BDSMST -Chapter 115 Gu Xuan’s New Friend

After the cooperation with Bai Yutang was finalized, Woniu Village seemed to return to its usual calm on the surface, but an undercurrent had already begun to stir quietly.

Gu Yan deliberately intensified the training of the village guard team. Their training now included many new subjects such as mountain combat and wilderness survival. Meanwhile, Jiang Suisui buried herself in the ancient books that Bai Yutang had sent over, trying to extract more clues about Medicine King Valley from the obscure texts and symbols.

A few days later, Bai Yutang had mostly recovered from his injuries. To show his sincerity—and also to facilitate their upcoming cooperation—he transferred a group of people from the Bai family’s main residence in Jinling. However, the person leading them was someone no one had expected.

That day, Jiang Suisui was teaching the children in the village school about the key points of growing cotton. Gu Xuan sat in the first row, listening especially attentively.

Suddenly, a crisp jingling of bells sounded from outside. A steward-looking man led a young girl into the classroom.

“Madam, Young Master Bai said this is his niece, Miss Bai Ling’er. She has been sent by the family head to assist you in studying the ancient texts and mechanical devices.”

Jiang Suisui’s gaze fell on the girl.

She looked about ten years old, wearing a delicate light-purple dress. Her hair was styled in twin buns, making her appear cute and lively. Yet her expression was nothing like the quiet elegance expected of a noble young lady. Her bright, dark eyes were curiously examining everything in the classroom, filled with intelligence and an undisguised hint of scrutiny.

Instead of books or embroidery tools, she carried a wooden toolbox that looked fairly heavy. A string of small brass bells hung from it, jingling softly as she walked.

“Ling’er greets the Marquis’s wife,” the girl said crisply, bowing politely.

“No need for formalities.” Jiang Suisui smiled gently. “Welcome to Woniu Village.”

Their eyes met briefly. Jiang Suisui saw in the girl’s gaze a level of intelligence and confidence far beyond her age.

After class, Gu Xuan, Wang Xiaopang, and several other boys gathered on the open ground behind the schoolhouse. They were tinkering with their newest invention—an improved catapult. They planned to use it to “defend” the orchard and scare away birds that stole fruit.

“Watch this! This time I’ll definitely hit that wooden post!” Wang Xiaopang said, struggling as he placed a fist-sized stone into the sling of the catapult.

Gu Xuan directed them from the side. “Pull it back a little more—raise the angle!”

Several boys pulled the lever together. At Gu Xuan’s command, the stone was suddenly launched into the air—but instead of flying straight, it traced a crooked arc and landed several meters away from the post.

“Ah, it missed again!” the children groaned in disappointment.

“Your torsion cords are made from the wrong material. The elasticity coefficient is far too low. The lever arm is also too short, which means the torque is insufficient. And that counterweight hasn’t been calculated at all—it only reduces the stability of the launch.”

A clear voice suddenly spoke from behind them.

The boys turned around. It was the newly arrived girl, Bai Ling’er. She had apparently been standing there watching them for a while.

As the leader of the group, Gu Xuan felt a little embarrassed at having their flaws pointed out so directly.

“Y-you… how do you know all that?”

Bai Ling’er walked over to the catapult and tapped the twisted cords made of cow tendon.

“This kind of cow tendon hasn’t been soaked long enough. Its toughness has already been damaged. You should use horse Achilles tendons instead, soaked repeatedly in tung oil and medicinal solution for forty-nine days. Only then can it withstand the maximum instantaneous tension.”

Then she pointed at the lever.

“If you want it to throw farther, you shouldn’t just lengthen the rear counterweight arm. You should shorten it while lengthening the front launching arm. According to the principle of torque balance, that’s how you most efficiently convert the gravitational potential energy of the falling counterweight into the kinetic energy of the stone.”

As she spoke, she took a small ruler and a charcoal pencil out of her toolbox and quickly sketched diagrams on the ground.

Technical terms and principles poured out of her mouth, leaving Gu Xuan, Wang Xiaopang, and the others completely stunned.

Wang Xiaopang protested stubbornly, “What kind of nonsense are you talking about? Who can understand that?”

“You don’t understand because you haven’t studied it.” Bai Ling’er raised her head, wearing the natural superiority of a top student looking down at underachievers. “This is basic introductory knowledge of the Mohist school. It’s explained in the very first chapter of On Mechanical Arts.”

“Then what’s the point of just talking about it?” Gu Xuan said, his competitive spirit ignited. “If you’ve got the skill—come fix it yourself!”

“Alright,” Bai Ling’er said. That was exactly the response she had been waiting for.

She opened her toolbox. Inside was a dazzling array of tools of all sizes and shapes: saws, chisels, drill bits, calipers… everything one could need. Each tool was carefully maintained and gleamed with a polished shine.

She began directing Gu Xuan and the others:

“Go bring the spare carriage axle from the stable. And fetch those gears that Uncle Wang the blacksmith forged yesterday. The carpentry workshop has the mortise-and-tenon connectors I asked them to prepare yesterday…”

For the next hour, the open ground became Bai Ling’er’s personal stage.

Like a commanding general directing troops, she instructed Gu Xuan, Wang Xiaopang, and the other “soldiers” to carry out a complete overhaul of the crude catapult.

She assembled several gears into a labor-saving winch, making it extremely easy to pull the torsion cords. She recalculated the proportions of the lever arms and reinforced the entire frame using precise mortise-and-tenon joints.

When the new catapult stood finished before them, it looked completely different—more complex, but also far sturdier.

“Try it again.” Bai Ling’er clapped the sawdust from her hands, confidence written all over her face.

Gu Xuan and Wang Xiaopang skeptically placed another stone of the same size into the sling. This time, they used only half the effort to pull the torsion cords to full tension.

“Release!”

With the command given, the stone shot out with a whistling sound. It traced a powerful, straight arc through the air and slammed into the wooden post fifty paces away with a loud bang, shattering it into pieces.

All the children stared in shock before erupting into loud cheers.

Gu Xuan looked at the shattered post, then at the girl beside him—who was half a head shorter than he was. The bit of stubborn pride on his face had long vanished, replaced entirely by admiration and curiosity.

“Y-you’re amazing!” he said sincerely.

Bai Ling’er lifted her chin, a proud smile spreading across her face.

“This is nothing. When I was three, I could already dismantle my father’s study. At five, I built doors that could open and close automatically. And when I was seven, I made a wooden bird that could walk on its own.”

From that day on, Woniu Village gained another “king of the kids.”
Or rather, Gu Xuan gained an inseparable “military strategist” by his side.

Jiang Suisui even had an unused warehouse in the village converted into their personal workshop.

Every day after class, Gu Xuan and Bai Ling’er would rush straight there. Soon, Wang Xiaopang and his group of mischievous companions became their loyal assistants. The workshop quickly filled with wood, metal parts, blueprints, and half-finished inventions. The clanging of tools would continue until nightfall.

Sometimes Jiang Suisui and Gu Yan would stand outside the workshop, watching the bustling activity inside.

“That little girl from the Bai family is no ordinary child,” Gu Yan commented as he watched Bai Ling’er arguing with Gu Xuan—both red-faced—over how two gears should mesh together.

“Indeed,” Jiang Suisui said with a smile. “Xuan’er always liked tinkering with these things, but he used to do it alone. Now he has someone who can actually talk about it with him—someone who’s even better than he is. That’s a good thing for him.”

Gu Yan didn’t argue. But he couldn’t help thinking: the Bai family had sent such a genius girl here—was their purpose really just to help study ancient texts?

Just then, the workshop door burst open.

Gu Xuan and Bai Ling’er ran out excitedly, holding up a sheet of paper densely covered with drawings.

“Mother! Father!” Gu Xuan’s face was glowing with excitement. “Look! Ling’er and I designed something that can bring water from the river to the fields by itself!”

Jiang Suisui took the blueprint.

On it was drawn a huge wheel-like structure, along with complex waterways and transmission mechanisms. In the corner of the drawing, Bai Ling’er had written three elegant characters:

“Dragon Bone Waterwheel.”