1.
Force
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In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity, force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity and it is measured in the SI unit of newtons and represented by the symbol F. The original form of Newtons second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. In an extended body, each part usually applies forces on the adjacent parts, such internal mechanical stresses cause no accelation of that body as the forces balance one another. Pressure, the distribution of small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of materials, or flow in fluids. In part this was due to an understanding of the sometimes non-obvious force of friction. A fundamental error was the belief that a force is required to maintain motion, most of the previous misunderstandings about motion and force were eventually corrected by Galileo Galilei and Sir Isaac Newton. With his mathematical insight, Sir Isaac Newton formulated laws of motion that were not improved-on for nearly three hundred years, the Standard Model predicts that exchanged particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known, in order of decreasing strength, they are, strong, electromagnetic, weak, high-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction. Since antiquity the concept of force has been recognized as integral to the functioning of each of the simple machines. The mechanical advantage given by a machine allowed for less force to be used in exchange for that force acting over a greater distance for the same amount of work. Analysis of the characteristics of forces ultimately culminated in the work of Archimedes who was famous for formulating a treatment of buoyant forces inherent in fluids. Aristotle provided a discussion of the concept of a force as an integral part of Aristotelian cosmology. In Aristotles view, the sphere contained four elements that come to rest at different natural places therein. Aristotle believed that objects on Earth, those composed mostly of the elements earth and water, to be in their natural place on the ground. He distinguished between the tendency of objects to find their natural place, which led to natural motion, and unnatural or forced motion
2.
Archimedes
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Archimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the scientists in classical antiquity. He was also one of the first to apply mathematics to physical phenomena, founding hydrostatics and statics and he is credited with designing innovative machines, such as his screw pump, compound pulleys, and defensive war machines to protect his native Syracuse from invasion. Archimedes died during the Siege of Syracuse when he was killed by a Roman soldier despite orders that he should not be harmed. Cicero describes visiting the tomb of Archimedes, which was surmounted by a sphere and a cylinder, unlike his inventions, the mathematical writings of Archimedes were little known in antiquity. Archimedes was born c.287 BC in the city of Syracuse, Sicily, at that time a self-governing colony in Magna Graecia. The date of birth is based on a statement by the Byzantine Greek historian John Tzetzes that Archimedes lived for 75 years, in The Sand Reckoner, Archimedes gives his fathers name as Phidias, an astronomer about whom nothing is known. Plutarch wrote in his Parallel Lives that Archimedes was related to King Hiero II, a biography of Archimedes was written by his friend Heracleides but this work has been lost, leaving the details of his life obscure. It is unknown, for instance, whether he married or had children. During his youth, Archimedes may have studied in Alexandria, Egypt and he referred to Conon of Samos as his friend, while two of his works have introductions addressed to Eratosthenes. Archimedes died c.212 BC during the Second Punic War, according to the popular account given by Plutarch, Archimedes was contemplating a mathematical diagram when the city was captured. A Roman soldier commanded him to come and meet General Marcellus but he declined, the soldier was enraged by this, and killed Archimedes with his sword. Plutarch also gives an account of the death of Archimedes which suggests that he may have been killed while attempting to surrender to a Roman soldier. According to this story, Archimedes was carrying mathematical instruments, and was killed because the thought that they were valuable items. General Marcellus was reportedly angered by the death of Archimedes, as he considered him a valuable asset and had ordered that he not be harmed. Marcellus called Archimedes a geometrical Briareus, the last words attributed to Archimedes are Do not disturb my circles, a reference to the circles in the mathematical drawing that he was supposedly studying when disturbed by the Roman soldier. This quote is given in Latin as Noli turbare circulos meos. The phrase is given in Katharevousa Greek as μὴ μου τοὺς κύκλους τάραττε
3.
Gear train
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A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, gearbox, prop shaft, differential. In American English, however, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are also used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may also be provided, single-ratio transmissions also exist, which simply change the speed and torque of motor output. The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
4.
Robot
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A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. Robots can be guided by a control device or the control may be embedded within. Robots may be constructed to take on human form but most robots are designed to perform a task with no regard to how they look. By mimicking a lifelike appearance or automating movements, a robot may convey a sense of intelligence or thought of its own. These technologies deal with automated machines that can take the place of humans in dangerous environments or manufacturing processes, or resemble humans in appearance, many of todays robots are inspired by nature contributing to the field of bio-inspired robotics. These robots have also created a branch of robotics, soft robotics. From the time of ancient civilization there have many accounts of user-configurable automated devices and even automata resembling animals and humans. As mechanical techniques developed through the Industrial age, there appeared more practical applications such as automated machines, remote-control and wireless remote-control. The word robot was first used to denote a fictional humanoid in a 1920 play R. U. R. by the Czech writer, Karel Čapek but it was Karels brother Josef Čapek who was the words true inventor. Electronics evolved into the force of development with the advent of the first electronic autonomous robots created by William Grey Walter in Bristol. The first digital and programmable robot was invented by George Devol in 1954 and was named the Unimate, there are concerns about the increasing use of robots and their role in society. Robots are blamed for rising unemployment as they replace workers in increasing numbers of functions, the use of robots in military combat raises ethical concerns. The possibilities of robot autonomy and potential repercussions have been addressed in fiction, the word robot can refer to both physical robots and virtual software agents, but the latter are usually referred to as bots. Closely related to the concept of a robot is the field of Synthetic Biology, the idea of automata originates in the mythologies of many cultures around the world. Engineers and inventors from ancient civilizations, including Ancient China, Ancient Greece, since circa 400 BC, myths of Crete include Talos, a man of bronze who guarded the Cretan island of Europa from pirates. In ancient Greece, the Greek engineer Ctesibius applied a knowledge of pneumatics and hydraulics to produce the first organ, in the 4th century BC, the Greek mathematician Archytas of Tarentum postulated a mechanical steam-operated bird he called The Pigeon. Hero of Alexandria, a Greek mathematician and inventor, created numerous user-configurable automated devices, the 11th century Lokapannatti tells of how the Buddhas relics were protected by mechanical robots, from the kingdom of Roma visaya, until they were disarmed by King Ashoka. Yan Shi proudly presented the king with a life-size, human-shaped figure of his mechanical handiwork made of leather, wood, in 1066, the Chinese inventor Su Song built a water clock in the form of a tower which featured mechanical figurines which chimed the hours
5.
Energy
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In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
6.
Chain drive
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Chain drive is a way of transmitting mechanical power from one place to another. It is often used to power to the wheels of a vehicle. It is also used in a variety of machines besides vehicles. The gear is turned, and this pulls the chain putting mechanical force into the system, another type of drive chain is the Morse chain, invented by the Morse Chain Company of Ithaca, New York, United States. Sometimes the power is output by simply rotating the chain, which can be used to lift or drag objects, in other situations, a second gear is placed and the power is recovered by attaching shafts or hubs to this gear. By varying the diameter of the input and output gears with respect to each other, for example, when the bicycle pedals gear rotate once, it causes the gear that drives the wheels to rotate more than one revolution. The oldest known application of a chain appears in the Polybolos. Two flat-linked chains were connected to a windlass, which by winding back and it is here that the flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance. The chain drive itself was given power via the works of Sus water clock tank and waterwheel. Roller chain and sprockets is an efficient method of power transmission compared to belts. Although chains can be stronger than belts, their greater mass increases drive train inertia. Drive chains are most often made of metal, while belts are often rubber, plastic, urethane, or other substances. Drive belts can slip unless they have teeth, which means that the side may not rotate at a precise speed. Wear on rubber or plastic belts and their teeth is often easier to observe, one problem with roller chains is the variation in speed, or surging, caused by the acceleration and deceleration of the chain as it goes around the sprocket link by link. It starts as soon as the line of the chain contacts the first tooth of the sprocket. This contact occurs at a point below the circle of the sprocket. As the sprocket rotates, the chain is raised up to the circle and is then dropped down again as sprocket rotation continues. This rising and falling of the line is what causes chordal effect or speed variation
7.
Bicycle gearing
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Bicycle gearing is the aspect of a bicycle drivetrain that determines the relation between the cadence, the rate at which the rider pedals, and the rate at which the drive wheel turns. On some bicycles, there is only one gear and the ratio is fixed. Many contemporary bicycles have multiple gears and thus multiple gear ratios, different gear ratios and gear ranges are appropriate for different people and styles of cycling. A cyclists legs produce power optimally within a narrow pedalling speed range, gearing can be optimized to use this narrow range as efficiently as possible. As in other types of transmissions, the ratio is closely related to the mechanical advantage of the drivetrain of the bicycle. On single-speed bicycles and multi-speed bicycles using derailleur gears, the ratio depends on the ratio of the number of teeth on the chainring to the number of teeth on the rear sprocket. For bicycles equipped with hub gears, the gear ratio depends on the internal planetary gears within the hub. For a shaft-driven bicycle the gear ratio depends on the bevel gears used at end of the shaft. For a bicycle to travel at the speed, using a lower gear requires the rider to pedal at a faster cadence. Conversely, a higher gear provides a speed for a given cadence. Different cyclists may have different preferences for cadence and pedaling force, there are at least four different methods for measuring gear ratios, gear inches, metres of development, gain ratio, and quoting the number of teeth on the front and rear sprockets respectively. The fourth method uses two numbers and is useful in comparing bicycles with the same drive wheel diameter. In the case of road bikes, this is usually around 670 mm, a 700c standard wheel has a 622mm rim diameter. The final wheel diameter depends on the tire but will be approximately 622mm plus twice the tire width. Front/rear measurement only considers the sizes of a chainring and a rear sprocket, gear inches and metres of development also take the size of the rear wheel into account. Gain ratio goes further and also takes the length of a pedal crankarm into account, gear inches and metres of development are closely related, to convert from gear inches to metres of development, multiply by 0.08. The methods of calculation which follow assume that any hub gear is in direct drive, multiplication by a further factor is needed to allow for any other selected hub gear ratio. Gear inches = Diameter of drive wheel in inches ×, normally rounded to nearest whole number
8.
Machine
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A machine is a tool containing one or more parts that uses energy to perform an intended action. Machines are usually powered by chemical, thermal, or electrical means, historically, a power tool also required moving parts to classify as a machine. However, the advent of electronics has led to the development of power tools without moving parts that are considered machines, a simple machine is a device that simply transforms the direction or magnitude of a force, but a large number of more complex machines exist. Examples include vehicles, electronic systems, molecular machines, computers, television, the word machine derives from the Latin word machina, which in turn derives from the Greek. The word mechanical comes from the same Greek roots, however, the Ancient Greeks probably have borrowed the word mekhane from the ancient Hebrews. The ancient Greeks were familiar with the Hebrew Scriptures and language, a wider meaning of fabric, structure is found in classical Latin, but not in Greek usage. This meaning is found in late medieval French, and is adopted from the French into English in the mid-16th century, in the 17th century, the word could also mean a scheme or plot, a meaning now expressed by the derived machination. The modern meaning develops out of specialized application of the term to stage engines used in theater and to siege engines. Simple Machines are commonly reckoned to be Six in Number, viz. the Ballance, Leaver, Pulley, Wheel, Wedge, compound Machines, or Engines, are innumerable. The word engine used as a synonym both by Harris and in later language derives ultimately from Latin ingenium ingenuity, an invention, perhaps the first example of a human made device designed to manage power is the hand axe, made by chipping flint to form a wedge. A wedge is a machine that transforms lateral force and movement of the tool into a transverse splitting force. The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines, lever, pulley and he discovered the principle of mechanical advantage in the lever. Later Greek philosophers defined the five simple machines and were able to roughly calculate their mechanical advantage. Heron of Alexandria in his work Mechanics lists five mechanisms that can set a load in motion, lever, windlass, pulley, wedge, and screw, however the Greeks understanding was limited to statics and did not include dynamics or the concept of work. In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, the complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche. He was the first to understand that simple machines do not create energy, the classic rules of sliding friction in machines were discovered by Leonardo da Vinci, but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons and were developed by Charles-Augustin de Coulomb. The word mechanical refers to the work that has produced by machines or the machinery
9.
Linkage (mechanical)
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A mechanical linkage is an assembly of bodies connected to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid, the connections between links are modeled as providing ideal movement, pure rotation or sliding for example, and are called joints. A linkage modeled as a network of links and ideal joints is called a kinematic chain. Linkages may be constructed from open chains, closed chains, or a combination of open, each link in a chain is connected by a joint to one or more other links. Thus, a chain can be modeled as a graph in which the links are paths and the joints are vertices. The movement of a joint is generally associated with a subgroup of the group of Euclidean displacements. The number of parameters in the subgroup is called the degrees of freedom of the joint, mechanical linkages are usually designed to transform a given input force and movement into a desired output force and movement. The ratio of the force to the input force is known as the mechanical advantage of the linkage. The speed ratio and mechanical advantage are defined so they yield the number in an ideal linkage. A kinematic chain, in which one link is fixed or stationary, is called a mechanism, perhaps the simplest linkage is the lever, which is a link that pivots around a fulcrum attached to ground, or a fixed point. As a force rotates the lever, points far from the fulcrum have a greater velocity than points near the fulcrum. Because power into the lever equals the power out, a force applied at a point far from the fulcrum equals a larger force applied at a point near the fulcrum. The amount the force is amplified is called mechanical advantage and this is the law of the lever. Two levers connected by a rod so that a force applied to one is transmitted to the second is known as a four-bar linkage, the levers are called cranks, and the fulcrums are called pivots. The connecting rod is also called the coupler, the fourth bar in this assembly is the ground, or frame, on which the cranks are mounted. Linkages are important components of machines and tools, examples range from the four-bar linkage used to amplify force in a bolt cutter or to provide independent suspension in an automobile, to complex linkage systems in robotic arms and walking machines. The internal combustion engine uses a slider-crank four-bar linkage formed from its piston, connecting rod, relatively simple linkages are often used to perform complicated tasks. Interesting examples of linkages include the windshield wiper, the bicycle suspension, in these examples the components in the linkage move in parallel planes and are called planar linkages
10.
Block and tackle
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A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. The pulleys are assembled together to form blocks and then blocks are paired so that one is fixed, the rope is threaded, or rove, through the pulleys to provide mechanical advantage that amplifies that force applied to the rope. Hero of Alexandria described cranes formed from assemblies of pulleys in the first century, illustrated versions of Heros book on raising heavy weights show early block and tackle systems. A block is a set of pulleys or sheaves mounted on a single axle, an assembly of blocks with a rope threaded through the pulleys is called tackle. A block and tackle system amplifies the force in the rope to lift heavy loads. They are common on boats and sailing ships, where tasks are performed manually. A block and tackle is characterized by the use of a continuous rope to transmit a tension force around one or more pulleys to lift or move a load. Its mechanical advantage is the number of parts of the rope that act on the load, the mechanical advantage of a tackle dictates how much easier it is to haul or lift the load. An ideal block and tackle with a moving block supported by n rope sections has the advantage, M A = F B F A = n. Consider the set of pulleys that form the block and the parts of the rope that support this block. If there are n of these parts of the supporting the load FB. This means the force on the rope is FA=FB/n. Thus, the block and tackle reduces the force by the factor n. Ideal mechanical advantage correlates directly with velocity ratio, the velocity ratio of a tackle is the ratio between the velocity of the hauling line to that of the hauled load. A line with an advantage of 4 has a velocity ratio of 4,1. In other words, to raise a load at 1 metre per second, therefore, the mechanical advantage of a double tackle is 4. In this case the block and tackle is said to be rove to advantage, rove to advantage – where the pull on the rope is in the same direction as that in which the load is to be moved. The hauling part is pulled from the moving block, rove to disadvantage – where the pull on the rope is in the opposite direction to that in which the load is to be moved
11.
Belt (mechanical)
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A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel. Belts may be used as a source of motion, to transmit power efficiently, belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. In a two pulley system, the belt can either drive the pulleys normally in one direction, or the belt may be crossed, as a source of motion, a conveyor belt is one application where the belt is adapted to carry a load continuously between two points. Belts are the cheapest utility for power transmission between shafts that may not be axially aligned, power transmission is achieved by specially designed belts and pulleys. The demands on a transmission system are large, and this has led to many variations on the theme. They run smoothly and with noise, and cushion motor and bearings against load changes. However, improvements in belt engineering allow use of belts in systems that only formerly allowed chains or gears. They are related as T1 T2 = e μ α, where, μ is the coefficient of friction, Belt drives are simple, inexpensive, and do not require axially aligned shafts. They help protect machinery from overload and jam, and damp and isolate noise and they need no lubrication and minimal maintenance. They have high efficiency, high tolerance for misalignment, and are of low cost if the shafts are far apart. Clutch action is activated by releasing belt tension, different speeds can be obtained by stepped or tapered pulleys. The angular-velocity ratio may not be constant or equal to that of the diameters, due to slip. However, this problem has largely solved by the use of toothed belts. Working temperatures range from −31 °F to 185 °F, adjustment of center distance or addition of an idler pulley is crucial to compensate for wear and stretch. Flat belts were used in the 19th and early 20th centuries in line shafting to transmit power in factories. Flat belts are used today, although not nearly as much as in the line-shaft era. The flat belt is a system of power transmission that was well suited for its day. It can deliver power at high speeds, in cases of wide belts
12.
Transmission (mechanics)
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A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, gearbox, prop shaft, differential. In American English, however, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are also used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may also be provided, single-ratio transmissions also exist, which simply change the speed and torque of motor output. The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
