Pulleys appeared very early in ancient China. At least since the Warring States period, pulleys have been widely used in combat equipment, water lifting in wells and other productive labor.
After Dayu cast Jiuding, in Xia, Shang and Zhou dynasties, emperors of all dynasties regarded it as an artifact of the world and a treasure of the country. Lost treasure and lost country, gained Jiuding and gained the world, so Jiuding became a symbol of controlling the world at that time. Later, it was said that after Qin Shihuang's east tour, he passed through Surabaya in Pengcheng, Xuzhou. When he saw a Zhou Ding in the water, he was overjoyed and ordered his followers to try to get the tripod. There is a scene of "fishing in Surabaya" in the stone reliefs of Han Dynasty.
In the picture, the senior manager of Yuding stands on the bridge and directs the Qin people to install a big shelf in the haunt. There is a beam on it, and a pulley runs through it.
What's more interesting is that this time the fishing tripod adopts the way of high pole and double pulley linkage. There are two tall poles in the river, each with a big pulley at the top, and a group of people pull the rope on the pulley. Between the two pulleys, a tripod ear is hung on each rope, and a tripod is held up.
Unfortunately, at that time, Qin people only got eight ding. Legend has it that when the magic tripod was about to be salvaged, a faucet in the tripod stretched out and bit off the rope that tied it. The tripod sank into the water and was never found again. Qin Shihuang ordered thousands of people to go deep into the water to salvage, but in the end they failed, leaving a lifelong regret.
Since Liu Bang entered Xianyang and Xiang Yu set fire to Qin Gong, Zhou Ding disappeared and became an eternal mystery in Chinese history. However, the stone reliefs in the fishing tripod in Surabaya in Han Dynasty tell us that Jiuding's shape is tripartite confrontation, which should be the consensus at that time.
The application of pulleys in ancient China began in Qin and Han Dynasties. At that time, there were many big projects and pulleys were widely used.
Pulley, the ancients called it "pulley". The application of crown block can change the direction of force; Using a set of properly matched pulleys can save manpower.
Another form of pulley is pulley. Fix a short log on a wooden frame beside that well, winding a rope on the log, and fix one end of the rope on the log; A bucket is hung at the other end, and the log can be rotated to lift water. As long as the rope is properly wound, wooden barrels can be hung at both ends of the rope, one barrel carries water and the other falls, so that the pulley can always do work.
Pulley probably originated in Shang and Zhou Dynasties. According to the song dynasty Ceng Gongliang's "Wu Jing always want? Water attack? "Ji Shui Fu" records that someone in Zhou Wuwang used a winch to cross a ravine.
The earliest discussion on pulley mechanics was the Mohist Classic. Mo Jing? "Xia Jing" means that the force of lifting a heavy object upwards is called "pulling", the free falling is called "retracting", and the whole pulley machine is called "tying".
Mohist classics say that "rope" is used to lift weights, and the forces of "pulling" and "receiving" are in opposite directions, but at the same time they act on a common point. It is hard to lift heavy objects and easy to "collect". If heavy objects are hoisted with ropes, people can save effort and relax.
In terms of "rope system", the longer the rope, the heavier the object and the lower the object; On the other side, the rope is shorter, the object is lighter, and the object is lifted up more and more.
If the rope is vertical and the weight of both ends of the rope is equal, the rope system will not be balanced. If the "rope system" is unbalanced at this time, then the lifted object must be on the inclined plane, rather than hanging freely in the air.
Mohism's exposition on pulley mechanics makes us admire his rich mechanical knowledge.
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