[Dan Howard]

I've been hearing that the trigger mechanism of the Han crossbow enabled a longer power stroke for this weapon and vastly increased its delivery energy. I was wondering whether anyone had actually done a proper experiment with this weapon to see what the impact energy of one of their projectiles would actually be? The theoretical calculations seem way too high to me.

The main one I see reckons that a 6 stone strength Han crossbow (387 lbs) with a 19 inch powerstroke can deliver 312 Joules to the target.

[Benjamin H. Abbott]

It depends on the efficiency of the bow, but if the power-stroke and draw-weight figures are correct then it should be high with any reasonable efficiency. 19 inches of power stroke is perhaps a bit much, but it's something along those lines based on the extant examples. 387lbs at 16 inches would still be 175 J at 50% efficiency, assuming a linear force curve. 70+% efficiency seems more likely, depending on arrow weight and whatnot.

As far as I know there aren't any published tests of Han-style or similar crossbows. I'd love to see some!

[T. Kew]

A back of the envelope calculation says that such a crossbow would have on the order of 400-420J stored in the bow, at full draw. Perhaps more if the bow is significantly pre-loaded or the draw-force curve is significantly non-linear.

Having said that, as long as the bow is wide enough*, I don't see why the trigger mechanism has much of a bearing on the available power stroke? The peak draw weight, certainly - a weak trigger will fail, and other designs might be impractical to fire at high load. But the power stroke isn't in and of itself a difference: two bows that draw to 300lbs will put the same pressures on the trigger, whether that's 300lbs at 5" or at 20".

I'm not directly familiar with Han crossbows, but I seem to recall they have quite large bows, in terms of width etc, which would seem to make a long power stroke quite a plausible feature.

*If too short, then the string angle at the trigger would be exceptionally acute, which might be problematic for some designs.

[Dan Howard]

I'm more concerned with impact energy. The theoretical initial energy of the device doesn't really mean much. We'd need the weight of the projectile and velocity at various ranges.

[Timo Nieminen]

[Benjamin H. Abbott]

[Dan Howard]

[Timo Nieminen]

[Dan Howard]

[Benjamin H. Abbott]

[Timo Nieminen]

[Timo Nieminen]

[Dan Howard]

[Benjamin H. Abbott]

A Deadly Art has a 177g central European crossbow bolt dated to the 15th century, which is the heaviest extant crossbow projectile intended for war I've seen. In theory Payne-Gallwey's bow might manage around or slightly over 300 J with such a bolt. Of course, no replica crossbow tests manage anything like that.

As always, we need more tests!

Also note that heavy Han crossbows were tricky to span. By many accounts crossbowers commonly spanned their weapons on their backs using arms and legs together. That's awkward. Spanning methods apparently improved later on but were still time-consuming in the Song era whatever they were - hence the rotating volleys. Having a long power stroke requires different and perhaps less desirable spanning techniques compared with shorter power strokes like 15th/16th-century European crossbows have. So thinking about the heavier Han crossbows as in some ways akin to the so-called European siege crossbows like Payne-Gallwey's has merit.

What we need are detailed replicas of a variety of different crossbow styles and then tests of these weapons and different spanning methods. It's likely the some or many of the designs that produce less kinetic energy were more convenient and faster to span. A goat's-foot lever appears to have considerable advantages over having to lie on your back to span, for example.

Finally, it's not completely clear why big honking 18lb crossbows don't seem to have been used in great numbers on the battlefield in 15th/16th-century Europe. (They appear more common for defending walls, castles, and so on.) Long muskets were as heavy or heavier and they saw mass employment in the field in the 16th century. A 18lb musket is presumably harder to hold steady than an 18lb crossbow because of the musket length; 18+lb target crossbows were apparently used without rests in the 17th and 18th centuries. The draw weight of one of these 18th-century windlass-drawn target crossbows is estimated at 1,848lbs (840kg), which would make it even more powerful than Payne-Gallwey's bow assuming a similar power stroke.

[Jean Thibodeau]

[Timo Nieminen]

[Benjamin H. Abbott]

Yeah, I suspect cost was a major factor. Additionally, the social and economic factors that produced the 16th-century armies that contained many musketeers weren't necessarily in place in the 15th century.

On the technical-theoretical level, another complication when thinking about European crossbows is that many or most of these weapons before 1500 had composite rather than steel prods. Composite prods should perform better than steel if properly made and maintained - and they're much lighter to aim or carry. In theory a 1,000lb composite-prod bow spanned by cranequin or windlass might perform as well as Payne-Gallwey's steel 1,200lb bow but only weigh 10lbs or even less. This 616lb crossbow stores approximately 67% of the energy the 1,200lb steel bow stores but only weighs 6.6lbs. So it's possible some European battlefield crossbows delivered well over 200 J - perhaps 300 J with a heavy bolt. Of course, the linked reconstruction performed miserably for it's draw weight, so we're a long way from confirming such speculation.

[Bartek Strojek]

[Benjamin H. Abbott]

The larger horn crossbows in the photo above look like they might draw around 1,000lbs or even more based on a quick visual comparison with this 616lb reconstruction. As mentioned before, though, this reconstruction performed poorly, so it might not even be worth anything as a guide. Unfortunately, I don't know of any other detailed tests of reconstructed European horn crossbows. I imagine horn crossbows did reach a practical limit at some point because of a limb thickness. I'm not sure that's why steel crossbow eventually became more common. There's evidence that manufacturing horn crossbow prods was a specialized and at times carefully guarded skill. Steel crossbow additionally should require less maintenance than horn ones. It's possible these economic and reliability factors made steel more desirable overall despite worse performance.

Finally, I'm not even sure how many steel crossbows actually saw use in historical European warfare. Steel prods appear to have gained popularity around the same guns replaced crossbows in most units. Based on artwork from Paul Dolnstein and the like, horn crossbows continued to see military service into at least the very early 16th century, especially for mounted crossbowers.

[Jean Henri Chandler]

By the late medieval era whether composite / horn or steel prods were used was largely a matter of regional preference. Composite prod crossbows performed better in extreme cold so they remained popular in certain areas (like the Baltic and the Alps) long after the steel prod weapons became available. The Teutonic Knights used both types.

By the second quarter of the 15th Century some quite small crossbows suitable for use on horseback (which you still see being used into the 18th century for hunting) were nearly as powerful as the larger siege crossbows, I think that is why the big siege weapons didn't necessarily have as much of a niche on the battlefield. That said, I don't think we have actual evidence that they weren't very widely used - most of the records of armies and battles don't distinguish them or get to that level of detail. What we do know is that crossbows were ubiquitous and were heavily used by the infantry of the late medieval period and we do see the windlass spanners which are most closely associated with the bigger siege crossbows in the artwork quite a bit. We also see plenty of the steel prod weapons. Like in the Wolfegg housebook images, Rhenish 1480's-1490's, here:

http://upload.wikimedia.org/wikipedia/commons...uselang=de

You can also see handgunners mixed in with the crossbowmen in that image, incidentally.

The crossbows in (1467) Talhoffer look like they might be composite but are small, comfortable for the horseman to use:

http://tnypic.net/5vgu3.jpg

http://tnypic.net/ake7z.jpg

Composite prod weapons weren't necessarily always lighter either. Obviously it depended on the size of the weapon. The composite prod crossbow which was the Higgins armoury (now at another art museum) in Ma was huge. Also cranequin spanned rather than windlass, in spite of the size.

I just don't think we know enough detail about how armies were equipped and wars fought in the medieval period to make some of these sweeping statements. There is clearly an enormous amount we don't know about how these weapons were used in this period, or in other eras like in China or ancient Greece.

Jean