9 replies to this topic

[Liang Jieming]

I'm not sure if you're still going to make a Medieval Workshop area but this is my next project.

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".

(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 academic interest.)



Magazine & Trigger Elevation & Details

Edited by Liang Jieming, 27 April 2005 - 03:56 AM.

[Liang Jieming]

Ok, let's start!

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)


Final picture (and the nicest one too I think ) with 7 iron tipped bolts ready for loading into the magazine.


Jieming

Edited by Liang Jieming, 12 May 2005 - 08:07 PM.

[Liang Jieming]

The trigger is proving a bitch 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.

BTW, the Chukonu or Zhugenu first came into use during the Warring States period before the Qin dynasty of 221 B.C. and was in use right up to the late Qing dynasty against Western arms in the 19th century during the Taiping Revolution!

Jieming
http://groups.yahoo.com/group/DragonSeedLegacy

Edited by Liang Jieming, 30 April 2005 - 01:51 PM.

[Ricker]

The trigger is proving a bitch 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.

How's the trigger coming along?

[Liang Jieming]

How's the trigger coming along?

<{POST_SNAPBACK}>

I cheated a little. 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 ass to correct since there is no way to get at the trigger after that.

Jieming
http://groups.yahoo.com/group/DragonSeedLegacy

Edited by Liang Jieming, 29 April 2005 - 01:49 PM.

[Liang Jieming]

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!) But the challenge of forming the bow was a given when I first started this. What I didn't anticipate was the precision required in the magazine, the trigger and the corking mechanisms!

The bolts too had to be refitted to be just right so that they were loose enough to not get stuck but yet stack well enough to fall into place and fire smoothly.

What really gets me is the fact that it's really easy to just slap a whole zhugenu together and it'll still work, kind of... but if you wanted one that works smoothly without jamming everytime you fire, and was powerful (ie. the bowstring is drawn back far enough to fire a bolt far) the angles have to be just right!

Here's my latest attempt. It snapped when I tried to get more oomp power out of it. Looks like I'll have to get a new bow... again. That was number 2.



Jieming
DragonSeedLegacy
ChineseCultureOnline

Edited by Liang Jieming, 09 May 2005 - 09:06 PM.

[Liang Jieming]

It's done! Yay!!!!

I've finally completed it. It shoots bolts clear across the room. I doubt I can get up to the 7 bolts in 15 sec fire rate but it comes pretty close. I used a longer bowarm this time and ground the support pieces to follow the curvature of the bow in it's final position so that lessened the moment stresses a little more.

This is a close-up of the trigger being engaged.


Go check out the completed pictures!

ZhugeNu ca. 200 B.C. (1:2 scale) : Completed 10th May 2005.

Edited by Liang Jieming, 10 May 2005 - 02:56 AM.

[Ricker]

Great job.

This definitely does look like it ended up being a lot more complicated than your ballista and mangonel.

Where do you find out the specs for your projects? Do you do your own research?

[Liang Jieming]

My own research. The internet is a great resource. I find what I can from websites of people who own actual zhugenus and either read off their dimensions or scale directly from pictures. It also helped that I got a change to examine a real one while I was in the HK Museum of Coastal Defense. Here's a picture of that ZhugeNu.



I then take off from there.

Yeah this was pretty challenging. I've had to do corrective work to fine-tune it. It originally had problems with alignment and insufficient power in the draw. I'm just glad the other potential problem didn't manifest itself... jamming. I guess I got the bolts and magazine right the first time. Luck I guess.



Jieming

Edited by Liang Jieming, 09 May 2005 - 10:41 PM.

[Liang Jieming]

My iron tipped bolts dipped in "tiger-killing poison".



Jieming