New Project - Chinese Repeating Crossbow

First topic message reminder :

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.

Dane

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I took videos and photos this past weekend. Those will be up soon with a summary of performance.

Sweet

Here are some test results and photos, gang.

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.

Dane Donato

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.

Dane

Great to see it action! I see your first post in the project was nov. 6th, but when did you actually start construction? I'm curious about how long it took.

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.

Dane

I agree completely, for me it's all about the process, not the product.