[Owen Bush]

[Jean Thibodeau]

[Owen Bush]

[Leo Todeschini]

Hi All,

Unfortunately I never have enough time to run all the tests I and we would like, but I have another big bow just finished.

The steel is pretty much like the one on my bow in that it is 15x 50 at the centre and is 700 tip to tip - so a pretty regular size for a medieval war bow. It draws to 165mm (6 3/8"), again the right kind of distance for these bows and pulls about 850lb

Interestingly for me I shot this side by side with my windlass bow with which it has some notable differences. They have similar sized steels but my bow draws to 140mm (5 1/2") and so is about 700lb. The string on mine was made a few years ago as is significantly heavier than the one on the new bow. In comparison the extra draw, extra power and lighter string has made an easily noticeable increase in performance - you can hear and see it. Nice kick too.

Pictures 1 and 2 show the bow

picture 4 shows the bolt heads at the rear of the boss - which was brand new and hard as nails. These were shot from the new bow.

Picture 5 shows a bolt from my bow and how far it penetrated, so not quite through the boss.

picture 7 shows the same bolt shot from the new bow and it again significantly penetrates the rear of the boss.

Picture 6 shows the two bolts shot from the new bow going through the same steel as before.

The old bolt (with the rounded fletch) weighed 62gm and were about 15mm 5/8" the new bolts weighed about 50g and were 12mm 1/2" diameter. The heavier and fatter bolt penetrated as far through the boss as the new lighter ones so of course given the choice you would pick the heavier. Through the steel they seemed to perform about the same but the heads are quite different on the two bolts so no comparison can be drawn from that. I will try and make up a heavier bolt and see what that does.

What is notable is that penetration on steel is still pretty poor but a heavier bolt may help this. I must get down to some more museums and measure weights because this is critical I think.

I also talked to the man I sold the last heavy bow to and he is about to start a series of tests with it down at Bristol Uni and I will keep you abreast of any hard data that comes from it.

Regards

Tod

[Josh Warren]

Very cool, Leo!

I looked, but I couldn't find a figure for the thickness of the sheet steel you were shooting through? Did I miss it somewhere?

[Jean Henri Chandler]

Great stuff Leo fascinating please keep posting. Very interested in the weight issue.

What was the distance and per above, thickness and type of the steel sheet? 1mm mild steel?

Can you tell me anything more about the 'strings' you used?

Have you tried this type of test with a cranequin style arbalest or only with the windlass type?

EDIT: Regarding the weight, it is interesting that, according to the English Warbow Society at any rate, while ordinary target and flight arrows were in the 50-60g range, the war arrows were close to double that weight.

http://www.englishwarbowsociety.com/EWBS_ARRO...TIONS.html

Finally, I notice you have what look like wooden vanes on the bolts, weren't leather or paper vanes more common, and have you done much investigation of vanes designed to impart spin?

J

[Jean Henri Chandler]

[Jean Henri Chandler]

Leo, did you ever try this with a heavier bolt?

J

[Kurt Scholz]

I think there's a relation between draw length and accuracy. In China the powerful multiple bow crossbows or the Spring and Autumn pistol-crossbows (a bow on a pistol crossbow prod) all had long draw lengths, but the precision instruments used by China's "barbarian" southern neighbors for hunting very small game seem to have very short draw length. Looking at the records about Chinese use of crossbows in warfare, they seem to have been very much into volume of fire, with one or more arrows per loose. On the other hand they employed mercenaries from the southern tribes as snipers with poisoned arrows. http://www.atarn.org/chinese/chin_arc.htm
Medieval Europe seems to me to have bought more into the sniper than into the volume use of crossbows as far as we know.

[Benjamin H. Abbott]

[Kurt Scholz]

These are MODERN crossbows. Looking at ANCIENT crossbows short draw length seems to be a principle of precision weapons. I'm sure you'll note that today we can do a lot more things with a lot more precision than in the Middle Ages and earlier.

[Bartek Strojek]

OK, but what could be possibly reason for longer power stroke to reduce accuracy/repetitiveness in any way?

And why wouldn't it affect modern crossbows similarly, with, all in all, relatively similar strings (working on the same principle, just usually lighter will being less prone to stretching).?

[Kurt Scholz]

[Aleksei Sosnovski]

The only thing I can think of is that with equal "muzzle" velocity bow with longer draw length will take more time to accelerate the projectile than bow with short draw length (time = distance / speed). That means that recoil (and crossbows do have recoil) would affect the shooter for a longer time. Nothing a proper shooting technique would not compensate for though. In middle ages people were able to create amazingly precise things. I think that variation in projectile shape and weight would have much greater effect on the accuracy than imperfections in bolt guide of a decently manufactured crossbow.

[Benjamin H. Abbott]

The short power strokes of European crossbows do confuse me, given the advantages of having a longer one. Ancient Han crossbows had a long power stroke similar to the modern design. They also sported precisely cast bronze trigger mechanisms and grid sights. European crossbows before the fifteenth century as well as many later Chinese ones appear crude by comparison. We could conclude simple technological superiority for the Han, but I don't find that completely satisfying. Anna Komnene's account of the penetrative force of Crusader crossbows is hard to explain if we assume short power strokes for that period.

With later European crossbows, technical details mandate short power strokes. Mechanical spanning devices such the goat's foot lever and cranequin as well steel prods make long draws impractical. The higher draw weight involved allows for sufficient impact without a long power stroke. However, it's interesting to note that the crossbow's glory days - at least judging by written accounts - came with the early designs rather than the complex later ones. Various records from Komnene's era extoll the virtues of the weapon. By the fourteenth century you have crossbowmen routed by English archers. In the fifteenth you have a volley of bolts described as inflicting no more damage than a shower of rotten apples. I can't think of positive accounts of crossbows during those centuries and only one from the sixteenth, by which time the weapon had already lost its place to the gun. I don't know what to make of it. Powerful crossbows existed across Europe during this time and saw widespread use, yet nobody appears to have been terribly impressed with them. The primitive English warbow, on the other hand, received regular acclaim.

[James Arlen Gillaspie]

Owen Bush said:

"Temper or hardness of a spring be it a crossbow or sword has no relation how stiff it is . this is counter intuitive and I have done experiments to confirm to my self that this is actually the case , a fully hard piece of steel will deflect the same as an annealed piece under a given load providing that the materials elastic limit is not exceeded."

This principle is known as the Fourth Law of Steel, at least here in the U.S. It seems to be little known among people who make or buy swords!

[Kurt Scholz]

[Benjamin H. Abbott]

[Leo Todeschini]

I am not sure why the bows were such a short draw beyond the earlier points I made, but they seem to be about 160-170mm approx (6.5-7"). I can't see why longer or shorter draws should effect accurracy particularly, but modern bows are more accurate because they are CNC made and computer designed using finite element and have longer bows because it is more efficient. You can bet that if our medieval cousins could have used 15 or 17" draws they would have done.

Military bolts were munition grade items, made by the hundreds and kept in store, but not made (on the whole) to a design specification. I suspect like anything similar these days, they were knocked out and basically were capable of going fast in the general direction of the enemy but not that much more in terms of accuracy.

I am still trying to work out the general power of big bows. As a rough look at a war longbow with a brace of 3" and a draw of 32" and a weight of 140lb compared to a 900lb crossbow with a 6.5" draw the pound/inch numbers are not that different and the projectile weights are not that different, so you could conclude that the performance should be similar in terms of distance, although my big bows seem to be a little down on what you would expect.

As regards penetration, the cranfield tests show the stop/start penetration of the longbow arrows due to the flexing of the shaft and the bolts don't have that ability so if we assume that we have two projectiles of similar energy, one being a bolt, the other an arrow; it is reasonable to assume the arrow will penetrate steel better.

Documents seem to show the crossbow bolts travel significantly further, though I am not sure why this should be the case. What I am currently thinking about is the truth surrounding power and penetration. I am certain that longbows effectively outshot crossbows as regards a cumulative effect ie 100 longbows verses 100 crossbows in open fields, I suspect that longbows and crossbows were comparative as to distance shot, with the crossbow possibly slightly outdistancing the longbow. I am also fairly certain that the crossbow was intially a relatively powerful weapon that could penetrate (or often enough to count) contemporary armour and this is where its reputation rose up. As armour improved its effect was lessened.

I am afraid Jean that I have not tried a heavier bolt yet and nor have I got to a museum to weigh some, but I was at the RA in Leeds and most of the bolts looked pretty as I make them, certainly not 20-30g heavier. But without getting some numbers and some tests I can't yet offer anything firmer. I did have a good chat about it with the curator I was with and he seemed of the opinion that accounts of distance and penetration may have been exagerated.

I still have a bow being tested by a private client at Bristol University and that will shed some information in due course. I also hope to get into some museums to measure this summer and make replicas based on these - all takes time though.

I am constantly trying to see where replica bows may fall short on performance and I have thought of two areas to currently look at, but I do wonder the fact of all this. I am slowly working my way through it all

Tod

[Benjamin H. Abbott]