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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Lever, block, inclined plane. History of invention and production
Directory / The history of technology, technology, objects around us Already in ancient times, people began to use simple mechanisms for lifting weights: a lever, a gate and an inclined plane. Later, a block and a screw were added to them. These simple devices made it possible to multiply the muscular efforts of a person and to cope with such weights that, under other circumstances, would be completely unbearable. The principle of operation of simple mechanisms is well known. For example, if you need to pull a load to a certain height, it is always easier to use a gentle slope than a steep one. Moreover, the lower the slope, the easier it is to do this work. This relationship has a clear mathematical expression. If the inclined plane has an angle d, then it will be 1/sin d times easier to drag the load along it than to lift it vertically. If the angle is 45 degrees, our effort will be 1 times less, if 5 degrees - 30 times less, with an angle of 2 degrees we will spend 5 times less effort, and with an angle of 11 degree - 1 times! True, everything that is gained in strength is lost in distance, for by how many times our effort is reduced, by the same number of times the distance over which the load will have to be dragged increases. However, in cases where time and distance do not play a big role, but the goal itself is important - to lift the load with the least effort, the inclined plane turns out to be an indispensable assistant.
Another simple mechanism - a lever - our distant ancestors constantly used to lift and move heavy stones and logs. The lever allows you to achieve a multiple gain in strength by the simplest and most affordable means. Putting a long and strong pole on a log stump (support) and slipping its other end under a stone, a person turned the pole into a simple lever. In this situation, two torques began to act on the stone, one from the weight of the stone, and the other from the hand of a person. In order for the stone to move, the "pushing" moment from the muscular strength of a person must be greater than the "pressing" moment from the weight of the stone. The moment, as you know, is equal to the product of the applied force and the length of the arm of the lever - in this case, the arm is the distance from the end of the pole (the point of application of force) to the log (the fulcrum).
It is easy to calculate that if the shoulder on which the person presses is 15-20 times longer than the one that is slipped under the stone, then the strength of the person, respectively, also increases by 15-20 times. That is, a person, without really straining, can move a stone weighing a ton! The fixed block - the third mechanism that became widespread in antiquity - is a wheel with a chute, the axis of which is rigidly attached to a wall or ceiling beam. Throwing a rope over the wheel and attaching its opposite end to the load, you can raise it to the height of the block attachment. A fixed block does not give a gain in strength, but it does provide an opportunity to change its direction, which is often of great importance when lifting weights.
For all their primitiveness, simple mechanisms greatly expanded the capabilities of ancient man. In order to be convinced of this, it is enough to recall the gigantic buildings of the ancient Egyptians. For example, the Cheops pyramid had a height of 146 m. It is estimated that 23300000 stone blocks were required for its construction, each of which weighed an average of about 2 tons. But this was not the limit - during the construction of temples, the Egyptians transported, raised and installed colossal obelisks and statues, the weight of which was tens and hundreds of tons! What mechanisms did these ancient builders use to raise gigantic blocks and statues to a great height? It turns out that all this can be done using the same simple devices - a block, levers and an inclined plane. Colossal statues and blocks of stone were dragged on massive sledges pulled by a large number of people. Each of the workers had a rope thrown over his shoulder. Rollers were placed under the sled, which, after pulling the load, were picked up and again placed under the skids.
To overcome obstacles, the sled was lifted with the help of levers. As they used hewn logs. Specially made wedges of different sizes served as stops. The work was accompanied by music. The main lifting device of the Egyptians was an inclined plane - a ramp. The skeleton of the ramp, that is, its sides and partitions, which crossed the ramp at a short distance from each other, were built of brick; voids were filled with reeds and branches. As the pyramid grew, the ramp was built on. On these ramps, stones were dragged on sleds in the same way as on the ground, while helping themselves with levers. The ramp angle was very slight - 5 or 6 degrees. Thus, for example, the sloping road to the pyramid of Khafre, with a height of 46 meters, had a length of about half a kilometer. Accordingly, for the construction of higher pyramids, it was necessary to build a ramp even longer. Other methods were resorted to when lifting long stone blocks and statues. Blocks were used for this. However, it is impossible to raise huge stones with the help of blocks, such as obelisks up to 300 tons in weight and giant statues of kings, reaching 1000 tons in weight, it is impossible. To install such statues and obelisks, considerable preparatory work had to be carried out. Here again, an inclined plane - a ramp - acted as a lifting device. First of all, stone walls were erected on both sides of the pedestal. An inclined plane was attached to one of them, a little less than the height of the installed obelisk. All four walls of the ramp formed, as it were, a brick well. A through corridor was made in one of its walls at ground level. The entire space inside was covered with sand. Then, along the inclined plane, the completed obelisk was dragged with the base forward. After that, sand began to be carried out through the corridor in the wall, and the obelisk, under its own weight, began to smoothly descend onto the pedestal, gradually assuming a vertical position. After installation, the wall and ramp were dismantled. With extensive use of the inclined plane and the lever, the ancient Egyptians seem to have given no thought to the laws that underlie simple mechanisms. At least not a single Babylonian or Egyptian text has come down to us describing their action. This work was carried out only by scientists of ancient Greece. Classical calculations of the action of a lever, an inclined plane and a block belong to the outstanding ancient mechanic Archimedes of Syracuse. Archimedes studied the mechanical properties of the moving block and put it into practice. According to Athenaeus, “to launch the gigantic ship built by the Syracusan tyrant Hieron, they came up with many ways, but the mechanic Archimedes alone managed to move the ship with the help of a few people; Archimedes arranged a block and through it launched a huge ship; he was the first to come up with a block device ". From this evidence it can be seen that Archimedes not only studied the properties of simple mechanisms, but also took the next step - he began to build on their basis more complex machines that transform and enhance movement. It is possible that he managed to move the ship with the help of a system of movable and fixed blocks (similar to modern hoists), using which you can multiply the applied force. When the Romans attacked Archimedes' hometown, he applied his knowledge to military technology. According to his drawings, the Syracusans built a wide variety of military vehicles. Among them were throwing weapons; swivel cranes that hurled huge stones onto Roman ships; iron paws tied to chains that captured and overturned enemy ships. Author: Ryzhov K.V.
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