Now the artillery team was faced with a choice: whether to use the solid casting deepening drill process to make the body tube, or to continue to use the hollow casting method.

"Let's do the Shiyan drilling method next, right? But you have to build a drilling machine first. "Several people from the Technic team were in high spirits.

"It's a little harder to drill." Lin Shenhe thought for a while, "The efficiency is also a bit low, I think I can try RodmanCasting." ”

"Center Cooling Casting?" Wang Luobin asked.

"You know what?" Lin Shenhe was a little surprised, "I thought there were not many people in China who knew about this aspect. ”

"A personal hobby, purely a personal hobby." Wang Luobin wants to be in a big aquatic country and not do as much as you in the decaying American imperialism, I have already cast a cannon.

The so-called Rodman Casting method is the inner mold irrigation and cooling method.

The principle is simple: the cooling rate of pig iron when it is cast will affect its mechanical properties, theoretically the higher the cooling rate, the harder the texture, the ideal cannon is the hardest in the middle (breech), but in reality it is the opposite, when casting the cannon, it is the slowest cooling in the middle. Because the first outer layer envelops the inner layer, the outer layer is not cold and the inside is not cold. Secondly, the surface area of the outer tube is also larger than that of the inner tube. Whether it is radiation or convection conduction, the heat dissipation speed is equal to the surface area, so the outside will be cold first. This makes the distribution of barrel density unsatisfactory, and the life of the barrel is greatly reduced.

Those who cool down first shrink first. If the outer layer is cooled and hardened, but the inner layer is not cooled, the outer layer will be harder than the inner layer, and the inner tube of the inner layer may be deformed, or cracks may occur when the inner layer cools. This leads to an increased scrap rate at the time of casting, a reduction in the life of the barrel, and sometimes the firing performance of the gun.

During the American Civil War in 1860, U.S. Army Major Thomas Din. Rodman invented this hollow casting process, casting the cannon around the core, and the inside of the core is cooled by running water, which is a method of hardening the inside of the barrel first. This is known as the RodmanCasting method. This craft was the logical result of the development of the earlier sleeve cannon Shiyan. When the outer metal cools, it shrinks inward and continues to pressurize the hardened inner layer. In this way, the explosive force of the propellant is absorbed by the entire thick metal layer around the chamber of the gun, rather than expanding outwards in layers. During the American Civil War and the next 20 years, most of the heavy cast-iron guns of the U.S. Navy were manufactured using this method. The greatest significance of the RodmanCasting method is to significantly reduce the scrap rate of the barrel during casting, especially when casting heavy guns.

From a cost perspective, the RodmanCasting method significantly reduces scrap rates and reduces the cost of gun casting. Secondly, this process greatly increases the life of the barrel of the gun and reduces the cost of use.

The enemies and potential enemies faced by the traverser are far greater than the traverser in terms of manpower and material resources. For the traverser to overcome them, he must control his various costs.

"This method can be tried, but in this case, we have to make a hard inner mold that can hold water, so that we can't use the clay mold just now." Ji Wusheng considered the issue of casting.

"Let's use the iron mold casting method, it seems that the Chinese are the first to use it."

"That's right, it was invented by Gong Zhenlin. He's a genius, too. ”

Gong Zhenlin is a county magistrate in Jiaxing County, Zhejiang, and he originally had nothing to do with the arms industry, but he had a reputation for "being ingenious", and during the Opium War, he was transferred to the Ningbo military camp by Yu Qian, the governor of Liangjiang, to be responsible for casting cannons.

At that time, China's cannon casting technology was very backward, and its methods were:

With water and mud, molds are made, and then Fan Jin is cast, and the bamboo shoots are put together layer by layer. The mud mold must be dried thoroughly, otherwise although the exterior is dry, the inside is moist, once it encounters metal molt, the moisture is self-generated, and the cast cannon has a honeycomb, and the barrel is easy to explode and hurt people when cast. It often takes up to a month to dry the clay mold, and if it is raining, snowy, and cold, it will take two or three months. Moreover, a clay mold can only cast one cannon, and then it is discarded and can no longer be used.

From these descriptions, it appears that the craftsmanship used by Chinese gunsmiths in 1840 is roughly the same as that used by the people in Europe before 1713. However, some of the very simple processing methods used by European gunsmiths 150 years ago, such as the stiffeners of clay molds, the roasting of clay molds, and the boring of iron cannons after casting, are completely unknown.

The craftsmen did not have any regulations for the manufacture of clay molds, and the dimensional techniques were completely in mind, and the proportional dimensions of the guns were not very important. These jishu, which are far behind the times, are the food capital of craftsmen, and are regarded as "secret methods", and there is neither any jishu exchange nor improvement. In this way, under the level of cannon casting, which is out of touch with the times, there are still many "schools" that are completely closed and kept secret from each other. As a result, the cannon is not even as good as the imitation Hongyi cannon of the Ming Dynasty.

Gong Zhenlin, because of the urgency of the war, the loss of artillery on the front line, and the huge demand, if a batch of artillery is to be formed in such a month, the Humen batteries that have been dismantled by the British will not be able to replenish for many years. After several shiyans, he finally invented the iron mold casting method.

The iron mold casting method is to make a hard mold from iron. When casting the gun, first brush the inside of each petal of the iron mold with two layers of slurry. The first layer of slurry is made of fine rice husk ash and fine sand mud; The second layer of slurry is made of fine kiln coal and water. Then, the two petals are combined, tightened with iron hoops, baked, and the metal melt is poured in a continuous manner. After pouring enough molten liquid and cooling and forming, the iron mold is immediately peeled off according to the order of the mold flaps, like peeling off the bamboo shoot shell, and the gun body is gradually exposed, and then the mud embryo in the gun core is removed, and the chamber is naturally smooth.

Compared with the traditional clay mold casting cannon, the advantage of the iron mold casting cannon is that the cast cannon body is of good quality, and the inner and outer surfaces are smooth, unlike the clay mold, which will make the cannon body produce bubbles. In addition, because there is no need to painstakingly apply clay molds and other drying, the manufacturing speed is fast and not affected by the weather. Because the mold can be reused, the production speed is fast, the output is large, and the cost can be very low. The greater significance lies in standardized manufacturing. Standardized manufacturing is essential for artillery to produce products that are almost identical in shape and performance.

Colleagues praised it: "Its method is simple, its use is the most convenient, one work reaps hundreds of profits, and one cannon saves dozens of times the capital." And spin casting spin out, no delay day, flawless, natural smooth, twice the result with half the effort, the use of infinite, the guide track of the public theory, open the door of the eternal law, which is beneficial to the country's armed forces, is not shallow and fresh! ”

Gong Zhenlin's invention of the mold casting method is 30 years earlier than that of the West, which is a rare scientific and technological achievement in modern China.

The artillery team continued to harass the wood processing factory, asking them to make a male mold out of wood first, and then Ji Wusheng and Zhan Wuya worked together to turn the sand and cast it into an iron negative mold, so that it could be used to cast cannons. The core is also made of iron, the interior is hollow, and there are pipes at each end for water intake and drainage.

When the molten metal is poured into the mold, the molten metal begins to cool slowly, and then the water in the inner mold comes in handy, the molten metal close to the inner mold is the first to cool and condense into steel under the action of water, and the molten metal in the outer layer cools slowly. Because of the principle of thermal expansion and cold contraction, after the whole casting is cooled, the outer layer will be cooled tightly, and the inner layer will be cooled first, so that the whole casting will produce an inward tightening force, which is the force that makes the barrel able to withstand greater chamber pressure. This method of controlled cooling of the inner mold can have the effect of "self-tightening of the body tube".

The service life of the body tube through the self-tightening process of the body tube is greatly extended, and the thickness of the body tube can be greatly reduced, the weight is reduced, and the mobility of the gun is increased.

The process of RodmanCasting casting is very simple, after having the mold, the artillery team quickly produced the first finished product, this gun is much better than the clay mold, especially the gun body no longer needs any polishing, the finish of the gun chamber is also greatly improved, although the boring process is also required, but the consumption of the tool is much smaller.

In order to test whether the cast cannon met the various jishu parameters, the artillery team decided to go to Bopu for a test firing. The shells are solid shells made of pig iron. When casting, the clearance accuracy is controlled as much as possible so that it does not differ too much. The mechanical group made a two-wheeled gun carriage for the two guns, and also brought an ammunition front car. It looks like that. Wang Luobin went to the second farm and lent 4 horses from the farm. However, when the horse arrived at the scene, he found a problem: there was no suitable harness for the horse to pull - the two-wheeled carts running on the road were all pulled by a single horse, and the harness was also bought directly from the original time and space. Although horse harness is not a high level of knowledge, no one knows how to make it. Zuihou had to continue to play the role of a repository and find the answer from a photo.

Before the harness could be built, the impatient navy heard that the cannon had been cast, and immediately sent a rowboat to transport it. Two 6-pounder guns and gun carriages were tied to a floating raft with empty oil drums and towed by rowboats to Bopu Harbor.

The cannon was placed in the open space next to the shipyard in Bopu, and there was an endless stream of people who came to see the excitement, especially the navy, almost all of whom loved these two black iron cannons. How cute it looks, a Navy man named Li Haiping simply proposed to load the cannon on the ship.

"Loaded onto the ship, okay? You see, this is a towed 6-pounder cannon, an authentic army gun. As soon as Zhang Bolin saw that his beloved cannon was about to be taken away by the navy, he immediately jumped out to stop it.

"Pull it down, it's still towed, you give me a self-propelled one?" Li Haiping looked disapproving, "This little broken cannon, the navy still can't look down on it." ”

"What did you say?!" Zhang Bolin suddenly became angry, and wanted to rush up and punch him and let him see Liliang in the army.

"What are you fighting for?" Wang Luobin hurriedly came over to play the round, "It's still unknown whether this cannon can be hit, what are you arguing about!" ”