I can give you a few more detail shots of the Higgins bow. It looks like there are 2 distinct layers under the covering - wood backed with something else?

[ Linked Image ]

more: http://www.flickr.com/search/?q=crossbow&...nt&z=e

These are great, thanks for posting. You are right I noticed some other layers but it seemed mainly on the surface so I figured that would be composite, but it occurs to me I really don't have any idea what the construction of a composite crossbow prod actually looks like internally.

So I guess maybe this could be composite? Are there any experts here on composite bows / prods?

Also, are we sure that crossbow was meant to be used with that cranequin (or any cranequin?)

If so I wonder why it has a foot stirrup? Maybe that is for emergency use in case you lose the cranequin or it breaks?

So many questions! It is definitely a serious bow. A scary weapon. Quite a bit of presence to it.

J

I'm not sure. Most cranequin spanned crossbows I've seen though did not have foot stirrups. So that is why I was wondering if they were actually linked.

J

I would be very surprised if that were not a composite, it looks like one, is very thick at the tips and has the snakeskin decoration of an overlay of printed paper or snakeskin and it was also the bow type of choice for these types of bow.

It is loaded using a cranequin and you can tell this from the position of the lugs. they are too far back to be for a goats foot and windlass don't use lugs.

I am not very familiar with these big bows but I would guess Jean has the nub of it in that the bow and cranequin will be too heavy to hold in the left hand while the right cranks like smaller bows so the stirrup will be to stabilise it while the ground takes the weight.

No idea about poundage, but the regular hunting bows needed cranequins so that would mean they are 500lb plus (approx) this is larger, but the length is also longer so as a complete stab in the dark I would guess 600-800

Tod

Very interesting, thanks guys! I wonder if anyone else has photos of other composite prod crossbows, spanned by cranequin?

J

I thought I would post up a video of me using a goats foot bow to show how it works.

It is a 300lb -320lb bow and managed a rate of fire of 5 shots a minute aiming and this could perhaps go upto 6 if I was a little more reckless.

You will find it here

http://youtu.be/iIkxyjVu9gc


Tod

Excellent.

A question - is the kneeling position attested in medieval sources? It seems very reasonable - you can easily pick up lever and bolts from the ground, and a pavise placed in front of you would provide 100% cover most of the time.

Blaz Berlec wrote

Quote:

A question - is the kneeling position attested in medieval sources? It seems very reasonable - you can easily pick up lever and bolts from the ground, and a pavise placed in front of you would provide 100% cover most of the time.

I am not sure; I have always shot goats foot that way. Different bows steer you in different ways.

A hand span and a windlass just make sense to shoot standing, a cranequin you can wind kneeling, but it is easier standing as your body interferes with the winding. Using a spanning belt, either straight or compound is done standing. The sort of goats foot where you invert the bow and use your thigh or belly to push against the lever must also be spanned standing (I have never made one, but seen in illustrations in Payne Gallwey).

So on balance it is easier to shoot bows spanned with small goats foot kneeling as everything is more at hand and all other bow configurations it is easier to shoot standing as you have to span them standing.

For the record you can span a 270lb with one finger and the heaviest to date I have spanned with this lever is 380lb and this will deliver about 40% of the energy of an 850lb in not very exhaustive trials.

Here is a (poor quality) video of me spanning a crossbow inverted with a very long goats foot. The bow is supposedly 450lb and I think I would have a hard time spanning it the "normal" way. It's a bit hard to see, but I start the spanning by using my right arm, and then my thigh and eventually my knee is involved, always with as much body weight applied as possible. And yes, I'm always afraid of battering myself should the goats foot slip ;-)

http://www.youtube.com/watch?v=fPsS1pahWjM

Great stuff guys, very interesting. I wonder what rate of shots you could get to if you had a lot of training, a professional level.

J

Anything new? Any new testing been done?

J

Nothing much from my end.

I have posted some musings before the great crash of '13 but nothing exciting. I made a 1250lb bow that was in performance much as the 900 was that I made before. I have another to make and will make a slightly different bow geometry and see what that turns up.

The string was about 16mm diameter and I wonder if I could get away with a lighter string to up the performance, but I don't really fancy finding out I made it too thin............

I made this video of me using the bow. [url] http://www.youtube.com/watch?v=WEOeZTV9wiA [/url]

What is daft is that I found out half way through a new method of unwinding the windlass that makes it much faster to shoot. I now span the bow and leave the windlass on the bow and then unwind it completely before shooting. This does necessitate putting you hands in the way of the string, so you do have to believe in your trigger (or the maker of it).

I am off to the Wallace in a few weeks to look at some originals of about the right weight, so will faithfully copy the geometry of one of those bows and put up the stats.

Also for those curious, I got the bug for catapultas last year and I have just laminated a set of arms for a 3 span machine and ordered up the oak and lined Owen Bush up to come and join in the fun, so some time over the summer I will make a faithfull reproduction. This will throw bolts around 70cm long. I will keep you informed as there were some questions about these.

As suggested in another of your Topic threads I'm keeping this discussion to this extensive Topic to not repeat a lot of the information and opinions expressed in this Topic without creating a duplicate Topic.

Quote:

FROM TOD'S other Topic: Jean is totally right; springs have a maximum speed they can return at and no faster. A bow made to medieval layout will move a bolt around 160-170fps on a good day, but no faster. As a bow of 1200 weighs around 5kg (from memory) the difference between a 100g and a 120 gram bolt makes no discernible difference to the bow, but quite a big difference to the target.

If 160/170 feet per seconds it the fastest one can expect to get from the maximum speed of return no matter how heavy or thick one makes the prod. ( Actually one probably reaches a point of diminishing returns where more draw weight gives you a slower moving prod and the energy that can be transmitted to a bolt falls off dramatically. )

So in experiments trying to find the optimum bolt weight instead of starting light and increasing the bolt weight why not start with a very very absurdly heavy bolt and working one's way down until one has at least 140/160 feet per second and see how heavy a bolt we end up with and it's calculated momentum from it's speed and mass.

With these low speeds compared to firearms I don't think that kinetic energy is as an important factor as momentum.

Now when we get a bolt that is at " the sweet spot " of maximum momentum/minimum loss of projectile velocity or a loss of velocity well compensated by the total momentum in the bolt being the greatest than with a slightly lighter and speeder bolt.

Once we have this ideal weight of bolt using the energy stored in the prod in the most efficient way possible one still has to make the projectile stable in flight and aerodynamically efficient so as to not waste the extra power when the range to target gets long.

My gut feeling is that the optimum bolt will be very heavy after scientific tests: Not sure if in period bolt weight would have been optimized empirically or lighter than modern science might prove better ?

I tend to believe that if they used somewhat lighter bolts, they then had good reasons to do so based on experience trying heavier bolt ? But who knows their perceptions of efficiency may have been influenced more by how fast the bolt moved rather than it's total momentum and used bolts a bit lighter than the mathematically optimum weight of bolt.

The final tests would be the relative effects on different thickness of steel plate. ( Period plate, complex shapes in armour, bolt/quarrel point hardness and type, etc .... are all important issues. but one could at least have a relative idea of penetrating power on modern uniform in harness and thickness plate ).

I actually started lower and with a 900lb found that a bolt of 80g leaves with a given speed and that increasing it to 125g gave only a loss of about 1-2 fps and then it started to drop quickly, so that you could assume that 125g would be the prefferred weight. The shaft weighs around 25-30g so the bolt head should be around 90g but museums very rarely have heads of this weight and more often 45-65g.

This perhaps suggests that although our ancestors were very good at empirical thought and actions they made bolts lighter than they needed to be. Why would they do this? Bolts do need to be certain sizes to work well and it could be that for them to fly cleanly at the required sizes, heavier bolts don't work. I have a feeling that this could be the answer.

The other view of this is that I have missed something here, but there are so many questions and so little time.

Tod

Economics? Transportability? Bolt heads could be just made longer, if aerodynamics would be the problem. But yeah, there are lots of factors in play here.

Sir Ralph Payne-Gallwey's famous 440-460-yard shot means that at least some of the larger crossbows could much exceed 170 fps. That distance would require 206 fps minimum in a vacuum. He made that shot with a 85-gram (three-ounce) bolt. At 170 fps, a crossbow's maximum range would have been significantly less than 300 yards (probably closer to 250 yards). I don't think that squares with the historical record, though we do have conflicting data points in that regard. Sir John Smythe, for example, gave 400 yards as the longbow's extreme range - and numbers from The Great Warbow make this plausible, assuming flight arrows and bows over 150lbs.

The 1200lb crossbow Payne-Gallwey used would presumably hit harder with a heavier bolt, but the approximately 200 joules of kinetic energy involved would have been sufficient for most purposes. There's no reason to employ a heavier, more expensive bolt when the cheaper, lighter one gets the job done. Especially if, as I'm arguing, period crossbows shot faster than current replica attempts, then lighter bolts probably did fly faster than heavier ones. That renders the observed predominance of lighter projectiles thoroughly understandable.

Can we review why the replica bows are so much slower than modern crossbows? I have a cheap 150 lb hunting crossbow which makes 285 fps with a 20 -30 gram arrow.

J