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Leo Todeschini




PostPosted: Wed 14 Dec, 2011 2:04 pm    Post subject:         Reply with quote

Touching on the last two posts.

If there are any mettalurgists out there, can you help with this question. We know that if a given piece of steel is full hard or normalised or anywhere in between, a given load will deflect the steel the same amount - counter intunitive, but true.

However does the temper effcet the rate of return , ie will a given sring act faster if the hardness is higher?

I temper my bows to be soft so they are totally safe in any temperature and indeed our medieval counterparts could have done the same which would have prevented any catastrophic breakages which makes me wonder why they did not?

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Sime Ivic




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PostPosted: Thu 29 Dec, 2011 8:05 am    Post subject:         Reply with quote

Leo, you can make musical tongue as if for a thumb piano or kalimba out of steel you commonly make prods from. Then measure frequency at full hardness and each time you soften the temper. Most musicians today have electronic tuners, you can borrow if you know any or you can plug microphone in the computer but it surely requires some sort of software to take the readings. Theoretically, the lower the pitch the slower the movement. Imagine difference between a fast and a slow pendulum. Instinctively I'd say it will stay the same but steel is a weird thing and I woudn't bet my money on it. If internal tension is the cause of brittlenes it could be akin to tightening a string. It might not be the best simulation of bow limbs but it's a simple test and would be worth a try if only a curious experiment. If the sound is too silent magnetic or piezoelectric pickup is an option.
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Alex Ostacchini




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PostPosted: Thu 29 Dec, 2011 10:17 pm    Post subject:         Reply with quote

Video here of a windlass crossbow with apparently 1000lb draw. might be interesting, sorry if it has already been posted.
http://www.youtube.com/watch?v=76mbOMFjlu0&feature=related

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Leo Todeschini




PostPosted: Fri 30 Dec, 2011 12:45 pm    Post subject:         Reply with quote

Thanks for the link.

Clearly I don't know for a fact, but I would say looking at the thickness of the bow limbs and the length of draw that the bow is more likely to be 400lb rather than 1000.

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Bartek Strojek




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PostPosted: Fri 30 Dec, 2011 12:50 pm    Post subject:         Reply with quote

Guys seem to have enough clue not to overrate the poundage of their bow by 150% though.....

Anyway, "armor" is supported in such way that this cannot be called "test" - whatever that armor actually is, but still very fun video!

I wonder what was the weight of the bolts and how did they estimated that 57 m/s.
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Randall Moffett




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PostPosted: Fri 30 Dec, 2011 2:21 pm    Post subject:         Reply with quote

Leo,

I agree looks light. First thing I though looking at it as well. We had several crossbows at the museum I worked at that were far thicker in the prod but less draw weight than 1000. Not sure without really testing it though.

Interesting test though. Looks like once again it shows that the force at impact needs to be evaluated. Looks like that breastplate is getting hit fairly hard.

RPM
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Jean Thibodeau




PostPosted: Fri 30 Dec, 2011 3:28 pm    Post subject:         Reply with quote

At times these kinds of tests are biassed by having the target set so solidly in place that it doesn't have any give and this increases the degree of penetration.

In this case the breast plate is not supported at all so a lot of the impact energy is used or wasted in moving it around but still penetrations of an inch to 3 inches seem to be happening under the least favourable conditions. Wink Eek!

I also have some doubts about how heavy a draw this crossbow actually has but it doesn't seem to be a " wimpy " 150 pounds.

Not scientific but still tells me that the armour is fairly effective but I wouldn't want to be hit by one of these crossbow bolts: A lot depends on the angle of impact to make a difference between a surface dimple, minor penetration that would probably not be more than a painful wound, or none at all if padding or distance of the surface of the plate to the " soft centre " of flesh under the armour was large enough, to some percentages of incapacitating wounds.

In other words the armour protection would greatly improve one's odds but not make one 100% safe from crossbow bolts coming in at a favourable angle and at closer ranges ..... oh, quality of plate would also be an important factor between soft iron and a surface heat treated plate armour or simply thicker armour at critical areas. ( Variable thickness of the plate ).

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Benjamin H. Abbott




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PostPosted: Fri 13 Jan, 2012 10:11 am    Post subject:         Reply with quote

That's a fascinating video. The claimed speed of 57 m/s, the 1000lb draw weight, and the 1.5mm work-hardened breastplate pierced all stand consistent with a delivered energy of 100-200 J. I'd like to see how the this crossbow would do against armor more reasonably mounted.
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D. Phillip Caron




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PostPosted: Fri 13 Jan, 2012 5:06 pm    Post subject:         Reply with quote

I know that a chronograph has been mentioned here somewhere. To get a good study of this beast it seems that a chronograph would be a must have. They can be had for about $80 and shipping at Cheaperthandirt.com. That's an online Walmart type place for shooters and reloaders.
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Jean Henri Chandler




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PostPosted: Mon 20 Feb, 2012 12:40 pm    Post subject:         Reply with quote

The guy from that video contacted me and told me that they measured the strength of the bow and said that it was actually 750 pounds. This is what he sent me:

Quote:
Ah hiya. I'll have to find them - plus I'd have to find a measure which would tell me accurately. At a guess I'd say they were roughly the weight of an iphone. Does that help? I did actually manage to accurately measure the draw strength of the crossbow recently and it's actually approximately 750lbs, not 1000lbs as it was at time of building. They do tend to lose strength in time and in humid environments though obviously.

in addition, we did quickly forge a really heavy bolt head (see the video) because when we didn't immediately pierce the breastplate we assumed just adding more weight would fix the problem. It turned out to be more a mechanical/physics problem. The larger the hole in the armour the more resistance and more momentum was taken away from the penetrating bolt. From this logic a thinner heavier bolt would have possibly gone straight through but there's no direct evidence of such thin bolts (that I know of). However, I hear tales of 3000+ lbs crossbows so perhaps these would easily pierce the breastplate. You can see the steel prod on my crossbow and, replacing that with a heftier lump of steel could easily provide the results we wanted. However, if the prod snapped under pressure it could return to remove an important part of your head - something I wasn't willing to test-fire!

Last bit of info - it was incredibly easy to fire accurately by a complete novice. Even at long range (100m) it's as easy as moving a computer mouse and pressing the button. The bolt didn't have time to dip or be moved by the wind etc - too fast.


So I haven't been able to find out yet how much the bolts weighed or even where this guy is from (I've asked him but haven't heard back yet- the email on youtube is really screwed up right now for some reason) but this is interesting anyway so I thought I'd share. An Iphone is 140 grams according to what I just looked up. I asked the guy to weigh one of his bolts with a kitchen scale if he could.

J

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Jean Henri Chandler




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PostPosted: Mon 20 Feb, 2012 1:00 pm    Post subject:         Reply with quote

By coincidence this teaser video about a "16th Century crossbow replica" from Hungary also claims a 140 gram bolt

http://www.youtube.com/watch?v=xvrQYeWR-3E&feature=related

Doesn't anyone have access to real weights of antique bolts? I know there are a lot around in museums and they show up on auction sites routinely. Maybe I need to buy one...

J

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Kurt Scholz




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PostPosted: Tue 21 Feb, 2012 10:45 am    Post subject:         Reply with quote

There was a regular crossbow-testing of armour in Nuremberg with tested armour being stamped during the Renaissance and Early Modern times. Such armour might give us some more information about this issue from another perspective.
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Edwin Gordon




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PostPosted: Wed 29 Feb, 2012 3:06 am    Post subject:         Reply with quote

Hello all,
I've received some communication in the recent past from Jean-Henri via youtube and he's drawn my attention to this excellent forum (which I haven't viewed for some time!). I'm the lucky owner of the crossbow mentioned above (English C15th) in this http://www.youtube.com/watch?v=76mbOMFjlu0 clip.

Anyway, yes, as mentioned above it's lost a bit of 'umpf' over the years so upon a recent electronic measurement at proper draw it was approx 750lbs. The prod is 70cm in arc length from the points at which the string touches. The string is 65cm in length measured from where it touches prod.

I got some scales yesterday (upon Jean's request!) and the bolts are on average 55 gram (0.121 lbs). The 'heavy' bolt which was 50/50 steel/wood was 120g (0.265 lbs). Of interest, an iphone is 136g so I was way off with my guess!

The speed of the bolt was calculated in 'post'. I measured the distance fired when testing the whistling bolt (55g) (last shot on the film...which didn't whistle...) and then timed the flight using the audio track (I occasionally work in film). It's a lot easier/cheaper than buying a chronograph. The recording was taken from the mid point of flight so the effect of the speed of sound from fire to hit should be cancelled-out.

Upon reflection, placing the breast plate the way we did probably did go some way to represent how a crossbow hit would occur on the field. If the bolt were to hit a real target he would absorb a certain amount of the punch with his body movement/reaction before hitting the floor, swearing at the nasty hole in his expensive armour. If we'd braced it firmly it might go some way to accurately calculate the damage caused by 100% kinetic energy transfer into the plate but it's not a great representation of field work. Video never really shows things like this very well but the impact of the bolt on the plate was akin to the effect of hitting the plate with a pointed claw-hammer. The wooden back-brace was a pretty hefty lump.

Steel hardness is key. Rock beats scissors every time. If you're firing at hardened steel (decent historical armour) you should use bolts of superior quality. I fired a soft steel bolt on the breastplate - we might as well have used a clay bolt as the tip bent 90 degrees over and the bolt didnt gain purchase on the steel - the energy was fully reflected away from the plane of the armour. This kind of hints possibly at why plate became harder through the development of armour until gunpowder came to the west and decided the winner. I'd suggest that incredibly hard armour would be more beneficial towards bolt and arrow protection rather than bladed or blunt weapons, although it would probably still be gaining some advantage in the latter category. I'd be more concerned with cracking the armour under concussive blows however but - well, I guess that's a topic for a different post!

I'd suggest the next stage of modern experimentation would be to calculate the perfect weight of a bolt per pound of draw weight which wouldn't lead to damage on the crossbow. There must be a happy medium. However, I wouldn't be happy using my crossbow for that kind of one-off experimentation for obvious reasons. I'd dearly love to try the crossbow with a full steel dart but, without knowing what the effect would be on the prod or string it's a bit of a risk.

Anyway, I hope that's of interest to someone. Jean - let me know if you'd like any more stats/measurements etc. I'd be happy to carry out some more experiments under more accurate conditions in the summer if you like. Bit damp here at the moment!

I'm sure I'm not the only one who wants to see an even more powerful crossbow. I seem to remember there were some crazy draw weights at the wallace collection last time I went - they were of composite construction however, not steel (which I would have assumed to be weaker to be honest).

Cheers.
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Jean Henri Chandler




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PostPosted: Wed 29 Feb, 2012 8:58 am    Post subject:         Reply with quote

Edwin,

Thanks very much for posting here! I was trying to reply to you on youtube again but they seem to be having a lot of problems with their email feature. That website is as flawed as it is useful. But I really appreciate your sharing testing information, both here and on youtube. A lot of good stuff in your post. How do you feel your string is holding up? What is it made of? And who makes your bolts? Are you forging the tips yourself?

I think I can speak for most people in the thread when I say that we would love to see you doing some further testing when the weather does improve.

As Kurt pointed out, 'proofing' with crossbows was routine in the late Medieval period, often leaving a dent. In addition to Swabia it was also routine in Lombardy (mainly Milan and Brescia) according to Alan Williams, IIRC they had a "balistarii piccollo" and a "ballistarii largo" category for armor, (or something similar, pardon my miserable Italian). This type of armor was sometimes hardened but the top quality armor was more often tempered, which is to say "toughened" rather than simply hardened, and therefore not brittle at all, more springy.

And it's worth remembering this armor did also apparently provide substantial protection from firearms up to this period, which were perhaps very roughly analogous to modern shotguns firing slugs. It wasn't until the heavy musket became ubiquitous that the top quality armor was really vulnerable to firearms, that's why you don't see a substantial decline in it's use until after 1520 ... but as you say that is a discussion for another thread!

Yes composite prods are also good, and seem to have played an important role in the development of the really powerful crossbows in the 14th - 15th Centuries. Which are better steel or composite is hard for me to estimate at this point, my best guess is that they could be roughly equivalent, but had different reactions to weather. Composite prods could be very vulnerable to moisture, steel prods could be very vulnerable to extreme cold according to some reports I've read. The composite prods also apparently took a long time to make and were probably more expensive given the ubiquity of high-end ferrous Metalurgy in the late medieval period. For whatever reason steel prods became popular in Burgundy (which was very technologically advanced due to the cities of Flanders) in the 15th Century but the Swiss, who were no slouches with the weapon, continued to use the composite prods. Both types seem to have been used by the Czechs and in the Baltic. Not sure about Italy or Spain where the weapon also played an important role (including with the Conquistadors in the New World and the Pacific).

Did I understand your post correctly that you were able to calculate the speed of the bolt? Was that listed in the original video I'll have to go back and look... how much is a chronograph anyway?

J

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Bartek Strojek




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PostPosted: Wed 29 Feb, 2012 9:37 am    Post subject:         Reply with quote

The way I see it, steel is pretty damn heavy for energy it can gather by bending.

On the other hand, in case of really heavy composite bows, prods were pretty morbidly thick and bulky in cross section, which is obviously not very optimal shape for the bow.

Those are just my layman guesses, but I would guess that both main technologies for heavy crossbows each had their ups and downs as far as building efficient and reliable bows goes.
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Edwin Gordon




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PostPosted: Wed 29 Feb, 2012 9:43 pm    Post subject:         Reply with quote

Hi Jean Henri (and forum!)
In answer to your questions;
The string composition- unfortunately I don't know what it's original thread is. It's hand made and doesn't appear to be of artificial material. The crossbow maker makes replacements but fitting a new one has got to be a challenge! He also supplies 6 standard quarrels with his product but the heads are of soft steel. The barrel and flights are of decent wood though. I don't know the forum rules on advertising and quoting suppliers so I can't mention his web page just yet - let me know if it's allowed.

Binsey (probably a regular here!) made a load of nice test bolts for the day from very tough steel. Some of quarrel design, some slightly elongated leaf shaped and one we ground right down to a long fine point of around 3cm long to see if it made a difference in penetration (it didn't).

My objective for the day was to test various authentic bolt designs. I'd spent considerable time researching bolt head designs (armour breaker, whisteling, fire bolt, dart, etc) but it was nigh on impossible to find graphical representation or even a physical example in a museum (if there are any curators reading this and you know what im looking for please let me know!).

I eventually found some nice drawings in a German book owned by the crossbow maker. I was particulary interested in testing an 'armour breaker'. It appears to be of the same design as some lance points - like a potato masher. The effect was a much more concussive punch and very little chance of penetration. I'd assume it was for dismounting people rather than damaging the armour - similar effect to a bird hunting arrow.

Regarding proofing - yes I seem to remember seeing some holes in breastplates at the tower of London. The description was that it was musket proofing and armour would only receive the makers stamp if it passed this last test. I'm sure that can't be the whole story though as I'd be a pretty upset client if my new armour was full of dents and holes. Perhaps the armour maker had to make just one suit on a yearly basis which was shot by an official - to gain some kind of license to sell armour, and possibly an official grading...A bit like how newly designed cars and planes are tested before being mass produced these days.

Speed test- yes, I ran a basic speed test - firing a bolt over a known distance, videoing the result and timing the points between the click of the firing and the bolt impact on target. Pretty rough but close enough - not for a scientific paper or quality academic research book however.

Cheers for now. Let me know specifics if you like for any further tests in the summer. No suggestions means we might have to do some Mellon bashing ( I'm talking about shooting fruit - its not porn slang....nor is 'shooting fruit').
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Randall Moffett




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PostPosted: Thu 01 Mar, 2012 6:23 am    Post subject:         Reply with quote

Edwin,

Are you looking at Liebel regarding the armour breaker? I agree not likely intended for penetration. Sadly you will likely see a very small amount of 'air time' has been given to crossbows in general, let alone bolts. I tend to think the heavier stout three and four sided points have a higher change or penetration. I tend to think some had to be hardened as we have accounts of this but the few tests done right now have not had many that showed high enough carbon levels.

There are a few in these pictures-
http://users.stlcc.edu/mfuller/novgorodmetalp.html
http://www.ancientresource.com/lots/medieval_...armor.html
http://www.ebay.co.uk/itm/Exceptionally-Rare-...0775629954
http://www.antiquescentreyorkeshop.co.uk/acat...1_2dSN5623

RPM
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Jean Henri Chandler




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PostPosted: Thu 01 Mar, 2012 9:49 am    Post subject:         Reply with quote

Hopefully one of the moderators can chime in but I think it is ok to link to the crossbow makers website.

The kind of certifications you describe were indeed done by Medieval craft Guilds in Northern and Central Europe and Italy and by Royal or town officials in England and France.

I have seen proofing dents which were 'part of the deal' but I think a hole would be unacceptable. Not too much armor would be musket proof except at a substantial distance, though a lot of it was pistol proof and effectively arquebus-proof.

So you said you estimated the speed but I must have missed what your estimate was. What was it?

Looks like you can get a Chronograph for around $80. Maybe we could pass the hat and buy you one :P

J

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Chad Arnow
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PostPosted: Thu 01 Mar, 2012 12:25 pm    Post subject:         Reply with quote

Jean Henri Chandler wrote:
Hopefully one of the moderators can chime in but I think it is ok to link to the crossbow makers website.


We only prohibit makers promoting their own wares. Someone else linking to a maker's site is not only allowed, it's encouraged.

Happy

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Edwin Gordon




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PostPosted: Thu 01 Mar, 2012 10:28 pm    Post subject:         Reply with quote

A great - cheers. The crossbow maker can be found here:

http://replicacrossbowworld.com

As you can see he makes some stunning hunting crossbows with bone inlay etc. He can sometimes be found attending the regular medieval markets in the UK. He makes prods and strings to order so get in touch if you want a real monster of 700lbs and above as they aren't listed on his page.

Jean - the speed is stated on the first few frames of the YouTube clip. I didn't do a very good edit on the movie as I wasn't expecting it to get much attention. Maybe I should re-edit it. Anyway, if you pause near the beginning you'll see the speed of 57m/s

Randall- many thanks for the links. I'm not a fan of Internet selling of metal detector finds due to the damage to the historical record, but the pictures are useful. The majority appear to be standard quarrels but there's a nice armour breaker in the Novgorod pics (bottom of that page). I forget which book I read about the fire and armour breaker bolts - id have to dig it out.

Cheers,
Ed
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