Here's my preliminary sketch for the Chu-ko-nu. The magazine in the original is usually made out of a single piece of wood with the centre hollowed out but I've decided to go with separate pieces instead to make it easier to build. I've yet to decide on the scale so there are no dimension on the sketch but I'm thinking of making one with an overall length of only about 10".

I will be posting periodically here to post the progress of the construction from start to finish.

(Disclaimer: Making a real cross-bow is illegal in most countries. If you make a life-sized one based on my designs, you do so at your own risk. These designs are meant only for a small scaled model "toy". The author will not be held liable for the use for the plans above. Usage is at your own risk and discretion and have been provided only for academic purposes.)



Magazine & Trigger Elevation & Details


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Construction Begins!

26th April 2005 - Finally worked out the required dimensions and material to use. Got most of the wood I need, mainly Basswood.


29th April 2005 - I'm somewhat finished machining most of the main pieces. The most complicated was the trigger pin and slot which took about 2 hours of careful chipping, cutting, planing and scrapping.


30th April 2005 - Ahh... I've started assembling the pieces. The trigger and magazine are a little tricky as every piece has to fit perfectly and once glued together, it'll be very tough to correct mistakes. Just cutting and fitting the grooves and slots took me hours to do, adjusting one way then another.


1st May 2005 - Finally it's taking on a more recognisable form. The magazine, trigger and pull-handle and main body are done, but I've yet to find the right piece for the bow arms.


2nd May 2005 - Ok, only the bow arms and bow string left to make. This will take a little bit to tuning to get it just right as the magazine must be able to catch the string and still have sufficient draw to shoot the arrow.


9th May 2005 - Still doing minor retuning. I've gone through 2 bows now, both snapping when tensioning... or rather overtensioning. This is the magazine cover in detail.


10th May 2005 - Done! 3rd attempt at the bow arm. Made it longer this time. Here's the completed zhugenu.


Another view with insert showing the corking action (magazine raised)


This post has been edited by Liang Jieming: May 9 2005, 10:09 PM

Just a couple of questions, Jieming.

When you go about making the, were you mainly interested in replicating them the way they were designed/made in the past?

Or did you also think about given the level of technology at that time, how the design could have been further improved?

For one thing, I am curious to know whether it would have been more useful to mount these weapons on tripods.

The modern tripods allowed most weapons to be set up in various terrains, including uneven, sloping, etc, because their legs were adjustable. They not only provide a stable base, but also allowed for the weapons to be redirected easily.

Would such an implement be achievable in the past before the sophisticated engineering of extendible metal/alloy hollowed legs?

I tend to go for historical accuracy though I do make slight modifications for ease of construction since I don't have the time or sometimes the tools for really complicated work. :-)

I don't know if they used them on tripods since these were relatively light weapons and could be carried by soldiers. This is the site I'm basing the chu-ko-nu on and it is a write-up on an actual weapon. According to the author, it weighs only 3 lbs.

I'm sure tripod technology wasn't beyond the ancients, especially the Chinese since if making hollow tubes are a concern, they did have bamboo! As for extendable legs, well... probably not but foldable legs are definitely possible.

http://www.arco-iris.com/George/chu-ko-nu.htm

Greetings,

Also see here:

http://www.atarn.org/chinese/yn_xbow/zhugehtm.htm

for a discussion and some more diagrams.

Good luck!

Daniel Slone

Cool stuff. ... I wonder if your cross-bow can be done with a lego set. ...
... If you were to build a "real deal" crossbow, What type of materials will you use to assemble the crossbow?

Cool stuff. ... Thanks!

Any type of hardwood would do except for the bow arms themselves. I'm still working out the dimension and material for my model at the moment.

will you also make the "tiger killing poison" to go with it?

Have you ever thought of making these on commission? I know I would pay (a reasonable price) for replicas of Chinese siege weapons!

People have made auto-crossbows before, you can google up some for examples.

and any thoughts of projects after this? Howabout a hampster powered trebuchet?
Or a multi-shot siege bow!

Ah... I just got back from HK 2 hours ago. I saw this beautifully crafted ancient chinese siege ladder at a heritage store at the Star Ferry terminal on Kowloon side. I was going to make one of those as Yun suggested but after seeing that, I think I'll just buy one. It looks absolutely beautiful. I'm flying back to HK next week again so I'll be going to take a look at it again and to see whatelse they have.

Commission? Nah, taking money will only kill the fun for me building stuff. Besides, I'm too lazy.

What's next? I don't know. I have yet to finish the Chu-ko-nu since I wasn't around over the weekend, but I'm kinda leaning to building the multi-bow siege crossbow after all that discussion on the other thread! Anyway, that'll have to wait until I'm done with the Chu-Ko-Nu. I'm going to go buy the material sometime this week. I need to settle back into the rhythm of things and clear work first. It's amazing how much work can pile when you're away even for just one day!

Tiger Killing poison??? ... How about the cobra stuf that you can import from India? ...

One more thing, you do mean a hamster not a hampter?? ...

The trigger is proving a ***** to make, especially since it's a small part made even smaller by having to scale it down even further for my model. It's got to be perfectly fitted into the hole and grooves for it to function well but just loose enough to move up and down easily when the crossbow is in operation.

The grooves/hole need to be done almost perfectly with all the edges sharp and vertical too.

I thought of modifying it to make it simpler but then abandoned that idea for historical accuracy. I'll just have to keep at it then. :-) I've modified the magazine a little bit to allow the trigger to be made just a little easier. I should have everything ready to cut and carve by tonight. I hope to finish up this Zhugenu before Sunday night or it'll be delayed another few days while I'm in HK.

Ok, I cheated a little in making the trigger. The whole assembly is supposed to be made out of a single piece of wood, but because of the small scale of this model, I don't dare try such minute chipping and carving on the slender pieces. So instead, I used two separate pieces and cut the half holes separately before joining the pieces together. This trigger should work but I'll only know for sure only when the whole chukonu is fully assembled. If it doesn't work, it's going to be a pain in the *** to correct since there is no way to get at the trigger after that.

A impressive feat of work.

Cardinal, thanks.

It's almost done except for the most important component, the actual bow itself. I'm still trying to find suitable material/pieces for it so I fear I won't finish it this week. I will complete the whole assembly except for the bow arms which will have to wait till I get back end of next week.

I hope you guys are having as much fun watching this as I am making it. My fingers are sore from having to stay steady while gripping tight enough to carve properly.

This is one challenging piece! It looks deceptively simple until you try and make one then you realise the precision required. I'm even more in awe of the original inventors of this thing now. And to think it was first built 2000 years ago. Dang, they were superb engineers!

Quite frankly, compared to the Mangonel and Ballista I built earlier, this zhugenu is much, much harder to build.

It's been slow going because I've had to reshape the magazine-mainbody interface yet again. It wasn't quite the right shape for the trigger to work while still remaining well within the movement groove.

My pull arm alignment is still a little off as the two pin joints are not exactly parallel. I'm working on getting them parallel at the moment or when pushing forward, the magazine will run off the grooves.

I've also hit a roadblock with the bow arms. My first one cracked in two during pretensioning. I'm using bamboo this time and am forcing it to creep with some long term stressing before trying to pretension the bow again. It's been a pain shaping both bow arms to match. (Can't have one side bending more than the other!)