The screw is a simple machine that is an inclined plane wound around a cylinder. It is used to keep things together or to screw something onto the wall. Screws are replacements for nails and are usually stronger. Screws are used to make furniture, electronic items, used to hang up things on walls, etc.
The pulley is a simple machine that changes the direction that the force is applied to. It has a grooved wheel that turns around the fulcrum. And a rope, chain or other of the sort is used in the grove to lift or pull heavy weights. Some examples of where pulleys are used in are window blinds, flagpoles, Mast of a sailboat, elevators, and industrial cranes.
Wheel and axel
The wheel and axel is a simple machine that was crucial to human evolution. It is a modified lever. The axel serves as the fulcrum and the wheel is the lever turning in circles. It makes moving around big and heavy objects easier. A few examples of the wheel and axel are the wheels in a car, bicycle handlebar, doorknobs, screwdriver, fan blades and airplane propellers.
The inclined plane is a tilted or sloping surface that makes moving objects to a height easier. It decreases the amount of effort that is required to move the object but does not decrease the amount of work that is required. Some examples are ramps, skateboard ramps, wheelchair ramps, stairs, ladders and escalators.
A lever is a stick with a fulcrum at different positions for different uses. Levers are qualified into three classes, 1st class levers, 2nd class levers, and 3rd class levers. In a 1st class lever, the fulcrum is in the middle. The effort force and resistance move in opposite directions. It is used to lift something, for example, the seesaw. A 2nd class lever has the fulcrum closer to one end; it is closer to the resistance. It produces a gain in the force. An example is the wheelbarrow. A 3rd class lever has the fulcrum on one end. The effort is excreted between the fulcrum and resistance. The amount of force becomes low but it results in an increase in speed and distance. A few examples are a baseball bat, broom, and shovel.
A wedge is a simple machine that similar to an inclined plane. There can be different forms of it. Some forms are like inclined planes; some are tapering to the edge from both sides. It increases the amount of force applied on the object. It is used with an object when the object stays in place and the wedge moves through it. Some examples are doorstops, axe, log splitter, knife, chisel, etc.
As is the case with many simple machines, the exact origins or discovery of the pulley is unknown. There is evidence that pulleys were first used in 2630 BC in Egypt to build the pyramids. The Egyptians used a pulley/ inclined plane combination to move stone blocks that weighed up to 15 tons. These were pulled using pulleys and only a few people pulled a block of stone almost 10 times their size. Pulleys were also used in Mesopotamia to hoist water in 1500 BC. Some other sources say that in 287 BC – 215 BC, the ancient Greek mathematician and philosopher Archimedes improved the pulley and is known to have invented the compounded pulleys. There were legends that Archimedes pulled a trireme filled with men into harbor using pulleys and his own strength. Archimedes is a known mathematician and philosopher and as a scholar, he studied about simple machines. He once said “Give me a lever long and enough and a place to stand, and I will move the world.”
An ancient civilization that benefited from the use of pulleys is the Egyptian civilization. The ancient Egyptians used the pulley to build one of the most magnificent monuments in the world; the pyramids. The pyramids were big structures made from huge blocks of stone for noble people as graves. Because the stone blocks were so big, they could not be moved by the average strength of one man. So the Egyptians used pulleys to increase the force and move the blocks. They also used ramps to move the blocks up to a height. The pulleys were made of wood, rope and sometimes copper for a stronger axle. Even though the Egyptians first used the pulley, Archimedes was the first to truly explain the concept of simple machines like the pulley and lever.
During the renaissance, the re-birth of arts, learning, and knowledge, the pulley was greatly used in many areas to create or change many things. Besides lifting heavy loads, changing the direction of the force, and lifting objects to a height, the pulley was also used for other things during the renaissance. An example is the lathe. The lathe is a machine that uses the pulley to do things like woodworking, woodcarving, and ivory working. The piece of ivory or wood is placed around a rod and with the help of a flat belt pulley it is spun in circles, and rotates very fast. A flat belt pulley is made up of two grooved wheels, and a belt or rope. The belt is wrapped around the wheels so that if one wheel is turned, the other wheel will also turn. A pedal was connected to the wheel and when the pedal was pressed and let go of rapidly, it turned the wheel. Decorations made from the lathe were part of the magnificent art in the renaissance period. Here is a design of a lathe:
Here is a video of a lathe in action:
Another time the pulley was changed and improved was during the industrial revolution. During the industrial revolution, the pulley was put to many uses, inside factories and outside factories as well. One use of the pulley in the industrial revolution was the machinery in textile factories. Big looms were made which implemented lots of pulleys to make fabrics from wool, yarn and other fibers. The machines that were used to make these, consisted of many pulleys, but thee pulleys were different then any made before. These pulleys were steam powered or motorized; instead of force being applied from people or animals, a steam engine or motor was used. The textile factories used something called a line shaft; a machine made from a combination of gears and pulleys that took power from a steam engine and distributed it to different looms in different locations. The pulleys were made of metal wheels and belts instead of wood and rope. This method of using pulleys was used from the industrial revolution to the early 20th century, when technological advances made line shafts out of date.
Here is an image of a line shaft that was used in the industrial revolution:
Since the Egyptians building the pyramids, to the renaissance lathe, and the textile factories from the industrial revolution, the pulley has changed a lot to the present time. A common everyday object that utilizes the pulley is in cranes. The ancient Greeks invented the first crane but it required people or animals to power it. The first mechanical crane, steam powered, was introduced in the 18th century. These cranes were used to lift loads in and out of harbors, and ports. Until now, cranes have been improved a lot and different types have been made to use for different uses. A very common crane is an overhead crane. An overhead crane is a crane that is on the ceiling of a building, hence the name overhead crane, and has a pulley system the goes sideways and back and forth to move objects around. Some applications of the overhead cranes are in factories, metal refinement, and storage areas. In metal refining, an overhead crane handles the hot liquid metal and moves it around. In factories, heavy loads are moved from places to place. And it is used in storage areas to move around heavy packages. The crane has changed from lifting loads in harbors to moving around molten metal, building skyscrapers, and moving cement hundreds of feet into the air.
Here is an image:
Here is a video to explain how the overhead crane works:
If the overhead crane was not invented, handling metals would be very difficult because overhead cranes are used to refine metals. A lot of the things around the world that made out of metal would be very difficult to make. Even the tip of a pen is made of metal, and metal has to be refined to be used to make something as small as that. The overhead crane has improved the world because it made many different things easy to do. Refining metals, moving big loads in confined places, and moving packages for shipment. In my opinion, life would be slower because a lot of the metals would not be refined quickly, loading ships would take longer, and factory work would be slow. The crane has probably made the world better because it makes things a lot easier for people. But then again, it uses oil to make them work, which causes a lot of pollution.
Here is a perzi about the pulley: