Although the thing parked in the Ministry of Heavenly Engineering is not the most beautiful one among the trains that Zhang Nan has ever seen, even the antique train that Zhang Nan has seen in the books is much stronger than the one in the Ministry of Heavenly Engineering, but Zhang Nan can still see at a glance that the black guy is the train.

Zhang Nan walked quickly to the side of the steam train and took a closer look, although limited by the limitations of the process, there were no lathes and other tools, but the craftsmen of the Tiangong Department still relied on their own skillful hands to make a simple train.

"Bang, bang." Zhang Nan knocked on the big guy with his hand, making a dull sound, and Zhang Nan also got a hand of grease.

It can be seen that in order to prevent this guy made of iron from rusting, the craftsmen of the Tiangong Department also took a lot of effort to coat the entire exposed body with oil, but what kind of oil it is, Zhang Nan does not know.

"Qingquan, why do you have time to come to the Heavenly Ministry of Works."

Zhang Nan turned his head, only to find that Mo Zu had just walked in from the gate of the Tiangong Department, and at first glance, he had just come back from going out.

"Ah, isn't this coming to Mozu, you want a few people who have attainments in building houses, recently I want to open a supermarket, I need to build a house, I originally wanted to find someone from the Ministry of Industry, but then I thought about it and it was too troublesome, so I came to the Ministry of Heavenly Industry." Zhang Nan said with a smile.

"Then you're looking for the right person, remember what we built in the mountains? That's all built by our Momen, what is this supermarket you are talking about? If you want to hide this supermarket, I guarantee that few people will be able to find it. Mo Zu said proudly.

Zhang Nan looked at the pride of Mozu, and he didn't know what to say.

"By the way, Mozu, how long have you been making this thing?" Zhang Nan said, and pointed to the steam train beside him.

"Ah, you said this, it's been half a month, but it's still improving, this thing is not a finished product, and there are still some things we still can't think of a good way to solve." Mo Zu scratched his head and said, it seems that this train has also caused some troubles to Mo Zu, who has been clever all his life.

"For example, what? I'll see if I can help with that. Zhang Nan said, after all, although Zhang Nan didn't know the structure of the train, but now the one Mozu took out was still a little different from the train, and Zhang Nan felt that he could still make some constructive suggestions.

"For example? This wheel alone has been bothering us for a long time, old man, I have been thinking for a long time, but the wooden wheel can not bear a large amount of weight at all, and the bronze wheel or the iron wheel, with the goods on the ground is almost an inch of difficulty, each line out of a mile, the ground is a deep rut marks, and the iron wheel is very easy to deform, after loading the measured goods, it will not take long to be able to use it again, can only be redone. ”

Mo Zu kicked the wheel of the train in front of him with his foot, it seems that Mo Zu has been worried about this problem for a long time.

Zhang Nan bent down to see that the iron wheels installed on the train were indeed a little deformed, and they were seriously worn.

"In that case, why not steel?" Zhang Nan thought for a while and said.

After listening to Zhang Nan's words, Mo Zu smiled bitterly, and then said: "Qingquan, you said it is easy, how can you get this steel if you say it, you must know that the smelting of this steel is more than ten times more difficult than this iron, and if you don't pay attention, it is easy to scrap a pot of materials, and the Ministry of Heavenly Industry doesn't have so much money for us to use steel to get this thing." ”

Zhang Nan nodded noncommittally, after all, Datang is not now, steel is not a consumable metal for Datang, although it has mastered the technology of steelmaking, but if you look at steelmaking, Datang can't do this step now.

Zhang Nan looked at the worn iron wheel, thoughtful, but he couldn't grasp the most important point in his mind.

Suddenly, Zhang Nan thought of what was missing from this simple train.

"Mo Zu, have you ever thought about laying a track for the wheels of this thing?" Zhang Nan asked.

"Tracks? That's what it is. Mo Zu said.

"To put it simply, it is to let this thing follow a specific trajectory, and with that thing, this train should be able to run stably."

"This seems to be a method, this iron wheel is very difficult to control, and as the body lengthens, the direction is more difficult to turn, and it would be great if it could be made to follow a specific route." Mo Zu thought about it, and it seemed that it was indeed much stronger than running around on the ground.

"Qingquan, do you call this car a train?" Mozu asked.

"yes, it's fuel-powered, after all." Zhang Nan nodded and said.

"Well, we were arguing at first that we didn't have a good name, but the train is a good name, so it's called a train." Mo Zu said as if he had solved a difficult problem.

"But even if the track you said is paved, the weight of this car will still remain the same, shouldn't this place sink as well? Isn't the action of force reciprocal? ”

Mo Zu suddenly came out of his mouth and said that the effect of force was mutual, but it also startled Zhang Nan, but Zhang Nan quickly thought that this sentence must have been seen by Mo Zu from the junior high school physics textbook, and he was immediately relieved.

"That's not true, the wheels are iron, this track is also made of iron, the wheels on both sides correspond to the two rails, the cross-section of the railway subgrade is trapezoidal, because the trapezoidal can disperse the force well, the top is the rail, then the sleeper, and the bottom of the sleeper is the gravel, the effect is also to disperse the force. Underneath the gravel is our dirt road. Zhang Nan said.

"Will this work?" Mo Zu said with a skeptical face, it seems that Mo Zu still doesn't believe it, just by adding two more railroad tracks, and then laying a few logs, this problem can be solved.

"It's okay, you have to try it to know, but if Mozu you use my method, the iron wheel will definitely not press the ground down anymore." Zhang Nan said with a smile.

"Well, then old man, I'll try it according to the method you said, if it succeeds, this train can pull very heavy goods, this is a national weapon." Mo Zu said excitedly.

"Mo Zu, don't get excited, you find out the person I want first, what kind of changes this train can cause to Datang, I know very well in my heart." Zhang Nan also said with a smile.