The trip to Chen Cang can be said to be very successful, and it is only in the afternoon when you get on the train and start to turn around, according to this time, when the sun sets, everyone can return to Chang'an City.

This was unimaginable before, in just one day, Li Shimin could leave the palace and go to another city three hundred miles away to attend the meeting, and then return to Chang'an?

It can be said that on the way back, everyone's mood was excited, including these ministers, and they were all thinking about using the railway to do something completely new.

"Oh, that's not right." Li Shimin suddenly spoke.

"Dad, what's wrong?" At this time, because they were not discussing the problem, Li Shimin was naturally replaced by the eldest grandson and queen here, and the ministers went to the other half of the carriage.

"It's not a good thing for me that this railway was built." Li Shimin said.

"Why isn't that a good thing?" Li Ke was stunned, what did his father think of?

"How is it not a good thing? Isn't that obvious? I can now go to a city 300 miles away in one day to attend a completion ceremony and then return to Chang'an, and in the future, the speed of this railway will be faster and more places will go, and it is not possible for me to arrange the itinerary for the next month, or even months? ”

"Is it even possible to arrange a car on this train where I can sleep and rest, I rest at night, wake up during the day and go to another place to continue working? Where are you going every day? Anyway, the train speed will be fast, and there will be many places to go, so will it be in time? Li Shimin asked with squinted eyes.

Li Ke: "......"

He was stunned for a moment, because he suddenly thought of those leaders in the future...... Cough...... If you want to do 996 in your seventies, you can't do it, you have to do 007 work...... Does that seem to be the case?

"Ahem, of course it's impossible, dad, what do you think? Where you travel so easily, the guards must keep up. Li Ke quickly coughed dryly and said.

"Really? There are at least a dozen trains, and half of the carriages are enough to carry the guards. Li Shimin looked at Li Ke and asked.

"Erlang, if you say this and let Zheng Guogong hear it, won't you want to impeach you for not wanting to make progress?" Empress Eldest Sun relieved Li Ke from the side.

"Yes, that's it, let's talk about it, Dad, this is a good thing, think about it, you are in the palace, in fact, you have been thrifty and diligent, although both the Taiji Palace and the Daming Palace are built very well, but any scenery will be like that for a long time."

"And if you work on the train, it's different, you think about it, you wake up and you have a different scenery to see, and you can go to various places to see new scenery in person, it's all work, and now you can see different things every day, which is a good thing." Li Ke quickly began to quibble.

"Is that so?" Li Shimin squinted at him.

"Of course yes, Erchen suddenly remembered some knowledge about bridges, and I went to communicate with Yan Shangshu and Duan Shangshu." Li Ke stood up.

"Wait, I see that you just want to trap me, do you think your father and I are not tired enough?" Li Shimin glared at him and said.

"No, Dad, you think too much, I really just had a flash of inspiration, and suddenly I have a new idea, I'll go and communicate with them." Li Ke said quickly.

"Come, go, let's go, I want to hear what you say, if you can't say something new, you wait......" Li Shimin also stood up.

Li Ke: "......"

What else can be said about this matter? Li Ke could only stand up silently and walked towards Duan Lun and Yan Lide, and it happened that the two of them were also communicating.

After all, there will definitely be a lot of cooperation between the Ministry of Industry and the Ministry of Construction in the future.

Seeing Li Shimin and Li Ke coming over, they naturally stood up and greeted Li Ke and them, but the two of them were somewhat confused, they didn't know what His Highness and His Majesty were doing, didn't they talk about everything they should have talked about just now?

"Well, Li Ke said that there are some things about the bridge to discuss with you, and I am also very interested, so come and listen to it." Li Shimin nodded lightly.

LI Ke; “……”

Dad, aren't you forcing me?

"Your Highness, please speak." Duan Lun and Yan Lide didn't care, but spoke very seriously.

And with their coming, the historian next to them naturally followed and sat next to them, listening silently.

"That's right, I mainly have some ideas about how the bridge is built, and you can record them all, and when you go back, you can find someone to make them out of wood and test them." Li Ke said quickly.

"The simplest, that is, the most common, is the beam bridge, that is, the bridge construction method we use on the Weihe Bridge, two piers and a section of the bridge, if the steel structure is adopted, the single span can reach about 120 meters, and this continuous beam bridge is the main way to build bridges for a period of time, and it will also be the most used bridge method in the future." Li Ke said seriously.

Duan Lun and Yan Lide immediately recorded it.

"But this kind of bridge has a fatal weakness, that is, its span is limited by structural problems, and the length cannot be too long, and if we want to cross a large cliff and deep valley at once in the future, such a structure is obviously not enough."

"And according to the principle of mechanics, if the span is too long, only the steel bridge can be used, but the cost of the steel structure is too high, and the engineering department is currently studying a new structural method, prestressed concrete technology."

"It is to implant pre-lifted steel bars in the concrete, and use the tensile desire of the steel to balance the external forces on the bridge, so that its cost can be reduced to a lower level, and it can also withstand higher loads."

"Prestressed? His Royal Highness really had a wonderful idea, and he also came up with such a technique. Yan Lide's eyes lit up, and he couldn't help but praise.

As the original master of the Tang Dynasty, Yan Lide was naturally the first batch to learn and contact new physics and mathematics, because he had a foundation and had also learned Gewu before, but he used new terms to count his previous knowledge.

So learning is naturally very fast.

"Wait, that steel can be stretched?" Li Shimin couldn't help but ask, because in his opinion, shouldn't steel be very hard?

"Yes, Your Majesty, in fact, everything in the world has a certain ability to deform, for example, dry wood, within a certain length, it will not bend."

"But when the length of this piece of wood continues to lengthen, then it will show a slight curve, and the steel is the same, although the minister has never seen it, but the minister thinks that if the length of the steel is one or two hundred meters, it may look as soft as noodles." Yan Lide's emotional intelligence is average, and he immediately explained it to Li Shimin.

"Oh?" Li Shimin actually didn't understand, but he nodded seriously and motioned for Li Ke to continue.