crossbow prod

Using horn and sinew for a crossbow prod at 300# + seems to me to be high risk. Although the Chinese did use that method in early times, they soon turned to the better method of bamboo leaf springs.

But if you really plan to go ahead, 1/4" to 3/8" would seem reasonable. The core doesn't really do that much: it is mainly a support structure for the working materials - the horn and the sinew. At that weight, I strongly suggest that you make the limbs quite broad because the risk of crossbow prods' becoming twisted is high.

S.

Jaroslaw:

For the short draw like this, you need a stout prod. Aim for at least 1" total (sinew+core+horn) thickness for mid limb. This depends on the width of your prod and the reflex, but 1" should be a good start. Make sinew thick, maybe even 10mm, the prod should survive the stresses with a thick sinew layer. And you can always scrape some away, if the prod is to heavy, or add some if underweight.

Good luck

Adam

Thank you Stephen and Adam.

Some of my archery friends have build prods entirelly out of wood for draw up to 200#.

This is late 15. century european weapon. Original has prod, which is probably without any wood, only horn and sinew.

It is 800 mm NTN. It has basically round shape 65 mm (2 1/2??) in diameter at median line, with little flat area on the belly. The nocks are round half horn/half sinew 25 mm or 1?? in diameter. It has cranequin.

The drawlenght is about 320 mm.

Anyway thanks again and have merry christmas!

Jaroslav

On a side note, I am curious about the picture of a crossbow above, from the Ming dynasty. Is it a hypothetical image of a crossbow with a bronze mechanism from earlier in China's history, or an accurate depiction of a contemporary crossbow in the Ming? If Chinese crossbow manufacturers had switched back to single/dual piece wood/antler mechanisms, does that not make this a hypothetical image? (Another clue to this effect is that the bolt groove does not extend to the mechanism; on a bronze mechanism, it would be optimal if the groove did extend to the lock, surely, whereas on a simpler crossbow, it is necessary that the groove start later.) In any case, the prod design is very neat.

West wrote:

Is it a hypothetical image of a crossbow with a bronze mechanism from earlier in China's history, or an accurate depiction of a contemporary crossbow in the Ming?

It was the standard Ming military crossbow. Although the lock looks like a Han bronze lock, it may still have been made with something else. Interestingly, no Ming bronze crossbow locks have survived that I know of (in contrast, say, to Tang and earler). Mao Yuanyi was very spicific about the absence of bronze crossbow locks in his time.

However, some Han crossbows were made in exactly the same way as that Mong one in the picture. I have just found a pottery figure of a man holding a crossbow just like this one!

That's interesting. It's a very good looking crossbow; however, I doubt that an antler lock could take a high weight, and this fits in with contemporary description of locks failing. Thank you for the information.

[However, some Han crossbows were made in exactly the same way as that Ming one in the picture. I have just found a pottery figure of a man holding a crossbow just like this one! ]

Do you have a picture that you can post?[/quote]

Get the new book by Holger Richter, Die Hornbogenarmbrust, even if you don't speak German! It is the single best work on the subject to this day, with plenty of actual examples described and measured to great detail. You will find the drawings and photos of crossbow prods sawn in two especially useful.

I am hoping to make a composite crossbow one day and have already prepared a lot of horn for the project. I would follow the methods used by medieval craftsmen as closely as possible as they have been well proven historically.

300# does not sound excessive. Some of the surviving composite crossbows were at least twice as heavy and the big wall mounted crossbows even more so. But I think the 30cm drawlength is a bit too much. Those prods were apparently quite stiff. I think 25cm would be more realistic and safer unless your prod is going to be very long.

1" seems a bit thin. I guess something in the range of 35mm would be more historically accurate. Also, the sinew would have to be thicker than the horn. Supposing that the horn is around 15mm, 20mm of sinew would be just about right at the thickest point (ignoring the wood as it is basically unnecessary and should not be any thicker than 5mm at any rate).

Also, the originals all seem to exhibit very similar proportions. E.g. regardless of the size and power, pretty much all crossbow prods display about the same width to height ratio. See Harmuth for additional details (complements Richter's book nicely).

The method of construction was apparently very complex, much more so than the making of an Asian composite bow. The horn must be sawn and shaped into splits carefully, then accurately grooved with a special tool so that the splits fit together without gaps. There are many layers of sinew (about 9 typically), mostly running lengthwise. But the final layers are done perpendicular to the long axis, effectively wrapping up the entire prod (including the back and sides of the horn, which is never exposed).