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Ryan S.
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 Posted: Thu 14 Apr, 2022 6:12 am Post subject: |
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In regard to prod material, is it the elasticity of the material that is important?
As far as effectiveness vs. efficiency, there is a limit to how much an increase in efficiency leads to an increase in effectiveness. For example; There is no use in being able to shoot farther than you can see. Ideally, you only need to be able to shoot farther than your enemy. Second, you only need for the bolt or arrow to pierce the armor and enter the target's body, coming out the other side is only useful if the bolt is still capable of wounding another enemy behind the first one.
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Jean Henri Chandler
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| Posted: Thu 14 Apr, 2022 7:25 am Post subject: |
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| Sean Manning wrote: | | Jean Henri Chandler wrote: | | The thing is we had a lot of 'back of the envelope calculations, many dating from the 70s, which claimed that swords could break your ribs and knock you out or give you brain hemhoragges through plate armor |
Which? All the claims like that I can remember are by innumerate, inexperienced people and they make anyone with physics training sad. At best people try things, don't get the results they want, and hand-wave about how blunt trauma could be a factor rather than trying to model it.
| Quote: | | Then we had all these assurances that medieval swords were 'sharpened crowbars', yada yada. Now we have Peter Johnsson. |
Again, by whom? And how do they compare to the experts I referred you to?
We all have our opinions, but if you want to convince other people, you need to provide evidence they can access and show that you understand why they hold the views that they do.
Mark Millman said some very important things that a weapon can be less efficient at sending stored energy down-range but not less effective so I won't repeat them. |
I'm not saying anything definitively about how these weapons performed, except to note that I don't yet see any real evidence thus far that medieval steel prod crossbows performed in any way less efficiently OR effectively than composite / horn prod crossbows. The most likely reason for the difference in performance of Bichler's weapons, IMO, is that he really did his research. You can't (apparently) make a functional composite prod crossbow that will even hold together for more than 2-3 shots without doing a lot of research first.
I have posted many period records and images on this forum, some in this thread and quite a bit in various others on this same topic.
As far as I can tell, the notion that the steel prod crossbows were less efficient is due to a few youtube videos made with modern replicas that are very... modern in design and construction.
I'm ready to be convinced otherwise in the face of actual evidence, but again, I have yet to see that. Meanwhile the records I'm looking at (some of which, again, I have posted in various other threads on this forum) indicate performance closer to what Bichler is starting to get. I don't see any reason to assume they are wrong, so far. Nor do any of them make any distinction in power or effectiveness between steel and composite prod weapons, except to note that the steel ones can snap in the cold. They* do, however, distinguish quite a bit between various grades of crossbows, as classified mainly by the spanners they used. They also had a special category for the wood prod 'knottelarmbrust') types which were basically rated as munitions grade weapons used only for defense of strongholds. Sven Ekdahl is a good source on all this (I posted one his essays several times previously).
*for example, in the records of the Teutonic and Livonian Orders, and also in town council records of Krakow and Nuremberg
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Leo Todeschini
Industry Professional
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| Posted: Thu 14 Apr, 2022 9:21 pm Post subject: |
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Apologies for not joining in here, but this is very (excellently) in depth and I just don't have time right now to engage with the level of consideration required to further it, but I may be able to help a little on the steel bow side.
Jean, although I do make my bows using modern methods and mess about with them on You Tube, please don't dismiss them quite so fast as there is much to learn from them.
To keep the cost as low as I can, some of my cheaper bows use bows that are single tapered and we can dismiss those from this discussion. However my heavier and higher end bows use bows that are double tapered and these are of interest here.
If we take the example of a 900lbs windlass bow. My bow has a width of around 700mm, which is within historic range. A taper in both directions down to around 60%, within historic range, a brace of around 120mm which is within historic range, does not reflex, which is normal, has a draw length of 160mm which is within historic range and the string only drags on the stock very slightly and a linen string. What is significantly different here to historic examples?
They shoot bolts of around 75- 80g
Where it does differ is here. The nut is metal which for heavier military bows was sometimes the case, I do it out of ease as antler for nuts is very hard to find.
I hope that helps
Secondly is the bow temper. They tempered hard and this can be attested by broken bows and talk of dangerous in cold weather and I suspect in the very short draw lengths that we see historically. From my own and my customers safety I am not prepared to do this, so I temper high, so they will bend before they break. This will of course change the characteristics of the bow, but in honesty I have been unable to find out to what extent or even in what way they would differ. However I have taken the same bow and tempered it medium and shot it and then tempered it high and it made no discernible difference to me.
So as far as my experience takes me, I suspect that bows do not perform as well a historical ones and I would be very arrogant to think they would, but I also believe with the one caveat of temper, that mine perform in manner that is close, as I cannot see where significant differences are.
I hope that helps.
Tod
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Ryan S.
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| Posted: Fri 15 Apr, 2022 12:52 am Post subject: |
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| Leo Todeschini wrote: |
Secondly is the bow temper. They tempered hard and this can be attested by broken bows and talk of dangerous in cold weather and I suspect in the very short draw lengths that we see historically. From my own and my customers safety I am not prepared to do this, so I temper high, so they will bend before they break. This will of course change the characteristics of the bow, but in honesty I have been unable to find out to what extent or even in what way they would differ. However I have taken the same bow and tempered it medium and shot it and then tempered it high and it made no discernible difference to me.
So as far as my experience takes me, I suspect that bows do not perform as well a historical ones and I would be very arrogant to think they would, but I also believe with the one caveat of temper, that mine perform in manner that is close, as I cannot see where significant differences are.
I hope that helps.
Tod |
That is very interesting. Do you know why they used a low temper? Was it because they didn't know how to make a high temper, or rather they wanted a harder because it shoots harder? As far as your test with the medium temper crossbow, did you measure the speeds, or just eyeball it?
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Ryan S.
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| Posted: Fri 15 Apr, 2022 1:22 am Post subject: |
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| Jean Henri Chandler wrote: |
I'm not saying anything definitively about how these weapons performed, except to note that I don't yet see any real evidence thus far that medieval steel prod crossbows performed in any way less efficiently OR effectively than composite / horn prod crossbows. The most likely reason for the difference in performance of Bichler's weapons, IMO, is that he really did his research. You can't (apparently) make a functional composite prod crossbow that will even hold together for more than 2-3 shots without doing a lot of research first.
I have posted many period records and images on this forum, some in this thread and quite a bit in various others on this same topic.
As far as I can tell, the notion that the steel prod crossbows were less efficient is due to a few youtube videos made with modern replicas that are very... modern in design and construction.
I'm ready to be convinced otherwise in the face of actual evidence, but again, I have yet to see that. Meanwhile the records I'm looking at (some of which, again, I have posted in various other threads on this forum) indicate performance closer to what Bichler is starting to get. I don't see any reason to assume they are wrong, so far. Nor do any of them make any distinction in power or effectiveness between steel and composite prod weapons, except to note that the steel ones can snap in the cold. They* do, however, distinguish quite a bit between various grades of crossbows, as classified mainly by the spanners they used. They also had a special category for the wood prod 'knottelarmbrust') types which were basically rated as munitions grade weapons used only for defense of strongholds. Sven Ekdahl is a good source on all this (I posted one his essays several times previously).
*for example, in the records of the Teutonic and Livonian Orders, and also in town council records of Krakow and Nuremberg |
I believe the efficiency here is talked about here is bow efficiency. When an archer draws a bow, it stores a certain amount of energy (the draw weight) this energy is released when the arrow is fired. However, not all the energy is transferred to the arrow, some of it is transferred to the bow and is essentially lost and is wasted. A more efficient bow gives you more firepower(is that the right word?) for the same draw weight.
A modern engineer should be able to make some theoretical statements about the relative energy efficiency of steel vs. horn prods. That is not practical evidence, but it is evidence. It may not convince you, but it does lend weight to certain theories. I am not sure that "steel prods are less efficient" actually conflicts with the idea that "steel and horn crossbows preformed the same" The difference in efficiency might be small to begin with, and other changes could compensate. Maybe size is just a bigger factor.
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Jean Henri Chandler
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| Posted: Fri 15 Apr, 2022 12:09 pm Post subject: |
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| Leo Todeschini wrote: | Apologies for not joining in here, but this is very (excellently) in depth and I just don't have time right now to engage with the level of consideration required to further it, but I may be able to help a little on the steel bow side.
Jean, although I do make my bows using modern methods and mess about with them on You Tube, please don't dismiss them quite so fast as there is much to learn from them. |
I wasn't dismissing your work specifically Leo, I didn't mention anyone specifically in fact, and as I noted upthread, I like the modern replicas a lot, yours included, and I like watching the experiments on YouTube. But I also do think there is a problem with it, which is more about how they are perceived.
You and I have discussed these matters several times over the years, and you have always been forthright about what you did and didn't know, and what you did and didn't do with your replicas, and so on. I'll also add that I've never made anything as beautiful as one of your blades or crossbows, so you can certainly be proud of your work, it's certainly impressive to me.
| Quote: | To keep the cost as low as I can, some of my cheaper bows use bows that are single tapered and we can dismiss those from this discussion. However my heavier and higher end bows use bows that are double tapered and these are of interest here.
If we take the example of a 900lbs windlass bow. My bow has a width of around 700mm, which is within historic range. A taper in both directions down to around 60%, within historic range, a brace of around 120mm which is within historic range, does not reflex, which is normal, has a draw length of 160mm which is within historic range and the string only drags on the stock very slightly and a linen string. What is significantly different here to historic examples?
They shoot bolts of around 75- 80g
Where it does differ is here. The nut is metal which for heavier military bows was sometimes the case, I do it out of ease as antler for nuts is very hard to find.
I hope that helps
Secondly is the bow temper. They tempered hard and this can be attested by broken bows and talk of dangerous in cold weather and I suspect in the very short draw lengths that we see historically. From my own and my customers safety I am not prepared to do this, so I temper high, so they will bend before they break. This will of course change the characteristics of the bow, but in honesty I have been unable to find out to what extent or even in what way they would differ. However I have taken the same bow and tempered it medium and shot it and then tempered it high and it made no discernible difference to me. |
Before I get into details, let me say this. It is perfectly rational to be cautious in making such powerful weapon replicas. There was indeed a risk of crossbow prods snapping historically, so much so that some of the Schützenfest regulations stipulate that prods had to be wrapped in wire before shooting so as to minimize risk to the audience. There is also no real need in the modern world for a crossbow that shoots 70 or 80 m/s bolts. They are not used for military purposes, you don't need that much power for hunting, and certainly not for target practice. It really just makes the weapons more dangerous.
Where there IS potentially a need for such weapons, which would I think require a deeper dive into the physical properties and methods of construction of the antiques, is for academic / research purposes. If you were interested in pursuing that further I think you could collaborate with an academic, but I'll circle back to that later.
First lets look at some details.
I suspect the temper / heat treatment may be very significant, though it could also be a matter of the steel used, or something else. If you will bear with me, I will cite two examples to do with armor, just as a kind of analogy.
In the famous Graz firearms tests in Austria in the 1980s, they shot an antique pistol from 7 meters at a piece of 16th Century horse armor, 2.8mm thick, and then shot the same pistol at a piece of modern rolled steel, 3mm thick. The bullet penetrated both pieces but after going through the antique armor, it was spent and didn't puncture the sandbag underneath. The bullet that hit the modern steel plate passed right through and went deep into the sandbag. The difference was most likely the heat treatment, or possibly the composition of the steel.
Similarly, in the NOVA documentary "Secrets of the Shining Knight", they shocked everyone, including such experts as Dr. Alan Williams (of 'Knight and the Blast Furnace' fame) by producing a steel cuirass which resisted a musket ball from a powerful musket at a very short distance of about 15 paces. In this case, not knowing precisely what the factor was that made the Greenwich armor what it was, they went so far as to literally smelt their own iron in a bloomery as a starting point. The armor was made as closely as possible to the methods used in the 16th Century. The results surpassed what we expected to see based on modern materials science.
Another even more far out analogy that probably nobody will credit, would be the now famous 1,000 year old eye remedy known as Bald's Eyesalve. A fairly simple recipe found in an ancient manuscript from an English monastery using garlic, onions, wine, ox gall, and rennet was said to cure eye infections. A grad student, more or less on a whim, decided to recreate it and see if it worked. It turned out, as many now know, that it did work and it in fact kills the deadly antibiotic resistant MRSA bacteria very efficiently. This naturally sparked a lot of scientific interest, since MRSA (among several other similar bugs) is a big problem now in hospitals and so on. They reproduced the test and based on modern perceptions, attempted several times to isolate what single element from garlic or onions or rennet actually had the anti-microbial effect, so they could synthesize it into a pill. But it turns out, there was no one element. The best results were obtained by following the recipe as closely as possible and using the combination of all the elements, as well as the precise time-intervals etc..
I mention this not to imply that there is anything magical about medieval armor or potions, but rather to suggest that when it comes to certain technologies which were common then and are much less common or important today, like crossbows, we may have actually lost some of the technological and cultural 'software' which went into making the most effective versions.
One final example I would cite would be the strange properties of wootz steel. I'm not going to get deep into that as most reading this know what I mean, except to point out that due apparently in part to some unusual trace elements present in the clay used to make the crucibles used in processing the steel, wootz steel blades have properties which are, to say the least, unexpected in modern materials science (in terms of the carbon content of the steel). In particular as regards 'springiness'.This may possibly reflect on the characteristics of the steel self-bows made in that part of the world.
| Quote: |
So as far as my experience takes me, I suspect that bows do not perform as well a historical ones and I would be very arrogant to think they would, but I also believe with the one caveat of temper, that mine perform in manner that is close, as I cannot see where significant differences are.
I hope that helps.
Tod |
It does help and I greatly appreciate your candor and openness about this. Where i see a problem is that given the popularity of your YouTube videos, combined with the near total lack of other information about a lot of the things you cover (like short powerstroke crossbows) the subtleties that you refer to above are often lost on your audience. There isn't much else besides your videos and other similar ones by other replica makers, and meanwhile there is a dearth of serious academic research on these weapons, let alone accurate popular literature, which means that a lot of people take your YouTube videos as the equivalent of going to the past in a time machine.
Is there a difference between your replicas and military grade weapons from four to six centuries ago? We don't know, but as you note, there probably were. Bichler's tests with horn prod weapons tell us there may be further to go, as do the period records, if there were a reason to do so. Assuming the older types did perform better, what would the difference be? Again we don't know. Elements like the precise temper of the prod, the exact type of steel used down to trace elements, the precise shape of the prod down to fine details, the type of nut (I think most historical ones were horn or ivory right?), and I believe in the past you and I had discussed the 'string' (cord?) used as well, any of these or some combination of them could make a significant difference. We just don't know.
(Incidentally, deer are very ubiquitous in the US I can promise you, and a lot of my friends hunt, let me know if you need some deer horn I may be able to get you some!)
Since you do seem to like doing those experiments, I wonder if you might be interested in partnering with some academics, museum curators and so on, to do a more serious survey and some 'next level' experiments? I know you are friends with a lot of people in these realms already. You wouldn't have trouble meeting others. Maybe NOVA would be interested in doing a film. 
Anyway, I am trying to walk a fine line here. I don't dismiss what you do, I enjoy watching your videos. I am also routinely approached by people who have seen one of them and half-understood it, and begin lecturing me about things I've studied for 20-30 years! But such is life.
I get the idea that you like to learn about these things. But of course you are also very busy with many projects and keeping your shop going. My instinct would be to dive deeper, expand the dataset. There are at least hundreds, probably thousands of antique crossbows from the era we are referring to all over Europe. It would be fun to see some up close, wouldn't it? Maybe stick a few in an electron microscope like Alan Williams did with armor. Maybe even shoot some like Payne-Gallwey did. I would certainly be fascinated to see the results...
Jean
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Benjamin H. Abbott
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| Posted: Sat 16 Apr, 2022 7:42 am Post subject: |
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Double post because of some technical issue. Please delate. The site has been very slow for me lately.
Last edited by Benjamin H. Abbott on Sat 16 Apr, 2022 8:05 am; edited 2 times in total
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Benjamin H. Abbott
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| Posted: Sat 16 Apr, 2022 7:43 am Post subject: |
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| Jean Henri Chandler wrote: | | In the famous Graz firearms tests in Austria in the 1980s, they shot an antique pistol from 7 meters at a piece of 16th Century horse armor, 2.8mm thick, and then shot the same pistol at a piece of modern rolled steel, 3mm thick. The bullet penetrated both pieces but after going through the antique armor, it was spent and didn't puncture the sandbag underneath. The bullet that hit the modern steel plate passed right through and went deep into the sandbag. The difference was most likely the heat treatment, or possibly the composition of the steel. |
Unless there's another version of the paper in question, this isn't accurate. I'm looking at "Material Culture and Military History: Test-Firing Early Modern Small Arms" by Peter Krenn, Paul Kalaus, & Bert Hall, published in Material History Review 42 (Fall1995). While this piece does compare the tests of the 2.8-3mm 16th-century horse armor & modern 3mm mild steel, it says they used a different weapon for each test & also describes the test conditions as slightly different (9m vs. 8.5m, soap block vs. sandbag, etc.). Additionally, the flintlock "musket" STG 1288 shot against the 3mm modern steel & two layers of linen "penetrated only a short distance" into the soap block behind according to the authors, though it does say this shot through steel by STG 1288 left a 25 cm3 wound cavity while a shot from the same 9m range from the flintlock pistol STP 1128 only left a 23 cm3 wound cavity against an unprotected soap block. Those are pretty small wound cavities, so I'm wondering how tough that soap block was or if something went wrong with STP 1128's shot.
| Krenn, Palaus, & Hall wrote: | The final set of tests undertaken focussed on the protection offered by body armour. Modern steel plate 3-mm thick (of the same standard as employed in the indenting test tabulated above), was lined with two layers of linen and placed before a soap block; the entire target was mounted nine metres from the muzzle. Flintlock musket STG 1288 (responsible for a 369-cm³ cavity in an unprotected target at nine metres) was fired again. The bullet penetrated the metal and the linen and entered die soap target. It penetrated only a short distance, however, and left a small-diameter cavity of only 25 cm³. There was splintering of the shot and the armour plate, leaving splinters some 80-mm deep in the cavity. A comparative test involved an unprotected soap target shot over a nine-metre range with one of the early modern pistols (STP 1128). In this test the unprotected target sustained a wound cavity of only 23 cm³ . This is virtually identical to the cavity in the protected target shot with a musket.
The most dramatic of the Austrian tests involved a pistol shot fired at a 16th-century breastplate from a distance of 8.5 metres. The breastplate was a fragment of a piece meant to protect horses; it was manufactured in Augsburg between 1570 and 1580, and made of 2.8-3.0-mm thick cold-worked mild steel (hardness 290 HB). It was mounted on a sandbag covered with two layers of linen (meant to simulate a normally clothed wearer). The pistol was RP 2895, with a shot weighing 9.54 gm and a calculated energy/surface ratio of 838 J/cm² at the muzzle, and 550 J/cm² at 30 metres. (This figure expresses the energy in die shot in a manner independent of the ball's size.) At the instant of impact, the ball was travelling at a calculated speed of 436 m/s and with a kinetic energy of 907 Joules. The breast-plate was completely penetrated by the bullet, but the shot lost all its kinetic energy in piercing the armour. The ball was highly deformed, lost 24 per cent of its initial mass, and was found lodged in the linen. It had not penetrated the sandbag. There were no secondary splinters from the armour plate to cause damage either. The experimenters judged that a human being struck in the same manner would have survived with only bruises to his chest. The fact that modern mild steel failed to absorb all the bullet's kinetic energy, while the 16th-century breastplate did, can probably be attributed to the early armourer's skill at cold-working the breastplate and hardening its surface. |
While far from a musket in the late-16th-century sense, STG 1288 is a much larger & more powerful firearm than RP 2895 used against the 16th-century armor. In the tests according to the article, STG 1288 shot with just over three times the kinetic energy at the muzzle. It penetrated (or indented) 3mm into the modern mild steel target at 30m while RP 2895 managed 2mm. So it's not surprising that a more powerful firearm that penetrated more at 30m also penetrated more at 9m or 8.5m. STG 1288 shoots larger bullets but the difference in kinetic apparently steel makes it penetrate better than RP 2895. Because of this difference in the weapons used, it's not clear that the 16th-century horse armor performs better than modern mild steel. That may well be true, but the described tests don't prove it.
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Jean Henri Chandler
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| Posted: Mon 18 Apr, 2022 6:20 am Post subject: |
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You may have a point about the difference between the two firearms, but that was not just my observation. My comment was based on the analysis here:
https://journals.lib.unb.ca/index.php/mcr/article/view/17669/22312
This is a direct quote which is also in the passage you highlighted:
The fact that modern mild steel failed to absorb all the bullet's kinetic energy, while the 16th-century breastplate did, can probably be attributed to the early armourer's skill at cold-working the breastplate and hardening its surface.
So the experimenters themselves seemed to draw that conclusion. There are of course other factors which effect penetration. Size of the bullet for example.
What I am calling for is more systematic experiments of the type they did at Graz. We learned a lot from their extremely rigorous tests, but these are rarely done. They discovered many other interesting things that were unexpected, such as that a couple of the pistols were far more accurate than a smoothbore weapon of that type should be, by our understanding . One, the flintlock STP 1128, was 99% accurate at 30 meters compared to 99.5% for the modern Glock they tested as a baseline, and the flintlock delivered twice the initial energy. Another wheellock pistol RP2895 was 85% accurate. This is far better than we would expect. - a direct quote from the report was "much better than we might have expected." But we don't yet know why this was the case.
I do think this forum is having serious trouble, I had to try to post this several times over a couple of days before it would take. Is there still a donation thread? I'm worried about the forum, it's such an incredibly valuable resource for so many different communities, we really should not let this go away.
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Ryan S.
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| Posted: Wed 27 Apr, 2022 12:55 am Post subject: |
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I recently read Holger Richter´s Die Hornarmburst it is about horn crossbows and mentions wood cross bows more than steel bows. Most relevant to this discussion is the terminology for crossbows. According to Richter, the meaning of most of the terms are unclear (For example, Knottelarmburst). However, it seems to imply that steel crossbows weren't in use in the Middle Ages, so that most of the terms refer to wood or horn bows. That was also implied in the paper I linked by Adam Thiele. Although after rereading it, the paper by Thiele, although containing some useful technical information, seems to have some factual errors that have already been mentioned in this thread.
I would also like to note that Bichler has also built steel crossbows, although in one case it was a reproduction of a horn bow.
| Jean Henri Chandler wrote: |
I think Bartek is wise to point out the work of herr Bichler. I'd also like to contextualize this by saying that Bichler is an academic who has made a very deep study of the historical methods for making crossbows. This is the big difference, IMO, between his results and those of some of our friends who have made replicas without really looking into let alone using historical construction methods. It is no small thing to emulate the accumulated skill of multiple generations of artisans or a lifetime of honing a craft. |
Where do you get the idea that Bichler is an academic? I have not been able to find out what his actual job is. The website of the club of which he is the president, describes the club as "a small group of people, who do work non-professionally with the theme Middle Ages." He is formally styled "Ing. Andreas Bichler B.A." Which means he is an engineer with a bachelor of the arts. I would suspect an Austrian academic to have a title like Professor Doctor (in German both titles are used together). The only description of his background is a renowned bowmaker. I can’t find out if he sells his bows, so it is possible that he is an amateur.
edit. I have confirmed it, Andreas Bichler is a hobby historian. So, I am not sure why you think someone needs to be an academic to build historically accurate crossbows.
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Benjamin H. Abbott
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| Posted: Tue 25 Apr, 2023 6:26 am Post subject: |
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The latest video featuring Andreas Bichler indicates the potential effectiveness of composite prods. A 210kg crossbow spanned by the belt delivered 94-105 J at 52-57 m/s, while a 330kg crossbow spanned by cranequin delivered 138-151 J at 63-69 m/s. The heavier crossbow outperforms most 160lb yew warbows.
I suspect the 330kg crossbow here could be spanned from the belt by someone sufficiently athletic, & that historical warriors spanned such heavy composite crossbows from the belt. Spanning heavy crossbows in this fashion is a key feat of strength in the 15th-century text El Victorial o Crónica de don Pero Niño by Gutierre Díez de Games. It describes events from circa 1400.
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Leo Todeschini
Industry Professional
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| Posted: Fri 28 Apr, 2023 4:19 am Post subject: |
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Going back a bit, Ryan S wrote | Quote: | | That is very interesting. Do you know why they used a low temper? Was it because they didn't know how to make a high temper, or rather they wanted a harder because it shoots harder? As far as your test with the medium temper crossbow, did you measure the speeds, or just eyeball it? |
The tests I did took a bow that had been tempered medium and I shot it through a chrono. I then took the same bow, tempered it high and remounted it and shot again through a chrono and it made no difference.
However the whole area I have found perplexing as I have to assume temper temperature is very important but not been able to find anyone who can answer me in this application. Either way my original statement stands, in that I have no desire to run these bows at a lower temper, but ultimately may mean my numbers are not typical.
Tod
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T. Kew
Location: London, UK Joined: 21 Apr 2012
Posts: 256
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| Posted: Fri 28 Apr, 2023 10:18 am Post subject: |
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As I understand it, changing the temper shouldn't change the stiffness of a bow - as long as it stays out of the plastic deformation range. If you're bending a softer bow permanently, then a harder bow might shoot stronger if you draw it the same - but it might also just shatter.
HEMA fencer and coach, New Cross Historical Fencing
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Ryan S.
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| Posted: Fri 28 Apr, 2023 11:01 pm Post subject: |
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| Leo Todeschini wrote: | Going back a bit, Ryan S wrote | Quote: | | That is very interesting. Do you know why they used a low temper? Was it because they didn't know how to make a high temper, or rather they wanted a harder because it shoots harder? As far as your test with the medium temper crossbow, did you measure the speeds, or just eyeball it? |
The tests I did took a bow that had been tempered medium and I shot it through a chrono. I then took the same bow, tempered it high and remounted it and shot again through a chrono and it made no difference.
However the whole area I have found perplexing as I have to assume temper temperature is very important but not been able to find anyone who can answer me in this application. Either way my original statement stands, in that I have no desire to run these bows at a lower temper, but ultimately may mean my numbers are not typical.
Tod |
Thanks for the answer, I know that you are very busy. I know that steel hand bows are also known to be less energy efficient, although I have been unable to find actual numbers, and I have read the modern composite bows with metal mixed with other materials are super efficient. I have learned a lot since I first posted, but my knowledge is still limited. Still, my understanding of the topic give me no reason to expect that steel prods would be more efficient.
Adam Thiele in his replica, the prod was heated to 860 degrees C and then hardened it in oil. Afterwards, it was heated again to 450 degrees. He says that made it flexible, but doesn’t comment on the hardness. Unfortunately, he didn’t test either replica.
Steel crossbows are that old of a technology. They not only came later, but they were used longer. After they were no longer used in war, they were used for hunting and shooting contests. Although the poundage was less, and the forms changed, a manufacturing technique for more efficient prods would still have been useful. I don’t see why it would have been lost.
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Pieter B.
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| Posted: Sat 29 Apr, 2023 3:41 am Post subject: |
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| Leo Todeschini wrote: | Going back a bit, Ryan S wrote | Quote: | | That is very interesting. Do you know why they used a low temper? Was it because they didn't know how to make a high temper, or rather they wanted a harder because it shoots harder? As far as your test with the medium temper crossbow, did you measure the speeds, or just eyeball it? |
The tests I did took a bow that had been tempered medium and I shot it through a chrono. I then took the same bow, tempered it high and remounted it and shot again through a chrono and it made no difference.
However the whole area I have found perplexing as I have to assume temper temperature is very important but not been able to find anyone who can answer me in this application. Either way my original statement stands, in that I have no desire to run these bows at a lower temper, but ultimately may mean my numbers are not typical.
Tod |
Did you find a difference in drawweight between the different tempers? If all is right you shouldn't!
If normal physics apply the temper or hardness of a spring shouldn't have much of an influence on the stiffness or force needed to bend a spring. In other words an annealed or a tempered steel spring should fire a bolt at the same speed provided both aren't bent beyond the elastic limit.
A video does a better job illustrating this: https://www.youtube.com/watch?v=SIFfY-MS3yA&ab_channel=moodlemech
You can see how both the hardened and unhardened spring take the same amount of force to deform an equal distance. Where hardness does play a part is in raising the elastic limit. The harder spring can be bent further while still springing back into shape whereas the softer spring takes a set and remains bent. Further to this hardness influences how a spring would 'fail' by altering ductility and brittleness.
I think something like armor and crossbows differ with regards to hardness requirements. For armor you want something moderately hard. Sufficiently hard to resist deformation on most impacts but once a sufficiently powerful blow hits it you want good ductility so that it experiences a lot of plastic deformation before fracturing. The raise the total amount of energy required to fracture a plate of armor medium hardness might be best.
With a steel crossbow prod it's only elastic deformation that you are after. Whether it breaks or bends beyond that point doesn't matter much, it is 'broken' beyond that point either way. Of course the user might disagree as you point out. What does matter though is that you wouldn't want to 'over temper' a crossbow prod because it would lower the elastic limit, potentially below the drawlength at which you want it to operate.
Keeping the elasticity high could have other benefits to which we aren't aware. A crossbow might spent a long time under tension as the string isn't removed periodically. Maybe a low temper might increase resistance to it taking a set. Thick and stubby crossbow prods might also benefit from having the lowest temper possible. A thicker piece of steel will experience a greater degree of stretching and compression. In wooden bows the elastic limit is given which is why really thick bows are often made from certain woods. Steel is more variable and perhaps carbon content and tempering were used to produce crossbow prods that couldn't function if made with different carbon contents or hardness.
Below is an 18th century excerpt dealing with the tempering of springs. Note that the author suggests tempering the spring at the lowest temperature possible while also saying different steels require a different temperature. Lastly he does not suggest the lowest temper is the best, merely that it suits this particular steel.
| Quote: | starting by tempering one end the colour which is wanted, and continuing to the other end. This operation is of great importance for the quality of the springs, and the workman must pay the utmost attention to it, since more or less colour fixes the degree of elasticity. In order to know the correct colour of tempering that the steel must have, to make as good a spring as its quality allows, take a piece of a hardened blade, whiten it, and then temper it to a purple colour. That done, fold it on round-nose pliers (Plate 6, Figure 1) and if the blade breaks, (which is common with this colour) it is necessary to heat it more and to advance the colour to blue. If it still breaks, it should be advanced to light blue, to grey, to the colour of dirty
brass, pale red copper, dark red copper, and finally to the colour of slate. If the piece continues to break it must be concluded that this steel is not suitable to make springs. Also, after the tests at these various colours, the steel no longer gives a true sign to recognize its degree of tempering, of heating or of its temperature after quenching. So you can no longer use sight, and the crude tests of burning oil or tallow on them, or seeing in the dark if the steel takes some shades of red, are not reliable.
In general Styrian steel requires less tempering than that of England, and usually it should not be advanced further than pale blue to be quite elastic and unbreakable. But of all steels the best is that made in England from Swedish iron. The operations which follow will show even better the qualities that the steel suitable for making good watch springs must have. |
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Augusto Boer Bront
Industry Professional
Location: Cividale del Friuli (UD) Italy Joined: 12 Nov 2009
Posts: 294
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| Posted: Sun 30 Apr, 2023 8:15 am Post subject: |
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| Ryan S. wrote: | | Leo Todeschini wrote: | Going back a bit, Ryan S wrote | Quote: | | That is very interesting. Do you know why they used a low temper? Was it because they didn't know how to make a high temper, or rather they wanted a harder because it shoots harder? As far as your test with the medium temper crossbow, did you measure the speeds, or just eyeball it? |
The tests I did took a bow that had been tempered medium and I shot it through a chrono. I then took the same bow, tempered it high and remounted it and shot again through a chrono and it made no difference.
However the whole area I have found perplexing as I have to assume temper temperature is very important but not been able to find anyone who can answer me in this application. Either way my original statement stands, in that I have no desire to run these bows at a lower temper, but ultimately may mean my numbers are not typical.
Tod |
Thanks for the answer, I know that you are very busy. I know that steel hand bows are also known to be less energy efficient, although I have been unable to find actual numbers, and I have read the modern composite bows with metal mixed with other materials are super efficient. I have learned a lot since I first posted, but my knowledge is still limited. Still, my understanding of the topic give me no reason to expect that steel prods would be more efficient.
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There's a few resources now on youtube, on various creators' channels regarding draweights, prod composition and their performance.
For example Andreas Bichler's 462 lbs composite crossbow, belt hook pulled, delivers a 58.6 grams bolt at 56.8 m/s, resulting in 94 joules of energy. One of Tod's steel prod crossbows, at 850 lbs, windlass spanned, throws a 60 grams bolt at 54 m/s, thus delivering 88 joules of energy.
It's only one example, but it goes to show how much more efficient composite prods can be compared to steel ones. This is of course without taking into account all the pros and cons of either one (maintenance, cost, production time, weakness to mousture, etc). This is purely an energy comparison.
Armourer-Artist-Blacksmith
www.magisterarmorum.com
Pinterest albums to almost all existing XIVth century armour.
Pinterest albums on almost all existing XVth century Italian armour.
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Ryan S.
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| Posted: Tue 02 May, 2023 1:23 am Post subject: |
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| Augusto Boer Bront wrote: |
There's a few resources now on youtube, on various creators' channels regarding draweights, prod composition and their performance.
For example Andreas Bichler's 462 lbs composite crossbow, belt hook pulled, delivers a 58.6 grams bolt at 56.8 m/s, resulting in 94 joules of energy. One of Tod's steel prod crossbows, at 850 lbs, windlass spanned, throws a 60 grams bolt at 54 m/s, thus delivering 88 joules of energy.
It's only one example, but it goes to show how much more efficient composite prods can be compared to steel ones. This is of course without taking into account all the pros and cons of either one (maintenance, cost, production time, weakness to mousture, etc). This is purely an energy comparison. |
Thanks for the data. The actual numbers help give an idea of the actual difference. You are right about the pure energy comparison. Because you need a spanning device to span a 462 lbs crossbow, it didn’t make much difference to the actual operation of the weapon.
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Augusto Boer Bront
Industry Professional
Location: Cividale del Friuli (UD) Italy Joined: 12 Nov 2009
Posts: 294
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| Posted: Tue 02 May, 2023 9:25 am Post subject: |
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| Ryan S. wrote: | | Augusto Boer Bront wrote: |
There's a few resources now on youtube, on various creators' channels regarding draweights, prod composition and their performance.
For example Andreas Bichler's 462 lbs composite crossbow, belt hook pulled, delivers a 58.6 grams bolt at 56.8 m/s, resulting in 94 joules of energy. One of Tod's steel prod crossbows, at 850 lbs, windlass spanned, throws a 60 grams bolt at 54 m/s, thus delivering 88 joules of energy.
It's only one example, but it goes to show how much more efficient composite prods can be compared to steel ones. This is of course without taking into account all the pros and cons of either one (maintenance, cost, production time, weakness to mousture, etc). This is purely an energy comparison. |
Thanks for the data. The actual numbers help give an idea of the actual difference. You are right about the pure energy comparison. Because you need a spanning device to span a 462 lbs crossbow, it didn’t make much difference to the actual operation of the weapon. |
Well the spanning method does make quite a difference on its operation.
A hook is quicker than a crannequin, and more practical on horse, for example.
Armourer-Artist-Blacksmith
www.magisterarmorum.com
Pinterest albums to almost all existing XIVth century armour.
Pinterest albums on almost all existing XVth century Italian armour.
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Ryan S.
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| Posted: Tue 09 May, 2023 6:03 am Post subject: |
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| Augusto Boer Bront wrote: | | Ryan S. wrote: | | Augusto Boer Bront wrote: |
There's a few resources now on youtube, on various creators' channels regarding draweights, prod composition and their performance.
For example Andreas Bichler's 462 lbs composite crossbow, belt hook pulled, delivers a 58.6 grams bolt at 56.8 m/s, resulting in 94 joules of energy. One of Tod's steel prod crossbows, at 850 lbs, windlass spanned, throws a 60 grams bolt at 54 m/s, thus delivering 88 joules of energy.
It's only one example, but it goes to show how much more efficient composite prods can be compared to steel ones. This is of course without taking into account all the pros and cons of either one (maintenance, cost, production time, weakness to mousture, etc). This is purely an energy comparison. |
Thanks for the data. The actual numbers help give an idea of the actual difference. You are right about the pure energy comparison. Because you need a spanning device to span a 462 lbs crossbow, it didn’t make much difference to the actual operation of the weapon. |
Well the spanning method does make quite a difference on its operation.
A hook is quicker than a crannequin, and more practical on horse, for example. |
Right, but if you are using a crannequin, then the difference between a horn crossbow and a steel one is reduced.
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