The workshop lights were still flickering, as if they might completely stop working at any moment. Chen Hao spread the blueprints on the workbench, pressing down half a rusty bolt along the edge to prevent them from being blown away by the draft. He stared at the "Manual Torque Wrench Prototype 1.0" for a full minute, then looked up and asked, "You think this thing can really tighten forty-five Newtons?"
Nana stood behind him, the terminal interface floating in the air, data streaming continuously. "Theoretical error ±4.7%, meeting safe usage standards."
"So, it was just a tiny bit too big to exceed the limit?" He scratched the back of his head. "What if I used too much force and the bolt burst? Whose responsibility would that be?"
"It will automatically disengage before the torque exceeds the limit." She tapped her finger lightly, zooming in on the spring structure on the drawing. "Once the triggering mechanism reaches the preset value, it immediately releases the torque and will not continue to apply pressure."
"It sounds plausible," he sighed. "But I still feel like we're risking our lives for an excuse not to fix the car."
He bent down and dragged a pile of scrap from the corner, searching for steel suitable for making a wrench arm. A metal strip with markings caught his attention; upon picking it up, he realized it was the bracket of an old dashboard.
“This can be used as a pointer,” he said, tossing it into the parts basket.
"We recommend preserving the original scale accuracy." Nana took over the inspection. "If recalibration is needed, it must be done in conjunction with a known torque source."
"We don't have any of those."
“Standard torque can be simulated using a fixed weight and lever arm.” She pointed towards the warehouse. “There are two 25-kilogram counterweights over there, which have been idle for three years and four months.”
"You remember it so clearly?"
“Memory doesn’t need to be selectively preserved.” After she finished speaking, she turned around to get the counterweight.
Chen Hao began cutting the steel. The angle grinder made a coughing noise when it started, its speed was unstable, and the sparks were intermittent. He frowned, removed the protective cover to check, and found that the retaining spring was loose.
"This machine is older than my grandfather," he muttered as he tightened the screws. "If it suddenly explodes, can I file for workers' compensation?"
“There’s no workers’ compensation insurance coverage.” Nana placed the counterweight on the table. “And you’re not a formal maintenance worker.”
"Not even a temporary worker?" He smiled bitterly. "Working for free and getting injured, typical fate of modern wage earners."
After reinstalling the protective cover, he restarted the machine. This time it ran more smoothly, but just as it was cutting halfway through, metal shavings flew out in the direction of rotation, and a red flash grazed the back of his right hand.
"hiss--!"
He abruptly withdrew his hand; his skin was already red, a small patch of epidermis had broken open, and tissue fluid was seeping out.
Nana immediately turned off the power, opened the first-aid kit, took out a gel tube, and squeezed it onto the wound. The coolness spread instantly, and the pain was relieved considerably.
"Disinfection mode activated." A faint blue light shone from her fingertips, illuminating the area for thirty seconds, "increasing the probability of infection prevention to 98.6%."
"You're quite professional." He pulled out a tissue to wipe his hands. "But next time, could you remind me to wear gloves in advance?"
“You did not request to wear it,” she said calmly. “And the risk assessment before the operation showed that the injury level was below level three, which is within the acceptable range.”
"It's infuriating that you robots can be so reasonable." He grinned and stopped complaining.
Nana adjusted the division of labor. She was responsible for assembling precision components, including adjusting the spring preload and engaging the tripping mechanism; Chen Hao assisted in fixing the components and recording the parameter changes at each step.
“Now you’re an engineering assistant,” she said.
“I feel like I’m more of a tool.” He took a marker and drew a simple diagram in his notebook. “The kind that doesn’t pay me.”
Time passed slowly, and the main body of the wrench gradually took shape. An extended arm connected to the main rod, with a socket welded to the end; a scale was fixed to the side, with the pointer made from a remnant of a balance; the most crucial spring system was encapsulated in an adjustable housing, and the knob was marked with coarse settings.
"First version complete." Nana placed the entire tool on the test bench. "Ready to perform static torque verification."
They established a baseline using a counterweight and lever arm: 25 kg hung at 80 cm, theoretically producing 19.6 Nm of torque. The wrench was set near this position, and force was applied slowly.
The pointer wobbled a few times before stopping at the target position.
"Click".
A slight clicking sound was heard, and the wrench head instantly disengaged from the simulated bolt.
"Triggering successful." Nana read the sensor data. "The actual trigger value was 19.8, with an error of only 1.02%."
"Wow!" Chen Hao's eyes widened. "It actually works?"
“The knowledge base solution has been validated in 37 extreme environments,” she said. “The success rate is 92.3%.”
What about the remaining 7.7%?
"Caused by user error."
"So you're indirectly saying I'm bad?"
"Statement of facts is not the same as evaluation ability."
He snorted and asked again, "So, can we get the real stuff out now?"
“I suggest we conduct a dynamic load test first.” She moved over a piece of discarded flange and fixed it to the fixture, “to simulate a real assembly scenario.”
In the second test, the wrench disengaged accurately again. The third time, Chen Hao deliberately applied a little more force, and just exceeding the threshold, the mechanism released immediately without any hesitation.
"I'm impressed." He flicked his wrist. "It's even more accurate than my barely passing grade on the exam."
“You can try a higher setting.” She pulled up the calculation table. “The next setting corresponds to 32 Nm, which is suitable for medium-sized connectors.”
"Our goal is forty-five." He cracked his knuckles, his eyes brightening. "Straight to the ultimate challenge?"
Nana didn't object. She reset the spring pressure, adjusting the setting to the highest. The test bench was fitted with M16 bolts of the same specifications as those on the windmill.
Chen Hao took a deep breath and put the wrench on.
Gradually increase the force.
The pointer crossed thirty and continued to rise.
Thirty-five... thirty-eight... forty-one...
"We're almost there." He gritted his teeth, sweat beading on his forehead.
Forty-four...forty-five!
"Click!"
A crisp sound exploded in the workshop, like a small celebratory cannon salute.
He paused for a moment, looked down at the tools in his hand, then looked up at Nana: "Was that shout just now particularly satisfying?"
“It’s a normal mechanical response,” she said. “It doesn’t represent emotional resonance.”
"It's no use denying it." He grinned. "You must have enjoyed it too."
Nana didn't respond, but simply nodded slightly, and the terminal simultaneously generated a test report.
Chen Hao carefully removed the wrench, wiped it clean with a cloth, and then solemnly affixed a label that read: "Windmill Nanny's Special Tool No. 1".
"I'll put a star on every part I repair," he said. "Once I collect ten, I'll reward myself by sleeping all day."
"Lack of sleep will affect your subsequent work efficiency," she said. "I suggest you take two hours of nap now."
“No.” He shook his head. “The bearings still need to be replaced. The windmill can’t keep raising its hands in surrender.”
He packed his tools into his backpack, along with a few spare springs and a small wrench. The brace on the back of his right hand was a bit in the way, but he didn't remove it.
Nana turned off the workshop's power and took one last look at the old welding machine before leaving.
“It won’t last long,” she said.
“Once this wrench proves useful, we’ll figure out how to get a new one.” He patted his backpack. “Let’s keep this guy alive first.”
The night wind was a bit colder than before, causing the steel frame to hum softly. The two walked side by side toward the windmill's base, their footsteps crunching on the gravel path.
In the distance, the towering tower stands silently, its leaves still suspended in mid-air, like soldiers awaiting orders.
Walking to the base, Chen Hao put down his backpack, unzipped it, and took out the newly invented manual torque wrench.
He looked up at the location of the generator compartment, then looked down at the tools in his hand.
"First real-world test," he said. "Don't mess it up."
He stepped onto the first step of the maintenance ladder, raised his arm, and placed the wrench on the first bolt.
The moment the metal made contact, a dull "clunk" was heard.
He pressed down hard.
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