The next day, the clay solidifies slightly, you can separate the mold to take out the wood screw, let the clay mold dry naturally, this is more time-consuming, it takes about half a month.

During this time, you can do other things, such as making brackets that hold the screws, that is, nuts, and of course you have to make molds first.

Screws and brackets are parts that are stressed a lot, and they must be wear-resistant, so they must be made of steel or iron, so they have to be molded and cast.

The key point is the nut, other parts are not important, but the male mold of the recast nut can no longer use the wood screw, which involves the principle of physical heat expansion and cold contraction, the clay model air drying shrinkage is not large, similar to nothing, but after the steel screw hot casting, the shrinkage is very large, and the wood screw has a significant difference. If the wood screw is used as the male mold, the real steel screw will have a large error when it is used, which is obviously not possible.

It should also be noted that the nut or bracket is cast from pig iron, while the screw must be steel. You may not know that the hardness of steel is not as hard as pig iron, so the nut is more wear-resistant when cast with pig iron.

The screw is a part that is directly stressed, and the toughness is in the first place, and the pig iron is too brittle, and it is easy to break if the force is too large, so the screw must be steel.

The thermal shrinkage rate of pig iron and steel is different, the shrinkage of pig iron is small, while the shrinkage of steel is relatively large, so Yang Wenli can't wait for the steel screw to be cast in the future and then cast the nut or bracket, so the error will be relatively large. It is best to use pig iron casting screws, and then use pig iron screws as male mold casting nuts, both are pig iron, the shrinkage rate is the same, and the maximum precision can be maintained.

……

"Hey, hey! It's so fun, husband, how do you know so many new ways to play? I've never seen it before. ”

Yang Wenli was doing something, Xiao Yan'er was watching curiously on the side, and asked him innocently.

Don't look at her, this question is very simple, Yang Wenli is really difficult to answer, did he say that he knew it from a book or someone else told him?

It's all shadowless things, he has never read at all in this life, staying in the almost isolated mountain nest of Maoshan Chong, he can't find an excuse for a master who knows everything, he is completely born to know, so Yang Wenli can only vaguely fool her: "I am much older than you, and you will understand more when you grow up." ”

"Oh!" Xiao Yan'er responded as if she understood, the child was so coaxing, she thought it was normal, she only thought that she would grow up and understand a lot of truths, so she was very happy.

Yang Wenli is using the sand modeling, which dries faster than the clay, which is just staggered and does not affect Yang Wenli's next plan.

Molding sand is not ordinary sand, it is made of a particularly clean and fine sand and graphite mixed in a certain proportion, which can withstand high temperatures, and is easy to shape after water, and is a commonly used sand turning raw material.

Fine sand and graphite are both substances that are not readily available in nature, and Yang Wenli does not know the mixing ratio, but fortunately, ancient China has used a large number of sand cast iron, so Yang Wenli bought ready-made sand, which is not a climbing tree, so there is no need to find guilt by himself.

The pig iron screw is only a temporary male mold, not the final use, so it can be recast with molding sand, which will not affect the actual use effect in the future.

"Good! Alright, let's go back! Yang Wenli finished the model of the type of sand, stood up, patted off the type of sand in his hand and said to Xiao Yan'er.

"What's the use of doing this? I don't think it's as nice as a house. Xiao Yan'er saw the long thing that her husband made, and she didn't understand what it was, so she proposed to build a house.

She still thinks of the family, the child is innocent and carefree, and all she thinks about in her head is to play.

"I'm going to have a lot of use for this, so don't mess it up." Yang Wenli was afraid that she would mess up, so he warned her.

"Humph! I won't! Do you think I'm a child? Xiao Yan'er snorted coldly and asked him dissatisfied.

"Hahaha!" Yang Wenli was amused by her words, the child said that he was not a child, and he was still very serious, is there anything funnier than this?

Time is passing day by day, Yang Wenli has been relatively leisurely recently, and the whole pace of life has slowed down. There is one reason to take a little wife, and another reason is that casting takes time, and if you don't do it, you can't do anything else at all.

The 10 teenagers finally finished their 5-day hellish wilderness survival training, and at first they were able to find food easily, and even went along with tree climbing training, but in the next two days, where could they find food? The time of the day is not only to find food, but also to find food.

The rhizomes of plants, roasted grasshoppers, raw white and tender insects, and even disgusting and ugly earthworms have become their food, and people are so hungry that they can eat anything.

After returning home, they ate their first meal of fragrant rice, as well as relatively light vegetables and tofu, and they felt that it was much more delicious than when there was a big fish and meat in the past, and each person ate 5 large bowls of rice, until their stomachs could not be stuffed, and they were hungry and afraid.

The reason why they only eat light things is because Yang Wenli takes special care of them, and those who have been hungry for a long time must avoid big fish and meat.

Yang Wenli ate less, finished eating earlier, he deliberately walked to the side hall, and saw that they were all like starving ghosts reincarnated, so he took the opportunity to educate: "What? Is it hard to survive in the wild for just 5 days? Do you think I'm trying to toss you?

You are lucky, staying in Maoshan Chong, a rare place for outsiders, with plenty of food and clothing, you don't know that there is a great drought in the north this year, and the land is thousands of miles away, let alone eating, and you don't even have bark and grass roots.

If, one day, some of you go to the north alone to spy on the enemy's intelligence, and you have limited baggage, what will you eat?

Your training in the past few days is a portrayal of the north at this time, and it is even worse there, and there is already a phenomenon of cannibalism.

Do you say, is wilderness survival training necessary? ”

In the last sentence, Yang Wenli asked loudly, deafeningly, and everyone in the side hall was stunned by the miserable situation he depicted, and the teenagers forgot to answer his question.

Xiaohong and Xiaolu were even more frightened, they grew so big, it was the first time they had heard of cannibalism.

The subordinates present, although they were all born poor and suffered since childhood, how could they eat a little mush, they didn't expect the north to be so miserable!

Of course, the north may not have reached this miserable situation now, Yang Wenli is actually talking about the future, but at this time, the life of the poor people in the north is indeed unbearable.

The climate drought caused by celestial anomalies is a reason, the inaction of the government is also a reason, and the fact that a few wealthy households are not able to help their neighbors but take the opportunity to exploit them is also a reason.

…… To be continued