Chapter 1166: The Artillery Expert
As for the design of the projectile's shape and the necessary molds, Joseph would need Carnot to recommend some specialists to take charge of the task.
He had no intention of allowing his father to dabble in any other weapon designs until the development of the steam forging machine was finalized.
The following morning, when Joseph arrived at the meeting room of the Royal Armory, the members of the breech-loading cannon project team had not yet fully assembled. This would be the headquarters for the design work moving forward.
Seeing that Carnot was already there, seated by the window and engrossed in a set of blueprints, Joseph prepared to discuss the Minié ball with him. However, the Director of the Engineering Design Institute looked up first and hurried over with an expression of intense excitement.
"Your Highness," Carnot said, bowing quickly before spreading the blueprints out on the table. "I stayed up all night designing a new iron cannon body."
Only then did Joseph notice the bloodshot streaks in the director's eyes. It was clear he hadn't slept a wink.
"What made you think of using iron to cast a cannon?" Joseph asked, his curiosity piqued.
Currently, bronze was the dominant material for artillery production.
Bronze possessed excellent toughness, making it resistant to catastrophic barrel bursts. It also had a low melting point, which made the casting process much simpler.
Since bronze was relatively soft, it was much easier to drill through.
Of course, some nations used iron barrels to cut costs. But because iron lacked the ductility of bronze, one had to significantly increase the thickness of the barrel walls to prevent it from exploding. This resulted in iron cannons weighing over twenty percent more than their bronze counterparts.
For the artillery corps, every kilogram saved meant better mobility on the battlefield. Consequently, iron cannons had never become the standard.
Carnot pointed eagerly at the drawing of a gun barrel.
"Your Highness, I gave it careful thought yesterday. The breechblock bolts and the bolt slots you described should ideally be made of iron. Copper is far too soft; under the sheer force of a discharge, the threads would deform easily.
"If we used a bronze barrel, we would face the problem of how to rivet the iron airtight components of the breech to the copper body.
"I believe that no matter how skilled the riveting process is, it will eventually loosen after repeated firing.
"Therefore, the optimal solution is to use an iron barrel and cast it as a single piece with the breech. That is the only way to ensure the overall reliability of the cannon."
Joseph looked at the director with genuine surprise. He had overlooked these technical hurdles, yet Carnot had not only identified them instantly but had also produced a draft overnight.
Joseph nodded slowly, acknowledging that Carnot's proposal was indeed more robust. However, he remained hesitant. "But what about the weight...?"
Carnot broke into a brilliant, proud smile.
"Your Highness, I reviewed the technical documents from the Namur Royal Ironworks. The alloy steel they are producing is two and a half times harder than ordinary steel, and its wear resistance is more than four times greater."
Due to the secrecy surrounding manganese steel, even Carnot only knew it as an alloy steel without knowing the specific elements involved in the melt.
"If we use this alloy steel to line the inner wall of the bore and wrap the exterior in wrought iron, the total weight shouldn't exceed that of a bronze cannon. Look, here is my calculation process..."
Joseph's head throbbed slightly at the sight of the dense, overlapping formulas, but he had full confidence that the Director of the Engineering Design Institute wouldn't make a mistake. The man had written Mechanical Theory and Geometry of Position; his mathematical foundation was rock-solid.
Furthermore, Joseph knew from the future development of artillery technology that iron cannons would eventually become lighter than bronze ones.
In the past, to ensure the durability of the bore, iron cannons had to be cast from high-carbon steel. While hard, this material was brittle, necessitating thick walls to avoid bursting.
Now, with an ultra-hard material like manganese steel, a very thin layer was enough to ensure the bore wouldn't wear down even after a thousand shots. The outer layer could then be wrapped in tough but less wear-resistant wrought iron or low-carbon steel to withstand the chamber pressure.
Since the density of iron was significantly lower than that of copper, it was entirely possible for the final product to be lighter than a bronze cannon.
Joseph nodded in approval.
"I believe your vision is highly feasible."
With France's current patent laws and incentive policies for talent, the enthusiasm of technical experts was at an all-time high. Combined with breakthroughs in precision machining, a blowout of new inventions was inevitable.
Carnot's cannon was a prime example.
Carnot rubbed his hands together excitedly. "My only concern is whether there will be difficulties in the casting process."
As he spoke, a slightly portly man standing nearly 1.9 meters tall walked into the room. Carnot waved to him immediately.
"Monsieur Védrine! Perfect timing, we need your expertise here."
The burly man was one of the casting experts on the project team.
A few minutes later, Védrine frowned slightly as he studied the blueprints.
"To be honest, this would work for light artillery. But for heavy cannons over 11 kilograms—specifically the 24-pounders—the wall thickness designed here would need to be increased by at least fifteen, maybe even twenty percent."
Carnot felt his technical prowess being challenged and protested, "That's impossible! I've double-checked the math. Even if we increase the powder charge by fifteen percent, this thickness is more than enough to withstand the chamber pressure!"
"You are ignoring the structural damage caused by expansion forces during the cooling of the steel," Védrine explained patiently. "If the barrel walls are very thick, the temperature difference between the inner and outer layers becomes immense.
"While the exterior is cooling and contracting, the interior is still red-hot.
"By the time the inner wall begins to cool, the outer layer has already solidified. As the inner wall shrinks, it will attempt to pull away from the outer layer, creating internal stress and micro-fractures.
"You are basing your calculations on the strength of fully cooled steel, but in reality, a cast iron cannon made this way is nowhere near that strong."
Carnot stood frozen. Uneven cooling could indeed drastically reduce the structural integrity of the cannon body.
Védrine suggested an alternative. "Perhaps you could use bronze for the outer layer. As you know, bronze has a low melting point. If we cast it that way, the inner layer of alloy steel won't be heated enough to soften."
Carnot shook his head dejectedly. "No, using a bronze outer shell brings us right back to the problem of riveting the iron breech."
Suddenly, a thought occurred to Joseph. He turned to Védrine.
"So, as long as the inner layer of alloy steel can maintain sufficient hardness throughout the process, we won't need to increase the barrel's thickness?"
"Theoretically, yes, Your Highness," the expert nodded. "We would only need to increase it by about three percent over Monsieur Carnot's calculations."
"Then I have an idea," Joseph declared. "What if we bore a hole through the center of the casting mold and let cold water flow through it? That way, the inner layer of the barrel can be kept at a low temperature during the entire casting process."
It was a stroke of genius—the Rodman casting method. By using this simple trick, the lifespan of iron cannons could be increased fivefold.
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