Looking at the mountains of wicker boxes, Su Song said: "In the past three years, I have worked the machine left in Yongcheng, but I haven't gained much. Now burning the same coal, the force is two or three times greater than before, but no matter what method is used, it is still such a behemoth. This kind of thing can only be used on ships, but if it is used to make cars, all roads will be crushed. ”

It has been ten years since Du Zhongxiao made the first model of a steam engine. Not only Du Zhongxiao, Su Song and Han Jiang, but also some other literati who were interested in the machine, there were also many capable craftsmen who joined in the improvement of the machine.

In fact, there are still many people in this era who are interested in these and are willing to devote themselves to it. However, technology is rarely related to industry and agriculture, and is more used in high-level projects such as astronomical instruments. Astronomical instruments were more sophisticated, and many mechanical mechanisms were invented.

However, in ten years, the development of the steam engine encountered a bottleneck. One is that it is too heavy, and it is either fixed in one place and does not move, or it can only be installed on the ship. Just like what is used on the Bianhe River now, a big ship is equipped with a machine, and the cargo ship can't do it, so it can only be used as a tugboat. Water transportation is limited by natural conditions too much, and everyone wants to use this machine to make cars that can run on the road. The second is that the power is too small, and the huge machine, which is really made into a car, cannot pull much goods.

Du Zhongxiao also wanted to build a section of railway, use a steam engine to pull the train, and slowly experiment. But where does the iron come from? Where is the shop? Not to mention that the power is too small, and the goods pulled are too small, it is not as good as a horse-drawn carriage. If this machine really wants to be practical, it must have more power and reduce the size, otherwise it can only be a principle machine for people to study.

The biggest problem now is the sealing of the pipes after the use of high-temperature and high-pressure steam. The calf leather and felt used in the Bianhe car and boat are very fast aging under high temperatures, and it is necessary to overhaul and replace all the sealing gaskets after a run. The busy Bianhe River can do this, the cost is affordable for the imperial court, and other uses are difficult.

Looking at Su Song's weak look, Du Zhongxiao was also a little helpless. I am a Chinese asset, and I have spent countless efforts to have my current achievements, searching my stomach every day to find the knowledge in my memory. People like Su Song are geniuses, not to mention this era, they can be counted for thousands of years. If he could have received his own education, he might have been able to build a car and an airplane, and the steam engine would be nothing.

Su Songdu felt that it was difficult to improve, and if there was no major breakthrough, it was likely that this machine had really reached the limits of the times.

The two discussed the bottleneck encountered by the machine for a while, and Du Zhongxiao said: "The temperature of the water vapor in the tube is too high, the pressure is too high, and it is not easy to seal. If not, the machine is huge and the strength is too small, which is a dilemma. At the beginning of the year, during the rebellion in Beizhou, I brought artillery to help break the city. Since then, I have been thinking about musket artillery, but the projectile and bore are not tightly sealed, and they do not shoot far enough and are not powerful enough. After months of hard thinking, I finally came up with a solution. That is, the projectile does not need to be round, but has a tail piece at the back, and after the gunpowder is ignited, the tail piece is pressed open with the gas inside to close the chamber tube. I've tried it these days, and it really works, but it doesn't work yet. ”

The firing range of artillery and muskets is mainly related to the pressure after the deflagration of sufficient gunpowder, that is, the bore pressure, and also related to the length of the bore, that is, the distance of the pressure work. Therefore, the method of increasing the firing range, increasing the caliber is actually not very useful, and increasing the length of the barrel and barrel is more effective. Again, the better the projectile and the chamber are sealed during launch, the higher the chamber pressure, and the greater the range. Du Zhongxiao tried a lot of methods, remembering that there was actually a nest behind the bullet shell in the previous life, and was inspired, so he remembered that if such a structure could be designed behind the projectile, and the gunpowder pressure could be used to deform it, so as to achieve closure, it could increase the chamber pressure. It's still an idea, and it's still going to take time to get it into practice.

Seeing Su Song's blank expression, obviously not knowing what the relationship between artillery and steam engines was, Du Zhongxiao smiled and said: "The same reason, the pipeline that passes through the steam has high pressure inside." If you use a copper pad instead of a leather pad when sealing, and let the water vapor press the copper sheet on the pipe wall, can it be sealed? The copper mat is much stronger than the leather pad, and it will not age and cannot be used after years of water vapor. ”

Su Song nodded, and finally understood what Du Zhongxiao meant.

In later generations, the sealing of steam engines was made of rubber, not only with rubber seals, but that rubber can withstand aging in a high temperature and high humidity environment. As long as you are willing to spend money and replace it frequently, cowhide can be sealed like felt. In fact, under normal temperature conditions, oil sealing felt is more widely used than rubber. Now that there is no rubber, is there any other way? With metal, it is nothing more than a higher cost.

Under normal pressure, the metal sheet has little sealing effect, but under high pressure it is different. The higher the pressure, the better the sealing effect, and metal seals will become mainstream. For copper sheets, in fact, the pressure of the steam engine is still a little low, but it can be used with felt, so as to replace the calfskin that is easy to age. The felt is retorted and can withstand high temperature steam.

This kind of complex machine, in fact, has a number of such technical details, some of which are very easy to solve. Some people can only think of solutions because their knowledge is relatively unpopular. From memory, it was actually much easier to make a steam engine in this era than it was in Watt in history, and there was no need to worry about patents, no need to think about profits, just to solve the problem of whether there was a problem. Moreover, Du Zhongxiao dealt with machines in his previous life, and he had seen countless mature structures, as long as he thought about them one by one and extended them, he would be infinitely useful.

Taking out a small piece of copper, Du Zhongxiao said to Su Song: "This is it." This side is concave and outwards when installed. The other side is convex and inward-facing when loaded. If there is moisture in the pipe, it will flatten the copper sheet and stick it tightly to the wall, thus sealing it. ”

If the pipeline is filled with atmospheric liquid and gas, the copper sheet has no sealing effect, and the higher the internal pressure, the better and more reliable the sealing effect. In this way, the steam pressure can also be further increased.

Holding the copper sheet in his hand, Su Song pressed it with his hand and tried it, and said with a smile: "When you think about it, if you can come up with this method, you can try it!" ”

Du Zhongxiao smiled bitterly in his heart, what ingenuity, this structure was remembered, and it was actually ordinary to recall. As long as I have seen a lot of structures such as high-pressure liquids, water pumps and the like are very common, but I don't think about them. By extension, it can also be used with threads, whether it is a faucet or a nut. The thread is not only easy to disassemble, but also a sealing method, sealing for the labyrinth.

Many common mechanical structures, people who are not designers, it is difficult to figure out what the principle is. If you really understand the principle, you can use it in many places. As long as you see a lot, a large number of problems are actually just a turn in the brain, and you can't remember it, but you don't put in enough effort.

For Du Zhongxiao, solving the sealing problem of high-pressure steam is equivalent to pushing open a door. In fact, I know enough that basic machinery is not practical and sophisticated knowledge, otherwise how could the inventor of the year do it? The first ones to be made must have been very rudimentary, and later over time, the technicians improved little by little.

Can threaded nuts be made? In the past, Du Zhongxiao would find it difficult. How do you thread without a machine tool? Now it feels like it's easy. Not to mention that it is not difficult to manufacture a single-function machine tool, it is possible to make threads without a machine tool, and it does not need to be accurate. First, use a screw to make it by hand, and then use the screw to directly cover the nut, which is nothing more than the hardness of the nut is smaller than that of the screw. If heat treatment is added, different hardness series, mass production of screws can also be done. It's just made in different places, and it can't be universal, so what does it matter?