically there is true, inherent spiritual faith, and there is something more like 'earned' or acqujred faith. I have an 'earned' faith that when I turn the knob on my sink water will come out of the tap, because it almost always has in the past. I have an earned faith that if I drink a whole liter of whiskey tonight, I'm going to end up with a headache tomorrow. Because that is what usually happens (though I can get away with a bit more of it if I stick to the single-malt Happy )

I have an acquired faith in the late medieval sources in aggregate. Time and again these people have proven smarter than we give them credit for. Time and again, with regard to weapons specifically, I have seen confident so called experts saying things like 'medieval swords were like (barely) sharpened crowbars' or that they 'weighed 10 or 15 lbs' or that 'medieval armor was so heavy that if the rider fell off of his horse, or fell down in the mud, he couldn't get back up again' and so on. From History channel or BBC / PBS documentaries to University courses. Then we (collectively, as a community in places like this and within the HEMA revival and so on) put it to the test, Ewart Oakeshotts work bubbled up. Alan Williams work became famous. Now we know better.

I should note though, it took more than 3 or 4 people making replicas, and a lot of research, and a lot of very close examination of antiques.

I personally also do have an acquired faith in empirical research and modern engineering. I do fly in commercial aircraft for example. But I know from my own professional life that as powerful as our modern approach is, it is only as good as the data that goes into it. Working backward from replicas without looking closely at antiques wouldn't qualify to me.

I have posted some raw data from schützenfest and some other records to this forum pretty recently, but as I said in the other thread, I'm not in a position right now where I can spend the (hours and hours of) time wading into detailed arguments. When I do have time I will write a paper on that specific subject (schützenfest records). The problem with posting some of that raw data here is that there is enough wiggle room to debate it, and inevitably that will just go on and on. Distances for example are recorded in units of measure like ells and cubits which could and did vary depending on the specific place. Each town and principality had their own units of measure then and they changed over time. Fortunately on the shooting contest invitations we have the length of the unit of measure they refer to physically drawn on the sheet, but we don't have that kind of verification in all the other records.

That said, here is some data to consider.

One invitation from Strasbourg to Rottweill in 1494 said that targets at 90 ells distance had to be hit 4 times out of six shots to qualify to enter the tournament. That was a 20 cm target. By our estimate it worked out to 102 meters distance. Other invitations from Strasbourg earlier in the 15th Century worked out to targets at 70-90 meters.

Another invitation (1549 from Landshut) said that the target (shown as a circle on the invitation as being about 18 cm) had to be hit 8 times out of 12 shots at a distance of 96 Landshuter cubits, which works out to 43 meters. Once qualified the shooters would have 24 shots at the target. The same invitation specified 260 cubits distance for the arquebus target.

That invitation can be viewed here https://digital.staatsbibliothek-berlin.de/werkansicht/?PPN=PPN1022206435

Keep in mind these are small targets not human or horse-sized.

I have 6 other ones that we haven't fully translated yet. But there are dozens out there.

In a letter in 1408 the Teutonic knights Komptur of Elbing mentioned a 'safe distance' of 300 ells from a defended castle against crossbows, with different ranges listed for culverin and hand-büschen.

In an earlier manuscript (Chronicon terrae Prussiae) from 1326 they listed a safe distance of 250 ells. So apparently the weapons got a bit more dangerous. Or possibly the ell meant a different unit of measure then. The Chronicler doesn't specify.

In a document from 1427 (just before attack by Hussite armies), the city of Wroclaw specified that certain defensive outworks be built at the limit of crossbow range from the wall, which they listed as 600 cubits, which works out (possibly) to about 270 meters.

I think Christine de Pisan actually may have something on this too in her war book but I can't remember, I'll need to scan that book again.

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Sean Manning




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PostPosted: Fri 26 Mar, 2021 1:04 pm    Post subject:         Reply with quote

There have been Europeans and settlers making horn bows since at least 1960 (Edward McEwan in London said "25 years" in 1983). Not as many work on the short-powerstroke European horn crossbows, which have an odd method of construction, but the basic idea of horn bows is not a lost art. But yes, the very high draw-weight, particular construction, and short draw might give different performance than other kinds of horn bows!

One of the Paston letters describes a group of 3 or 4 steel crossbows which need to be repaired because they are shedding splinters of steel and won't shoot well any more. The citation is in Hardy and Strickland's Great Warbow.

Edit: John Paston III to John Paston II (year 1469), 05 in Paston letters and papers of the fifteenth century, Part I p. 543 in Michigan and other places online

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Jean Henri Chandler




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PostPosted: Fri 26 Mar, 2021 1:41 pm    Post subject:         Reply with quote

The crossbows are a different thing, they use different materials. Nobody makes a 1200 lb draw recurve self bow either.
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Sean Manning




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PostPosted: Fri 26 Mar, 2021 2:20 pm    Post subject:         Reply with quote

Jean Henri Chandler wrote:
The crossbows are a different thing, they use different materials.

The horn bows in crossbows are made from horn, sinew, wood, and often a waterproof coating. Horn handbows draw on the same types of materials, although every tradition is a bit different and every batch of bows is different. In the 13th century the Venetians liked Alpine steinbock horn, the Bronze Age Takalamakan bows were made of a different cervid which lived in their mountains.

Probably, the earlier, long-draw horn crossbows in Europe were more like horn handbows in western Eurasia than the horn crossbows from the 15th century and later which have been dissected or X-rayed (the article about Ulrich V of Würtemberg's crossbow is in the public domain, but the specific link is not -edit).

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Jonathan Dean




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PostPosted: Fri 26 Mar, 2021 2:43 pm    Post subject:         Reply with quote

Jean Henri Chandler wrote:
I think Christine de Pisan actually may have something on this too in her war book but I can't remember, I'll need to scan that book again.


If I'm thinking of the same passage you are, she mentions that English archers practice against barges at a range of 600 feet (213 yards if she meant Parisian feet). I don't recall her giving a range for crossbows, though. That broadly tallies with 16th century sources (including Henry VIII's archery law), which put the maximum range of a bow with a livery arrow at 220 yards.

The crossbow targets and ranges are interesting. I don't believe we have anything similar from England - although apparently wherever there are pairs of butts they're generally 70-100 meters apart and a early 16th century Venetian source suggests English targets were ~25cm in diameter - which is a shame.
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Andrew Gill





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PostPosted: Fri 26 Mar, 2021 3:12 pm    Post subject:         Reply with quote

Thanks Jean and Sean. Some good information!

Jean, I take your point about faith - I'd perhaps use the word "trust" instead, but I understand what you are saying.
For what its worth, I don't believe that people of the renaissance were any less reliable observers or recorders in this regard than modern people - I mistrust both equally. No measurement is ever perfectly accurate, and no observer is perfectly reliable. We always need to cross-check from different sources and different approaches. I tell my students that if they are to be good researchers, they should question and check everything, including what I tell them.

The range data which you did post now is already rather useful. If I understand you correctly, we can say with reasonable certainty that between 270 and 300m was considered outside crossbow range in the early 1400s? I suppose the question then becomes what they considered safe from crossbow bolts, ie. no crossbow bolts land beyond this point, or they might still reach here, but have lost so much energy that they're not much of a threat. Do any sources that you know of comment on this? I can now check various scenarios and see how much energy the crossbow bolts retain at these distances - maybe effective range and maximum range are not very different, maybe they are. This won't give us certainty, of course, but hopefully it gives some more insight. Naively, though, it actually seems pretty close to modern range measurements? Tod shot about 250 or 260m, Lebel estimated about 270m, and Andreas Lebel got about that much with his 1200lb horn bow, though with a much heavier bolt, I admit (which does make a big difference). Or am I missing something?

The accuracy data is quite impressive and pretty conclusive - but I didn't really have any quibble on that score for military or hunting crossbows at least.

Sean, thanks for the link to the Paston letters. Those look very interesting indeed! I had a look at your website and found lots of great stuff. The information on the italian crossbow-guild rules was fascinating. It gives a little window into the sort of maintenance that horn crossbows required, and the sort of sharp practise that was presumably common enough to need to banned. It sounds like they were particularly fiddly and temperamental pieces of equipment, even by the standards of the day. It was also interesting that some kinds of damage seem to have been considered irreparable. For these reasons alone, I'd probably have considered getting a steel bow if I could (or at least I thought so until you mentioned them shedding steel splinters -eek!).

Andrew
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Jean Henri Chandler




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PostPosted: Fri 26 Mar, 2021 5:45 pm    Post subject:         Reply with quote

Andrew Gill wrote:

Jean, I take your point about faith - I'd perhaps use the word "trust" instead, but I understand what you are saying.
For what its worth, I don't believe that people of the renaissance were any less reliable observers or recorders in this regard than modern people - I mistrust both equally. No measurement is ever perfectly accurate, and no observer is perfectly reliable. We always need to cross-check from different sources and different approaches. I tell my students that if they are to be good researchers, they should question and check everything, including what I tell them.


Right, but there is a limit to that, I don't think you understand the scale I'm referring to. I don't plan for the possibility of water not coming out of my tap unless there are special circumstances. There is always a possibility that it might not, but experience has taught me that it usually will.

Similarly, it is ludicrous to me to assume that records across centuries and hundreds of different countries in 20 or 30 different languages and dialects are all wrong by a wide margin. It's on the level of a Flat Earth conspiracy. You have too many different people writing these things from two many different backgrounds and in too many different contexts. It's not like some outlier thing like Sir John of Mandeville's fantastic tales or some bizarre grimoire, it's prosaic, basic, routine military data. I think the notion that this is likely springs from the sort of misunderstanding of the period that I alluded to with the ten pound swords, armor too heavy to lift out of the muck, and all the other cliche's from the era.

Quote:

The range data which you did post now is already rather useful. If I understand you correctly, we can say with reasonable certainty that between 270 and 300m was considered outside crossbow range in the early 1400s? I suppose the


See, this is where it gets complicated. Those particular (Teutonic Order) references were between 270 and 300 ells, not meters. There is some reason to believe they were referring to English ells, which would be ~45 inches, so 300 ells could mean 340 meters, or they might be referring to French Ells (51 inches) which would make it 386 meters, or one of the many German ells which range from 15 to 31 inches (which would mean roughly 100 to 232 meters respectively).

But the range of roughly 300-350 meters figure is fairly typical for early to mid 15th century references of this type. The crossbows do seem to have been getting gradually stronger or more effective over time, (and guns were getting better too) so they kept revising these kinds of estimates upward.

The other ambiguity is the context of what that distance refers to. The gist is that it's the distance at which one is relatively safe from being killed (but not necessarily safe from being wounded) by crossbows. This is where they would typically set up the fascine and mantlets for the feldschlange (long range field culverin or basilisk). So the idea is that someone walking between them or lifting their visor won't easily get killed. They did in fact get wounded however doing exactly that. That was how Henry V got shot in the face with an arrow (from a longbow) at the battle of Shrewsbury in 1403 when he lifted his visor. This is why it was important to quantify these distances.

The same happened to some of the Teutonic Knights and their Crusader guests during the siege of Vilnius in 1390 at a distance of 250 ells, where they thought they were safe from the typical Lithuanian bows and thrown missiles- but the Lithuanians had some Bohemian and German crossbowmen working for them. During the sieges this was also incidentally at the maximum range for the English longbowmen Henry of Bollingbroke (future King Henry IV) had brought with him for the Crusade.

Similarly the Wroclaw / Breslau manuscript refers to the distance within which they could with some reliability kill men and horses. In this case it's more definitive. The point was specifically that the defenders on the wall could kill anyone making it past the first line of outer defenses.

So while superficially you could say yeah sure 270 meters sounds close to what we are getting - but that isn't the point at which the bolt feebly falls to the grass completely spent, it refers to the effective range, or the danger range in other words. The German records also refer to loft schüß, which were shots made at a very high angle, which shot further but only for harassing or signalling purposes - often using special bolts like the bremsen (gadfly) one of the whistling bolts meant to scare horses (also used for signalling). That was one of the tricks they learned from the Mongols.

Quote:
The accuracy data is quite impressive and pretty conclusive - but I didn't really have any quibble on that score for military or hunting crossbows at least.


My understanding is that both for the accuracy at either 50 or 90 meters or for the effective range figures (according to my interpretation of them) referred to above, you need higher velocity than we are currently getting with replicas, in fact closer to the 80 m/s you mentioned (which is why that caught my eye). I've seen estimates of 80 - 100 m/s. Andreas Bichler was apparently close to this in 2016 at 69 m/s, so he may have surpassed it by now. I don't know of anyone else who has done that well yet with a medieval type (i.e. short powerstroke etc.) crossbow of either composite or steel prod. It's quite a recent development, in other words.

I should also add, that the figures I've quoted seem to be for the standard heavier military crossbows, as the larger 'wall crossbows' like what Ralph Payne Gallwey seem to be another special case.

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Bartek Strojek




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PostPosted: Sat 27 Mar, 2021 3:23 am    Post subject:         Reply with quote

From what I've seen, Bichler famous 190+J, 69.8 m/s shots were made with pretty hefty, 81 g bolts.

So, quite possibly, he could have came close, or surpass it with lighter ones, only he (?) knows obviously.

Adam Karpowicz needed arrows below 40g to surpass 80 m/s with very powerful and fast Turkish bows, while he was going at almost 55 m/s with 100g arrow.

https://www.atarn.org/islamic/akarpowicz/turkish_bow_tests.htm

So doing very rough math, if reducing arrow weigh to just ~30% (34g) drops the efficiency by 15%, then reducing bolt weight to this ~34 g would drop efficiency by about 12.5%.

We would then still be looking at about 170J with 85 m/s velocity. Lots of assumptions though, particularly assuming that this crossbow would be as phenomenally efficient with lighter arrows as this turkish bow.

Given the weight and bulk of 1200 pounds prod it may not be the case, hard to say.

As mentioned, Tod's steel bows so far seem to have very limited efficiency with smaller bolts, barely any difference in velocity between 80 and 125 gram projectile.
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