Ok, this is my next project.

I'll be building this very, very slowly since I'm still doing lots of research. I haven't found any information on the trigger mechanism but according to Needham, the details have been lost as subsequent copies of this Song dynasty siege engine (which in itself was copied from Tang dynasty designs) have been made without proper attention to details so the later Ming dynasty references all contain vague sketches of the trigger. No one knows for sure but from what I've been able to gather, the trigger was not unlike that of the normal handheld crossbow trigger which has remained relatively unchanged since the Warring States period 4-3rd century B.C. It just seems quite conceivable that they would have scaled up the trigger to fit.

I'm also still wondering how I will build the recurve bow arms. Building longbow type arms would be simple, but to build recurved bow arms would require some tweaking to the bamboo I'll be using. I've yet to figure out how. Anyone have ideas how?

Here's my initial exploded sketch of the crossbow.



Ok, I think I'm just about ready to start.

28th May 2005 - Bought lots of nice pieces today. Here we go.


29th May 2005 - Made the trigger housing and after a lot, and I mean a lot of fitting and adjustments, I've gotten it working smoothly enough.


30th May 2005 - I had a bit of problems with guessing the overall dimensions for the supporting frame as there have not been any clear description or sketch of these siege crossbows with dimensions anywhere. I finally scaled it off various sketches, using people as reference in some of the drawings to extrapolate.


1st June 2005 - Finished the base frame. Got one critical dimension wrong and ended recutting two extension pieces. Thankfully the correction can't be seen.


2nd June 2005 - It's definitely beginning to take on it's final form now. I will be adding the bows and the finishing soon.


4th June 2005 - It's done! Recurving the bamboo bowarms worked in the end though I had them reinforced with straightened paperclips and minute adjustments to equalise the 6 arms.

Heat and pressure would bend bamboo very nicely.

If you have a lot of time, you can bend the bamboo, and have it held at the same state, and then give it more pressure everyday. If you burn it, you should apply, and reapply water on it as you heat the bamboo.

Ah, thanks guys. I know they did that for cane furniture but wasn't sure if it would work for larger bamboo strips. I'll have to try it out. When you say heat, are you talking about open flame or oven?

You know, it just occured to me that Liang should make a public announcement about where he's making all these stuff, where he's experimenting and where he's testing them.

I just want to be sure I don't inadvertently walk into a hot zone, since Singapore is small. I read even an overheated bamboo could explode because of the trapped gas.

Hmmm.... I'm only making small scale model! What are you expecting? Some live firing area like the army uses? kekekeke

Yeah, bamboo explodes if you heat it too fast but only if you heat the whole septa. We used to play with the kampong malay boys by throwing whole bamboo into fires. The noise is like a cannon going off! Anyway, just heating stripped bamboo wouldn't explode.

Click to view attachment

Ah thanks Klamath. That's a very common sketch of the triplebow crossbow, a modern impression I believe. It differs slightly from the one I'm building. There isn't one fixed design and all the images I've seen vary to some degree or other.

The winch axle on your sketch is mounted on the upright while mine is based on a design mounted on the horizontal beams. There is an advantage in mounting it on the horizontal. The high tension from the bowstrings would compress the frame and having the winch directly on the compression horizontal will be more efficient than on the vertical leg. If the frame is not built rigidly enough, the winch on the vertical leg would cause the leg to bend forward due to the fairly large lever arm to the horizontal compression beam. In the sketch, that vertical leg to horizontal compression beam connection doesn't look like it could take a bending moment on it IMHO.

The other major difference is in the bowstring arrangement. I'm in favour of Needham's reconstruction (as shown in my sketch). That's because that double loop arrangement will load the bow arms more or less equally. In your sketch, it looks like the 1st and 2nd bows are tied together with the bowstring looped only over the 2nd bow and then back to the 3rd bow. This makes the two forward bows (1 and 2) to flex less than the 3rd bow, ie. unbalanced flexure unless the 3rd bow is made exactly the same strength of the two forward bows combined. I doubt I could do that. I just don't have the bow making skills to do that!

But great sketch nevertheless. It gives a very good idea on how a triplebow crossbow should look like.

Here's what my design is based on.

from that sketch, it looks like they just scaled up a hand crossbow's mechanism

Try using rope, or string. Tie the string on both ends of the bamboo, make sure the string is shorter so that when you tie it, it will bend the bamboo. After you're done, shove it in the oven.

I think you can drill two holes into it and tie it. Kind of like an erhu bow.

Yeah it does look like it's the same mechanism but yet I've been looking around, no large scaled crossbow triggers have been found (at least none I've managed to find in antique stores yet!). I'm beginning to suspect that they might have been roughly the same size as the normal crossbow triggers, at most slightly oversized (and not some massively huge trigger as you and I would have expected). Afterall, these triggers would have survived to the present day if Han triggers can survive! Except of course that they were a lot rarer than the mass produced handheld crossbow. Hmmm...

I'm playing around now with epoxy and paperclips to create the trigger mechanism. The paperclip would be bent into shape to form the tensile reinforcement within, while the epoxy hardens into something resembling stone to encase this reinforcement. That should give me some fascimile of a trigger that is very, very strong (enough to take the bowdraw) but yet small enough to fit into the bowstock. I'm not sure if I can get the tolerances just right for all three pieces to fit and work smoothly.


I've been playing with bamboo chopsticks last night, heating over an open flame. It kinda works but you need to heat the bamboo practically to surface charring before it yields. I'm still experimenting but I'm starting to think that I might need to strengthen the bamboo especially on the tensile side because even after molding it to the recurved shape, it is still fairly weak and I fear would snap when I tighten the bowstring later. Maybe I need to cheat a little here since I can't make the composite sinew/bamboo/wood combo that gives the bow it's strength. I'm thinking of my humble paperclip again. Maybe I'll groove the heat-curved bamboo on the tension side and glue in a length of straightened paperclip length-wise then recolor the whole thing to hide the strengthening. That's the best way I can think of to mimic the composite construction strength-wise.

It is hard trying to heat it enough to bend, but not to burn. Especialy when this is much much smaller than a real bamboo strip.

Maybe there is a chemical you can pu ton the bamboo so that it doesn't char. Maybe boiling water?

Interesting idea. I'll have to try boiling water and see. It should work if heat is the only thing required, unless the physical act of charring to change the properties in the bamboo is what's allowing for the deformation. Hmm...

Well, don't put too much water, put jsut enough to cover the bamboo strips, and use string. lol. I love using string.

Boiling doesn't work. I suspect it doesn't reach the temperature required. After all, boiling water is only 100 degrees C. Doesn't matter. I'll deal with the charring with some nice brown/black paint!

My trigger mechanism is almost done! hehehe I never thought I'd build an exact minature replica of the Han crossbow trigger. But it seems to work. Won't know for sure until I actually mount it and test.

woohoo!

after teh siege weapons and crossbows are done, why not post a picture of each in the Zhan Guo mod thread?

I bet the Modding team would be dying for them...
(I'm dying for them)

Good idea Seph.

Ok will post pictures there later... but not everything is Warring States period though.

Ah took me hours to get it right! But finally I think I got it. It should work, but I'll only know only after I actually mount it into the crossbow stock.

Here's the minature trigger.

Hi Jieming


Sorry for the delay... I understand that you wanted to view this picture??

http://forums.swordforum.com/attachment.php?s=&postid=588167


Regards
TC

Dude,you can start your own miniature siege now with those war machines you are making.Keep those pictures coming.

Hehehe, yeah more pictures are on the way. I need to redo the frame a bit because I underestimated one critical dimension. I'm recutting some of the main pieces again.

His house is like the great wall, let's hope he doesn't destroy it with his siege weapons. lol. Great job Liang!

I can almost see where this is heading...
Eventually Liang would start a topic:
"Making the Hui Hui Pao"
And then goes on to make a counter weight trebuchet of Arabic design and bashes up something.

His ambition increases and he starts a new topic:
"Making a Yuan cannon...."
And after a while half of his house disappears...(jk jk!!) Hee hee.

Seph, you're already too late. I made a hinged counterweight treb in 2001.


It was my first model.

LOL!

The bows are hard!!!!

I did a test mounting of all three recurved bamboo pieces but then realised, the bow arms don't all bend in equal amounts owing probably to differences in thickness between the 6 different arms! Tolerances are less critical on a full scale siege crossbow, but when you scale it down to the sizes I'm making, a difference between one bow arm of say 0.5mm with another will give a perceptable unequal bending angle!!!!! Arrrggghhhh!!!!

What makes it worse is, because all three bows are mounted in parallel, any deviation in unequal bending shows up very, very obviously. Sigh.

*grumble* *grumble*

What's good however is that despite having bows which were not bending equally, I did managed to mount and string them sufficiently to test my trigger... and it works! Perfectly! It fires on cue with a yank of the trigger, and re-corking is smooth too! Yay! *clap* *clap* *clap*

... now back to the problem of the arms... sigh.

Awesome work on all your projects!

And if you actually blow up your house it will mark your passion as a siege engineer...

Ah, sawadeecup Sawa,

SnowyB has already requested I make a public warning announcement during my weapon testing incase he happens to unwittingly enter a live fire zone.

I think I'll comply with his request.

***********************
Siege Engine Live Firing Exercise
4th-5th June 2005
10am to 10pm daily
Affected areas include Tanjong Katong, Geyland Serai and Paya Lebar.
Exercise boundaries will not be cordoned to maintain operational security.
Residents are advised to stay indoors.
Entry into live firing areas at your own risk and discretion.
***********************

Sawasdee krub, nin hao

LOL!!

I'll jump on the next plane to Singapore the next day just to see this masterpiece of military engineering...

*pointing out from plane*
'look! howitzers!'

But ... but ... these are the areas where the good food and the ... where the good food are ...
Ah well, guess I'll stay away for this weekend ... thanks for the warning.

And it's Geylang, your Freudian slip is showing ...

三弓床子弩 (San Gong Chuang Zi Nu) 3-Bow Arcuballista A.D. 1016: Completed 4th June 2005

I think the United Nations need to sponsor a resolution to discourage you from making ballistic projectile machines, these Weapons of Mass Destruction.... North Korea might utilize your siege crossbow and fire a giant nuclear tipped wooden arrow (wood is steathy against radar detection) across the sea to Tokyo... Hehehehe just kiddin...

So Liang, you're in Singapore right now?

Yup. I'm in Singapore. Why?

thank god, i found here and thank you for your practice.
please see the following:
质疑中国古代弩的射程
that guy declared that it's impossible for Chuang Nu or Chin Nu to shoot those big, heavy arrows over 1,000 meters through his/her model's analysis because the initial velocity must be supersonic and since i'm only a B.A., i can only doubt his/her model's sphere of application and find some documents to dispute.
please help to prove the range if you can

Actually, according to Stephen Turnbull in his Siege Weapons of the Far East (1), he states;

"The range of this early weapon is not given, but later versions used during the Tang dynasty are said to have attained a maximum range of 1,160 yards. This amazing range is actually supported by a Persian source describing the use of similar machines fired from a position on the top of a mountain during the Mongol attack on one of the castles of the Assassins in 1256. The normal operating range of a single-bow siege crossbow would be between 270 and 500 yards. Up to a certain distance, the bolts were armour piercing; these weapons were much feared because of their penetrating power."

thanks. i see, there's a only ancient record and no proof now. maybe one day, someone can rebuild that Triple-bow Siege Crossbow capable of shooting big arrows over thousand meter ranges ( "with noise of thunder") and test the actuall data.

Not that I know. Chinese siege weaponry is not a very well researched subject and I don't think a Chinese Chuangzi Nu has been built for at least the last 200 years. Maybe you could build one and test it yourself.

Measuring the maximum range using my model would not be accurate as they don't necessarily scale upwards properly though I could try and see what results I get.

yep, waiting for one guy has enough time, and money and knowledge...
it was said that a Chinese Chuangzi Nu needs several bulls to pull...

i'm looking forward to your test and it's better than nothing.
it seems that you are the first one, just like those people http://arco-iris.com/George/alavekiu.htm and maybe that will be a historic event.

Ok, will test it this weekend and measure the maximum range for you.

Are you interested in Chinese siege weaponry or just the ChuangziNu?

ancient projectile weapons, archery, i think.
just a beginner.

Oh good! You're in the perfect place to do research too if you interested. The Shanghai National Library publishes many reproductions of old documents. You should try and get your hands on some of them. I've been trying for awhile now but my access is limited here in Singapore. Even HK has better access.

My main interest is forming up to be in Chinese siege weapons from the Mohist engines of the Spring and Autumn period right up to the early gunpowder weaponry of the Song.

really admire your elaborate attitude, good luck!

Hehehe ok thanks. It's also one big learning process for me too.

BTW, my test of max range with my model this weekend isn't going to be accurate since I'm not using composite bows similar to what a real ChuangZiNu would use.

Assuming a perfectly scalable equivalent javelin represented by a short bamboo stick would represent a direct proportional reduction in projectile weight and flight characteristics, we are left with only the dimensions of the ChuangZiNu itself.

Here's my preliminary calculations.

Estimation of overall length of a life sized ChuangZiNu (bow tip to winch) = 4m

Overall length of my model ChuangZiNu = 0.17m

So, to (inaccurately) scale a max range of 1000m with the real ChuangziNu, we need to achieve a max range with the model of approximately 170/4000 x 1000 = 42.5 metres

I seriously doubt I can reach that kind of range. Maybe if I change the bows to steel I may.

I'll try anyway.

hope it can reach 20m

No good. The maximum I could get with 45 degree arc was 9-11m which would translate to just about 210-260m which is only typical Roman Ballista ranges. Its probably due to the bows not being of proper material. Let me sleep on this and see how I can make better bows and then I'll do a retrial to see if I can get at least your stated 20m range.

thank your for your effort, maybe material is the key.
do you think the ancient Chinese crafts or processes have been lost for many years, so maybe we cannot restore a crossbow as powerful as before.

Yeah, material is the key. I don't have the bows done well enough or properly enough. Chinese traditional bows are composite bows in three primary materials, the tensile sinew, central core bamboo and wood in the compression face. There is one traditional bow maker left in China, in Beijing. I'm quite sure he could still make large enough bows in the traditional way to mount onto a Chuangzi to make the San Gong Chuang Zi Nu!

I intend to purchase one of these traditional bows. Possibly in my next trip to Beijing I'll pick up one.