to build the Forbidden City in Ming dynasty stone hold hundreds of tons, workers have a car not make, use land boat; With road does not walk, on ice tunnel. What is the mystery? Scholars of China and the United States a cooperative study has found that, in addition to the time of the vehicle does not have this kind of load capacity, in the case of low speed and heavy loading, slip ratio scroll is more efficient and safer. The paper published in the latest issue of the journal proceedings of the national academy of sciences.
in Ming dynasty recorded in the two GongDingJian ji: 1557, 120 – ton rocks on land boat, starting from the quarry of fang shan magmatic rock fossa region, along the artificial ice tunnel & other; Slide & throughout; The 28 days, 70 kilometers, eventually came to the Forbidden City.
one hundred tons of rock along the way how the taxi? Lead author associate professor, school of mechanical engineering, Beijing university of science and technology to our reporter li jiang reduction in detail the stones & other; Slip & throughout; First ship of the scene: workers in carry stones about digging a well in every other way, in the dead of winter chilly days, draw water from a well poured into ice tunnel; Transport, the workers to take well water on the ice, instantly make ice tunnel surface forming a layer & other; Water film & throughout; , and then pull forward land boat carrying stone.
don’t look down upon this & other; Water film & throughout; , it ACTS as lubricant, make land boat and the friction between the ice decrease sharply. Li jiang et al. Research has shown that this kind of circumstance of kinetic friction coefficient is only 0.03, while ordinary ice is 0.22. If you want to carry 120 tons of heavy stones, & other; Ice tunnel + water film & throughout; Only 50 people; If on the dirt road and ice, at least need 1500 and 330, respectively.
li jiang said, many classic literature is generally believed that the ancient represented by wheel rolling mode of transportation, more advanced than sliding. Vehicles on the road, however, is demanding, it is bound to daxing road, affect the construction time limit for a project. At that time, Beijing’s winter average temperature at minus 5 ℃ or so, ice tunnel is firm and smooth. In addition, during the late 16th century ten six-wheel car, used by the highest capacity of about 95 tons. And stones to build the Forbidden City with more than hundreds of t, is the heaviest piece put in Kowloon, and behind the house, engraved with the play a large stone beads, more than 300 tons, is heavy than a Boeing 747. With land boat instead of wheeled vehicles, the ancients have realized at this time, in the case of low speed and heavy loading, & other; Slip & throughout; Is more efficient to ship than to cart, more secure.
and, according to the analysis of the quarry is mostly located in the shallow mountain, basic is downhill all the way to the Forbidden City area, the terrain is also helped. Now, it seems, the Forbidden City yun stone road is the best optimal, still line of difficult & ndash; & ndash; Speed limit only 8 centimeters per second, and the snail crawling about 2 cm per second.
li jiang told reporters that the study is the result of a. Last summer, she and state key laboratory of tribology, tsinghua university associate professor hao-sheng Chen, accompanied by the visiting professor of mechanical and aerospace engineering at Princeton university, for the first time Mr Howard & middot; Stone visiting the Forbidden City, three of the great stone during transportation problem is rather curious. Afterwards they refer to the literature, but found no correlation analysis of data from the viewpoint of engineering science, 3 people therefore decided to find out.