# Han Dynasty Crossbow III

• #### HackneyedScribe

A French guy apparently made a replica of a one stone Han crossbow, the weakest version of Han crossbows: arbalète chinoise "classique" (pas repetition)
Brace height seems pretty high being ~30% of the full draw length from eyeballing it.
Draw Weight = 61 lbs
Arrow Weight = 30.1 grams
Velocity = 54 m/s
Potential Energy = 61 lbs * ~19 inches /2 = 579.5 inch lbs = 65.5 Joules
Energy = 54*54*.0301/2 = 43.9 Joules
Dynamic Efficiency = 43.9 Joules / 65.5 Joules = 67%

The problem with this is that the crossbow have very large siyahs that the Han crossbow prod lacked. Large siyahs are great for shooting heavy arrows relative to the bow's draw weight, but bad at shooting light arrows relative to the bow's draw weight. Han crossbows may have shot heavy quarrels, but they were light relative to its draw weight. Hence Han crossbows lacked large siyahs despite the fact that Han bows had significant siyahs. This is why Manchu bows are so efficient at shooting 100 gram arrows but inefficient at shooting 30 gram arrows.

Another experiment was done by a carpenter who appeared in CCTV. He also used a Song style crossbow to fire against lamellar armor. The difference is that whereas Song crossbows had a composite prod, this reconstruction used bamboo laths bound together. The draw weight of the reconstruction is also weaker than historical crossbows, the former being at only 160 lbs draw weight. Unfortunately there were no direct hits against a set of lamellar armor, but the two quarrels which made glancing hits did pop off scales and punch a hole through the scales they hit. The quality of the lamellar armor is unknown. It also managed to completely pierce through a wooden plank at 90 meters.

The final replica was the only one which was made by historians from the college of Qinghua. An 88 lb crossbow, prod length 75 cm, shot to a distance of 273.3 meters. Unfortunately they did not provide the weight of the quarrel, but given the draw weight and range, the quarrel was probably light.

Another problem is that if the excavated Qin crossbow is any judge, ancient Chinese crossbow prods were pretty thick relative to width (which increases efficiency), but these crossbow replicas not so much.

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• #### HackneyedScribe

Andreas Bichler also gave the following information on two of his composite crossbows, to be found in the German journal: Jahrblatt der Interessengemeinschaft Historische Armbrust 2016 and 2017.

Great Crossbow (1270lb), shot at roughly +25 degrees Celsius
Powerstroke: 14.76 inches
Stored potential energy: 1276.9 Joule
155 g bolt; 67.96 m/s; 357.94 J - 28 % efficiency
260 g bolt; 57.74 m/s ; 433.41 J - 34 % efficiency
348 g bolt; 52.92 m/s; 487.79 J - 38 % efficiency

Cranequin crossbow (1200lb), shot at around -6 degrees Celsius
Powerstroke: 7.48 inches
Stored potential energy: 589.43 Joule
81.1 g bolt; 69.85 m/s; 197.84 J - 34 % efficiency
98.1 g bolt; 64.17 m/s; 201.98 J - 34 % efficiency
105.1 g bolt; 61.47 m/s; 198.56 J - 34 % efficiency

Same Cranequin crossbow (1200lb), shot at around +30 degrees Celsius
Powerstroke: 7.48 inches
Stored potential energy: 589.43 Joule
82 g bolt; 64 m/s; 167.94 J - 28 % efficiency

That last one came from Peter O. Stecher's video of Andreas Bichler shooting his 1200 lb cranequin crossbow in the middle of summer. Note that Andreas Bichler calculated stored potential energy using the actual stored potential energy, not the linear estimate "draw weight*powerstroke/2" equation that we had been using. If we calculate by the linear estimate, it would result in the following (bolded parts are the numbers which changed due to switching to the more popular method):

Great Crossbow (1270lb), shot at roughly +25 degrees Celsius
Powerstroke: 14.76 inches
Stored potential energy: 1059 Joules
155 g bolt; 67.96 m/s; 357.94 J - 34 % efficiency
260 g bolt; 57.74 m/s; 433.41 J - 41 % efficiency
348 g bolt; 52.92 m/s; 487.79 J - 46 % efficiency

Cranequin crossbow (1200lb), shot at around -6 degrees Celsius
Powerstroke: 7.48 inches
Potential energy (linear): 507.12 Joules
81.1 g bolt; 69.85 m/s; 197.84 J - 39 % efficiency
98.1 g bolt; 64.17 m/s; 201.98 J - 40 % efficiency
105.1 g bolt; 61.47 m/s; 198.56 J - 39 % efficiency

Same Cranequin crossbow (1200lb), shot at around +30 degrees Celsius
Powerstroke: 7.48 inches
Stored potential energy:
507.12 Joules
82 g bolt; 64 m/s; 167.94 J - 33 % efficiency

So as you can see, stored potential energy went down because we are calculating it linearly, efficiency went up to compensate, ergo the resulting joules imparted into the projectile is still the same. Also note that the weather affects crossbow power because as Andreas Bichler noted, composite prods lose draw weight in hot/wet weather but gain them back in cold/dry weather. Compare this with what I translated from the CuiWei XianSheng Bei ZhengLu:

During the hot summer, when it's raining and there's steam, the horn [composite prod] should be easily taken off, and use a wooden [simple prod] crossbow. During the spring and winter, where there is wind and bitter cold, the wood (simple prod) is heavy and sluggish, and horn [composite prod] crossbows must be used.

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• M

#### MJuingong

Thank you. I was almost driven nuts by your earlier articles with the indecipherable characters (I wondered if you had written in Chinese and the characters were oddly converted).
I expect to peruse this often.

• #### HackneyedScribe

Welcome. Most of the reason for the weird characters is because the new forum didn't successfully convert the Chinese characters I wrote. Hence this new thread, with reduced usage of Chinese characters just in case.

Futurist

• I

Did Chinese crossbow trigger ever made of cast steel instead of cast bronze?

• #### HackneyedScribe

Not that I know of, steel needs to be hammered into shape, and the shape of the Chinese crossbow trigger would be difficult to be hammered into the precise shape it needs to be. Bronze could simply be poured into a mold, so it's much easier if you want precise instruments. This is especially true with the Chinese piece mold process in which case such triggers could be mass produced. This is because the piece mold process allow you to preserve the mold for casting over and over again. Whereas in the lost wax process the clay mold is destroyed after each casting, so if you want multiple cloned copies then you need to create the exact same mold over and over again.

• I

Not that I know of, steel needs to be hammered into shape, and the shape of the Chinese crossbow trigger would be difficult to be hammered into the precise shape it needs to be. Bronze could simply be poured into a mold, so it's much easier if you want precise instruments. This is especially true with the Chinese piece mold process in which case such triggers could be mass produced. This is because the piece mold process allow you to preserve the mold for casting over and over again. Whereas in the lost wax process the clay mold is destroyed after each casting, so if you want multiple cloned copies then you need to create the exact same mold over and over again.

Didn't the Chinese create cast steel objects?

What is the difference in casting a steel object and a bronze object?

There is not much stress that could a cast steel to break in pieces, the main concern, in my opinion, would be rusting that could jam the mechanism. Bronze did not rust in the way iron and steel did.

Why would the lost of bronze casting technology affect Ming crossbow design, when they could make it out of steel?

• #### HackneyedScribe

I think you meant cast iron, steel wasn't that special at the time, I'm not sure about this 'cast' steel. Cast iron were generally too brittle to be used as weapons, however the ancient Chinese did manage to create malleable cast iron, which was soft enough to be used as weapons.
Steel is iron with a certain amount of carbon. The higher the amount of carbon, the harder and more brittle the steel. Too much carbon and it becomes cast iron (very brittle).
Bronze is copper with a certain amount of tin. The higher the amount of tin, the harder and more brittle the bronze.

Bronze is easier to cast than iron because it has a lower melting temperature. However, tin was an expensive material so bronze was more expensive than iron.

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• I

I have often read that the Chinese decarburize cast iron object, so they would have the more malleable property of steel. I assume that there would be no great change in the shape of the object during decarburization or else the cast object would need to be reworked.

Also cast iron, while brittle, wouldn't be stressed enough to break in a crossbow trigger.

• #### HackneyedScribe

I have often read that the Chinese decarburize cast iron object, so they would have the more malleable property of steel. I assume that there would be no great change in the shape of the object during decarburization or else the cast object would need to be reworked.

Also cast iron, while brittle, wouldn't be stressed enough to break in a crossbow trigger.
The most common way of steelmaking for the Han dynasty was hammering/folding high carbon iron. The process definitely changed the shape of the object for a number of times, depending on how many "foldings" you want. The more times it was folded, the lower the impurities, the higher the quality of steel.

From Donald Wagner: Flow diagram of iron production in a Han state ironworks. The fuel was charcoal. Cast iron was produced in blast furnaces, and this was either cast into useful products in a cupola furnace or converted to wrought iron in a fining hearth. Steel was made from wrought iron by any of a number of processes and used in the making of implements which a hard sharp edge.

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