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Repeating Crossbows

Gwen Huskins, Stephen Selby, David Watson, 1999/2000

The following is email correspondence about repeating crossbows initiated by Gwen Huskins, and involving myself and David Watson. Many thanks for their contributions.

See also:

Vitt Jr, George G Chu-Ko-Nu, The Manchurian Repeating Crossbow Society of Archer-Antiquaries 1995 JSAA Vol. 38 p.10

From: Gwenhwyvar
Sent: 28 December, 1999 12:32 PM
Subject: Need Chu Ko Nu Research

To Stephen Selby,

I am looking for research and especially pictures of a Chinese repeater crossbow called the "Chu Ko Nu". I read about it initially in a role-playing game book and I wish to incorporate it in a novel I am writing. However, all of my research has proved fruitless and I was really hoping you could help me out.

Does the Chu Ko Nu exist at all? Is that the proper name? Was it used extensively or was it merely a fluke invention.

I deeply appreciate any help you can give me on this subject.


Gwen Lorraine Huskins

From: Stephen Selby
To: Gwenhwyvar
Sent: 30 December, 1999 9:59 AM
Subject: Re: Need Chu Ko Nu Research

Now I have reviewed the material I have got on the Chu Ko Nu. It is quite extensive. As you are researching for a novel, pehaps you don't need documentation and all the technical details. But I will be happy to supply them if you do.

The "Chu Ko Nu" existed. It was named after the famous Chinese military strategist Zhuge Liang (AD 181 - 234) who is credited with having invented it. (Note that in the standard transliteration of Chinese we use here, it would be spelled 'Zhuge Nu'. It is the same word, though.) But in fact, well-developed examples of this crossbow design were excavated from a Chu culture tomb dating from about 250 BC, showing that it had already been invented well before the time of Zhuge Liang. I think it would be safe to put it into the hands of a Chinese fictional characted dating any time from 300 BC onwards.

The Zhuge Nu belonged to a group of crossbows which could fire a succession of darts from a magazine without the user having to handle the individual darts. In some versions, it could fire two darts simultaneously, as the magazine had two channels of arrows which would fall onto a pair of arrow guides on the top of the crossbow stock. The attached picture was drawn in the Ming Dynasty (1368 - 1644) and shows a single-loading, multiple shot Zhuge Nu.

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After the darts had been loaded into the magazine (which in the Ming Dynasty held up to ten darts), an iron lever was drawn back and this allowed the next dart to fall into the arrow-guide and at the same time drew back the magazine with the string caught underneath, over the guide below the dart to where the string was held in a small trough in the top of the stock. After the lever was drawn back to the fullest point, the string was released with a trigger made of deer-antler, propelling the dart along the arrow guide towards the target. The lever was then pushed forward and drawn back again repeatedly, and the trigger released until all the darts had been fired.

The Ming Dynasty text says, "The Zhuge Nu is a handy little weapon that even the Confucian scholar (i.e. a weakling) or palace women can use in self-defence. It fires weakly so you have to tip the darts with poison. Once the darts are tipped with 'tiger-killing poison', you can fire it at a horse or a man and as long as you draw blood, your adversary will die immediately. The draw-back to the weapon is its very limited range."

From this, I would assume that the draw-weight is about 25 pounds, no more. The darts were quite small (8 inches.) The body of the crossbow and the prods were made of mulberry. Although the only part of the illustration for which a measurement is given is the arrow, we can interpolate from that that the overall length was 30.7 inches.

The string was subjected to the friction of the mechanism, so the centre part of the string was reinforced with goose-feather quills which had been split and sanded down and tightly bound on.

From these notes, you will see that you can put the weapon into the hands of either a man or a woman; that the weapon was defensive, not offensive, and the attacker would have to be quite close in. The poisons were probably based on Aconitum.

From: David R. Watson
To: Stephen Selby
Sent: 31 December, 1999 5:46 PM
Subject: Using the Chu Ko Nu

Stephen: Your account on the Chu Ko Nu looks pretty much on to me,  except that the iron lever that draws back the machine gives you about a 3  or 4 to one mechanical advantage, so the actual draw on the prod can be as  much as 100 lb (at about 6-7 inches), with the draw on the lever still  being only about 25 lb. This still makes a pretty weak bow, with about as  much power as perhaps a 35 or 40 lb. handbow. (Compared to English  Longbows from ship Mary Rose, that are calculated as a minimum of 100 lb.  draw at about 22 inches, and the average bow from that find of 139 bows   coming out at about 125-130 lb. draw. (The heaviest max out at about 175  lb. of draw. That oughta take a pretty beefy fellow to draw.....! )

I have made several of the Chu Ko Nu repeaters, so I can speak of this  with some authority from experience. First, the maximum practical rate of  fire is about 1 shot a second. Attempting to go faster than that can lead  to misfires and scattering bolts all over creation. Sometimes the thing  misfires, and 3 or 4 of the top bolts in the magazine hop right out of the  magazine if it is not closed. With a little practice you can keep the 10  or so bolts of a magazine pretty much in a 3 foot circle at 15-20 yards.

This is not a precision instrument. To some degree, you walk your shots  on, like a badly handled machine gun. The first shot may be low, but you  can raise your aim point with later shots. Since the bolts stack atop one  another, the last shot has slightly more power than the first. The  clearance of the moving parts necessary to make the machine run smoothly  and quickly increases the inaccuracy of the delivery. There just has to be a little slack in the machinery.

The system does have a fair amount of internal friction, so it is not  very efficient. The use of Mulberry for the prod is certainly about right.

Mulberry is probably the best bow wood generally available in Asia, and it   compares pretty well with Osage Orange (Bois'd'Arc) and Yew.  The bolts for this machine are generally unfletched, or have at most  a  very long, very low (1/8 inch or less in height) spiral fletching around  the shafts. It is possible to groove the back half of the shafts to  improve balance and flight, if you are using hardwood for bolts. Without  any grooving or fletching, the bolts do not fly quite so accurately, though  bamboo bolts with fairly heavy heads should fly reasonably well. If you  fletched the bolts, you would get better flight, but the fletchings tend to   tangle together in the magazine, and the machine almost certainly jams up  one or more times in a 10 bolt run.  The double magazine, that carries two bolts at a time would be less  accurate, as the two bolt grooves are slightly off center, but it would  spread more bolts around in the target area.  The machine is generally shot from the waist, with the butt against the  abdomen or hip. It is not generally accurate in any sense, though with  practice, you might shoot better than I expect. Presumably you could put  some sort of rudimentary sight atop the magazine, to make the first shot a  bit closer to your preferred point of impact.

The Chu Ko Nu is bulky and unwieldy, though not particularly heavy. It  may weigh 10 lb. with bolts in magazine. It should be quite effective in  the way of point defense, like defending a gate or doorway, and a few  people could certainly produce a cloud of arrows for a limited amount of  time. I think you could consider it a poisoned shotgun. The weight of  bolts adds up. When one is carrying a large number of bolts for such a  machine, the weight really begins to matter. If you shoot such a bow in a  field, the featherless bolts disappear under weeds, grass or vegetation  right away. I have painted bolts for Chu Ko Nu's that I built a bright   Chinese red, so I could find them a bit easier. It looks rather  appropriate that way.

Most illustrations show the magazine fitted with a top plate, that keeps  the bolts from hopping out in shooting (that can happen). Apparently most surviving machines have the top cover removed from the magazine, as the  cover seriously impedes fast loading. You can dump bolts into the top  pretty quickly, but if they are poisoned, I think you would want to wear gloves. That might slow the loading process.  I am particularly interested in the use of goose quill to reinforce the serving around the center of the string. I have found it is necessary to  serve the center with some really hard, strong stuff, like a fairly thick  Nylon monofilament, such as is used for substantial fishing lines or nets.  The thin, flexible goose quill would probably work as well.

Even so, the string wear is pretty fast. Since the bow is not very  strong, it is not too difficult to replace bowstrings, but if someone is  writing a story featuring these weapons, they should include a bit of  string changing or worry. Breaking a string would give a good excuse for  bow failure at a critical time in a story.  The illustrations and plans featured in Ralph Payne-Galwey's "The   Crossbow" work pretty well, though the actuating lever should be iron, not   wood. A wood lever, as illustrated in P-G's plan, does not stand up to  fast shooting well. Also, I use a striker plate on the top of the stock,
where the bone or iron push-pin for the lock hits the wood. Otherwise, you  wear a hole in the stock at this point rather quickly, and the thing won't  shoot at all!

The machine is certainly a useful weapon for certain limited  applications. Photos I have seen from the "Boxer" uprising of 1900 show a  number of Chu Ko Nu's lying about the ground in the Taku forts, after they  were taken by European forces, in preparation to the march to Peking, and  the relief of the foreign legations. So it looks like they may still have  been in use as late as 1900. Or perhaps the Europeans found them in  storage, and placed them about the fort for the pictures, just for interest, or as an insult to the Chinese military.

Feel free to forward these comments to your correspondent.
Happy New Year. DRW/NWA

Last up-dated April 29, 2001