"Ladies and gentlemen, the little ones are polite, the little ones are polite!"

Chen Qiankun bowed all the way, with a smile on his face, and when he got to the shade of the tree, he saluted Xu Parallel and said, "The little one has seen the deputy envoy." Pen %Fun %Pavilion www.biquge.info"

Xu Ping said: "This carriage is made by your supervisor, come to tell you the officials, why you can use two wheels to pull more goods than four wheels, and the horse is easy?" ”

Chen Qiankun was stunned for a moment, and hurriedly bowed down again: "What kind of person is the little one?" Dare to speak in front of all the officials! ”

"You are a very good craftsman, and the carriage you make is sturdy, durable, and light. If it sells well, none of the officials here may be able to make more money for the court than you, so why look down on yourself? ”

Seeing that Chen Qiankun was still panicked, Xu Ping said again: "Don't hide it from you, your monthly salary is more than the monthly salary of half of the officials here." If you work hard, you will not be treated badly by the court. Of course, everybody has their own ministry, and you can't do what the officials do, and you can't do what the officials do. There are differences in people's status, but you also rely on your own craftsmanship to eat, you don't owe anyone anything, and you don't need to be careful from time to time. ”

When Chen Qiankun heard this, he saluted again and again: "The deputy envoy is a family, how can the little one be worthy?" Kill the little one! ”

"Okay, don't talk about these lies, just go to the table and talk about it!"

Chen Qiankun made a gesture again and again, and when he arrived at the table, he bowed his hand to everyone: "The little one is ugly, don't be strange to the officials." ”

After speaking, he put the burden in his hand on the table, opened it, and said: "These things were made when the carriage was made, and Deputy Envoy Xu came to the scene to discuss the shape with a few of our craftsmen, and they were waiting to be made there. Looking at it concisely and clearly, all the officials are used to reading the books of the sages, and their brains are nimble, unlike us rough people, you can understand it at a glance. ”

As he spoke, Chen Qiankun put a small two-wheeled car and a small four-wheeled bicycle in his baggage on the table.

Pressing the two-wheeled vehicle with his hand, Chen Qiankun said: "Official, please see, when the two-wheeled vehicle system is made, what you want is the front sinking, that is, when the empty car is placed on the ground, the front wheel will fall to the ground." Of course, we really made the car, and there was a shelf in front of it, and the shelf supported the car after the horse was unloaded. ”

Speaking of this, Chen Qiankun cleared his throat and said: "Officials all know that both horses and mules are accustomed to carrying heavy loads, and if they are used to pull plows to plough the fields, they will soon get tired, which is not good. The same is true of the horse-drawn carriage, if it is only pulled forward by horsepower, like a four-wheeled vehicle, it will not go far, and the horse will not be able to support it, and the horsepower will be overdrawn. The two-wheeled carriage distributes part of the weight of the body to the horse, which is equivalent to making the horse both carrying and pulling, and it is not so easy to get tired. ”

After speaking, Chen Qiankun looked back at Xu Ping, who was standing not far away, and saw Xu Ping nodding to himself with a smile, and unconsciously had confidence, and pointed to the model on the table again to explain.

Gently holding the two-wheeled carriage with his hand, Chen Qiankun said: "Official, please see, as long as you hold this carriage up, you don't need to use force, and the cart can walk forward on its own." What is the reasoning behind this? At that time, several of us craftsmen got together, and we couldn't figure it out. Later, Deputy Envoy Xu explained to us that the weight of the car is in front, and this weight can be regarded as gathering at a point, and then it is equivalent to such a force pulling the wheel forward. ”

Xu Ping secretly said in his heart, it is called the center of gravity, and he talked about this concept at that time, but unfortunately this craftsman still can't understand it and can't remember it. The center of gravity is equivalent to the gravity of the car to this point, vertically downward, acting on the wheels, resulting in a gravitational moment opposite to the frictional moment, and then gravity becomes the driving force to move the car forward.

The center of gravity of the four-wheeled carriage is between the front and rear axles, and the gravity is equivalent to the forward power of the car for the rear wheels, while the resistance of the forward movement of the car is increased for the front wheels.

In fact, how many wheels are just the appearance, the real key is to let the center of gravity be located in front of all driven axles, so that the moment of gravity on the driven wheel is opposite to the friction moment, and become the driving force for the car to move forward, which is equivalent to reducing the load of the car.

The key to using a two-wheeled carriage is two points, the horse can carry the weight, under this premise, the rational use of gravity, the load in the body is divided into two parts, so that the horse can both carry and pull, so as to make full use of the horsepower.

This is designed according to the characteristics of the use of draft animals, such as cattle can not carry weight, and the traction force is much greater than that of horses, and it is really suitable for transporting goods in the shape of four-wheeled carriages. The same is true if a pull-back horse is used.

This is best reflected in the freight trucks of Xu Ping's previous life, from the very beginning of the full-trailer trailer, which is equivalent to a four-wheeled horse-drawn carriage, and then more and more inclined to heavy loads, the mainstream has been changed to semi-trailers. Semi-trailer alias "draped", the biggest feature is that the center of gravity is located in front of all driven wheel axles, one is to increase the adhesion of the driving wheel, and the other uses gravity moment to reduce the traction load of the car, and the two-wheeled carriage is basically the same. Those vehicles with very small frictional moments do not have this demand, such as trains, which have always used the form of pure traction.

Although these mechanical knowledge is not complicated, it is still very difficult for people of this era to explain it clearly in this way so that they can understand it. Xu Ping can only use the model, plus his own explanation, plus the wisdom of these craftsmen, so that they can understand and accept this truth.

Although Chen Qiankun is timid, his eloquence is good, and he speaks clearly and fluently all the way.

After finishing speaking, Chen Qiankun arched his hand to everyone: "The little one is ugly, I don't know if the officials have anything to ask?" ”

Hu Su in the crowd said: "This edict, you just said that you lifted the two-wheeled car with your hands, and when you flatten the car, it will move forward by itself." But we lift the car by hand, and our arms are not tired? Instead, use a trolley or pull cart to make it easier to move forward, isn't that the truth? ”

Chen Qiankun smiled and nodded: "The official is right, the car will be sour after a while." ”

Wang Zhu and Hu Su glanced at each other, and asked with a smile: "Isn't that still a four-wheeled carriage light!" ”

Chen Qiankun arched his hand: "At that time, some of our craftsmen also asked Deputy Envoy Xu like this, and I told several officials what the Deputy Envoy said at that time. We feel tired of carrying the car by hand, because we can't carry heavy things by hand, but we can move heavier things by pulling or pushing. And horses are different from us, carrying a strong man can still walk like flying, and it is not a problem to travel dozens of miles a day. Besides, we people carry things on our shoulders, which is not as heavy as the things we pull, but we feel tired after pulling heavy objects for a while, but we can carry the burden for a long distance. It's the same with horses. Speaking of returning to the carriage, if we do not carry the carriage by hand, but hang it on our shoulders, will the officials still feel that the two-wheeled carriage is more tiring than the four-wheeled carriage? (To be continued.) )