Ming Dynasty Crossbow Replica

jaeger22 -- John -- is building a replica of a Han Dynasty (206 BC - 220 AD) crossbow lock, with the intent to set them up for production using CNC milling technology.  The originals were made from bronze.  For prototype purposes, John is using a combination of brass and steel parts. See pages.  See the development discussions at 
https://thearbalistguild.forumotion.com/t1231-universal-standard-crossbow-nut

China, for all its inventiveness in some ways, was ultra conservative in others (still is for that matter).  That Han crossbow lock was still seeing service 1200 years later (!!) during the Ming Dynasty (1368-1644 AD).  "If it ain't broke, don't fix it." as they say!   The design is simple and efficient what more can one ask?.

I'm going to beta test John's lock in a Ming Dynasty crossbow replica featuring a six-leaf loose laminate prod made from bamboo laths:

http://www.atarn.net/images/ming_xbow/ming_xbow.htm

Stephen Selby's commentary on the pages is just enough to tease a crossbow builder!

I've had some other folks at the Asian Traditional Archery Network translating some of the text of the illustrated encyclopedia sections which describe the design, construction and use of that military crossbow.  The article gives detailed Chinese measurements which are also being converted into metric and English measurements.  Many thanks to Peter Dekker and Justin Ma for their translation skills in this endeavor.

With some of the measurements in hand, I used a drawing program to scale up the illustration of the tiller (from the second page) to "full size", and printed it out.  The sketch is at best a 'cartoon', but does give the basic profile shape of the tiller, subject to some changes to make it actually functional .  Little things,  like a pistol grip that is too far away from the trigger, and a trigger guard hole in the stock that's far too small in diameter.  Otherwise, I'm staying as true to the original shape as I can.  The overall length, depth and thickness dimensions seem perfectly normal.

I also found (after much searching) appropriate bamboo slats that didn't cost an arm and a leg, and a second arm and leg for shipping!  I got three 6 ft  x 1-3/4" x 1/4" slats for $10, and another $10 for shipping!!!  They're coming from an outfit in Orlando, John!

The prod shown in the encyclopedia is six laminations: 30”, 29.5”, 28.5”, 22.5”, 17” & 12”   There is no detailed measurement of the thickness of the laminations, but ones I'm getting will give me a nominal "Stack Height" of  1.5”.  What the draw weight will end up is anyone's guess.  The power stroke from the  back of the prod to the latch is 9.25".  We're looking for a brace height number.  Six hundred years ago, this style of crossbow was described as "waist-braced" and there are illustrations on how to use a rope around one's waist, and one's feet, to bend the prod with a bastard string while an assistant slips on the operating string.

Now to go find some appropriate "plankage" for the tiller.  Basically I need a 2x6 about 30" long.  Maple?  Mahogany?  Oak?  Should I use a single 2x6 plank or glue up two 1x6s?  Single plank is historically correct, so I'll probably go that route.

slats crossbow interpretation!! It's suppose to be a tiger trap

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Wow! That is a serious bow!  
I made some progress on Ken's trigger. The internal parts are about done except for final tuning. Here they are mounted to a board for the trigger notch fitting:




I made a short video showing how the parts fit and work:

How wide is the wood piece there, John?   The Ming tiller is 2" deep from the top to the opening in the trigger guard, but can be scaled a bit up or down.

One thing about the Chinese trigger which seems very unusual is the release claw mounting on some examples is far forward of the pivot pin. The following question was probably brought up a few millennia ago.
 Will that spacing contribute to an awkward string release?

Tom

Kinh wrote:How wide is the wood piece there, John?   The Ming tiller is 2" deep from the top to the opening in the trigger guard, but can be scaled a bit up or down.

Kin, that board is 1 5/8". Total trigger length is 2 3/4 "from the hole to the very bottom. Here is a picture of it set into one of my old test stocks. It it 2 1/4" thick at the lock:

If you need it longer, let me know. It is not that big a deal to make another trigger.

SEPTUA wrote:One thing about the Chinese trigger which seems very unusual is the release claw mounting on some examples is far forward of the pivot pin. The following question was probably brought up a few millennia ago.
 Will that spacing contribute to an awkward string release?

Actually I am no expert but I think that offers several advantages. First it results in less pressure on the lock making for less trigger pull weight all else being equal. To help understand that, think of it in extreme. Like if the claw was 2 FEET ahead of the pivot pin, Think how easy it would to hold the claw back from rotating. Also when a European style nut rotates the claw first forms a ramp that can cause the string to rise and possibly jump over the arrow. One common technique to help avoid or minimize this is to deliberately make the claw forward of the pivot instead of directly above it. That results in reduced ramp effect.

Thanks John.  That's perfect.  Looking really good there.

Just noticed I typed Kin not Ken.   Sorry about that. Well, I never said I could type or spell. . . .

Kenh
I post some(very bad, sorry) photos I collect 5 or 6 year ago,I could never know ho build this but it seem pretty good example and It help me a lot to do My own one. It may help you to. 

Thanks Jeep.  Those pix are pretty close to the original sketches.  They're the only photos I've seen of someone else's attempt at re-creating this particular bow.

There are minor differences around the trigger guard/pistol grip, and the area between the lock mortise and the cocking rope hole, but that is to be expected.   Interesting that the builder used what appears to be buffalo horn inserts rather than the antler specified in the ancient manual.  I'm having trouble locating big enough slices of deep antler myself, and am considering bone or horn alternatives.

I've done one 4 years ago inspired by the same drawing but it was a free interpretation (longer bow, and canted,7slats,larger trigger guard etc..) I had not any measurement and I used garden shop bamboo, tiller is cheap pine wood .I build it after betting with a friend :Doing a cheap crossbow, quickly(2days),with raw left over wood from the shop!The idea : Having a trigger set only and build a workable crossbow where ever you are with what ever you find .  I got finely 95#, 30cm from bow belly to trigger,cost 15€ and pretty well working tool. Of course it will be easier  if your fighting zombie in Asia !!! 

I finally add 2 more slats to reach 95#. I am sure it is possible to get more power with proper bamboo and I think they have to be heat treated (like the bamboo pole for carrying 2 buckets)to be stiffer.

Got the bamboo for the prod today.  Three  6ft sticks 1.75" wide by more than 1/4" thick.  Three pieces are about 1.25" thick, so the prod will be close to double that.

Each stick set me back $3.00 US, from AmaZulu, Inc. in Orlando, FL  one of the few companies I've found online which is willing to sell individual slats, with or without charging two arms and a leg for shipping.  The next cheapest site would have cost me more for shipping than the total of my order from Amazulu ($23)

http://www.amazuluinc.com/bamboo-slats

Here's the "rough" prod stack; nearly 3" thick!   30", 29", 28", 22", 17" and 12".  Gonna take a gorilla to brace that prod!

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Wow! I can't wait to see what it looks like when you have it strung up. How strong do you expect it to be?
Here are some pictures of the trigger as it is now. I am building another test rig so I can test and tune it. I plan to leave it some what rough so Ken can finish it to his taste. 
Ken, do you see anything so far that you would like to change?
One note, don't cut the slot for the trigger box all the way through the stock. It needs a bit of floor about 1" below the box to keep the fork from dropping down too low and locking up. If you think that is a problem I can see if I can come up with some kind of mechanical stop

jaeger it a jewel ! You are absolutely right with the box floor. You make it different with the original: one of the two slot of the nut (the left one) is normally higher to level with the deck. 

No problem about the mortise.  Lookin' good there.  Even after I thin and shape those leaves it's going to be plenty powerful  I'd guess over 200#.

Slack string prod.  Now that's interesting.

Your right is just for the fun...

I've seen slack string prods used very successfully on Montagnard and Hmong crossbows in the highlands of SE Asia.  The prods were very powerful but the strings were made from bamboo pounded into a material similar hay bale "binder twine", and couldn't stand the stress of being constantly under tension.

I got to mount Ken's trigger in one of my old test rigs with a 95 LB bow and shoot it some yesterday. I expected to have to spend some time tuning the trigger notch to get it so that it holds solid and still releases without too much pressure. But I was pleasantly surprised. I felt great from the start! I really like it! It locks back reliably and solid and releases fairly crisply. It has a small amount of creep and then breaks cleanly. Not light by any means but not too heavy either. (I need to get a fish scale so I can measure!) I like it as is but this is a very individual thing and Ken may want to play with it.
Also it does not make the loud "clack" that the last one did but that may be because in my setup, the fork hits the wood below the trigger block just before the left "arm" hits the block.
So it is ready to ship any time.
Ken, please PM me your address.
Question, the steel trigger parts are made of tool steel. I can easily harden them if you like. But that will make it harder for you to do any future tuning because they will be too hard to file. (But you can grind them.) So would you like them hardened?
I only shot a few dozen times so far but then I took it apart to check for wear. The trigger notch and fork are polishing each other a tad (as they should) but other than that there is no noticeable wear.
Also, I have just been using 5/16 bolts for the through pins. It looks like the originals used a tapered pin with a square head on one side and a small hole for a clip on the other. So let me know if you want me to make something like that. Just not tapered because the trigger housing holes are not tapered.
For my test rig, I made a captured pin for the front trigger hole and in the back I just put a bolt through the stock and the rear trigger hole.
Please let me know your thoughts.
Thanks,