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Randall Moffett




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PostPosted: Tue 13 Mar, 2012 6:08 am    Post subject:         Reply with quote

Ben,

Why are you assuming all breastplates of high quality were proofed. The vast majority of high quality armour of the late 15th shows no evidence of this and we only have a few accounts of this. It is not even until mid to late 16th this becomes common with firearms and even then it is questionable at best if they were using charges anywhere near battlefield conditions. As well the bulk of medieval proofing I know of seems to have been done with lighter crossbows, nothing near what Liebel's is likely.

What accounts are you looking at that indicate a windlass crossbow could never penetrate plate. I can think of a few off the top of my head fairly easily. I tend to think of this much like longbows. They have their strengths and weaknesses. I have no doubts under certain conditions a 750lb crossbow could pierce plate under certain conditions. BTW, a 750lb crossbow would need a windlass or canequin to span as the belt orf goats foot tops out well under this. A 750lb crossbow must have been a fairly heavy one. I figure 650-1000lb being about what the upper end personal crossbows got to. Anything past this they either get to large, heavy or both. That said I doubt in the later medieval period anything less than 400lbs was used but not enough research has been done to be sure.

As far as Liebel's numbers. Unless you can disprove them with some real evidence I see no reason why to discount them. Years of solid physics , testing and research in my play book is fairly good evidence. He gives his powerstroke info and how it breaks out as well in one of his tables to make it even easier. I'd certainly read the book before deciding his numbers are off though as his work is fairly solid. I have doubts about a few things but mostly interpretation. I think it is even more likely a high powered crossbow would be able to pierce armour than a bow. The big question to me is how and when.

Timo,

Thank you for the explanation. I will have to interlibrary loan some of these to take a look at them once my current projects are out of the way.

Regarding distance. A heavier bow with a lighter projectile can go further as the arrowguided darts show. Do we have any reason to assume the Turkish arrows always were as heavy or heavier than a Manchu bow?

RPM
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Jean Henri Chandler




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PostPosted: Tue 13 Mar, 2012 9:56 am    Post subject:         Reply with quote

According to Allan Williams, the Milanese were regularly proofing breastplates with the "big" and "little" crossbow at this time (two different grades). I believe that was also common in the Swabian armor centers like Augsburg by the mid 15th C. I've also seen prices from Teutonic Order records and town records from Krakow listing 'proofed' and not proofed, and munitions armor (proofed is about twice as expensive as regular lancer armor)

J

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Benjamin H. Abbott




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PostPosted: Tue 13 Mar, 2012 11:01 am    Post subject:         Reply with quote

Randall Moffett wrote:
What accounts are you looking at that indicate a windlass crossbow could never penetrate plate.


I specified quality plate, though evidence suggest even lower-grade stuff resisted bolts rather well. As far as proofing goes, see The Armourer and His Craft and The Knight and the Blast Furnace. Writing in the middle of the sixteenth century, Fourquevaux considered bows and crossbows equally unable to pierce armor expect perhaps lower-quality harnesses during an close-range barrage. The gun, on the other hand, he noted could pierce any armor. Despite this difference, Fourquevaux still favored the bow and crossbow because of their reliability and accuracy; he gave the example a crossbowman at a siege who got more kills than the five or six best gunners combined. If crossbows had the consistent ability to penetrate good armor, the gun's rapid adoption in the early sixteenth century becomes inexplicable.

Quote:
That said I doubt in the later medieval period anything less than 400lbs was used but not enough research has been done to be sure.


The Spanish used 250-500lb steel crossbows in the Americas. The article claims they've made replicas and tests should be published soon, but I've yet to find the test results anywhere. Barring extraordinary efficiency, there's no way bolts from such crossbows hit harder than arrows from warbows; they'd be lucky to get in the same ballpark. Yet the Spanish apparently employed significant numbers of such crossbows on their warships.

Quote:
As far as Liebel's numbers. Unless you can disprove them with some real evidence I see no reason why to discount them. Years of solid physics , testing and research in my play book is fairly good evidence. He gives his powerstroke info and how it breaks out as well in one of his tables to make it even easier. I'd certainly read the book before deciding his numbers are off though as his work is fairly solid.


I have read the book. If I recall correctly, they're theoretical numbers and not based on performance tests. Also, I remember the two-foot crossbow that Liebel gave a 750lb draw shot 2ft bolts and was dedicated siege weapon rather than a personal crossbow for the battlefield. That would explain the 331 J, because a 2ft bolt goes along with a longer power stroke. But it doesn't say anything about personal battlefield crossbows.

Quote:
I think it is even more likely a high powered crossbow would be able to pierce armour than a bow.


I agree but doubt either pierced quality armor with any reliability.

Quote:
Regarding distance. A heavier bow with a lighter projectile can go further as the arrowguided darts show. Do we have any reason to assume the Turkish arrows always were as heavy or heavier than a Manchu bow?


We know the Turks used much lighter arrows than the Manchus.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Gary Teuscher




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PostPosted: Tue 13 Mar, 2012 12:52 pm    Post subject:         Reply with quote

Quote:
The Spanish used 250-500lb steel crossbows in the Americas. The article claims they've made replicas and tests should be published soon, but I've yet to find the test results anywhere. Barring extraordinary efficiency, there's no way bolts from such crossbows hit harder than arrows from warbows; they'd be lucky to get in the same ballpark.


They may have had a different mix of weapons in the Americas - a different target where armour piercing was not the prime concern.

Not that I think the 250-500 pounders were not used, just the mix could well be different in the americas. This is also a later period, when armour was beginning to be phased out, so lighter crossbows could have been common at this time.

And depending upon drawlength, a 250 pound draw crossbow should be relatively similar to a 100 pound self bow.

The 500 pounder would of course be a fair amount stronger.
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Timo Nieminen




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PostPosted: Tue 13 Mar, 2012 1:27 pm    Post subject:         Reply with quote

Randall Moffett wrote:
Regarding distance. A heavier bow with a lighter projectile can go further as the arrowguided darts show. Do we have any reason to assume the Turkish arrows always were as heavy or heavier than a Manchu bow?


Manchu arrows: 100g

Turkish long-range war arrows: 20g
Turkish short-range war arrows: 40g

Indian arrows seem to be comparable to Turkish arrows in weight. Pant ("Indian Archery") gives a table of weights, which look to average about 30-33g (they vary from 15g to about 50g, with most in the 20s and 30s).

The Korean archery component of the military exam (i.e., most of the practical component) used: "iron arrows", for short-range shooting with a heavy-draw weight bow, from 60g to 240g, a standard target arrow of 32g (presumably similar in weight to standard war arrows), and very short flight arrows, about 30cm long - so these might be perhaps 10-15g.

Lighter arrows give you more speed, and less energy. Whether you get more range depends on drag, but flight arrows are optimised to reduce drag. (Manchu arrows are not; they have very long flights, to stabilise a heavy arrow quickly, for short-range shooting.)

Longer draw lengths mean you need heavier arrows (and they need to be thicker, too, to maintain the same stiffness), so going to longer draw lengths gives you more energy, but not more speed. Thus, not more range. Keeping the same draw length, and increasing the draw weight means you need heavier arrows, but you won't increase the drag by much by making the arrows a little thicker.

So, the high-draw-weight short-draw-length crossbows make sense as long-range weapons. Nice flat trajectories, so easy to use. Keep those pesky besiegers away from your walls, and out of bow range even. The high draw weight doesn't come for free, so there had better be an advantage. (Short draw means you can have short limbs, so light limbs for the draw weight, which means higher efficiency, so you can use lighter bolts, which comes back to giving you more speed, and more range.)

At least some late Chinese crossbows appear to have been much larger. Long limbs, long draw length. These would shoot much heavier bolts than a European crossbow. The optimisation principle seems to have been that once they outrange bows, the crossbow has enough range. For longer range, use light artillery/heavy muskets (i.e., jingals). Han crossbows outranged bows by enough to be able to keep cavalry (i.e., mounted archers) out of range.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Benjamin H. Abbott




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PostPosted: Tue 13 Mar, 2012 1:45 pm    Post subject:         Reply with quote

Gary Teuscher wrote:
They may have had a different mix of weapons in the Americas - a different target where armour piercing was not the prime concern.


Yeah, definitely, though such light crossbows may have been a general-purpose naval weapon. They would have performed as a similar role to bows used a warships. While significantly slower to shoot than bow, light crossbows cocked by a goat's-foot lever could still manage around five shots per minute. And a the crossbow allows for greater accuracy and ability to take cover while shooting than the bow.

Quote:
And depending upon drawlength, a 250 pound draw crossbow should be relatively similar to a 100 pound self bow.

The 500 pounder would of course be a fair amount stronger.


Because of the short power stroke - 5 to 6 inches - only a 500lb version would be likely to perform as well as a 100lb English yew warbow. I'd guess that bolts from the heaviest of these crossbows hit about as hard as the arrows from Turkish horse archers: 80-100 J. We'd have to see actual replica tests to know for sure, of course.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Gary Teuscher




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PostPosted: Tue 13 Mar, 2012 2:02 pm    Post subject:         Reply with quote

Because of the short power stroke - 5 to 6 inches - only a 500lb version would be likely to perform as well as a 100lb English yew warbow. I'd guess that bolts from the heaviest of these crossbows hit about as hard as the arrows from Turkish horse archers: 80-100 J.

A common misconception. This is mixing the idea of a powerstroke with that of a drawlength. You have to compare powerstroke to powerstroke. A longbow with arrows the length of the most common on the Mary Rose has about a 29" draw, corresponding with a 23.5 inch powerstroke if a 5.5" brace, which was also abut the norm.

So it's 23.5/5.5 = 4.27 times the draw length. It would hit with the equivalency of a 117 pound longbow (the 500 pound draw)

That is assuming a 5-6 inch draw also. I'm not sure where this came from, but I think many look at powerstrokes from renaissance hunting bows and apply these to a crossbow.

I'd guess a longer powerstroke, unless someone has a true find of this type of a military bow?
[
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Randall Moffett




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PostPosted: Tue 13 Mar, 2012 6:39 pm    Post subject:         Reply with quote

Ben,

I still think the numbers of proofed armour is likely fairly small. As far as I know 0 remaining armours of high quality show this process. KatBF even recounts this issue. Williams is simply using a town ordiance that requires it for a specific qualification. Seemingly the highest. It would be a mistake to think all high quality armour was made to these specifics. This by no way shape or form means most or even the majority of quality armour was handled in such a way. Of course there is evidence plate of all types did well against bolts, that was not the question. Nor did I ever once say crossbows ever were able to penetrate armour most or even much of the time only that they clearly have and many have the power to do so.

As for the Padre bow there is a great deal of debate as to if it were a standard type of bow for the Spaniards and warfare. Several people have assumed it was for hunting even. Having handled dozens of late medieval and early modern crossbows I know there is a variety of crossbows, both for martial and nonmartial uses. I suppose it could have been specifically for naval warfare but since we know men used specialty bows and crossbows for hunting and such just finding a crossbow does not make it a military one. Hunting would have been fairly vital in many non developed places for food. That said I assume that light, medium and heavy crossbows were used along side ecah other in war because they all had specific strengths and weaknesses. Faster to load a belt winched or goatfoot crossbow but it has no where near the power of a windlass or cranequin spanned one. So for the Padre crosbow I agree they would never get near the 331j initial or 126j on impact at a distance. I just doubt anything near 250-350 and under was intended for war in the late medieval period. I guess it is better than throwing rocks but even with a belt winch one can span a 400-450lb bow relatively quickly.

Liebels numbers are not all simply theoretical but based on various models he created for the testing. That of the crossbow itself based on an actual crossbows so it is not an issue. He does create a system of theoretical values for angle of fire and such and distance but the power is based on his models that he created and mathematical calculations so. You have the single and two foot crossbows mixed up or something. The single crossbows were a composite at 750lbs and the other was steel and 880lbs. His two foot was not the 750lb but was nearly 1800lbs (listed as 800kg). This was clearly a siege engine as he figures it far to heavy for for a man to run about a field of battle with. And of course he mentions one foot crossbows.

I would not argue either penetrates armour the majority of times even but that they did and enough to be more than accidents on occasion.

Timo,

Thanks for the further information. I have to say the world archery scene is very interesting. I have seen some pictures from the late 19th of Machus still using bows and they were indeed fairly massive.

Gary,

Makes sense to me. I think the difficulty in IDing crossbows for war and hunt is perhaps an issue as hunting weapons were made for completely different purposes.

RPM
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Benjamin H. Abbott




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PostPosted: Tue 13 Mar, 2012 6:45 pm    Post subject:         Reply with quote

Gary Teuscher wrote:
So it's 23.5/5.5 = 4.27 times the draw length. It would hit with the equivalency of a 117 pound longbow (the 500 pound draw)


You're saying almost exactly the same thing I'm saying. Arrows from a 117lb English warbow would deliver 86-113 J.

Quote:
That is assuming a 5-6 inch draw also. I'm not sure where this came from, but I think many look at powerstrokes from renaissance hunting bows and apply these to a crossbow.[


Please read the linked article if you have access to it. It includes all the specifications of the type of Spanish crossbow I'm discussing. The goat's-foot levelers in question move the string 5-6 inches. Cranequins tended to do about the same; from what I've seen, 5-6 inches is a common power stroke for at least Renaissance-era crossbows.

Randall Moffett wrote:
You have the single and two foot crossbows mixed up or something.


Last year, you assigned the 331 J figure to Liebel's two-foot crossbow. This also reflects my recollection of the book. I got the draw weight wrong but not the impact energy. The 350-450kg crossbow mentioned by Liebel delivers only 126 J. In short, there's no evidence any medieval or Renaissance personal crossbow managed significantly more than 200 J. The 1200lb crossbow Payne-Gallwey used probably could get up to around 230 J with a heavier bolt, but that's already a borderline siege weapon.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Randall Moffett




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PostPosted: Wed 14 Mar, 2012 6:16 am    Post subject:         Reply with quote

Ben,

Yes that is correct- for impact joules. The 331k is for initial joules on the one foot. If you are going to quote me make sure you're doing it right Wink The 126 joules is at impact for the one foot. So start at, or around 330 and end up at 126j on the other side of the field. Seems fairly logical. Williams through his research indicates on Earlier crossbows, 13th and before, closer to 200J in KatBF, p.919, when it appears. He estimates the impact about half this, which is how he ends up with the conclusion mail yes but not plate. But we can assume with the addition of steel bows and heavier draw bows something much higher than 200J intial, so 331J for later crossbows does seem right, considering the draw weight is many times higher than the one Williams discussed. As well this puts it right around the area where Williams states are needed for armour penetration for impact Joules, KatBF, pgs, 918-930.

As far as PG's crossbow, yes could be. At 18lbs of weight it is a bit heavy to carry around all day but it is borderline but still its draw weight is around the upper weight likely for field crossbows.

RPM
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Jean Henri Chandler




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PostPosted: Wed 14 Mar, 2012 6:57 am    Post subject:         Reply with quote

How much did a 15th Century arquebus weigh? An arquebus a -croc? A 16th Century musket or Caliver?

J

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Benjamin H. Abbott




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PostPosted: Wed 14 Mar, 2012 8:16 am    Post subject:         Reply with quote

Randall Moffett wrote:
The 126 joules is at impact for the one foot. So start at, or around 330 and end up at 126j on the other side of the field. Seems fairly logical.


Actually, no, that doesn't make much sense, nor does it reflect my recollection of the book. Unfortunately, I don't have access to copy at the moment, so I can only go from memory and how others refer to the book on the web. See this thread for how Tomaz Lazar places the initial energy of Liebel's 350-450kg crossbow at 126 J. Could you post a quotation in which Liebel writes that the initial energy is 331 J? None of the arrows tested in The Great Warbow lost anywhere near 62% of their initial kinetic energy at extreme range, so that would be weird. As far as other crossbow numbers, Bartek Strojek cited Die Armbrust by Egon Harmuth. According to that book, a roughly 1000lb steel crossbow shoots a 80-gram bolt at 67 meters per second. That's 180 J.

Quote:
Williams through his research indicates on Earlier crossbows, 13th and before, closer to 200J in KatBF, p.919, when it appears. He estimates the impact about half this, which is how he ends up with the conclusion mail yes but not plate.


Williams' weapon kinetic numbers - especially for crossbows - shouldn't be taken too seriously. They're thoroughly approximate and explicitly guesswork. Nor does Williams anywhere claim steel crossbows managed anything like 331 J. I'm not actually convinced crossbows spanned by windlass and cranequin performed dramatically better than their earlier cousins. As I've mentioned before, the crossbows commanded the most respect from the eleventh through thirteenth centuries. Earlier spanning mechanisms allowed for a longer power stroke but required considerable exertion. As late as the mid fourteenth century, crossbow power depended on the wielder's strength. You encounter the same with ancient Chinese crossbows, though Han-era design allowed for an even longer power stroke than any European crossbow because of its compact trigger mechanism. It's plausible that spanning contraptions and extreme draw weights gave only a modest increase in penetrating power but made it available to anyone regardless of strength. (Though, I should note, the simple weight of powerful steel crossbows would have required some brawn to employ effectively even if the spanning process proved effortless.)

Quote:
As well this puts it right around the area where Williams states are needed for armour penetration for impact Joules, KatBF, pgs, 918-930.


A 2.5mm breastplate of the best quality (Innsbruck medium-carbon hardened steel) would require about 400 J to penetrate according to Williams, so even 331 J would be insufficient.

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Randall Moffett




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PostPosted: Wed 14 Mar, 2012 4:24 pm    Post subject:         Reply with quote

Ben,

Sorry, but your recollection is off then and Ben Tomaz is wrong here as well. I was wrong slightly but I purposely erred low as I was going off my memory as my book was being borrowed by some one. I have the book right in my hands now.

Initial Joules-

Springals-5748.6J
Great Crossbows-1962J
Twofoot Crossbow-981J
Onefoot Crossbows-392J
pg.64

Impact Joules

Springalds-1782J
Great Crossbows- 627J
Twofoot Crossbows-331J
Onefoot Crossbows-126J
pg. 68

So off but in favor of what I am saying. Regardless it changes nothing but adding yet more power to the initial joules of energy. In the Great Warbow this is explained in more efficient projector of the bow over crossbow. Truth is I could not say why it losses so much. Just that it does.

I think Helmuth is right. a 1000lb crossbow would have a 180J impact energy. Since the 750lb bow is 126J that seems about right, or within reasonable proximity.

As far as Williams numbers go I never said he stated later crossbows could penetrate plate. What I was saying is that his numbers of armour penetration and energy needed is excelled by what Liebel's findings show.

Regarding earlier and later crossbows, well if you need a machine to span it compared to earlier you did not I cannot see what other option is left besides them being mechanically more powerful. Clearly this power had a benefit that was seen as better than the older ones or they would not have replaced them. Now I do not think they are more efficient. I think they lose much more energy that their earlier counterparts do. That said I think all the real numbers attacked by Egon and Jean follow this.

Crossbows were considered the major missile weapon of the 14th and 15th as well for all of Europe basically with a few exceptions. Into the 15th crossbowmen from all over Europe are looked at as being the elite missile force. It is not till the end of the 15th they begin to lose ground and not till the 1st half of the 16th much of Europe drops them, though some keep them even longer.

I was not relating it to Williams estimate for the best armour of the day, which is several times stronger than the vast majority of armour of the day. Williams gives 80js to penetrate plate of 1.9mm and with padding some 125j. I was only stating according to his figures the joules needed for plate penetration were achieved.

RPM
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Benjamin H. Abbott




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PostPosted: Wed 14 Mar, 2012 8:58 pm    Post subject:         Reply with quote

I'll probably have to request the book again through my library to definitively clear this up, but I reiterate that those numbers make little sense. First of all, assuming a 80g bolt, 392 J means 99 meters per second. In a vacuum, this bolt would fly 1000 meters. By contrast, 67 m/s gives a vacuum range of 458 meters. Either Liebel's crossbow shoots an extremely heavy bolt or it achieves a range much greater than anything appearing in period accounts. Second of all, the difference between initial energy and impact far exceeds the ratio found with warbows. Finally, 392 J goes well beyond other kinetic energy figures for crossbows. Harmuth is talking about initial energy. So we've got the following:

Liebel: 770-990lbs - 392 J
Payne-Gallwey: 1,200lbs, 5.5in power stroke - at least 171 J, probably 208 J (calculated)
Harmuth: 1,000lbs - 180 J
W. L. Rodgers: 1,640lbs, 5.5in power stroke - 169 J
Bichler: 616lbs, 9in power stroke - 95 J
Bichler: 288lbs, 8in power stroke - 68 J

Which one of these is not like the others?

Read my historically inspired fantasy fiction in here. I walk along a winding path set by Ludovico Ariosto, William Morris, J. R. R. Tolkien, and Ursula Le Guin.

Out of doubt, out of dark to the day's rising
I came singing in the sun, sword unsheathing.
To hope's end I rode and to heart's breaking:
Now for wrath, now for ruin and a red nightfall!
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Randall Moffett




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PostPosted: Thu 15 Mar, 2012 7:30 am    Post subject:         Reply with quote

Yes but not all of those are initial joules of energy Ben. I would double check Harmuth.

RPM
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PostPosted: Thu 15 Mar, 2012 8:48 am    Post subject:         Reply with quote

Quote:
So off but in favor of what I am saying. Regardless it changes nothing but adding yet more power to the initial joules of energy. In the Great Warbow this is explained in more efficient projector of the bow over crossbow. Truth is I could not say why it losses so much. Just that it does.


Randall, are you stating that the bow tranfers stored energy to initial impact much better than a bow? If so, I fully agree.

If you look at any specific testing of bow with different weight arrows (I'll limit this to true replicas, not modern bows, which can tranfer energy more efficiently to lighter projectiles), as arrow weight drops, velocity increases, but the overall energy tranferred also drops.

Even a 60 pound bow is more efficient in transmitting stored energy with a 1500 grain arrow than it is with a 500 grain arrow. Not saying the 1500 grain arrow is the ideal arrow for this bow - while energy transmiited is better, it's at a great trade off for range and accuracy.

But pretty well across the board, the heavier the arrow, the more efficient the transfer.

Now when you are talking about the very heavy draw crossbows, they store immense amounts of energy compared to a selfbow. If they use the same weight of arrow as the self bow, they will of course get more initial velocity, but not to the degree that they excede the self bow in stored energy.

This is not really an inherent fault of the design of the crossbow - but more along the line of diminishing returns by higher stored energy being used to propel a light object.

I'm sure there as a "maximum" in feet per second that an arrow can be propelled - based on the acceleration of the bowstring - and there seems to be a lot of energy bleed off the closer you get to this theoretical maximum (which can probably vary based on construction of the bow, issues with the string, and the ability of the arrow not to lose energy be deformning).
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PostPosted: Thu 15 Mar, 2012 9:10 am    Post subject:         Reply with quote

Randall Moffett wrote:
As far as PG's crossbow, yes could be. At 18lbs of weight it is a bit heavy to carry around all day but it is borderline but still its draw weight is around the upper weight likely for field crossbows.

RPM


According to this website, 16th Century muskets weighed up to 20lbs so it would seem that even such a heavy crossbow might not be unthinkable as a field weapon.

http://www.alderneywreck.com/index.php/artefa...capability

Though from what I've read I suspect the really powerful cranequn-spanned ones were fairly small and light compared to that.

J

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PostPosted: Thu 15 Mar, 2012 9:49 am    Post subject:         Reply with quote

Ben,

I had a few minutes of free time and looked up some impact energies in Halmuth and have no idea where you are getting your info from for initial energy for Halmuth. Page 130 in his Crossbow book (1975) gives the impact energy of a crossbow of 760lb draw as 127.3J, a bit higher than Liebel but considering the scenario about what one would expect and supporting my initial theory. So no the numbers you provided do not change things as they seem inccorrect.

I would recommend taking a second look at these works before being so sure Liebel is incorrect as all I am seeing simply reasserts his work. As well he had several engineers and physicists work on his project with him. Some working at fairly prestigious institutes. I'd be wary to assume they are all incorrect without some major revision which with my specialty not being physics but having done some earlier in life seem very solidly based and executed.


Gary,

Yes that follows what I was thinking. I think steel especially is just mechanically not as efficient as wood and both are less effective than a longbow. That said I think in part it is smaller draw lengths. Though I assume in part this was compensated by heavier bolts. I have weighted several that were in the 150s and 160s grams region which is near double to double what most testing uses. This would have a serious change in impact energy in short distances especially.

Jean,

I agree. It certainly could have been used on the field. I think it more likely for siege use but not exclusively. I just think it likely this was not the most common type of crossbow on the field. AS well these muskets had stands which as far as I can tell we have little evidence for crossbows with these outside of siege environs.

RPM
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Gary Teuscher




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PostPosted: Thu 15 Mar, 2012 10:11 am    Post subject:         Reply with quote

Quote:
Yes that follows what I was thinking. I think steel especially is just mechanically not as efficient as wood and both are less effective than a longbow. That said I think in part it is smaller draw lengths. Though I assume in part this was compensated by heavier bolts. I have weighted several that were in the 150s and 160s grams region which is near double to double what most testing uses. This would have a serious change in impact energy in short distances especially.

Are you familiar with the below listed testing, Randall?

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

It's not particularily illuminating, but does point out that the heavier grain of the arrow, the more efficient the bow, even the light pound pulls. The Heaviest of bows tests are not very efficient with a lighter arrow - and a crossbow is going to see even more of this bleed off, as the increased energy assuming similar weighted projectiles can only be transmitted one way , to velocity - and it seems the closer you get to that maximum, the more serious the energy bleed. It seems to progress more exponentially than in a straight line.

As far as wood being less efficient than a longbow - both are wood, correct? and if meaning the D shape bow with sapwood on one side, that's pretty well how all wooden D shaped self bows were made, I would assume the same method would be used on a D shaped type crossbow.

From waht I have seen, the most effective self bow is the recurve composite, at least in regards to transference of energy. That probably has more to do with the higher initial draw weight as a percentage compared to maximum draw weight due to the recurve bow desiring to get back to straight, and it is further from it's "straight" than a longbow style selfbow.

What I am trying to say is that the increased efficiency of a composite is not as much due to the materials but due to the physics of how the bow is strung - but I guess the materials of the bow allow it to be strung differently giving it the different physics, so indirectly the material do matter.

I have not heard that wood is more efficient than steel though - I've heard arguments onboth sides of the fence here.

I think it's extremely tough to truly compare efficiencies, as they were used for two different types of bows, and the steel bows are generally or far greater pull, skewing efficiency tests against them.
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Randall Moffett




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PostPosted: Thu 15 Mar, 2012 12:44 pm    Post subject:         Reply with quote

Gary,

Very interesting experiment. I often have wondered if that was not why crossbows show such ineffectiveness because the light bolts used. The problem ultimately is that we need a great deal of testing on them to see what effect arrow weight plays. I often think they likely had bolts of similar types just like warbows.

One thing regarding bows and bows on crossbows is limitations of the bow themselves. They tend to be short. Some of them are squat but you cannot make them thicker after a certain point and still gain power from it. So for wood bows for crossbows there are many limitations that are less difficult on a longbow as you gain power by both length and width.


RPM
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