Kinematics: Simple Machine and Prime Mover

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  • Topic: Simple machine, Machine, Linkage
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  • Published : March 6, 2009
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What is Kinematics?

Kinematics is the geometry of pure motion - motion considered abstractly, without reference to force or mass. Engineers use kinematics in machine design. Although hidden in much of modern technology, kinematic mechanisms are important components of many technologies such as robots, automobiles, aircraft, satellites, and consumer electronics, as well as biomechanical prostheses. In physics, kinematics is part of the teaching of basic ideas of dynamics; in mathematics, it is a fundamental part of geometric thinking and concepts of motion. The development of high-speed computers and robotics, and the growth of design synthesis theory and mechatronics have recently revived interest in kinematics and early work in machine design. Working in the decades following Ampère's death, Franz Reuleaux (1829-1905) is considered the founder of modern kinematics. Reuleaux called it "the study of the motion of bodies of every kind…and the study of the geometric representation of motion" (Kinematics of Machinery 56). Kinematics flourished in the 19th century as machine inventors learned to transmit information and forces (power) from one element in the machine to another. Steam- and water-based machines revolutionized the l9th century, but both of those energy sources generate circular motions, creating the need to convert these steady circular motions into nonsteady linear and curvilinear motion for machine applications. Practical inventors as well as mathematicians [Artobolevskii 1964] took up the challenge to create input-output kinematic devices that could convert circular motion into noncircular, complex, three-dimensional, intermittent motions. Thousands of mechanisms were invented, designed, and built, nurturing the widespread use and manufacture of machines. Reuleaux set out to codify, analyze, and synthesize kinematic mechanisms so that engineers could approach machine design in a rational way. He laid the foundation for a systematic study of machines by defining clearly the machine and mechanism, determining the basic mechanical building blocks, and developing a system for classifying known mechanism types. Reuleaux was the author of Theoretische Kinematik: Grundzüge einer Theorie des Machinenwesens, which appeared in English in 1876 as The Kinematics of Machinery: Outlines of a Theory of Machines. He also published another important work related to design of machines in 1861, which was translated as The Constructor (1893). Mechanical models designed by Reuleaux to embody his classification of kinematic mechanisms are the basis for the Kinematic Models for Design Digital Library (KMODDL).

Mechanics

Mechanics, branch of physics concerned with motion and the forces that tend to cause it; it includes study of the mechanical properties of matter, such as density, elasticity, and viscosity. Mechanics may be roughly divided into statics and dynamics; statics deals with bodies at rest and is concerned with such topics as buoyancy, equilibrium, and the principles of simple machines, while dynamics deals with bodies in motion and is sometimes further divided into kinematics (description of motion without regard to its cause) and kinetics (explanation of changes in motion as a result of forces). A recent subdiscipline of dynamics is nonlinear dynamics, the study of systems in which small changes in a variable may have large effects. The science of mechanics may also be broken down, according to the state of matter being studied, into solid mechanics and fluid mechanics. The latter, the mechanics of liquids and gases, includes hydrostatics, hydrodynamics, pneumatics, aerodynamics, and other fields.

• Although technology is constantly changing, it's helpful to remember that all machines are made of the same basic parts. The term simple machine is used to refer to devices that have few moving parts, if any, but use energy to work. If two or more simple machines are joined together to make a...
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