Curious stone cannon

[fernando]

It seems as these things were not that uncommon in the Great Wall arsenals.
More uncommon appears to be nowaday's knowledge of how they worked in those days

http://www.greatwallforum.com/forum/...te-cannon.html

I still call them fantastic ... almost unbelievable

[Matchlock]

Hi 'Nando,


This one I completely understand: a breechloader with the interchangeable breech missing.

But two touch holes in line??!!


Best,
Michl

[fernando]

I would surmise that the orifice on the back has a different purpose

[Jim McDougall]

Amazing!!! As Nando says, just when we think we've seen it all.
I think back on the perplexing anomaly of the leather cannons of Tibet, and some of the European attempts at light, portable cannon (I think 'light' and portable eliminated their thoughts of this particular material).

In our minds we think of the powerful charge from detonating powder, and how can these cannon fashioned out of less than expected materials withstand those contained explosions. I am wondering if possibly the gunpowder used in earlier times might not have been as potent as of course more modern types.
With admittedly meager understanding of cannon and firearms I am curious.
Michael, you know I'm looking for your key insight here

Also, would these, like the smaller forms of cannon often seen which seem too small to be effective possibly be for signaling and using lesser charge?

Thank you so much for sharing this Andi! as Nando notes, another for the files. Fascinating!!!

All best regards,
Jim

[fernando]

Well Jim,
It is of general knowledge that gunpowder was infinitely less potent in those days (Ming dinasty), as also the signaling hypothesis must not be discarded; indeed they had signaling systems in the wall, so called Beacon Towers.
But i take it that the explanation for this stone cannon phenomenum must reside somewhere else.
It would be great to get enlightened by some of our forum mates ... the first to find out about it .
Without such explanation, i would even wonder whether the loading breech is not occupied with a (shifting) chamber but simply filled directly with gunpowder and closed with a locking lid ... or some other sort of Colombus egg .

.

[kronckew]

Originally Posted by Jim McDougall

...I am wondering if possibly the gunpowder used in earlier times might not have been as potent as of course more modern types.
...

initially gunpowder was a mechanical dry mix of powdered sulphur, charcoal and saltpeter. much less efficient. vibration in transport would also mechanically separate the components to some extent. knowledgeable gunners would re-mix their powder, if they had time, on arrival at the guns emplacement. fine powdered gunpowder also readily absorbes moisture ands loses it 'strength'.

someone in the 14th c. finally figured out that wet mixing the components mixed the disparate chemicals more intimately, resulting in a more efficient bang for your buck (and was safer).

the mix was ultimately corned - formed into grains of various sizes, the grains were screened to standard sizes, larger sizes for cannon, smaller for muskets, smaller still for pistols and the finest for priming. space between the grains allowed for more rapid and even combustion. the grains, even the smaller priming ones, did not absorb moisture near as much as the fine powder. modern powder is usually made (since the 19c) with potassium nitrate rather than sodium nitrate, and is normally coated with graphite to cut down the risk of static sparking.

i recall someone from the period stating that a charge of 18 pounds of properly grained cannon gunpowder was equivalent to 300 pounds of the old powdered gunpowder.

for more detailed info, see

this linky

[Andi]

Here is a very competent group practically investigating the production of medieval black powder, the Medieval Gundpowder Research Group at Middelaldercentret Nykøbing, Denmark http://www.middelaldercentret.dk/pro...gunpowder.html

They also published their experiments on an Open Source base you will find them here http://www.middelaldercentret.dk/pro...ogkanoner.html

[Marcus den toom]

Matchlock, you are right i noticed this too. But when looking better, i wonder if the other side might have a same hole (the picture is taken from the left, but i notice a similiar chisseling at the right side).
Maybe these aren't touch holes but some kind of carrier holes (maybe with sticks to move the barrel around or up and down?)
just trowing something into the discussion.

[Jim McDougall]

Thank you so much guys for adding information on the powder, and Kronckew, thanks as always for such well presented detail. It really helps to get a better perspective on how this might have been used.

I imagined that it might be pretty dangerous being the guys firing this thing! and recall tales of firearms before the use of cartridges being often more dangerous to the guy firing it than the targets. Too much powder and the thing would explode.
Thanks again Andi for posting this and for the links.

Marcus, excellent suggestion I would think for carrying.

Another question...are there any examples of more than one touch hole in cannon? would such a configuration ensure firm detonation?

[Matchlock]

Originally Posted by Marcus den toom

Matchlock, you are right i noticed this too. But when looking better, i wonder if the other side might have a same hole (the picture is taken from the left, but i notice a similiar chisseling at the right side).
Maybe these aren't touch holes but some kind of carrier holes (maybe with sticks to move the barrel around or up and down?)
just trowing something into the discussion.

Hi Marcus,


I think these cannot be aything else than touch holes because

1. they are drilled vertically while carrying loops for bars etc. would only have worked horizontally.

2. there are small raised recesses cut out behind each of them to act as fireshields for the gunners.


Quod erat demonstrandum: there is one two many touch holes.


Best,
Michael