Chapter 103: Casting Cannons (II)

“We’re not in a hurry to become arms dealers,” said Zhang Bolin. “We can also equip ourselves with smoothbore cannons. There are too many firepower gaps right now. The three blockhouses on the Bopu road have no cannons, and Bairen City doesn’t have a single one either. Besides, we’ll have to build up a native army eventually, and they can use smoothbore cannons to form artillery units. That way, when we upgrade to Armstrong cannons later, we’ll have a batch of qualified gunners trained.”

Zhang Bolin, a big artillery enthusiast, was most concerned with his dream of an artillery team. Any cannon was better than no cannon.

Everyone felt this suggestion was reasonable. Even ignoring the manufacturing cost and the need to arm a native army, the cost of using smoothbore cannons was much lower. Because smoothbore cannons had no rifling, the projectiles could theoretically be anything that could fit into the barrel. They didn’t require carefully manufactured shells; the simplest was just a solid iron ball. The killing power of this kind of projectile was still acceptable on both land and sea even in the 19th century. In fact, solid shot was still the most fired projectile until smoothbore cannons withdrew from the stage of war, much more reliable than the questionable shrapnel.

“Well, we can also develop some special spherical projectiles, like high-explosive shells and incendiary shells.”

“There’s another benefit that you might not have realized,” said Wang Luobin. “Chief Wen’s generation gap theory.”

“Generation gap theory?”

“In this time and space, at least in our lifetime, we are all outsiders. And to conquer and rule, we have to rely on the help of the locals. Sooner or later, a native army will be established.”

Once a native army was established, due to its large numbers, it would inevitably become the main armed force of the transmigrated nation.

No matter how much effort you put into brainwashing, political work, and control, the army, as a machine of violence, would become greedy once it realized its own power. They would strive for more power and benefits, and the transmigrators’ own power was limited. The only way was to maintain a technological generation gap.

If the native troops were equipped with 20mm flintlock rifles, the transmigrators would have to have bolt-action rifle-level weapons to counter them. This would ensure that a very small number of people could suppress a large group. Similarly, if the transmigrators could manufacture 92-type infantry guns themselves, the best artillery to equip the native army with should not exceed 37mm recoilless guns.

Wen Desi had not yet perfected this theory. He now spent every night thinking about the future military organization and political structure—”the eternal rule of the transmigrators” was his goal.

After a few days of preparation, the cannon casting work began. As a technical reserve and practice, the artillery team would first cast traditional smoothbore cannons. Generally speaking, it was best to use bronze for smoothbore cannons, with a lifespan of about 1,000 rounds, compared to cast iron cannons, which had a lifespan of only 600 rounds. But bronze was much more expensive than iron, and for the transmigrators, it was a precious industrial raw material. The pig iron bought from Guangdong by the Dengyingzhou was of excellent quality, with a very low sulfur content, making it very suitable for casting cannons.

Historically, the pig iron from the Fujian and Guangdong regions in the Ming Dynasty was famous for its superior quality. The ironworks in this region used charcoal as fuel for ironmaking, and the sulfur content was much lower than the pig iron produced in the north using coal. Sulfur was a major factor that made pig iron brittle and reduced its quality. The Ming people could not understand this reason, but it became a consensus at the time that the cannons cast in the south were stronger than those in the north. As a result, the Ming court’s large-scale cannon casting was carried out in Guangdong. In the 47th year of the Wanli reign, when Xu Guangqi was ordered to train troops to defend the capital, he suggested that the court recruit craftsmen from Fujian and Guangdong to come to the capital to cast cannons. In the third year of the Chongzhen reign, he volunteered to go to Guangzhou to cast cannons. The reason was: “There are many craftsmen, the iron is particularly fine, and the price can be saved by one-third…” And in the early years of the Chongzhen reign, the governor of Guangdong and Guangxi, Wang Zunde, cast two hundred cannons at one time.

Wang Luobin suggested whether to recruit a few masters skilled in cannon casting from Guangzhou to demonstrate the traditional Chinese cannon casting technology once, so that everyone could have a visual concept before making improvements. Lin Shenhe said it was not necessary: in 1628, not to mention the level of Chinese cannon makers, even the level of European cannon casting technology they were imitating at that time was not very high. The transmigrators had no need to learn from them.

Matteo Ricci mentioned in his book the problems with Chinese cannons at that time: less gunpowder, short range, no sights, unable to aim, the muzzle of the cannon was wide and the inside was small, which could not effectively gather the gunpowder gas, the inside of the barrel could not be made into a qualified circle, and the barrel was not bored. The size and even the shape of the cannonballs were arbitrary, the windage between the ball and the cannon was too large, the cannon had no trunnions, and it was top-heavy. If the gunpowder was packed too tightly, it would overturn and explode when fired.

The Hongyi cannon introduced at that time was essentially the same as the various traditional cannons manufactured and equipped by the Ming army. They were all smoothbore, muzzle-loading cannons that used black powder and solid cannonballs. However, benefiting from scientific knowledge, European artillery already had some obvious advantages in design, such as thicker barrels, larger cannon caliber, and the cannon body gradually thickened from front to back. Therefore, they had advantages in range, lethality, and safety. Sights and rear sights were common on the cannon body, and trunnions were cast on the cannon body, which was convenient for mounting on a gun carriage, adjusting the firing angle, and moving.

The smoothbore cannon that the transmigrators wanted to manufacture could also be regarded as a kind of Hongyi cannon, but the blueprint was slightly more advanced, imitating the French 6-pounder cannon of the early 19th century. This cannon had an effective range of 500 meters and a maximum range of 1,500 meters, and the barrel weighed about 250 kg.

Lin Shenhe and Wang Luobin decided to first adopt a Western cannon casting method from the 17th-18th centuries, which also required the creation of a clay mold.

They asked the wood processing factory to process a batch of special wooden molds: a tapered material used as a support, and a lathed cannon breech mold. After completion, they first started on the rough model of the male mold. First, they tightly wound straw rope around the tapered wood as a support to form the shape of the cannon. At this time, the rough male mold was still about 25 cm away from the final size. Then, they evenly applied a layer of mud mixed with clay and water to the rough male mold. They had to wait for the previous layer to dry completely before applying the next layer.

When applying, they made the entire male mold slightly larger than the actual size of the cannon, because the casting would shrink. After the last layer of mud was dry and the shape was corrected, a layer of wax was applied to the outside of the rough male mold—lacking paraffin, they used beeswax instead. The surface of the male mold would be very smooth and would not stick to the female mold in the next process. The cannon breech was a lathed wooden mold, fixed to the rough male mold with screws.

After the male mold was completed, they began to use it to make the casting mold. The casting mold was made by applying a semi-liquid mud mixed with clay, pottery clay, fine sand, and water to the male mold layer by layer. Similarly, they had to wait for one layer to dry completely before applying the next. After it was completely dry, iron bars were added to the outside of the casting mold for reinforcement.

After the mold was completely dry, the male mold had to be taken out. The method was to cut the head and tail of the casting mold, take out the tapered wood of the inner core of the male mold, and then pull out the wound straw rope. Because of the layer of wax between the male mold and the casting mold, it would be easier to take it out. If it was really difficult, the wax surface could be melted by heating to create a gap for separation. The mold for the cannon breech was made separately.

The third part of the mold was the core, which was made of clay attached to an iron bar. It was generally cylindrical, but it might have a special shape at the part where the gunpowder was loaded. The core was loaded into the main mold, and the iron core support at the tail of the main mold and the clay ring at the muzzle of the mold would fix the core in the proper position.

The separately made female mold for the cannon breech and the female mold for the cannon body were reassembled. After the three molds were firmly assembled, they were fired to make the mold completely solid. Finally, the mold was buried muzzle-up in a tightly packed earth pit next to the furnace. Jiang Ye designed and installed a wooden derrick that could lift the entire mold, because when the iron melting furnace was built, the need for cannon casting was not considered, and the floor of the steelmaking workshop had been hardened. They had no choice but to build another iron melting furnace in the casting workshop. However, since there was no need for ironmaking, just simply melting the metal, the furnace did not use a regenerative furnace. The runner was one-out-four. Ji Wusheng personally came to guide, and Zhan Wuya himself had some casting experience, so the first casting was very successful.

After the casting was completed, it was kept warm for 24 hours before being dug out of the mud pit. After further cooling, the reinforcing bars on the outside of the female mold were removed, the casting mold was broken, and the artillery team used hammers and chisels to remove the remaining slag from the cannon body.

Finally, the casting of this cast iron 6-pounder cannon was completed. It still needed further processing, boring the barrel. The machinery group built a simple boring machine to process the barrel. The power was not even an electric motor or a diesel engine, but a donkey. The donkey drove a winch to drive a boring bar, and the top of the boring bar was a high-carbon steel boring cutter.

The boring operation could greatly improve the smoothness of the inner wall of the cannon, but after measurement, it was found that the boring process could not really cut a cylinder or correct the deviation of the core during the casting process, and the hard residue in the whole process also caused great damage to the boring bar. In other words, this process was too costly.

“No wonder they switched to the drilling method in 1713.” Lin Shenhe was a little frustrated. The drilling method was to first cast a solid iron rod, and then use a drilling machine to drill out the barrel. This technology was first used by the Dutch, but it was not fully promoted until the late 18th century. The British Royal Naval Arsenal was still using the above-mentioned casting method to manufacture naval guns until 1770.