One such device is the strappado, mostly used to extract information from alleged heretics and witches. This device consisted of a pulley over a rope that passed over a beam or hook on the roof and was tied to the hands of the victim.
Additional weight could be added to the feet. The strappado dislocated joints and limbs causing long-term damage to nerves and muscles, and permanent paralysis and loss of sensation in the arms. Another torture device was the upright jerker.
A cord was wrapped around the neck of the condemned who was positioned on a platform. Rather than dropping through a trap door, a system of weights and pulleys would jerk the victim into the air violently.
Today, pulleys have a variety of configurations. A class 1, or fixed pulley , is stationary. It redirects the force in the rope or cable. A single anchored pulley has the mechanical advantage of one. In contrast, a class 2, or movable pulley, has a free axel with a mechanical advantage of two, meaning if one end of the rope is anchored, an operator pulling on the other end of the rope will have double the lift force on the object attached to it. A compound pulley combines fixed and moveable components.
Block and tackle pulleys use a single continuous rope to disperse tension force around one or more pulleys to lift or move an object. It is interesting to consider how pulleys have transformed everyday life. For example, there are , elevators in the U. That is one elevator for every people. The average ride on an elevator is 40 feet floors , and the average number of elevator trips by U. In terms of distance traveled, that translates to million miles per year or about rounds to the moon!
Without pulley-enabled elevators, high-rise buildings would be impractical, of course. And, without pulleys, the construction of multi-story buildings would be impractical as well.
Mobile cranes with telescopic booms have become essential in the construction industry, as have tower cranes for extremely tall structures, with the strongest hydraulic tower cranes able to lift 70 tons. Other uses of pulleys in everyday life include garage door openers, fitness equipment, curtains and blinds, extension ladders, flagpoles, and safety harnesses. Heron is most renowned for Metrica, a three-volume compendium of observations of the mathematics and engineering of Babylonia, ancient Egypt, and the Greco-Roman world.
More recent discoveries, however, have prompted scholars to credit the invention of gears to the Chinese. Though there are many stories in Chinese folklore about its invention, the South Pointing Chariot is the earliest known mechanism to use gears, Emperor Huang Di was probably the original designer in the 27th century B.
The chariot had geared wheels and an indicator that functioned as a compass always pointed southward. Since the chariot relied on mechanics instead of magnetism, the rider could adjust the pointer to face in any direction. Essentially, the chariot consisted of a series of gears connected to a pointing figure. The figure would continue to point in the same direction irrespective of where the chariot moved. Scholars generally agree that the mechanism was a differential gear train like the mechanism in cars that allows the outer drive wheel to rotate faster than the inner drive wheel.
During a turn difference in rotation speed would allow for traction. The device was often used for ceremonial purposes such as imperial processions and for leading soldiers into a battle. The ancient Greeks were using metal gears with cylindrical teeth in early computing equipment and astronomical calendars by B.
Support for this conclusion comes from the discovery of the Antikythera mechanism, the oldest known gear machine. The mechanism was found in in a wreck near the Greek island of Antikythera. The device incorporated more than 30 gears for complicated astronomical calculations of time. Inside the mechanism — and a bit obscured by corrosion — are gears with triangular teeth resembling the inside of a clock, as well as a protractor-like ring divided into degrees.
Nothing this sophisticated has been discovered in antiquity, nor would anything like this appear again for more than 1, years.
Scientists were baffled by the purpose of this device for decades after its discovery. It was not until x-ray imaging of the device in the s that experts determined the device replicated the motion of the heavens, and that a user could accurately track the paths of the Sun, Moon, and planets.
Mainstream historians, though, disregarded the artifact initially because the x-ray images were difficult to interpret. About the size of a mantle clock, the device seems to have been encased in a wooden frame based on the wood fragments found on it. Likely the mechanism would have had a large circular face with rotating hands and a knob for winding it forward or backward. A pulley is a wheel with a rope on it to lift heavy objects. W hat is a Pulley? A pulley makes it easier to lift heavy stuff.
Who invented the first gear? Emperor Huang Di was the one who made the first gear in the 27th century B. A gear is a wheel with teeth that mush together with other gears. Open Questions : What types of gears are there? There are lots of types of gears I will give a example spur gear, helical gear and many more!
Pulleys are used for lifting easier objects What are gears use for? How many things does a pulley have on it? All About Explorers-Opinion.
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