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X Zhang
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 Posted: Wed 04 Dec, 2013 6:57 am Post subject: |
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i think……you can try a Pistol grip……just like a chinese crossbow ......
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David J.
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| Posted: Sun 08 Dec, 2013 3:35 pm Post subject: |
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| Quote: | | Various torsion weapons saw use in medieval times until replace by gunpowder weaponry. |
Indeed. However, they appeared primitive when compared to those employed by the romans. Despite what some authors may claim, the Springald, with its wooden frame and large size, seemed archaic and immobile when compared to Roman iron framed weapons. Furthermore, medieval torsion devices appear to have utilized horse hair for their torsion springs. Much like today, large quantities of sinew, which was considered superior to horse hair, may have been hard to come by.
| Quote: | | Oh, and apparently there are claims of 1,000+ yards for triple crossbows. |
That is not supported by modern reconstructions. My best guess would be an effective range of 125 to 175 meters (250M max).
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One big difference between the European single bow crossbows and the Chines triple bow crossbows seems to be that the power stroke and the bolt are much longer, so probably they get a lot more speed out of their crossbows because of better use of the stored energy in the bows. |
True, the triple crossbow would have a longer power stroke, but that power stroke would be hampered by the substantial mass of the prods. A long bolt is likely a heavy bolt. A long bolt would have to be rigid enough to weather the acceleration when launched, thus it could not be too thin. A heavy bolt suggests a low velocity launch ( +/- 50m/s).
| Quote: | | Keep in mind that my drawing is a fantasy design and if it was to be actually made it would need more attention to details like friction that could wear away the crossbow string and how it would be armed using a pulley system. |
Realistically, a pulley system would be essential. It's not just the friction, it is the forces that would be applied to the limbs as the weapon is cocked and fired. Museum reconstructions tend to exclude pulley systems. Functional reconstructions use a pulley system or equivalent device(carabiner). The performance of the system would be negatively impacted by such a device, since they would be positioned at tips of the limbs. Those pulleys would be primitive and heavy when compared to modern compound bow pulleys/cams which are ultra thin, constructed of lightweight alloys and are shaped to maximize the draw force curve.
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Ken Speed
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| Posted: Sun 08 Dec, 2013 8:14 pm Post subject: |
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David wrote:
Realistically, a pulley system would be essential. It's not just the friction, it is the forces that would be applied to the limbs as the weapon is cocked and fired. Museum reconstructions tend to exclude pulley systems. Functional reconstructions use a pulley system or equivalent device(carabiner). The performance of the system would be negatively impacted by such a device, since they would be positioned at tips of the limbs. Those pulleys would be primitive and heavy when compared to modern compound bow pulleys/cams which are ultra thin, constructed of lightweight alloys and are shaped to maximize the draw force curve.[/quote]
I'm in partial agreement. I do think that if Jean's conceptual drawing were to be made in reality sheaves would be very desirable if not absolutely necessary to eliminate excessive wear. Although we do see the Asian reconstruction that has no sheaves, maybe they just accepted a lot of broken strings.
Actually the sheaves wouldn't have to be either particularly heavy nor crude. Many early machine parts were made from Lignum Vitae and were not excessively heavy and lasted for years under very taxing mechanical strains.
I don't see why the sheaves or rollers would negatively impact the efficiency of a triple cross bow when the cams of a compound bow don't seem to be a problem.
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Benjamin H. Abbott
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| Posted: Sun 08 Dec, 2013 10:55 pm Post subject: |
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Part of the issue regarding range comes from interpreting the pu/pace unit of measurement. Here it's a question of either 2 or 5 feet, but other authors give other figures depending on the period in question. Roger Hart gives the post-Qin pace as a 1.386m or about 4.54 feet. It's a complicated topic, but beyond Franke and Smith, I don't see anybody claiming the Chinese pace (pu/bu) as 2ft.
Also note that reconstruction performance varies. Firefly far outperforms any other Roman ballista reconstructions. Just because nobody's done it yet doesn't mean it didn't happen back when these things were more than curiosities.
As far springalds go, Jean Liebel's model and calculations suggest they performed reasonably well, shooting a 1.4kg bolt 180m at an elevation of 15 degree from a tower top.
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David J.
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| Posted: Mon 09 Dec, 2013 8:08 am Post subject: |
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| Quote: | | Although we do see the Asian reconstruction that has no sheaves, maybe they just accepted a lot of broken strings |
Are these modern reconstructions? Are they functional weapons or museum pieces? Original drawings of the triple crossbow do not show sheaves. Overall, those drawings are not very detailed.
| Quote: | | Many early machine parts were made from Lignum Vitae and were not excessively heavy and lasted for years under very taxing mechanical strains |
Lignum vitae has a high specific gravity. "Excessively heavy" is a relative term. A pound may not seem like a lot, but adding it to the tips of a limbs makes a big difference.
| Quote: | | don't see why the sheaves or rollers would negatively impact the efficiency of a triple cross bow when the cams of a compound bow don't seem to be a problem. |
Modern pulleys are generations ahead of ancient pulleys. Modern pulleys/cams increase the power stroke and fatten the draw force curve. In a triple crossbow, the pulleys would not do any of these things. The longer power stroke occurs as a result of the limb/string configuration.
http://www.worldarchery.org/en-us/results/rec...s/men.aspx
As you see, modern conventional flight bows still outclass compound bows in range. I am sure a current, top of the line compound bow would set a new record, but conventional flight bows would still be competitive.
| Quote: | | Part of the issue regarding range comes from interpreting the pu/pace unit of measurement. |
Perhaps it’s not the unit of measure, but the accuracy of the text. I can show you a journalist article that claims a .50 rifle will take out a tank. That does not mean it has any truth behind it. Extraordinary claims require extraordinary evidence.
| Quote: | | Also note that reconstruction performance varies. Firefly far outperforms any other Roman ballista reconstructions. Just because nobody's done it yet doesn't mean it didn't happen back when these things were more than curiosities. |
Nick Watts had previously constructed a wooden ballista that managed approximately 750 yards.
This machine claims an exit velocity of up to 105+m/s.
From here: http://www.cerco21.com
| Quote: | | From the equations above we can compute our exit velocity based solely on our construction variables (overall size and spring size). Using our Medieval Balista we've computed and exit velocity of 132m/s however field testing and high speed photographs showed an exit velocity of around 120 m/s. |
Modern onager reconstructions shoot well over 200 m/s.[/url]
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Semih Koyuncu
Location: Turkiye Joined: 23 Oct 2013
Posts: 15
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| Posted: Thu 19 Jun, 2014 1:57 am Post subject: |
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There is a paper about this weapon. Below comment and image is belong to Bede, a member of ATARN society.
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McEwen, E., "The Bow of the Ox", Journal of the Society of Archer-Antiquaries, 1985, Vol. 28, pp. 15-21. He details a reconstruction he made with straight self bows that had an extraordinary draw length and was very efficient. It details the different strengths that the bows must have to draw evenly (i.e the forward bow must have half the draw weight of either of the two rear bows). He speculated on the potential performance of a similar set up with composite bows and believed it might have equalled the historical accounts.
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This study is beyond my reach but if someone could get it. A detailed review would be good to hear.
Further, there are bunch of theories about how Mongol invasion of middle east bring that weapon to west. The Persian historian of age, Juvayni while recording campaign of Mongol leader Hulagu against Assassins castle of Maimundiz mentions some Khaitan( Chinese) specialists using kaman-ı gav, literally meaning ox bow in persian (remember another name is for this type of crossbow was eight ox crossbow in Chinese litrature) and burning and killing defenders with it's meteoric shafts.
In case of immense distance given by historical resources (some claims that even 2500 paces) Stephen G. Haw in his article Cathayan Arrows and Meteors:The Origins of Chinese Rocketry claims that the javelins of this sort of crossbow was gunpowder aided thus enabling them to traverse such great distances. Another interesting claim to be researched in my humble opinion.
Lastly, could anyone provide additional information about trigger of below reconstruction? It looks like different from ordinary Chinese triggers.
http://www.youtube.com/watch?v=86Nv1Yz9x1g
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