White Snow pushed the last gear into the Mechanism Hub.
Click. The gear turned halfway around and jammed.
The chain inside the hub let out a dying groan, then a plume of black smoke rose from the whole machine.
Tie Rushan stood beside her, covering his face with his Iron Hand. A long sigh escaped between his fingers.
"Fat Bird, I told you to fix the Ventilation Fan, not see it off to its grave."
"Don't blame me!" White Snow sprang out of the black smoke, machine oil smeared on her beak. "This busted thing's missing a screw!"
"It's missing a screw because you just took the panel off the left side!"
"Can't see the right side without taking off the left!"
"There was nothing wrong with the right side!"
Tie Xiaoqi crouched nearby, holding a battered volume of Mechanism Blueprints. The expression on her little face hovered somewhere between "I really want to laugh" and "I really want to cry."
"Um... Teacher Bai," she said, raising her hand cautiously, "actually, the problem with the Mechanism Hub isn't the gears. The Drive Chain is half an inch too long, so it's catching on the Third Pulley. You just need to shorten the chain a little."
White Snow and Tie Rushan both turned to look at her.
Tie Xiaoqi shrank back, her voice growing quieter. "I... I fixed one like this when I was five..."
An incense stick's worth of time later.
Tie Xiaoqi sat cross-legged in front of the Mechanism Hub, her toolbox spread open across her knees. She held a small file in her left hand and half a chain in her right, with a thin copper measuring wire clenched between her teeth.
"First, we need to measure the chain's excess length." Her voice had changed. She was no