This drawing of the massively powerful Chinese triple bow crossbow was associated with a 17th century book, but I’m not sure if it was contemporary with the book, or a later addition. So many drawings of ancient mechanisms are fictitious! But this weapon is reputed to have have had awesome power and range. But how were the string(s) arranged? I made an effective working model using pulleys. But would they have used pulleys?

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That looks a lot like some the stuff Jörg Sprave has been making using a second bow to help with pulling a heavy bow to full draw.

https://youtu.be/xH2uVMJTt2s

Here’s my model made from carbon fibre kite rods, a wooden garden stake and some boating pulleys. It has a draw weight of 14 pounds (~6.5kg) and shoots a light dart very fast.
My first attempt used metal loops instead of pulleys but the friction made it unworkable.

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Here’s a modern illustration of a stringing method which I don’t believe would work.

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Kick wrote on May 31^st, 2020 at 6:16am:

That looks a lot like some the stuff Jörg Sprave has been making using a second bow to help with pulling a heavy bow to full draw. https://youtu.be/xH2uVMJTt2s

Thanks! Thought provoking. But Joerg’s bows are back to front and arranged to assist loading rather than to increase the power of the weapon. However, I suspect the answer to this mystery may be totally different to the various ‘artists impressions’.

Now I see your model I've got a better idea of it. Yeah that other illustration really doesn't look like it would work. Interesting design :D

Reminds me of my first crossbow made from fiberglass tent poles. Although yours is infinitely cooler! Any possibility of a video of this bad boy in action?

Morphy wrote on May 31^st, 2020 at 6:58am:

Reminds me of my first crossbow made from fiberglass tent poles. Although yours is infinitely cooler! Any possibility of a video of this bad boy in action?

A video wouldn’t show much more. The dart is 5mm dowel and very light. It flies fast and easily penetrates several sheets of strong corrugated cardboard carton.

the point of this design is to have long power stroke by bending each bow very little?

Morphy wrote on May 31^st, 2020 at 6:58am:

Reminds me of my first crossbow made from fiberglass tent poles. Although yours is infinitely cooler! Any possibility of a video of this bad boy in action?

No video, but this is what it did to an empty lager can.

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The painting, I think, is of an object that the painter has no idea how to work, so he used the line drawing and his imagination. 

Yes, the Chinese had pulleys, they are way older than those weapons and date to at least the bronze age.

I think the bows would have been composite and the tips super recurved to keep the strings on.  The faster the bow tips move, the faster the projectile, which usually translates to longer range.  Pulleys would have added weight, which would have slowed the tips down.

The backwards bow would have also acted as a shock damper to keep the recoil from shaking the weapon apart and from over flexing the bow at the shot.

I'm not an expert in this at all but this guy in Washington has made one that you might be interested in seeing:  https://www.facebook.com/100004290976178/videos/1138198456333176/

That thing looks beautiful. Real craftsmanship.

don't really see the point of the reversed bow behind the main cord.
Won't that simply pull power away from the cord ?

I can see  how sevaral bows can work with just simple connections - that's ingenious :-)

But what's the purpose of the rear bow that looks to be pullling the cord back. That just doesn't make any sense.

Love the one you made with the rods !

The back bow is the shock.  There is actually a lot of recoil when you shoot a bow or cross bow.  You can see the muscles of the archers forearm ripple if you look at an extreme slow motion arrow shot.

The rigid frame can't flex, so all that energy goes back into the bow and frame.  Bad things happen then.

When shooting a modern compound bow, they come with all sorts of shocks and dampeners to control the recoil to keep from shaking the bow apart.  Or breaking it.

On a wooden or composite bow, if the arrow is not of heavy enough weight to absorb the force, either the arrow or the bow can break when it is shot.  Or both.  It will also be unpleasant to shoot, the shock to the shooters' hand and arm can be painful.

Very interesting ! This crossbow is a terrifying weapon.
More, it ruins the enemy's beer stocks.  :'(