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Block And Tackle
A block and tackle or only tackle is a system of two or more pulleys with a rope or cable threaded between them, used to provide tension and lift heavy loads. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and one moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies the force applied to the rope. Hero of Alexandria described cranes formed from assemblies of pulleys in the first century. Illustrated versions of Hero's ''Mechanica'' (a book on raising heavy weights) show early block and tackle systems. Overview A block is a set of pulleys or sheaves mounted on a single frame. An assembly of blocks with a rope threaded through the pulleys is called tackle. The process of threading ropes or cables through blocks is called "reeving", and a threaded block and tackle is said to have been "rove". A block and tackle system amplifies the tension force in the rope to lift heavy loads ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Machines
A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems. Renaissance natural philosophers identified six simple machines which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today as mechanical advantage. Modern machines are complex systems that consist of structural elements, mechanisms and control compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Three Snatch Blocks
3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies. Evolution of the Arabic digit The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically. However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a with an additional stroke at the bottom: ३. The Indian digits spread to the Caliphate in the 9th c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bight (knot)
In knot tying, a bight is a curved section or slack part between the two ends of a rope, string, or yarn.. "Any slack part of a rope between the two ends, particularly when curved or looped." A knot that can be tied using only the bight of a rope, without access to the ends, is described as in the bight. The term "bight" is also used in a more specific way when describing Turk's head knots, indicating how many repetitions of braiding are made in the circuit of a given knot. Bight vs. open loop Sources differ on whether an open loop or U-shaped curve in a rope qualifies as a bight. treats bights and loops as distinct, stating that a curve "no narrower than a semicircle" is a bight, while an open loop is a curve "narrower than a bight but with separated ends". However, ''The Illustrated Encyclopedia of Knots'' (2002) states: "Any section of line that is bent into a U-shape is a bight." Slipped knot In order to make a slipped knot (also slipped loop and quick release knot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Petroleum Institute
The American Petroleum Institute (API) is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in extraction of petroleum, production, oil refinery, refinement, pipeline transport, distribution, and many other aspects of the petroleum industry. It has advanced climate change denial and blocking of climate change mitigation, climate legislation to defend the interests of its fossil fuels lobby, constituent organizations. The association describes its mission as "to promote safety across the industry globally and influence public policy in support of a strong, viable Petroleum in the United States, U.S. oil and natural gas industry". API's chief functions on behalf of the industry include advocacy, negotiation and Fossil fuels lobby, lobbying with governmental, legal, and regulatory agencies; research into economic, toxicological, and environmental issues, environmental effects; establishment and certificati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southern Illinois University Press
Southern Illinois University Press or SIU Press, founded in 1956, is a university press located in Carbondale, Illinois, owned and operated by Southern Illinois University. The press publishes approximately 50 titles annually, among its more than 1,200 titles currently in print. Southern Illinois University Press is a member of the Association of University Presses. History Southern Illinois University Press was founded by President Delyte Morris in the mid-1950s, and its first book—Charles E. Colby's ''A Pilot Study of Southern Illinois''—was published on October 20, 1956. Publishing primarily in the humanities and social sciences, in a wide range of subject areas: art and architecture, classical studies, history (world and American), literary criticism, philosophy, religion, rhetoric and composition, speech communication, and theatre. The Press has become especially well known for its publications in First Amendment Studies, Restoration and Eighteenth Century Theatre, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Efficiency
In mechanical engineering, mechanical efficiency is a dimensionless ratio that measures the efficiency of a mechanism or machine in transforming the power input to the device to power output. A machine is a mechanical linkage in which force is applied at one point, and the force does work moving a load at another point. At any instant the power input to a machine is equal to the input force multiplied by the velocity of the input point, similarly the power output is equal to the force exerted on the load multiplied by the velocity of the load. The mechanical efficiency of a machine (often represented by the Greek letter eta ''η'') is a dimensionless number between 0 and 1 that is the ratio between the power output of the machine and the power input \eta = \frac Since a machine does not contain a source of energy, nor can it store energy, from conservation of energy the power output of a machine can never be greater than its input, so the efficiency can never be greater ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Force
In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitude (mathematics), magnitude and Direction (geometry, geography), direction of a force are both important, force is a Euclidean vector, vector quantity. The SI unit of force is the newton (unit), newton (N), and force is often represented by the symbol . Force plays an important role in classical mechanics. The concept of force is central to all three of Newton's laws of motion. Types of forces often encountered in classical mechanics include Elasticity (physics), elastic, frictional, Normal force, contact or "normal" forces, and gravity, gravitational. The rotational version of force is torque, which produces angular acceleration, changes in the rotational speed of an object. In an extended body, each part applies forces on the adjacent pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ergonomics
Ergonomics, also known as human factors or human factors engineering (HFE), is the application of Psychology, psychological and Physiology, physiological principles to the engineering and design of products, processes, and systems. Primary goals of human factors engineering are to reduce human error, increase productivity and system availability, and enhance safety, health and comfort with a specific focus on the interaction between the human and equipment. The field is a combination of numerous disciplines, such as psychology, sociology, engineering, biomechanics, industrial design, physiology, anthropometry, interaction design, visual design, user experience, and user interface design. Human factors research employs methods and approaches from these and other knowledge disciplines to study human behavior and generate data relevant to previously stated goals. In studying and sharing learning on the design of equipment, devices, and processes that fit the human body and its Cog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity Ratio
A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. Features of gears and gear trains include: * The gear ratio of the pitch circles of mating gears defines the speed ratio and the mechanical advantage of the gear set. * A planetary gear train provides high gear reduction in a compact package. * It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly. * The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing. The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the Renaissan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
