Part 248: The Fuze

That day, Lin Shenhe and Jiang Ye conducted several mechanical tests on the pressing machine. They used an inert powder with physical properties similar to black powder, confirming that all mechanical parts were functioning perfectly. Jiang Ye then applied sufficient lubrication to all moving components to ensure smooth operation.

This wasn’t the first time the Mechanical Department had built a pressing machine for ordnance work—they had used one when making the brown prismatic powder charges—but they had never before attempted pressing at such high pressures and densities.

The next morning, Lin Shenhe and the naturalized workers volunteering to help him donned explosion-proof suits and special helmets provided by Panda. They cautiously approached the machine.

The temperature inside the room was stable at 13 degrees Celsius, and the hygrometer showed the humidity was at 90%.

“All clear,” gestured a naturalized worker assigned to monitor the thermometer and hygrometer.

Lin Shenhe took a deep breath and opened the sealed barrel of gunpowder.

Inside was freshly made powdered black powder. The black powder in Lingao was typically granulated for storage, as powdered black powder was prone to component separation over time.

Using a copper scoop, he carefully took out the gunpowder and precisely weighed 1000 grams on a scale. He placed it in a large porcelain container and poured in a specific concentration of alcohol solution. A naturalized worker began to stir slowly with a wooden stick until the mixture was completely uniform.

“A 75-gram charge,” Lin Shenhe instructed. So far, everything was proceeding normally—this was the safest stage. The critical steps were next.

Following his instructions, the naturalized workers retrieved the corresponding mold from a box and secured it to the base. There were several types of molds for different charge shapes and weights, all made of copper.

After the mixed black powder was precisely weighed, it was loaded into the mold. Unwilling to trust the workers with the next step, Lin Shenhe operated the press himself. The press’s pressure was applied by a hand-turned wheel that drove a hydraulic cylinder, which slowly exerted force on a screw rod.

He turned the wheel slowly and evenly, ensuring the pressure wasn’t applied too quickly or forcefully, which could easily cause an explosion. The EOD suit was stuffy and hot, and his nerves were on edge. Soon, he was drenched in sweat, which gave him the false impression that the room’s temperature was rising.

“Check the temperature!”

“Temperature 14.5 degrees, humidity 90%! Normal!”

He had calculated the dimensions for a 75-gram charge using a formula to ensure it wouldn’t be over-pressed. However, this was only a theoretical result; he had no absolute certainty it would hold true in reality. As the charge was compressed closer and closer to the target size, the beads of sweat on Lin Shenhe’s forehead grew larger. He turned the wheel a few more times until the powder surface reached the marker line—the first charge was formed.

Lin Shenhe carefully removed the charge from the mold and placed it on a special tray to air dry.

The ordnance factory had a dedicated drying room, but this was an experimental product with unknown properties, so it couldn’t be mixed with mass-produced items. A separate drying room was set up in the lab, where the air humidity and temperature were also controlled. The charge would dry naturally at a room temperature below 40 degrees Celsius.

“Let’s do the next one!” Lin Shenhe’s confidence surged. Since the pressing process had gone without incident, it meant the entire workflow was sound.

He went on to press charges of various sizes and weights, including some intended for hand grenades. The current hand grenades were little more than large firecrackers in terms of power, with negligible killing capacity—what the Americans would call “concussion grenades.”

Another use for the pressed charges was as propellant for rockets. Uniformly shaped and dense charges were a crucial guarantee for consistent rocket trajectories, making this a significant development. He estimated that with these new pressed charges, the range and accuracy of their Hale rockets could be taken to the next level.

Of course, the primary use for high-density black powder charges was to fill artillery shells, elevating their previously decorative high-explosive (HE) rounds to a new level of lethality. Lin Shenhe believed that while the army’s widely used 12-pounder and 24-pounder smoothbore cannons had the advantages of being simple to manufacture and use, making them suitable for a low-tech army, their low power and slow rate of fire were insurmountable long-term weaknesses. They were not, as some claimed, “good enough for the next twenty years.”

The mass production and deployment of rifled artillery was an inevitable choice for the Senate’s military. At present, only the Navy and coastal artillery used a few rifled guns, both muzzle-loading and breech-loading, but none were standard issue. They were installed sporadically, on an experimental basis. The main reason, besides cost, was that the chamber pressure in rifled guns was far higher than in smoothbores. The fuzes used for spherical HE shells were unusable in rifled guns, so until now, all their rifled guns could only fire solid shot.

The conical solid shot fired from rifled guns was far less effective against personnel than the round shot from smoothbores—the latter could still cause casualties by bouncing and rolling after landing, whereas a conical shot would just bury itself in the ground. Its advantage was its immense penetrating power, making it highly effective against fortifications and warships.

To unleash the full potential of rifled guns, the first problem to solve was the fuze.

While the charges were drying, Lin Shenhe had people start manufacturing fuzes.

He had wanted to solve the fuze problem for a long time. The main issue he faced was the poor state of the Senate’s industrial materials science. To make a safe and reliable fuze, springs were essential.

In the old world, springs were inconspicuous trinkets, but in Lingao, manufacturing them was a high-tech endeavor. The springs needed for a rifled gun’s fuze were the culmination of industrial technology, involving steelmaking, alloy materials, and heat treatment. Lingao’s industry could produce springs, but they were low-end products, barely adequate for simple applications like carriage suspensions and sofas—they just had a shorter lifespan and needed frequent replacement. Using them in an artillery shell was another matter: at best, they would be duds, affecting combat; at worst, they could detonate prematurely, causing a major accident.

Because of this issue, although Lin Shenhe, Wang Ruixiang, and various other military enthusiasts among the Senators had all tried to solve this problem, none had succeeded. No matter the design, they always hit the “qualified spring” roadblock.

Fuzes were consumable items. They had to be cheap enough to be mass-produced and used in large quantities. At the same time, the skill level of the Senate’s machinists was generally low, so the manufacturing process had to be as simple as possible to ensure consistent quality.

Lin Shenhe consulted a large volume of materials on the subject and finally decided to base his design on the fuze of the Japanese Type 91 grenade. It was a simple impact-detonating design that relied on the inertia of the shell body moving forward upon impact to overcome the resistance of a creep spring and trigger detonation. The safety mechanism was a simple pin removed before firing. The entire fuze design required only one creep spring, and the performance requirements for that spring were not high. It was well-suited to Lingao’s current industrial capabilities.

In this fuze design, the detonator was located at the base of the fuze. The front of the fuze consisted of a long, rod-shaped inertial body with a firing pin. The inertial body was separated from the detonator by the creep spring and held in place by a horizontally inserted safety pin. To ensure a high detonation rate, the inertial body had a crown-like pressure plate at its tip. Before firing, the safety pin was pulled, arming the fuze. When the cannon fired, the inertial body was held at the front by the creep spring, preventing a premature explosion. Upon impact with a target, the inertia of the shell body compressed the creep spring, causing the firing pin to strike the primer and detonate the fuze.

The machine shop quickly produced one hundred fuzes according to his blueprints—half were made by Senators, and the other half by naturalized technicians. Lin Shenhe wanted to see what the qualification rate would be for the naturalized technicians in actual production.

Visual inspection and simple tests showed that the naturalized workers had a qualification rate of about 40%. This rate was roughly acceptable to Lin Shenhe. This was with manual assembly; with mass production using specialized jigs and tools, and as the workers became more skilled, the qualification rate would increase significantly.

Lin Shenhe believed that his design’s requirements for the creep spring were not high, and the best springs they could currently produce—phosphor bronze springs—should be up to the task. He conducted dozens of tests in the lab with fuzes using phosphor bronze springs, and each time, the spring reacted correctly.

However, the lab had no specialized equipment to simulate the high-temperature, high-pressure environment of a cannon firing, nor could it simulate the high-g forces on the shell during flight. Simple drop tests with weights couldn’t reflect the fuze’s true performance. Lingao’s military engineers could only resort to the simplest method: live-fire testing to validate their designs.

Lin Shenhe went to Ying Yu and borrowed a rifled cannon—one of the 70mm breech-loading rifled guns originally made for the four Type 8154 gunboats. It had been removed from a ship and kept in storage ever since.

Since no HE shells had ever been made for the 70mm rifled gun, Lin Shenhe first had the machine shop produce twenty HE shell casings, which he fitted with the fuzes and filled with sand as a substitute for explosives.

He carefully marked and separated the shells with fuzes made by Senators from those made by naturalized workers. Then, he borrowed some horses, towed the cannon to the firing range, and began the experimental shooting.

Lin Shenhe acted as the gunner himself. He used the safer brown powder for the propellant and, for the first shot, used a reduced charge instead of a full one.

The firing range had sections of hard-packed earth, medium soil, and wetlands. The first round of tests yielded excellent results. After accounting for failures caused by manufacturing defects in the fuzes themselves, they achieved a 90% detonation rate on hard and medium soil, and over 70% in the wetlands. From a practical standpoint, this was a complete success—the average detonation rate for their current smoothbore HE shells was only about seventy percent.