Black Corporation: Joseon [EN]: Chapter 387

387. That, Jang Yeong-sil. (4)

The next morning.

A new notice was posted on the bulletin board.

“Another Challenge Log entry? There have been a lot of entries lately.”

“What is it? What is it?”

“Hey, move your head!”

Researchers and artisans crowded around the bulletin board to read the contents of the new notice.

The first thing the researchers and artisans checked was the grade of the entry. After the Challenge Log was established, checking the grade first had become a habit for everyone.

And the eyes of those who checked the grade widened.

“Huh?”

“What grade is it…?”

The newly posted notice had two grades applied simultaneously.

Grade: Hard Struggle (Lower), Sisyphean Task (Upper).

Extremely opposite grades were assigned at the same time.

People examined the contents more closely, surprised by the unexpected grade assignment.

-New Challenge Log Entry Notice.

Date: March 17th, Gy 축 year (1433).

Proposer: Jang Yeong-sil

Content: Creates a ship propulsion device by applying the shape of a windmill.

Grade: Hard Struggle (Lower), Sisyphean Task (Upper)

“Ah!”

“Damn it!”

“How could I not think of this? What an idiot!”

The researchers and artisans of the Jo team, who were in charge of developing the propulsion device, read the contents and blamed themselves, hitting their foreheads.

* * *

Windmills were not unfamiliar to Joseon people. It was one of the toys that every boy had played with.

Windmills, called ‘Palang-gaebi’, ‘Doreurami’, and ‘Hoehoe-a(回回兒)’ depending on the region, had been toys since before Joseon. Initially, they had a magical character wishing for a good harvest – typically attached to ‘Boreum-byeotgari’ [stacks of grain for the first full moon] with grains on the first full moon of the year – but later became children’s toys. (Note 1)

Despite having something they had grown up with, they were blaming themselves for looking for answers in the wrong places, hitting their foreheads.

After the time of self-reproach, the researchers and artisans all had the same question.

“But why did it receive extremely opposite grades at the same time?”

The researchers, unable to think of a suitable answer no matter how much they thought about it, talked to their colleagues.

“Do you know why the grade came out like that?”

“I don’t know. Do you happen to know?”

“Shall we ask His Highness?”

When one researcher mentioned Hyang, the other researchers answered at the same time.

“Do you think he will answer?”

* * *

To the researchers and artisans of the institute, Hyang was a ‘good but difficult boss’.

If they failed at their assigned tasks or missed deadlines, Hyang carefully examined the reasons. If it was not due to the negligence or carelessness of those in charge, and if there were no casualties, Hyang rarely punished them.

Instead, what Hyang wanted from those in charge was a clear lesson learned.

Hyang was a good boss in this respect, but in other aspects, he was a difficult boss.

The areas where Hyang was picky were only two.

One was the budget, and the other was asking about the assigned task without even trying to figure it out.

‘Thinking about why this grade was given is the first step to success.’

Because Hyang said this, the researchers had to rack their brains from the question of ‘Why this grade?’

“His Highness always wants us to do our best.”

“Doesn’t that mean he trusts us that much?”

Although they had to suffer a lot from the beginning, the researchers believed that all of this was for them and did their best.

However, this was only half the truth.

“To continue the development through generations, we must thoroughly digest it and move on.”

One reason was the belief that what the researchers and artisans had learned must be properly digested in order to pass it on to the next generation, while other reasons were due to Hyang’s selfishness and limitations.

“Are you just trying to get a free ride? Even in group projects, you get criticized for that. Are you a deeply rooted spoon-rider [someone who leeches off others]? And….”

Hyang looked at the reports with a troubled face.

“I was a maker who just wanted to build things first, but this thinking stuff is not for me…. If I were good at this, would I have gone to liberal arts in the first place? Why else would I be told that I have a 19th-century inventor style?”

The evaluation of the doctor who consulted Hyang in the 21st century was as follows.

‘He is an inventor like Leonardo da Vinci, not a theorist like Kepler or Einstein.’

Due to the limitation of ‘not being good at advanced mathematics,’ Hyang, who had reached his limit, gave up explaining under the pretext of ‘You have to find the answer yourself to make it your own.’

* * *

Anyway, since there would be no answer even if they asked Hyang, the researchers immediately started their research.

And as soon as they started the research, they could understand why they had received two grades at the same time.

Since the content of ‘copying the shape of a windmill’ was already there, it was very easy to grasp the shape.

While making windmills using paper, bamboo, and sorghum stalks, the researchers quickly made progress.

“As expected, four blades receive the wind better than two. Then wouldn’t it be better to have four blades on the propeller as well?”

“That would be good.”

“Ah! Have you ever flown windmills in a competition?”

“Yes, I have.”

“Then wouldn’t it be better to make the shape of the blades similar to those of windmills used for height flying competitions?”

“Oh! That’s very good!”

The other researchers welcomed and agreed with one researcher’s suggestion.

When playing windmill competitions, there were two methods.

One was to run continuously to a designated place, or to stand in place and compete to see whose windmill spins better in the wind.

The other was to carve bamboo into the shape of wings, connect them to a shaft, rub them with both hands, and compete to see who flies higher.

(Note 1)

Because they had the memory of windmills, a toy that they were familiar with since childhood, regardless of whether they were children of noble families, commoners, or the lower class, progress was rapid.

“We’ll get results soon at this rate, right?”

“I guess so. Is it really a Hard Struggle (Lower)?”

The researchers were optimistic about the results, but soon they realized why it had received the grade of ‘Sisyphean Task (Upper)’.

* * *

The first thing that blocked their progress was the ‘optimal blade angle’.

“If we think simply, these inclined blades push the water… then the angle would be….”

While researching to find the optimal angle, another variable occurred.

‘Even at the same angle, the efficiency changes if the shape and size of the blades change.’

“Damn it! Let’s do it, shall we!”

The researchers and artisans cursed at the appearance of a variable that slyly appeared and grabbed their ankles, then rolled up their sleeves and stuck to design and experimentation.

The researchers and artisans carved wooden boards in various ways and made dozens of types of screw propellers.

A method of making and combining the shaft connection and blades separately, a method of carving the connection and blades in one piece, blades with narrow and wide widths, changes in the number of blades such as 4, 6, and 8 leaves, etc….

Before they knew it, the workshop and warehouse of the development department were filled with wooden screw propellers that were too numerous to count.

Amidst all the trial and error, another variable grabbed their ankles.

It was vibration.

On one side of the development department’s laboratory, there was a clockwork mechanism made by Jang Yeong-sil. The researchers attached a screw propeller to the shaft connected to the clockwork mechanism to investigate its performance.

Whee-ing!

As the screw propeller connected to the clockwork mechanism began to rotate at high speed, the power shaft began to vibrate slightly up and down.

“Huh? Why is the shaft shaking? Everyone!”

A researcher with good eyesight discovered the abnormality and called his colleagues.

The colleagues also confirmed the vibration, but here the researchers made a fatal mistake.

“Isn’t it the vibration caused by the clockwork turning? We had a similar incident with the waterwheel before.”

“Is that so?”

“Let’s quickly attach it to the ship and experiment.”

Thus, a model ship equipped with the most efficient 8-leaf screw propeller was floated in a water tank.

“Start!”

When the experiment using the model ship began, the researchers’ faces turned white.

“Why is the ship like that!”

The ship was shaking back and forth, unable to go straight, and moving diagonally while leaning to one side.

“Stop! Stop!”

The researchers, who urgently stopped the experiment, searched the ship thoroughly and pondered to find the cause, but could not easily find the reason.

“I can’t help it. Let’s stop here for now and write a report to submit.”

* * *

Hyang, who received the report, forcibly suppressed the urge to speak.

‘The ship’s crooked movement is clearly due to torque, and the vibration problem…. Isn’t it because the blades are matched in even numbers? As far as I know, ship screws always go out in odd numbers?’

In fact, large ships use two screw propellers to prevent the case of hindering the straight movement of the ship due to the reaction torque (Heeling torque/moment) acting between the ship and the propeller. (Note 2)

And the screw blades of ships are made in odd numbers. The reason is that in the case of even numbers, resonance frequencies occur as many as the divisors, but in the case of odd numbers, only one resonance frequency occurs, creating various problems including vibration.

‘Because of this, even in the 21st century, all kinds of advanced technologies were mobilized to make that simple-looking screw propeller, and in severe cases, Japan suffered?’

During the Cold War, Toshiba of Japan violated the COCOM (Coordinating Committee for Multilateral Export Controls) agreement and exported ultra-precision large machine tools to the Soviet Union. As a result, the United States and other NATO countries began to have difficulty tracking Soviet submarines.

The United States, which found out that the culprit was Toshiba, immediately banned Toshiba from exporting, and from this time on, the decline of Japanese electronic products and semiconductors began.

It was long before Hyang was born, but Hyang remembers this because when Japan excluded Korea from the whitelist and imposed trade sanctions, the internet mentioned this incident, saying, ‘The Japanese cause more accidents!’

Therefore, Hyang had to forcibly suppress the itchy mouth.

‘This is something that must be learned by embedding experience in the body through trial and error! Only then will you be able to use it better in the future!’

Torque and resonance problems were applied to various fields, so it was a part that had to be known and passed on.

* * *

While they were struggling with a difficult problem that was not easily solved, another variable grabbed the developers’ feet.

This time, it was the problem of the material for making the screw propeller.

The wooden screw propellers made of wood broke down faster than expected in repeated experiments.

“Wood won’t work! Let’s try other things!”

Thus, screw propellers were made of iron and copper.

The size of the prototypes made due to the problem of manufacturing technology was quite large, and thanks to this, Jang Yeong-sil had to make a model ship that was 1/10 the size of the actual ship.

The model ship, which was made large and even had a small steam engine mounted on it, was tested in Han River, and similarly failed.

Vibration and leaning were basic, and this time the blades of the screw propeller were deformed.

In the end, the researchers could understand why this task was a ‘Sisyphean Task (Upper)’.

* * *

While the researchers were struggling, Jang Yeong-sil visited Hyang again.

“Your Highness, I have something I have been thinking about.”

“Bring it out right now!”

* * *

Note 1) Korea Creative Content Agency. Cultural Prototype Library. Windmill.

http://www.culturecontent.com/content/contentView.do?search_div=CP_THE&search_div_id=CP_THE013&cp_code=cp0205&index_id=cp02050075&content_id=cp020500750001

Note 2) https://m.blog.naver.com/bjgim21/130161709562