Four days later, the backyard of the North Slope Mine's kiln.
Two deep holes had been dug in the ground of the yard, each in a circular shape, narrow at the top and wide at the bottom. The inner diameter of the front section was about twenty centimeters, and the inner diameter of the rear section expanded to twenty-six centimeters. These holes were the molds that Roland planned to use to cast cannon blanks. The inner walls of the holes had been baked by Anna, and the surface soil was sintered into a whole, like a layer of shell attached. The powder chamber faced down to obtain better tube wall quality during casting, with more dross and bubbles contained in the upper part. The size of all the holes was calculated based on the cannonballs. He vaguely remembered that the so-called six-pound cannons and pound cannons in history were named after the weight of the cannonballs, so he first cast a few twelve-pound iron balls, and then calculated the inner diameter of the mold according to the diameter of the iron balls plus the thickness of the cannon barrel wall.
In the absence of measuring tools, Roland simply defined his own standards. He cut a section of iron strip about the width of his ring fingernail to set as a basic unit, one centimeter, and then used it to make other sizes of iron strips, and engraved segment lines.
Under the crude iron bar ruler measurement, the diameter of the twelve-pound iron ball was about twelve centimeters. He set the thinnest part of the barrel wall thickness at four centimeters, and the wall thickness of the rear powder chamber was increased to seven centimeters to prevent explosion, thus obtaining the inner diameter of the mold. As for the length, although he knew that cannons had a caliber ratio, he only had impressions of the caliber ratios of battleships and main battle tank main guns. As for antique muzzle-loading cannons, he really didn't know.
Considering that the shorter the barrel, the lighter the weight and the more material it saves, Roland waved his hand and took the value of one and a half meters. If the test firing effect is not satisfactory, he can adjust it later.
When cannons were first invented, iron strips were wrapped around a wooden core and sealed with iron powder, then reinforced with iron hoops, and finally the core material in the barrel was burned away, just like a storage wooden barrel. Roland certainly knew that this type of cannon had the risk of air leakage and explosion, so he directly adopted the overall casting and boring process. For steam boring machines, there is no essential difference in the difficulty of drilling six-pound cannons or twelve-pound cannons.
Based on the concept that caliber is justice, he naturally chose the twelve-pound cannon with a larger muzzle and thicker barrel. Any larger than that would not be easy to use as a field gun. As for whether the weight of the cannonball is calculated with lead balls or iron balls, it doesn't matter, as long as it can be fired. After all, he is learning from history, not playing with replicas.
"Let's begin," Roland took a deep breath and said to Anna. The latter nodded, grabbed a steel ingot, and suspended it above the hole. Green flames ignited, and the steel ingot quickly turned red, then melted, forming a small waterfall of molten steel, flowing into the hole. The surface of the molten steel was red-orange, and the core turned incandescent, its brightness was difficult to look at directly. To protect the witch's eyesight, Roland also specially erected supports at the edge of the hole. She only needed to determine the position in advance and rest her arm on the support pad, so she didn't have to stare at the molten steel to observe whether it flowed into the hole.
These steel ingots were slowly accumulated over time. Anna alone could not start a large-scale steelmaking era, but small-batch production was easy for her—after the most difficult temperature barrier was solved, relatively high-quality steel could be obtained by the stir-frying method.
This is also why Roland dared to customize the size of the cannon barrel. Compared with cast iron cannon barrels and bronze cannon barrels, steel cannon barrels obviously have higher strength. Even if the size is wrong, the cannon will not easily explode.
The molten steel gradually rose, and the stored steel ingots were also rapidly decreasing, which made Roland feel a little heartache. When will he be able to build a pile of chimneys and blast furnaces on his territory and refine endless steel? For a long time, steel production was one of the standards for measuring the strength of great powers, and he now felt it personally.
After filling the two molds, Anna's cheeks became flushed. Roland took out a handkerchief and gently wiped the sweat off her nose. At first, Anna would show some resistance, but now she obediently remained still, closing her eyes and letting Roland do as he pleased.
The drooping bangs were stained with a touch of red under the reflection of the molten steel, and the soft neck made people want to take a bite. When he looked down, the half of her slender collarbone exposed through her collar would enter his field of vision. Getting closer, he could also smell the faint fragrance from her body.
"Cough, cough, okay..." Roland put away the handkerchief and retracted his restless emotions at the same time, "Let's stop here today. Good job, I'll tell the kitchen to reward you with an extra portion of black pepper steak for dinner."
Not now, he thought, doing so would inevitably be suspected of taking advantage of the situation. Wait a little longer, until she truly gains freedom...
Anna opened her eyes, although the sweat had been wiped away, her face seemed even redder than before. She nodded to Roland and responded with a soft "mm."
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In the following days, Roland traveled back and forth between the castle and the North Slope Mine.
In addition to the cannon barrels, he also needed to make a sufficient amount of boring tools.
The manufacturing method of this tool for drilling holes is similar to that of cannon barrels. Its diameter is exactly the same as the cannonball. After taking it out of the mold, Anna heats it again and shapes it with a hammer. It is very different in appearance from ordinary spiral knives, and looks like a blunt-headed iron rod at first glance. The only difference is that a notch is knocked out on the top to discharge metal debris. The last step is quenching to increase the hardness of the boring tool.
Unlike the high-precision drills of modern boring machines, Roland only needs an iron rod that can make holes. Considering the high wear rate, he and Anna made five simple boring tools in a week. Prior to this, the steam boring machine had fully verified its capabilities—the production of cast iron gun barrels increased rapidly from two per month to ten per day.
When everything was ready, the cannon blanks were dug out of the pit by miners, the surface slag was cleaned off, and they were loaded onto a cart and transported to the blacksmith shop.
These two cannon blanks almost consumed all of Roland's accumulated steel, and it would not be an exaggeration to call them priceless treasures. During the transportation, the prince ordered Carter and two knights to be responsible for guarding the entire process, which made the chief knight feel a little redundant. Who would steal such heavy things?
The blacksmiths leveled and polished the surface of the cannon blanks according to the prince's requirements. After polishing with a whetstone, they were transported to the backyard of the castle without stopping. At this time, the two round, solid steel rods were dark gray in appearance and exuded a thick metallic luster.
Roland couldn't wait to change the boring tool and fixed the cannon blank in place with Carter, so that the tip of the tool was exactly at the center of the steel rod.
Facing this historic moment, Roland pulled down the valve of the steam engine. The boring tool began to rotate slowly, and soon rose to a stable speed.
"Advance the tool!" the prince shouted.
The chief knight pushed the sliding base to control the depth of contact between the cannon blank and the boring tool. When the tool head touched the cannon barrel, the piercing noise immediately drowned out the roar of the steam engine. Lard, which served as a lubricant, was squeezed into the bore, and what came out was black foam and curled metal filaments. The surrounding witches withdrew from the wooden shed one after another, and only Lightning insisted on staying in place. It seemed that these dark mechanical objects were more beautiful to her than any scenery.