The Hard Truth of a Simple Balance
'This wasn't easy at all.'
In my previous life, I had heard from a science teacher during a seminar on generators that the real difficulty with building a steam turbine for power generation was perfect rotational balance. The instructor had explained why he never used the ultra-efficient Tesla turbine. High-speed turbines like that couldn't achieve perfect balance. When the rotor edges hit the speed of sound, they would inevitably deform or break. 'And that's also why a whip snaps with a loud crack,' he'd added. 'When you swing it, the tip moves, but the large radius at the end breaks the sound barrier and produces that sound.'
So I had told Yi I to make a turbine about fifty centimeters across. For a large power plant, the diameter needed to exceed ten meters, five meters and up was considered large, three meters and up medium, and one meter and up small. I figured that size would be safe. But I was wrong. The rotor shaft and blades, though I thought they were precisely machined, weren't truly balanced. Vibration problems kept appearing. Yi I had assumed it was caused by one-sided steam flow and had tried changing the design to send steam to both sides instead. 'Your Majesty, then, lowering the steam pressure to slow the speed and connecting it through gears should work, right?' 'Right now that seems the best option. Efficiency will suffer, though.' 'Does that mean there are other methods?' 'We'll need to examine the rotational axis as well. The turbine blades also appear to have issues. The weight seems to be shifted to one side, causing the vibration. But at present, there's no way to determine which side.' 'Your Majesty, then, why not measure with a thirty-nine gold weight instead of nineteen and reprocess it?' 'That's a good idea, but problems could still arise. So, let's keep the speed lowered until we find a way to confirm the weight shift.' 'I understand, Your Majesty.'
In my previous life, when I changed tires, I had used a wheel balancer to measure, then added lead to correct the vibration. Unfortunately, I never learned the principle behind it. That's why I could only use the tire at reduced speeds until it stopped shaking. But there was one thing that puzzled me. 'How did you measure the revolutions per minute?' 'I used the device there and a generator connected to the rotational axis.' 'Whoa!'
Yi I pointed to a spot where something shaped like a metronome sat. 'When did you even make that?' 'After Your Majesty went to Dong Joseon, I was thinking of ways to know exact time. Following Your Majesty's instructions, I made it using a spring and weight, and have been using it.' 'How impressive.' 'You're too kind, Your Majesty. I still haven't made a pendulum clock that uses the spring method.'
I had a water clock called a clepsydra, but it broke often, so I'd told Yi I the principle of a pendulum clock using a spring and weight. Knowing the exact time was very important. But instead of making the pendulum clock I'd asked for, he had created what was also called a box clock—a metronome. Moreover, he had developed a device that attached a pencil lead to the needle tip of a voltmeter to draw waveforms. By combining those, he measured revolutions per minute. 'Damn! I should have explained it more clearly.' If I had, he might already have made a pendulum clock. A metronome could be turned into a pendulum clock with just a little tweaking. But I hadn't. I figured explaining too much would cause trouble, and Yi I had understood even the rough version. But since a basic box clock existed, I figured he could build one right away. So I explained the method. 'A pendulum clock can be easily made by applying the freewheel principle on a bicycle rear wheel axle.' Chromium and nickel would be hard to translate into Joseon terms. Naming them after their properties would make the names too long, like Latin. I couldn't use Chinese characters either, because the sounds would be similar and cause confusion. I had seen it happen several times before. So I just told him substances whose names no one knew, as they were. Common ones like bitumen or wheel I had combined with Chinese characters after considering their properties and given new names. After telling him to pave the Yudo-ro with petroleum bitumen, I explained the freewheel principle I thought was most important when building bicycles, and told him to build a factory capable of mass production. Since the Gongdan already had paved roads, that would make movement and transport much easier. 'Ah, I didn't think of that method at all.' 'It couldn't have been that.' 'Eh?' 'No genius like you could have overlooked such a simple thing. He simply didn't feel the need, so he never thought of it.' 'Forgive me, Your Majesty. I got so caught up thinking about steam turbines that I neglected what Your Majesty said.'
Yi I, despite his small stature, loved powerful devices with great strength. He was even more hooked on steam turbines than steam engines. 'It's fine. In any case, we can make the pendulum clock using the spring right away.' 'Thank you for your consideration, Your Majesty.' Yi I bowed politely. Those watching from the side, including Kim Ji and the artisans, copied him. Shin Rip and the guards could only blink in confusion, not understanding a word. 'By the way, have you made the induction generator?' 'Yes, Your Majesty. It was easier than I thought, so I made both the induction generator and the induction motor.' 'Really?' 'Yes, Your Majesty. The tricky part was winding the coil precisely, but I solved it by attaching a rotation number plate to the pulley.' 'Well done.' As iron usage kept rising, I wanted to expand the steel mill, but without an efficient, high-performance induction motor with little downtime, it was impossible. I had to move enormous, heavy crucibles. Plus, after drilling the blast furnace, I would need induction motors to pump up crude oil. Even if we had internal combustion engines burning gasoline or diesel, steam engines that burned actual fire could cause fires. We also needed induction motors to build air conditioners and refrigerators. Since accurate speed wasn't as important as sustained power and durability, I had asked him to make an induction generator almost identical in structure to the induction motor. That he had made both showed how talented he was. The only regret was not knowing when the steam turbine would be finished. 'I guess I have to wait longer for nitrogen fertilizer production?' Steam engines couldn't supply constant voltage. I couldn't keep heat and pressure steady, so I couldn't set the generator's speed as I wanted. The voltage waveform became unstable. I couldn't make a constant-voltage device either. My high-school science level knowledge of electricity didn't tell me how. So I was charging lead-acid batteries with unstable voltage to obtain needed substances through electrolysis. Of course I was still generating electricity with generators run by steam engines. But I only used it for electric welding where constant voltage wasn't required, or to light fires and run fans. Pumping water and running machines was directly connected to steam engines. That was more efficient. Unlike steam engines that converted linear motion to rotational motion, steam turbines did rotational motion directly, making speed control easier. They were also more efficient, so they could produce not only nitrogen fertilizer but also enormous amounts of aluminum that gobbled electricity. 'Damn! I should have built a dam for hydropower. Until a stable steam turbine is developed, nitrogen fertilizer production will have to wait.' Yi Yeon pushed the regret aside and headed toward the dock, intending to return to Gyeongbokgung. If the steam turbine was developed, he would look at the chemical plant being built in Geompo. But it probably wouldn't do any good. 'Whoa!' However, at the dock there was a mountain of sand piled in heaps everywhere. Children were playing there. 'Where did you get that sand?' 'We took it from the Han River.' 'What are you going to use it for?' 'We collected it while building a weir in the Han River and maintaining the riverbank. We're using it to expand the shipyard and dock.' 'Hm...' Yi Yeon let out a sigh and stood there blankly for a while. Then he turned and said, 'There is something I need to discuss. Let's go back.' 'Eh?' Yi I, puzzled, tilted his head and followed. The garden he had found again after a long time was much tidier than before. The path to it had previously been covered in crushed stone; now it was paved with petroleum bitumen. Concrete channels had been dug along both sides, and trees were planted at regular intervals. On the sloping hillside, flowers of unknown species were blooming. The moment Yi Yeon sat in the garden, he asked Yi I, 'Do you know what "induction" means in induction motors and generators?' 'It's electromagnetic induction, right?' 'Correct. Heat is generated at that time.' 'Eh? What do you mean by that?' Instead of answering directly, Yi Yeon called for Kim Yang-bo. 'Yang-bo! Bring paper and a pencil.' 'Yes, Your Majesty.' Yi I's eyes sparkled more brightly than ever. Every time the king revealed new knowledge, he swallowed hard. Yi Yeon took a long breath to calm his racing heart. He had finally found a way to melt the sand he had waited so long for. When Kim Yang-bo brought the paper and pencil, Yi Yeon began sketching quickly. Yi I watched, still swallowing saliva. 'This is the basic structure of a Yudo-ro using electromagnetic induction.' 'Eh?' 'Send alternating current from an induction generator into a copper coil wrapped around a refractory-lined blast furnace like this, and a magnetic field will form, generating heat.' 'Is that true, Your Majesty?' 'It is.' Yi I gazed at the simple drawing several times in astonishment. Yi Yeon smiled, knowing it all along. Of course. In my previous life, there had been a craze to replace gas stoves with induction, but the principle always looked like that. After staring at the drawing for a while, Yi I asked, 'Your Majesty, induction generators and motors produce and use alternating current. Is only alternating current the one that produces electromagnetic induction?' 'Correct.' Yi Yeon drew the AC waveform on the paper and explained. 'When electricity alternates from positive to negative, the magnetic field also alternates according to that interval and generates heat.' 'Ah... so it's utilizing the frictional heat of invisible electricity?' 'Hm...' Yi Yeon found himself at a loss for how to explain. Yi I's question had come completely out of nowhere. 'That would work, but a more precise term would be utilizing the phenomenon of an invisible magnetic field converting to thermal energy.' 'Eh?' 'To explain it more scientifically, crossing magnetic fields induce eddy currents in the metal inside the furnace, generating heat.' 'Eddy current means electric current that spins around, right?' 'Correct. That's why we need alternating current where positive and negative cross.' 'Ah... now I understand.' 'What do you mean?' This time Yi I smiled. 'The friction heat I mentioned earlier doesn't fit the facts. Frictional heat is heat generated by two objects rubbing together, so it was wrong.' Yi Yeon grinned. It felt good to hear him admit his own mistake first. But since the exact answer wasn't yet perfect, he asked, 'So what?' 'Earlier, Your Majesty said electricity becomes magnetism and magnetism becomes electricity as electricity flows. Therefore, this principle is not frictional heat but electromagnetic induction heat.' 'Good expression. Let's call it that from now on.' 'Yes, Your Majesty.' However, Yi I tilted his head. 'Your Majesty, even if we can produce heat this way, the efficiency might not be good.' 'Why do you think so?' 'There will be energy loss during conversion. Wouldn't that lower the efficiency?' 'In exchange, we can obtain very high heat.' 'Eh?' Yi Yeon looked down at the sand piled below the garden and pointed. 'Even that sand can be melted.' 'Is that true, Your Majesty?' Yi I looked surprised. He knew melting sand required much higher temperature than melting steel. 'Correct.' But Yi I tilted his head again. 'Your Majesty, isn't sand not a metal?' 'Correct. Sand is not metal, so it can't have eddy currents flow through it. But...' Yi Yeon pointed to the first drawing he had made and continued. 'If you wrap the furnace with a copper coil like this, induction heat will be generated inside.' 'Ah... so that's the principle?' 'Correct.' 'Then why are you melting sand and using it for what?' 'When sand is melted, you can obtain silicon.' 'Silicon? What is that?' 'You can make various products stronger in heat than rubber and harmless to humans.' 'Eh?!' Yi I looked extremely surprised. Making rubber-like things out of hard sand. Actually, Yi Yeon was also extremely excited. At 1,700 degrees he could melt sand; with the Yudo-ro he could reach 2,500 degrees. 'Then I can make almost anything.' Titanium, for example, could be melted easily. Tungsten, which melts above 3,400 degrees, could be softened and used to make fine lightbulb filaments. Moreover, 2,500 degrees was enough temperature to produce not only tungsten alloys but various alloys, so high-performance tools and parts could be manufactured. In addition, production of the silicon products he had so long wanted was now possible. 'I guess I need to start with silicon pipes for heating.' Silicon didn't melt at high temperatures and wasn't harmful to the human body, so it was suitable for heating pipes or medical use. Yet he hadn't used it for heating pipes. 'It was too expensive.' * * *