Roman Steam Punk!

[KV7]

Regarding composite cannons, they were a notable Qing-Ming invention:

Here is one example, the Ding Liao Da Jiang Jun (定遼大將軍, lit. 'Great general of Liaoning-pacifying), made by casting bronze over an iron core.



And see also:

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It’s important to note that the Ming and the Manchus didn’t merely copy
Western cannon. They improved on them. Ming and early Qing metallurgical
practices were in certain ways superior to those of Europe, which allowed
Chinese cannon makers to develop new designs. In one composite design, for
instance, the interior of the barrel was made of iron, the exterior of brass.
Taiwan-based scholar Huang Yi-long describes the process: “They ingeniously
took advantage of the fact that the melting temperature of copper (which is
around 1000C) was lower than the casting temperature of iron (1150 to 1200C),
so that just a bit after the iron core had cooled, they could then, using a clay or
wax casting mold, add molten bronze to the iron core. In this way, the shrinkage
that attended the cooling of the external brass would [reinforce the iron, which
would] enable the tube to be able to resist intense firing pressure.”30 The
resulting guns, with their iron cores and bronze exteriors, were lighter, stronger,
and longer lasting than iron cannons, and they were cheaper than bronze
cannons. They also cooled faster.

Chinese artisans also experimented with other variants, such as wrought iron
cores with cast iron exteriors. Such iron composite guns were even cheaper than
the bronze-iron composites and considerably safer and more durable than
standard iron cannons. Both types of composite cannon—bronze-iron and iron-iron—
proved enormously successful, “among the best in the world.”31 Indeed,
Chinese cannon casting technology was considered so effective that Iberian
imperial officials sought to hire Chinese gunsmiths and send them to Goa to
impart their methods at Portuguese cannon foundries in India.

 

Edited September 28, 2021 by KV7

[KV7]

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Ordnance historian John Guilmartin analyzed bronze cannon from the
Sacramento, a Portuguese galleon that sank in 1668. He used a stud finder magnet to
detect traces of iron on several guns, some of which were from the 16th century, resulting
in interesting and unexpected finds. Two of the guns, which he believes are English and
cast before the 1580s, showed signs of an iron element along the cascabel, as well as in
the trunnions, and on the lifting rings. He found that a wrought iron sleeve was placed
on the inside surface of the rings. These finds imply a more complicated use of iron
elements in the manufacture of bronze guns than described by Biringuccio, for example,
and would suggest the existence of composite guns. This type of construction would
not have been technologically inferior, a point argued by the fact that these two guns
were in use on board a first class warship of the 17th century, around a century after they
were cast.44

The wreck of the Dutch East Indiaman Batavia, lost on the coast of Australia in
the 1620s, yielded at least two composite guns. These guns are of a slightly later date
than any of those in the Museu de Angra collection, but they show a remarkably different
method of construction than that previously described. They were made using
a combination of iron bands, copper sheeting, and lead solder. The copper formed the
skin of the guns (both outside and around the bore) while the iron provided the internal
structure and mass. Any spaces between the iron bars and the copper were filled with
solder.45 This example presents an interesting deviation from what is generally regarded
as the standard process of gunfounding, and provides us with the possibility that any
oddities found in the guns of the Museu de Angra collection could be caused by
departures from what were considered the normal practices.

 

[sunday]

Interesting.

[KV7]

Section of the composite cannon from the Batavia, using thin bronze sheet, wrought iron rings and staves, and lead solder as a filler.

Note that in this case, they have used very poorly fitting wrought iron pieces. These particular  guns (though definitely not the very strong Ming pieces above) were too weak for firing solid shot and were used for anti personnel loads:

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The Batavia carried 30 cannon: 22 of iron, six of bronze and two of composite construction, one of which is shown here. Composite guns were experimental. They attempted to combine the reliability of bronze with the cheapness of iron to give a much lighter gun. These guns were only one third the weight of a bronze gun of the same calibre. However, composite guns were not strong enough to fire cannon balls and were therefore used for firing anti-personnel shot such as wired musket balls, nails and stones.

Markings on the cannon show that it was owned by the Amsterdam Chamber of the VOC and weighed 1715 Amsterdam pounds, about 850 kg. It was raised from the wreck of the Batavia by the Western Australian Museum in 1973. The cannon was damaged when the ship foundered. A small hole revealed an unusual internal structure. It was decided to cut out a long section which could be studied then replaced.

A sheet of copper for the bore of the gun was moulded to form a tube. Six flat iron bars running the length of the gun were mounted around the copper tube and fixed in place by 30 wrought iron bands ranging in thickness from 16 to 56 mm.

The gunpowder chamber in the breech was formed separately, strengthened with additional iron bands and held in place by hammering over the ends of the long iron bars. The trunnions (projections on each side which supported the gun on its wooden carriage) were then attached and iron pins mounted around them. Copper sheathing was then fitted to the outside of the whole gun forming an ornamental casing.

At this stage, the gun was covered in clay, upended and heated. Molten lead solder was then poured into the top until all the spaces between the different metals were filled. A copper disc was then soldered onto the end and the bronze cascabel (the knob at the end) screwed into place with an iron screw. This has since corroded away on the example shown here.

https://www.donsmaps.com/batavia.html

Edited September 28, 2021 by KV7

[sunday]

12 minutes ago, KV7 said:

Section of the composite cannon from the Batavia, using thin bronze sheet, wrought iron rings and staves, and lead solder as a filler.





https://www.donsmaps.com/batavia.html

That web page is a treasure. Good insights into the manufacturing process of those guns, and the reasons they were not used more.