The production of wheel rims requires the use of Xunzi's famous saying.
"The wood is straight and the rope is shaped like a wheel, and its curves are regular."
It means to burn the wood in the fire and use the burning flame to bend the wood.
The principle of this step is actually very simple. It is the thermal expansion and contraction that Yang Cheng used before. If the flame only burns one place, that place will bend due to the different degree of thermal expansion.
The biggest difficulty for the ancients in making wheel rims was to control the flame. If the flame was too big, other parts of the wood would be burned. If the flame was too small, it would not be able to bend the wood, which would take a lot of time and effort.
But this is not a problem in the Qingque tribe.
It's very simple. Yang Cheng knows "fire magic". He can micro-manage the size and angle of the flame. He can burn it wherever he wants, and he can burn it at any angle he wants.
The question is, what size and length of wood should be used, and how much curvature should be burned into the wood?
To make a rim, it is definitely not possible to use a whole piece of wood and burn it directly into a rim. That is completely unrealistic. Let's not talk about how long it takes to burn the wood strips and how to accurately control the flame.
Even wood does not have that kind of plasticity. Wood is not an iron bar, a copper bar, or a plastic plastic. It is completely unfeasible to directly burn a wood bar into a whole rim.
Therefore, if you want to make a rim, you cannot rely on one wooden bar, but multiple wooden bars are bent and combined.
This involves arithmetic problems.
After eating dinner and taking a short rest, Yang Cheng threw a light ball into the air, lighting up the entire house.
The house he was in was recently built and was relatively small. The house he lived in next to it was used by Yang Cheng as a study room.
On weekdays, when he has nothing to do or when he is thinking about things, he will be in this newly built room.
The tribesmen also knew that this was Yang Cheng's private space, and even the witches were not allowed to enter, so no one dared to disturb it.
Even when passing by, you have to stay dozens of meters away, walk softly, and don't dare to speak loudly.
At this time, the fragrance of mugwort filled the air.
Yang Cheng was under the light ball technique, with an animal skin spread in front of him and a delicate quill in his mouth.
"Well, where does the arc calculation formula come from?"
Yang Cheng's face turned bitter as he tried to think about what his junior high school math teacher had taught him.
When he was in junior high school, the next period of math class was often physical education. Although physical education class was often occupied, every time Yang Cheng was in math class, he would be distracted and think about playing. His math scores were never very good. .
After experiencing severe beatings from society, I have forgotten almost all the knowledge I learned in school.
It's a bit difficult to remember the formula right now.
"Forget it, forget about the arc formula, just calculate the circumference of the circle. After you calculate the circumference of the circle, you can divide it into segments."
Yang Cheng thought for a long time, but still couldn't figure out the formula for arc calculation, so he simply gave up.
"I remember that the circumference of a circle is the radius times the square of Wu... Hey, that doesn't seem right. This is the formula for calculating area..."
*****
the next day.
Dragging Yang Cheng, who had thick dark circles under his eyes, he continued to the open space, ready to continue making wheels.
He was so busy last night. I thought it would not be difficult to calculate the length of a wheel rim.
However, reality gave him a big stick.
Originally, the circumference of the circle could be calculated directly from the data of the wheel spokes, but Yang Cheng forgot to add the diameter of the wheel hub.
After hurriedly adding the diameter of the wheel hub, I forgot to subtract the diameter of the hole.
After calculating the diameter of the hole, I forgot to include the diameter of the two narrow ends of the spokes...
And after struggling like this for a long time, Yang Cheng suddenly realized a problem, why did he bother so much? Couldn't he just calculate the diameter of the entire wheel...
In the open space, Lulu, Yan Lin and Xing were waiting.
Yang Cheng didn't go back to the house to sleep last night, which made them a little confused. Now when they saw Yang Cheng's haggard face and big dark circles under his eyes, the three of them were instantly frightened.
"Wu, what's wrong with you?"
Lulu asked anxiously.
"Wu Wu, were you punched by someone? Why are there circles under your eyes?"
Yan Lin was shocked, thinking that Yang Cheng had been attacked.
"Witch, tell me who beat you. In the Qingque tribe, there are still people who dare to beat the witch!"
Xing on the other side was eager to fight and resentful.
"It's okay, I just didn't sleep well last night."
Yang Cheng waved his hand and directly ignored the topic and said, "Okay, let's not talk about it anymore. Today's task is a bit heavy and I need you to be more serious."
Yang Cheng didn't give the beast-eared girls any time to ask questions, and directly ordered them to work.
First, the wood was made into strips of calculated length and width, and then Yang Cheng used "fire magic" to bend them step by step.
Yang Cheng also calculated the bending angle of the wooden strips last night.
There are a total of twelve wooden bars, and the curvature of each wooden bar is 30°, and the method to determine the arc of the wooden bar to 30° is also very simple.
Yang Cheng first drew a line on a wooden board with the same arc and length as the wooden board using a ruler and compass.
Every time after burning, put the wood strips on the wooden board for comparison. If they match, it means that the wood strips have been burned successfully and are qualified.
If they don't match, it means that the wrong wood stick was burned. Then depending on the specific condition of the wooden stick, continue firing, or just give up and get another one.
Firing the rims consumed far more time and energy than Yang Cheng expected. Compared with today's rim making, yesterday's spoke making was simply child's play.
After a whole day's work, Yang Cheng could only burn eight wooden sticks.
One of the reasons was that it was the first time to burn and he had no experience. Another reason was that Yang Cheng didn't sleep well last night. Bending the wooden strips was another careful project that required concentration.
So progress is slow.
At dinner, Yang Cheng ate in a hurry, yawned and went to bed.
His tired look was obvious to everyone.
After Yang Cheng left, Yan Hu, Cang Shi and other backbone members of the Qingque tribe surrounded Yan Lin and the others.
Yan Hu asked with a serious face: "Yan Lin, what's going on? Wu, why don't you look good these days?"
"Anu, tell me, what's wrong with Wu? Is he sick?"
Cang Shi on the other side looked equally serious as he looked at Yan Lin.
If a witch gets sick, this is a big deal!
Yang Cheng is the backbone of the Qingque Tribe. Once he has a problem, the Qingque Tribe will have a big problem!
After hearing Yan Hu and Cang Shi's inquiries, Yan Lin and the others looked anxious as if they had found someone to talk to.
Yan Lin urged: "Father, Uncle Cang, hurry up and take care of the witch, he seems to have been possessed by some evil witchcraft these days!"
"Evil witchcraft?"
Everyone was shocked and did not dare to neglect.
