Hi, fellow Guild members. Having always wanted to shoot one of these little weapons, I decided to do a fairly simple project and build a Chu-Ko-Nu, and am writing a how-to article for Primitive Archer magazine.
So far, this has been a real pleasure to build. Tuesday some bamboo is coming from a vendor so I can get the bow built and installed, as well as some cedar shafting to make the little bolts. What is neat about this project is that I have been able to use scrap hardwood, so it isn't costing me much. Aside from the bolt materials (already had some field tips sitting around I can use) and two 1/'4" brass threaded machine screws and washers, plus the bamboo slates, there has been no special outlay of money.
I expect to have this little weapon completed in the coming week or two, and will eventually post more photos and video of the weapon in action. If anyone wants, I can do a quick buildalong. These are just random photos to show various stages of progress.
Chu ko nu are my favorite historical crossbows and I have built several of various sizes. The biggest issue is string wear. Second one is getting bolt accuracy with no fletching. I have found that an articulating joint in the lever will keep the shuttle section flat and reduce the seesaw string destruction. Also, fairly heavy points and light arrow material, say birch or cedar work well.
Thanks for sharing. Maybe I will post some of my chu ko nu.
Thanks for the comments, everyone. Todd, the lever gives you a 4/1 advantage, so in theory, the bow can be fairly powerful. I am not sure what the bow I am making will give me, as I am using exact dimensions from an actual bow someone published research on in the 1990s, and I found online.
I do plan to use relatively heavy metal tips on light shafting. I believe that the original bolts did have fletching, very slight though, as they will bind up in the magazine if the vanes are very big. I am thinking of using parchment maybe, or perhaps goose feathers, two vane probably.
Jake, I'd like to see your bows. And I agree, the string is the weak link in these machines. The original I based this on used rawhide string, but an old document states that you bind on goose quilles to minimize string wear.
Here is a quote from a Ming era document:
“The [Chu-Ko-Nu] is a handy little weapon that even the Confucian scholar or palace women can use in self-defense. 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.”
So yup, poison is the secret. What I find very interesting about the Chu-Ko-Nu is that it was in use in warfare for at least 2000 years. The last time it was used in modern combat was during the Boxer Rebellion circa 1900.
Hey guys: Geezer here with a few observations concerning chinese repeating crossbows. I have made a few of them, so can speak from some experience. First: string wear is inevitably pretty bad, given the geometry of the machine. Using a really hard string-serving and lots of lubricant will help, as will making the bolt-track really slick, with rounded edges and paying close attention to detailing the lock/notch and the push-pin that releases the whole thing. Of course, adding things like goose-quills to the string could increase string-life, but will also add to the string-weight and cost some modicum of performance... not that you should expect particularly high performance in the first place. Try to keep any slack in the parts, particularly where the magazine and table slide on the lower stock, down to a minimum. That will really help accuracy. I found I could keep all my bolts near the middle of the target, shooting from the hip at 20 yards, shooting about one shot a second. You can walk them on target as you go. Much more than that may be beyond the machine's ability. As for fletching bolts, there are two fairly workable solutions. I have made bolts with heavy heads and grooves cut from about mid-way to the tail. 3 or 4 grooves should suffice to give you higher friction at the tail and heavier weight at the head of the bolt. This helps accuracy a LOT, and the grooves won't hang up in the magazine like feathered bolts will do. The original Chinese solution is to fletch the bolts with a very low (1/8 of an inch high?), thin line of feather or even twine, spiralling down the length of the bolt. Start your spiral about midway and go all the way aft. One single line of fletching will do, if it makes a couple of turns around the bolt as it spirals aft. The spiral fletching won't lighten the tail of your bolt, but as long as you use narrow heads, like target points or bodkins, you should have enough fletching to make the bolts spin and keep 'em straight. There's one more problem with Chinese repeaters that hasn't been mentioned yet. Well okay, there are two problems. Payne-Gallwey's plan shows a handle made of wood. If you shoot at all fast, you'll probably tear your wooden handle to pieces in a day or two. Get some mild-steel strap from the hardware store and make your handle from that. Second, unfletched bolts disappear beneath the grass MUCH easier than fletched bolts do. Be prepared to make a whole bunch of bolts and don't be surprised when they disappear. Hint: If you take off your shoes and walk slowly back and forth between your firing-line and the target-butt, you should be able to feel the bolts buried beneath the grass. Anyway, have fun with the repeaters. Geezer.
Thanks for the input, Geezer and Ivo. Fei chang gan xie.
I never expected a high performance weapon, and keeping in mind what these were used for goes a long way toward enjoying such a weapon. Since my nasty old next door neigbor died already, alas, I can't test out the tiger killing poison and see how that goes lol.
The bolt suggestions are excellent, thank you for that. I will try at least two of the methods and see how they play out, and provide video of the whole affair, dead tigers and all.
I expect that historically, extra strings would have been on hand.
I made very careful mortise and tenon joints for the handle, and hope that helps. We will see.
With one simple joint and a slightly different sliding diaphragm trigger nearly all string wear can be negated. Also, putting the bow itself on a solid pivot point solves it. I have one toy-bow with two bottom handles on here somewhere that demonstrates both improvements. I should draw up the trigger design, its really simple.
Essentially, the repeater is finished. I still have some bits of touchup, testing it and so on, but overall, this project is complete. I will be testing it at the range this weekend. I have a dozen bolts made up.
This was a totally fun project. I recommend anyone to build one of these. I've only scratched the surface, I suspect, of this particular weapon and the varients I can produce.
Performance photos, videos, and more thoughts through the testing process will follow. But I wanted to share this now. Happy T-day, everyone.
Overall, not a hard project. I was suprised how weak this bow is, but then again, I probably tillered the bamboo bow so it is on the whimpy side. The next one I build, I will shoot for a 30 to 40 pound draw. As it is, the little bolts dont penetrate the target very well, and one hits the next and knocks it out. I guess that if you were shooting with poisoned tips, just a scratch to any exposed flesh would be enough, but at this rate, this weapon won't even penetrate normal clothing.
I made the string using an extra 15 strand reverse twist flemish bowsting (B50), and it seems to be holding up really well to the excessive rubbing that this little machine creates.
For a finish, I ended up staining the wood with black and a dark red stain. The magazine lid and bow are black, the rest being that red shade. The symbol I painted on the side of the weapon is the Chinese symbol for rain using clerky script, which dates to the Han and Qin dynasties. The idea being of course that I will create a rain of arrows. I used a brush and India ink for this, and wish I had been a bit more careful.
I was surprised how accurate the groupings were. I know I was shooting at ultra close range, but figure that these little bows were intended for up close and personal combat. I did try fletching some arrows, but I had not factored that into the build, and so I didnt have enough clearnance in the little barrel section of the bow. Next time
Notice too that I have to give a bit of a nudge to the string to catch it in the notch as I push the lever forward. I have to tiller the bow so the tips are further back, or string it with more tension. I didnt want to risk breaking the bow by bracing it back too agressively at first, but still got a good rate of fire overall.
One other issue I found with this weapon is that it can jam if a bolt slide back and jams between the back of the magazine well and the string. Not sure what do to do about that yet. There is I am sure a solution.
Overall, it was a satisfying project, and very cool looking. I do plan to try building more of these, including a big one after an image I saw of ship to ship combat. The double barreled ones look pretty groovy too.
Your Chinese repeater looks very nice. Concerning jamming/misfire, it's important that your magazine/string interface is so designed that the bolts CANNOT come down atop the string/lock-notch. They can fall a bit ahead, with only a bit of energy-loss, but atop the string guarantees misfire. Now you have identified the problem, a bit of shimming in the right place should fix things up. A few linear grooves cut into the back-half of the bolts will increase air-friction at the tail and move weight forward. That'll give you more accurate flight. I see your cocking-handle makes contact with the top of the magazine... that might be interfering with getting the string into the notch. Adjustment of the handle, or cutting a bit of relief in the top of the stock would solve that, but of course you'd have to remove the magazine top-plate. Apparently those plates were commonly lost or discarded from ancient bows. I never bothered to fit top-plates to my repeaters. They load faster without 'em. However, a misfire will often send bolts flying out of the top of an unsecured magazine. It's pretty entertaining. So keep having fun with your repeater. Geezer
Thanks, Geezer. I appreciate your critique. I am thinking the top magazine plate is pretty important in that it minimizes the chance of a poisoned bolt scratching the operator, and if you were running around ancient (name your city or hamlet) fighting off invaders, you want to keep your bolts in the magazine. Slapping the little plant on top also feels a bit like sliding a magazine home into a semi auto handgun or rifle, and that is kinda fun. Not, of course, that you should be slapping anything into anything, as I believe the originals had slots in the upper insides of the magazine and you slide it in and out.
Some shimming is indeed required to solve the jamming issue. I will revisit the handle as well, or just incorporate changes into my next repeater. I have found it is good to keep projects like this around to remind you of important lessons.
Hopefully others can learn from my mistakes and insights. That is what this site is all about.
Thanks much, Gnome. I'd say it took about 35 hours over a bit over a month's time to make this. I took my sweet time on it, as it such a new kind of project, and I expect other repeaters will take much less time, maybe 20 or so hours? For me, the process of building and solving problems is probably more fun than actually finishing a weapon. Maybe you or others feel that way? Time at the workbench is relaxing time, almost meditative.