• Machine Design An Integrated Approach Solution Manual 4th

The English word machine comes through Middle French from Latin machina, which in turn derives from the Greek (Doric μαχανά makhana, Ionic. Solution Manual - Engineering Mechanics Statics 12 Edition By R.C Hibbeler - Free - Best E Books Club. Professional Topics for Mechanical Engineers. Prerequisite(s): MATH 31. Introduction to statistical methods applied to analysis of engineering.

A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process, or the result of that plan or specification in the form of a prototype, product or process. The verb to design expresses the process of developing a design. In some cases, the direct construction of an object without an explicit prior plan (such as in craftwork, some engineering, coding, and graphic design) may also be considered to be a design activity. A design usually has to satisfy certain goals and constraints^{[disambiguation needed]}, may take into account aesthetic, functional, economic, or socio-political considerations, and is expected to interact with a certain environment. Major examples of designs include architectural blueprints, engineering drawings, business processes, circuit diagrams, and sewing patterns.^[1]

The person who produces a design is a designer, which is a term generally used for people who work professionally in one of the various design areas - usually specifying which area is being dealt with (such as a textile designer, fashion designer, product designer, concept designer, web designer (website designer) or interior designer), but also others such as architects and engineers. A designer's sequence of activities is called a design process, possibly using design methods. The process of creating a design can be brief (a quick sketch) or lengthy and complicated, involving considerable research, negotiation, reflection, modelling, interactive adjustment and re-design.

• 1Design as a process
  • 1.1The rational model
  • 1.2The action-centric model
• 3Philosophies and studies of design
• 4Terminology

Design as a process[edit]

Machine Design An Integrated Approach Solution Manual 4th

Substantial disagreement exists concerning how designers in many fields, whether amateur or professional, alone or in teams, produce designs. Kees Dorst and Judith Dijkhuis, both designers themselves, argued that 'there are many ways of describing design processes' and discussed 'two basic and fundamentally different ways',^[2] both of which have several names. The prevailing view has been called 'the rational model',^[3] 'technical problem solving'^[4] and 'the reason-centric perspective'.^[5] The alternative view has been called 'reflection-in-action',^[4] 'co-evolution',^[6] and 'the action-centric perspective'.^[5]

The rational model[edit]

The rational model was independently developed by Herbert A. Simon,^[7][8] an American scientist, and Gerhard Pahl and Wolfgang Beitz, two German engineering design theorists.^[9] It posits that:

1. Designers attempt to optimize a design candidate for known constraints and objectives.
2. The design process is plan-driven.
3. The design process is understood in terms of a discrete sequence of stages.

The rational model is based on a rationalist philosophy^[3] and underlies the waterfall model,^[10]systems development life cycle,^[11] and much of the engineering design literature.^[12] According to the rationalist philosophy, design is informed by research and knowledge in a predictable and controlled manner.

Example sequence of stages[edit]

Typical stages consistent with the rational model include the following:

• Pre-production design
  • Design brief or Parti pris – an early (often the beginning) statement of design goals
  • Analysis – analysis of current design goals
  • Research – investigating similar design solutions in the field or related topics
  • Specification – specifying requirements of a design solution for a product (product design specification)^[13] or service.
  • Problem solving – conceptualizing and documenting design solutions
  • Presentation – presenting design solutions

• Design during production
  • Development – continuation and improvement of a designed solution
  • Testing – in situ testing of a designed solution
• Post-production design feedback for future designs
  • Implementation – introducing the designed solution into the environment
  • Evaluation and conclusion – summary of process and results, including constructive criticism and suggestions for future improvements
• Redesign – any or all stages in the design process repeated (with corrections made) at any time before, during, or after production.

Each stage has many associated best practices.^[14]

Criticism of the rational model[edit]

The rational model has been widely criticized on two primary grounds:

1. Designers do not work this way – extensive empirical evidence has demonstrated that designers do not act as the rational model suggests.^[15][5][4]
2. Unrealistic assumptions – goals are often unknown when a design project begins, and the requirements and constraints continue to change.^[3][16]

The action-centric model[edit]

The action-centric perspective is a label given to a collection of interrelated concepts, which are antithetical to the rational model.^[5] It posits that:

1. Designers use creativity and emotion to generate design candidates.
2. The design process is improvised.
3. No universal sequence of stages is apparent – analysis, design and implementation are contemporary and inextricably linked.^[5]

The action-centric perspective is based on an empiricist philosophy and broadly consistent with the agile approach^[17] and amethodical development.^[18] Substantial empirical evidence supports the veracity of this perspective in describing the actions of real designers.^[15] Like the rational model, the action-centric model sees design as informed by research and knowledge. However, research and knowledge are brought into the design process through the judgment and common sense of designers – by designers 'thinking on their feet' – more than through the predictable and controlled process stipulated by the rational model.

Descriptions of design activities[edit]

At least two views of design activity are consistent with the action-centric perspective. Both involve three basic activities.

In the reflection-in-action paradigm, designers alternate between 'framing', 'making moves', and 'evaluating moves'. 'Framing' refers to conceptualizing the problem, i.e., defining goals and objectives. A 'move' is a tentative design decision. The evaluation process may lead to further moves in the design.^[4]

In the sensemaking–coevolution–implementation framework, designers alternate between its three titular activities. Sensemaking includes both framing and evaluating moves. Implementation is the process of constructing the design object. Coevolution is 'the process where the design agent simultaneously refines its mental picture of the design object based on its mental picture of the context, and vice versa'.^[5]

The concept of the design cycle is understood as a circular time structure,^[19] which may start with the thinking of an idea, then expressing it by the use of visual or verbal means of communication (design tools), the sharing and perceiving of the expressed idea, and finally starting a new cycle with the critical rethinking of the perceived idea. Anderson points out that this concept emphasizes the importance of the means of expression, which at the same time are means of perception of any design ideas.^[20]

Design disciplines[edit]

Philosophies and studies of design[edit]

There are countless philosophies for guiding design as design values and its accompanying aspects within modern design vary, both between different schools of thought^[which?] and among practicing designers.^[21] Design philosophies are usually for determining design goals. A design goal may range from solving the least significant individual problem of the smallest element, to the most holistic influential utopian goals. Design goals are usually for guiding design. However, conflicts over immediate and minor goals may lead to questioning the purpose of design, perhaps to set better long term or ultimate goals. John Heskett, a 20th-century British writer on design claimed, 'Design, stripped to its essence, can be defined as the human nature to shape and make our environment in ways without precedent in nature, to serve our needs and give meaning to our lives.'^[22]

Philosophies for guiding design[edit]

Design philosophies are fundamental guiding principles that dictate how a designer approaches his/her practice. Reflections on material culture and environmental concerns (sustainable design) can guide a design philosophy. One example is the First Things First manifesto which was launched within the graphic design community and states 'We propose a reversal of priorities in favor of more useful, lasting and democratic forms of communication – a mindshift away from product marketing and toward the exploration and production of a new kind of meaning. The scope of debate is shrinking; it must expand. Consumerism is running uncontested; it must be challenged by other perspectives expressed, in part, through the visual languages and resources of design.'^[23]

In The Sciences of the Artificial by polymath Herbert A. Simon, the author asserts design to be a meta-discipline of all professions. 'Engineers are not the only professional designers. Everyone designs who devises courses of action aimed at changing existing situations into preferred ones. The intellectual activity that produces material artifacts is no different fundamentally from the one that prescribes remedies for a sick patient or the one that devises a new sales plan for a company or a social welfare policy for a state. Design, so construed, is the core of all professional training; it is the principal mark that distinguishes the professions from the sciences. Schools of engineering, as well as schools of architecture, business, education, law, and medicine, are all centrally concerned with the process of design.'^[8]

Approaches to design[edit]

A design approach is a general philosophy that may or may not include a guide for specific methods. Some are to guide the overall goal of the design. Other approaches are to guide the tendencies of the designer. A combination of approaches may be used if they don't conflict.

Some popular approaches include:

• Sociotechnical system design, a philosophy and tools for participative designing of work arrangements and supporting processes – for organizational purpose, quality, safety, economics and customer requirements in core work processes, the quality of peoples experience at work and the needs of society
• KISS principle, (Keep it Simple Stupid), which strives to eliminate unnecessary complications.
• There is more than one way to do it (TIMTOWTDI), a philosophy to allow multiple methods of doing the same thing.
• Use-centered design, which focuses on the goals and tasks associated with the use of the artifact, rather than focusing on the end user.
• User-centered design, which focuses on the needs, wants, and limitations of the end user of the designed artifact.
• Critical design uses designed artifacts as an embodied critique or commentary on existing values, morals, and practices in a culture.
• Service design designing or organizing the experience around a product and the service associated with a product's use.
• Transgenerational design, the practice of making products and environments compatible with those physical and sensory impairments associated with human aging and which limit major activities of daily living.
• Speculative design, the speculative design process doesn't necessarily define a specific problem to solve, but establishes a provocative starting point from which a design process emerges. The result is an evolution of fluctuating iteration and reflection using designed objects to provoke questions and stimulate discussion in academic and research settings.
• Participatory Design (originally co-operative design, now often co-design) is the practice of collective creativity to design, attempting to actively involve all stakeholders (e.g. employees, partners, customers, citizens, end users) in the design process to help ensure the result meets their needs and is usable. Participatory design is an approach which is focused on processes and procedures of design and is not a design style^[24]

Methods of designing[edit]

Design methods is a broad area that focuses on:

• Exploring possibilities and constraints by focusing critical thinking skills to research and define problem spaces for existing products or services—or the creation of new categories (see also Brainstorming)
• Redefining the specifications of design solutions which can lead to better guidelines for traditional design activities (graphic, industrial, architectural, etc.);
• Managing the process of exploring, defining, creating artifacts continually over time
• Prototyping possible scenarios, or solutions that incrementally or significantly improve the inherited situation
• Trendspotting: understanding the trend process.

Terminology[edit]

The word 'design' is often considered ambiguous, as it is applied in varying contexts.

Design and art[edit]

Today, the term design is generally used for what was formerly called the applied arts. The new term, for a very old thing, was perhaps initiated by Raymond Loewy and teachings at the Bauhaus and Ulm School of Design (HfG Ulm) in Germany during the 20th century.

The boundaries between art and design are blurred, largely due to a range of applications both for the term 'art' and the term 'design'. Applied arts has been used as an umbrella term to define fields of industrial design, graphic design, fashion design, etc. The term 'decorative arts' is a traditional term used in historical discourses to describe craft objects, and also sits within the umbrella of applied arts. In graphic arts (2D image making that ranges from photography to illustration), the distinction is often made between fine art and commercial art, based on the context within which the work is produced and how it is traded.

To a degree, some methods for creating work, such as employing intuition, are shared across the disciplines within the applied arts and fine art. Mark Getlein, writer, suggests the principles of design are 'almost instinctive', 'built-in', 'natural', and part of 'our sense of 'rightness'.'^[25] However, the intended application and context of the resulting works will vary greatly.

Design and engineering[edit]

In engineering, design is a component of the engineering process. Many overlapping methods and processes can be seen when comparing Product design, Industrial design and Engineering. The American Heritage Dictionary defines design as: 'To conceive or fashion in the mind; invent,' and 'To formulate a plan', and defines engineering as: 'The application of scientific and mathematical principles to practical ends such as the design, manufacture, and operation of efficient and economical structures, machines, processes, and systems.'.^[26][27] Both are forms of problem-solving with a defined distinction being the application of 'scientific and mathematical principles'. The increasingly scientific focus of engineering in practice, however, has raised the importance of more new 'human-centered' fields of design.^[28] How much science is applied in a design is a question of what is considered 'science'. Along with the question of what is considered science, there is social science versus natural science. Scientists at Xerox PARC made the distinction of design versus engineering at 'moving minds' versus 'moving atoms' (probably in contradiction to the origin of term 'engineering – engineer' from Latin 'in genio' in meaning of a 'genius' what assumes existence of a 'mind' not of an 'atom').

Design and production[edit]

The relationship between design and production is one of planning and executing. In theory, the plan should anticipate and compensate for potential problems in the execution process. Design involves problem-solving and creativity. In contrast, production involves a routine or pre-planned process. A design may also be a mere plan that does not include a production or engineering processes although a working knowledge of such processes is usually expected of designers. In some cases, it may be unnecessary or impractical to expect a designer with a broad multidisciplinary knowledge required for such designs to also have a detailed specialized knowledge of how to produce the product.

Design and production are intertwined in many creative professional careers, meaning problem-solving is part of execution and the reverse. As the cost of rearrangement increases, the need for separating design from production increases as well. For example, a high-budget project, such as a skyscraper, requires separating (design) architecture from (production) construction. A Low-budget project, such as a locally printed office party invitation flyer, can be rearranged and printed dozens of times at the low cost of a few sheets of paper, a few drops of ink, and less than one hour's pay of a desktop publisher.

This is not to say that production never involves problem-solving or creativity, nor that design always involves creativity. Designs are rarely perfect and are sometimes repetitive. The imperfection of a design may task a production position (e.g. production artist, construction worker) with utilizing creativity or problem-solving skills to compensate for what was overlooked in the design process. Likewise, a design may be a simple repetition (copy) of a known preexisting solution, requiring minimal, if any, creativity or problem-solving skills from the designer.

Process design[edit]

'Process design' (in contrast to 'design process' mentioned above) refers to the planning of routine steps of a process aside from the expected result. Processes (in general) are treated as a product of design, not the method of design. The term originated with the industrial designing ofchemical processes. With the increasing complexities of the information age, consultants and executives have found the term useful to describe the design of business processes as well as manufacturing processes.

See also[edit]

References[edit]

1. ^Dictionary meanings in the Cambridge Dictionary of American English, at Dictionary.com (esp. meanings 1–5 and 7–8) and at AskOxford (especially verbs).
2. ^Dorst, Kees; Dijkhuis, Judith (1995). 'Comparing paradigms for describing design activity'. Design Studies. 16 (2): 261–274. doi:10.1016/0142-694X(94)00012-3.
3. ^ ^abcBrooks, F.P. (2010) The design of design: Essays from a computer scientist, Addison-Wesley Professional. ISBN0-201-36298-8.
4. ^ ^abcdSchön, D.A. (1983) The reflective practitioner: How professionals think in action, Basic Books, USA.
5. ^ ^abcdefRalph, P. (2010) 'Comparing two software design process theories'. International Conference on Design Science Research in Information Systems and Technology (DESRIST 2010), Springer, St. Gallen, Switzerland, pp. 139–153. doi:10.1007/978-3-642-13335-0_10.
6. ^Dorst, K.; Cross, N. (2001). 'Creativity in the design process: Co-evolution of problem-solution'. Design Studies. 22 (2): 425–437. doi:10.1016/0142-694X(94)00012-3.
7. ^Newell, A., and Simon, H. (1972) Human problem solving, Prentice-Hall, Inc.
8. ^ ^abSimon, H.A. (1996) The sciences of the artificial, MIT Press, Cambridge, MA, USA. p. 111. ISBN0-262-69191-4.
9. ^Pahl, G., and Beitz, W. (1996) Engineering design: A systematic approach, Springer-Verlag, London. ISBN3-540-19917-9.
10. ^Royce, W.W. (1970) 'Managing the development of large software systems: Concepts and techniques,' Proceedings of Wescon.
11. ^Bourque, P., and Dupuis, R. (eds.) (2004) Guide to the software engineering body of knowledge (SWEBOK). IEEE Computer Society Press, ISBN0-7695-2330-7.
12. ^Pahl, G., Beitz, W., Feldhusen, J., and Grote, K.-H. (2007 ) Engineering design: A systematic approach, (3rd ed.), Springer-Verlag, ISBN1-84628-318-3.
13. ^Cross, N., (2006). T211 Design and Designing: Block 2, p. 99. Milton Keynes: The Open University.
14. ^Ullman, David G. (2009) The Mechanical Design Process, Mc Graw Hill, 4th edition ISBN0-07-297574-1
15. ^ ^abCross, N., Dorst, K., and Roozenburg, N. (1992) Research in design thinking, Delft University Press, Delft. ISBN90-6275-796-0.
16. ^McCracken, D.D.; Jackson, M.A. (1982). 'Life cycle concept considered harmful'. SIGSOFT Software Engineering Notes. 7 (2): 29–32. doi:10.1145/1005937.1005943.
17. ^Beck, K., Beedle, M., van Bennekum, A., Cockburn, A., Cunningham, W., Fowler, M., Grenning, J., Highsmith, J., Hunt, A., Jeffries, R., Kern, J., Marick, B., Martin, R.C., Mellor, S., Schwaber, K., Sutherland, J., and Thomas, D. (2001) Manifesto for agile software development.
18. ^Truex, D.; Baskerville, R.; and Travis, J. (2000). 'Amethodical systems development: The deferred meaning of systems development methods'. Accounting, Management and Information Technologies. 10 (1): 53–79. doi:10.1016/S0959-8022(99)00009-0.
19. ^Fischer, Thomas 'Design Enigma. A typographical metaphor for enigmatic processes, including designing', in: T. Fischer, K. De Biswas, J.J. Ham, R. Naka, W.X. Huang, Beyond Codes and Pixels: Proceedings of the 17th International Conference on Computer-Aided Architectural Design Research in Asia, p. 686
20. ^Anderson, Jane (2011) Architectural Design, Basics Architecture 03, Lausanne, AVA academia, p. 40. ISBN978-2-940411-26-9.
21. ^Holm, Ivar (2006). Ideas and Beliefs in Architecture and Industrial design: How attitudes, orientations and underlying assumptions shape the built environment. Oslo School of Architecture and Design. ISBN82-547-0174-1.
22. ^Heskett, John (2002). Toothpicks and Logos: Design in Everyday Life. Oxford University Press.
23. ^First Things First 2000 a design manifestoArchived 2011-12-19 at the Wayback Machine. manifesto published jointly by 33 signatories in: Adbusters, the AIGA journal, Blueprint, Emigre, Eye, Form, Items fall 1999/spring 2000
24. ^'Co-creation and the new landscape of design'(PDF).
25. ^Getlein, Mark (2008) Living With Art, 8th ed. New York, p. 121.
26. ^American Psychological Association (APA): designArchived 2007-01-08 at the Wayback Machine. The American Heritage Dictionary of the English Language, Fourth Edition. Retrieved January 10, 2007
27. ^American Psychological Association (APA): engineeringArchived 2007-01-02 at the Wayback Machine. The American Heritage Dictionary of the English Language, Fourth Edition. Retrieved January 10, 2007
28. ^Faste, R. (2001). 'The Human Challenge in Engineering Design'(PDF). International Journal of Engineering Education. 17 (4–5): 327–331.

Bibliography[edit]

A machine (or mechanical device) is a mechanical structure that uses power to apply forces and control movement to perform an intended action. 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.^[1]

Modern machines are complex systems that consist of structural elements, mechanisms and control components and include interfaces for convenient use. Examples include a wide range of vehicles, such as automobiles, boats and airplanes, appliances in the home and office, including computers, building air handling and water handling systems, as well as farm machinery, machine tools and factory automation systems and robots.

• 6Mechanisms
• 7Machine elements
• 11Impact
• 12Mechanics

Etymology[edit]

The English word machine comes through Middle French from Latinmachina,^[2] which in turn derives from the Greek (Doricμαχανάmakhana, Ionicμηχανήmekhane 'contrivance, machine, engine',^[3] a derivation from μῆχοςmekhos 'means, expedient, remedy'^[4]).^[5] The word mechanical (Greek: μηχανικός) comes from the same Greek roots. 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 military siege engines, both in the late 16th and early 17th centuries. The OED traces the formal, modern meaning to John Harris' Lexicon Technicum (1704), which has:

Machine, or Engine, in Mechanicks, is whatsoever hath Force sufficient either to raise or stop the Motion of a Body... Simple Machines are commonly reckoned to be Six in Number, viz. the Ballance, Leaver, Pulley, Wheel, Wedge, and Screw... Compound Machines, or Engines, are innumerable.

The word engine used as a (near-)synonym both by Harris and in later language derives ultimately (via Old French) from Latin ingenium 'ingenuity, an invention'.

History[edit]

The hand axe, made by chipping flint to form a wedge, in the hands of a human transforms force and movement of the tool into a transverse splitting forces and movement of the workpiece. The hand axe is the first example of a wedge, the oldest of the six classic simple machines, from which most machines are based. The second oldest simple machine was the inclined plane (ramp),^[6] which has been used since prehistoric times to move heavy objects.^[7][8]

The other four simple machines were invented in the ancient Near East.^[9] The wheel, along with the wheel and axle mechanism, was invented in Mesopotamia (modern Iraq) during the 5th millennium BC.^[10] The lever mechanism first appeared around 5,000 years ago in the Near East, where it was used in a simple balance scale,^[11] and to move large objects in ancient Egyptian technology.^[12] The lever was also used in the shadoof water-lifting device, the first crane machine, which appeared in Mesopotamia circa 3000 BC,^[11] and then in ancient Egyptian technology circa 2000 BC.^[13] The earliest evidence of pulleys date back to Mesopotamia in the early 2nd millennium BC,^[14] and Ancient Egyptian during the Twelfth Dynasty (1991-1802 BC).^[15] The screw, the last of the simple machines to be invented,^[16] first appeared in Mesopotamia during the Neo-Assyrian period (911-609) BC.^[17] The Egyptian pyramids were built using three of the six simple machines, the inclined plane, the wedge, and the lever, to create structures like the Great Pyramid of Giza.^[18]

Three of the simple machines were studied and described by Greek philosopher Archimedes around the 3rd century BC: the lever, pulley and screw.^[19][20] Archimedes discovered the principle of mechanical advantage in the lever.^[21] Later Greek philosophers defined the classic five simple machines (excluding the inclined plane) and were able to roughly calculate their mechanical advantage.^[1]Heron of Alexandria (ca. 10–75 AD) in his work Mechanics lists five mechanisms that can 'set a load in motion'; lever, windlass, pulley, wedge, and screw,^[20] and describes their fabrication and uses.^[22] However, the Greeks' understanding was limited to statics (the balance of forces) and did not include dynamics (the tradeoff between force and distance) or the concept of work.

The earliest practical water-powered machines, the water wheel and watermill, first appeared in the Persian Empire, in what are now Iraq and Iran, by the early 4th century BC.^[23] The earliest practical wind-powered machines, the windmill and wind pump, first appeared in the Muslim world during the Islamic Golden Age, in what are now Iran, Afghanistan, and Pakistan, by the 9th century AD.^{[24][25][26][27]} The earliest practical steam-powered machine was a steam jack driven by a steam turbine, described in 1551 by Taqi al-Din Muhammad ibn Ma'ruf in Ottoman Egypt.^[28][29]

The cotton gin was invented in India by the 6th century AD,^[30] and the spinning wheel was invented in the Islamic world by the early 11th century,^[31] both of which were fundamental to the growth of the cotton industry. The spinning wheel was also a precursor to the spinning jenny, which was a key development during the early Industrial Revolution in the 18th century.^[32] The crankshaft and camshaft were invented by Al-Jazari in Northern Mesopotamia circa 1206,^[33][34][35] and they later became central to modern machinery such as the steam engine, internal combustion engine and automatic controls.^[36]

The earliest programmable machines were developed in the Muslim world. A music sequencer, a programmable musical instrument, was the earliest type of programmable machine. The first music sequencer was an automated flute player invented by the Banu Musa brothers, described in their Book of Ingenious Devices, in the 9th century.^[37][38] In 1206, Al-Jazari invented programmable automata/robots. He described four automaton musicians, including drummers operated by a programmable drum machine, where they could be made to play different rhythms and different drum patterns.^[39] The castle clock, a hydropowered mechanical astronomical clock invented by Al-Jazari, was the first programmableanalog computer.^[40][41][42]

During the Renaissance, the dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from the standpoint of how much useful work they could perform, leading eventually to the new concept of mechanical work. In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, and it was included with the other simple machines. The complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche ('On Mechanics').^[43][44] He was the first to understand that simple machines do not create energy, they merely transform it.^[43]

The classic rules of sliding friction in machines were discovered by Leonardo da Vinci (1452–1519), but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699) and were further developed by Charles-Augustin de Coulomb (1785).^[45]

James Watt patented his parallel motion linkage in 1782, which made the double acting steam engine practical.^[46] The Boulton and Watt steam engine and later designs powered steam locomotives, steam ships, and factories.

The Industrial Revolution was a period from 1750 to 1850 where changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times. It began in the United Kingdom, then subsequently spread throughout Western Europe, North America, Japan, and eventually the rest of the world.

Starting in the later part of the 18th century, there began a transition in parts of Great Britain's previously manual labour and draft-animal-based economy towards machine-based manufacturing. It started with the mechanisation of the textile industries, the development of iron-making techniques and the increased use of refined coal.^[47]

Simple machines[edit]

The idea that a machine can be decomposed into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane. The modern approach to characterizing machines focusses on the components that allow movement, known as joints.

Wedge (hand axe): Perhaps the first example of a device designed to manage power is the hand axe, also called biface and Olorgesailie. A hand axe is made by chipping stone, generally flint, to form a bifacial edge, or wedge. A wedge is a simple machine that transforms lateral force and movement of the tool into a transverse splitting force and movement of the workpiece. The available power is limited by the effort of the person using the tool, but because power is the product of force and movement, the wedge amplifies the force by reducing the movement. This amplification, or mechanical advantage is the ratio of the input speed to output speed. For a wedge this is given by 1/tanα, where α is the tip angle. The faces of a wedge are modeled as straight lines to form a sliding or prismatic joint.

Lever: The lever is another important and simple device for managing power. This is a body that pivots on a fulcrum. Because the velocity of a point farther from the pivot is greater than the velocity of a point near the pivot, forces applied far from the pivot are amplified near the pivot by the associated decrease in speed. If a is the distance from the pivot to the point where the input force is applied and b is the distance to the point where the output force is applied, then a/b is the mechanical advantage of the lever. The fulcrum of a lever is modeled as a hinged or revolute joint.

Wheel: The wheel is clearly an important early machine, such as the chariot. A wheel uses the law of the lever to reduce the force needed to overcome friction when pulling a load. To see this notice that the friction associated with pulling a load on the ground is approximately the same as the friction in a simple bearing that supports the load on the axle of a wheel. However, the wheel forms a lever that magnifies the pulling force so that it overcomes the frictional resistance in the bearing.

The classification of simple machines to provide a strategy for the design of new machines was developed by Franz Reuleaux, who collected and studied over 800 elementary machines.^[49] He recognized that the classical simple machines can be separated into the lever, pulley and wheel and axle that are formed by a body rotating about a hinge, and the inclined plane, wedge and screw that are similarly a block sliding on a flat surface.^[50]

Simple machines are elementary examples of kinematic chains or linkages that are used to model mechanical systems ranging from the steam engine to robot manipulators. The bearings that form the fulcrum of a lever and that allow the wheel and axle and pulleys to rotate are examples of a kinematic pair called a hinged joint. Similarly, the flat surface of an inclined plane and wedge are examples of the kinematic pair called a sliding joint. The screw is usually identified as its own kinematic pair called a helical joint.

This realization shows that it is the joints, or the connections that provide movement, that are the primary elements of a machine. Starting with four types of joints, the rotary joint, sliding joint, cam joint and gear joint, and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints called a mechanism .^[51]

Two levers, or cranks, are combined into a planar four-bar linkage by attaching a link that connects the output of one crank to the input of another. Additional links can be attached to form a six-bar linkage or in series to form a robot.^[51]

Mechanical systems[edit]

A mechanical system manages power to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source and actuators that generate forces and movement, (ii) a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement, (iii) a controller with sensors that compare the output to a performance goal and then directs the actuator input, and (iv) an interface to an operator consisting of levers, switches, and displays.

This can be seen in Watt's steam engine (see the illustration) in which the power is provided by steam expanding to drive the piston. The walking beam, coupler and crank transform the linear movement of the piston into rotation of the output pulley. Finally, the pulley rotation drives the flyball governor which controls the valve for the steam input to the piston cylinder.

The adjective 'mechanical' refers to skill in the practical application of an art or science, as well as relating to or caused by movement, physical forces, properties or agents such as is dealt with by mechanics.^[52] Similarly Merriam-Webster Dictionary^[53] defines 'mechanical' as relating to machinery or tools.

Power flow through a machine provides a way to understand the performance of devices ranging from levers and gear trains to automobiles and robotic systems. The German mechanicianFranz Reuleaux^[54] wrote, 'a machine is a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion.' Notice that forces and motion combine to define power.

More recently, Uicker et al.^[51] stated that a machine is 'a device for applying power or changing its direction.' McCarthy and Soh^[55] describe a machine as a system that 'generally consists of a power source and a mechanism for the controlled use of this power.'

Power sources[edit]

Human and animal effort were the original power sources for early machines.

Waterwheel:Waterwheels appeared around the world around 300 BC to use flowing water to generate rotary motion, which was applied to milling grain, and powering lumber, machining and textile operations. Modern water turbines use water flowing through a dam to drive an electric generator.

Windmill: Early windmills captured wind power to generate rotary motion for milling operations. Modern wind turbines also drives a generator. This electricity in turn is used to drive motors forming the actuators of mechanical systems.

Engine: The word engine derives from 'ingenuity' and originally referred to contrivances that may or may not be physical devices. See Merriam-Webster's definition of engine. A steam engine uses heat to boil water contained in a pressure vessel; the expanding steam drives a piston or a turbine. This principle can be seen in the aeolipile of Hero of Alexandria. This is called an external combustion engine.

An automobile engine is called an internal combustion engine because it burns fuel (an exothermic chemical reaction) inside a cylinder and uses the expanding gases to drive a piston. A jet engine uses a turbine to compress air which is burned with fuel so that it expands through a nozzle to provide thrust to an aircraft, and so is also an 'internal combustion engine.' ^[56]

Power plant: The heat from coal and natural gas combustion in a boiler generates steam that drives a steam turbine to rotate an electric generator. A nuclear power plant uses heat from a nuclear reactor to generate steam and electric power. This power is distributed through a network of transmission lines for industrial and individual use.

Motors:Electric motors use either AC or DC electric current to generate rotational movement. Electric servomotors are the actuators for mechanical systems ranging from robotic systems to modern aircraft.

Fluid Power:Hydraulic and pneumatic systems use electrically driven pumps to drive water or air respectively into cylinders to power linear movement.

Mechanisms[edit]

The mechanism of a mechanical system is assembled from components called machine elements. These elements provide structure for the system and control its movement.

The structural components are, generally, the frame members, bearings, splines, springs, seals, fasteners and covers. The shape, texture and color of covers provide a styling and operational interface between the mechanical system and its users.

The assemblies that control movement are also called 'mechanisms.'^[54][57] Mechanisms are generally classified as gears and gear trains, which includes belt drives and chain drives, cam and follower mechanisms, and linkages, though there are other special mechanisms such as clamping linkages, indexing mechanisms, escapements and friction devices such as brakes and clutches.

The number of degrees of freedom of a mechanism, or its mobility, depends on the number of links and joints and the types of joints used to construct the mechanism. The general mobility of a mechanism is the difference between the unconstrained freedom of the links and the number of constraints imposed by the joints. It is described by the Chebychev-Grübler-Kutzbach criterion.

Gears and gear trains[edit]

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 renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of the involute tooth yielded a standard gear design that provides a constant speed ratio. Some important features of gears and gear trains are:

• The 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.

Cam and follower mechanisms[edit]

A cam and follower is formed by the direct contact of two specially shaped links. The driving link is called the cam (also see cam shaft) and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of the cam and follower determines the movement of the mechanism.

Linkages[edit]

A linkage is a collection of links connected by joints. Generally, the links are the structural elements and the joints allow movement. Perhaps the single most useful example is the planar four-bar linkage. However, there are many more special linkages:

• Watt's linkage is a four-bar linkage that generates an approximate straight line. It was critical to the operation of his design for the steam engine. This linkage also appears in vehicle suspensions to prevent side-to-side movement of the body relative to the wheels. Also see the article Parallel motion.
• The success of Watt's linkage lead to the design of similar approximate straight-line linkages, such as Hoeken's linkage and Chebyshev's linkage.
• The Peaucellier linkage generates a true straight-line output from a rotary input.
• The Sarrus linkage is a spatial linkage that generates straight-line movement from a rotary input. Select this link for an animation of the Sarrus linkage
• The Klann linkage and the Jansen linkage are recent inventions that provide interesting walking movements. They are respectively a six-bar and an eight-bar linkage.

Planar mechanism[edit]

A planar mechanism is a mechanical system that is constrained so the trajectories of points in all the bodies of the system lie on planes parallel to a ground plane. The rotational axes of hinged joints that connect the bodies in the system are perpendicular to this ground plane.

Spherical mechanism[edit]

A spherical mechanism is a mechanical system in which the bodies move in a way that the trajectories of points in the system lie on concentric spheres. The rotational axes of hinged joints that connect the bodies in the system pass through the center of these circle.

Spatial mechanism[edit]

A spatial mechanism is a mechanical system that has at least one body that moves in a way that its point trajectories are general space curves. The rotational axes of hinged joints that connect the bodies in the system form lines in space that do not intersect and have distinct common normals.

Flexure mechanisms[edit]

A flexure mechanism consists of a series of rigid bodies connected by compliant elements (also known as flexure joints) that is designed to produce a geometrically well-defined motion upon application of a force.

Machine elements[edit]

The elementary mechanical components of a machine are termed machine elements. These elements consist of three basic types (i) structural components such as frame members, bearings, axles, splines, fasteners, seals, and lubricants, (ii) mechanisms that control movement in various ways such as gear trains, belt or chain drives, linkages, cam and follower systems, including brakes and clutches, and (iii) control components such as buttons, switches, indicators, sensors, actuators and computer controllers.^[58] While generally not considered to be a machine element, the shape, texture and color of covers are an important part of a machine that provide a styling and operational interface between the mechanical components of a machine and its users.

Structural components[edit]

A number of machine elements provide important structural functions such as the frame, bearings, splines, spring and seals.

• The recognition that the frame of a mechanism is an important machine element changed the name three-bar linkage into four-bar linkage. Frames are generally assembled from truss or beam elements.
• Bearings are components designed to manage the interface between moving elements and are the source of friction in machines. In general, bearings are designed for pure rotation or straight line movement.
• Splines and keys are two ways to reliably mount an axle to a wheel, pulley or gear so that torque can be transferred through the connection.
• Springs provides forces that can either hold components of a machine in place or acts as a suspension to support part of a machine.
• Seals are used between mating parts of a machine to ensure fluids, such as water, hot gases, or lubricant do not leak between the mating surfaces.
• Fasteners such as screws, bolts, spring clips, and rivets are critical to the assembly of components of a machine. Fasteners are generally considered to be removable. In contrast, joining methods, such as welding, soldering, crimping and the application of adhesives, usually require cutting the parts to disassemble the components

Controllers[edit]

Controllers combine sensors, logic, and actuators to maintain the performance of components of a machine. Perhaps the best known is the flyball governor for a steam engine. Examples of these devices range from a thermostat that as temperature rises opens a valve to cooling water to speed controllers such as the cruise control system in an automobile. The programmable logic controller replaced relays and specialized control mechanisms with a programmable computer. Servomotors that accurately position a shaft in response to an electrical command are the actuators that make robotic systems possible.

Computing machines[edit]

Charles Babbage designed machines to tabulate logarithms and other functions in 1837. His Difference engine can be considered an advanced mechanical calculator and his Analytical Engine a forerunner of the modern computer, though none were built in Babbage's lifetime.

The Arithmometer and the Comptometer are mechanical computers that are precursors to modern digital computers. Models used to study modern computers are termed State machine and Turing machine.

Molecular machines[edit]

The biological molecule myosin reacts to ATP and ADP to alternately engage with an actin filament and change its shape in a way that exerts a force, and then disengage to reset its shape, or conformation. This acts as the molecular drive that causes muscle contraction. Similarly the biological molecule kinesin has two sections that alternately engage and disengage with microtubules causing the molecule to move along the microtubule and transport vesicles within the cell, and dynein, which moves cargo inside cells towards the nucleus and produces the axonemal beating of motile cilia and flagella. '[I]n effect, the [motile cilium] is a nanomachine composed of perhaps over 600 proteins in molecular complexes, many of which also function independently as nanomachines...Flexible linkers allow the mobile protein domains connected by them to recruit their binding partners and induce long-range allostery via protein domain dynamics. '^[59] Other biological machines are responsible for energy production, for example ATP synthase which harnesses energy from proton gradients across membranes to drive a turbine-like motion used to synthesise ATP, the energy currency of a cell.^[60] Still other machines are responsible for gene expression, including DNA polymerases for replicating DNA,^{[citation needed]}RNA polymerases for producing mRNA,^{[citation needed]} the spliceosome for removing introns, and the ribosome for synthesising proteins. These machines and their nanoscale dynamics are far more complex than any molecular machines that have yet been artificially constructed.^[61]These molecules are increasingly considered to be nanomachines.^{[citation needed]}

Researchers have used DNA to construct nano-dimensioned four-bar linkages.^[62][63]

Impact[edit]

Mechanization and automation[edit]

Mechanization or mechanisation (BE) is providing human operators with machinery that assists them with the muscular requirements of work or displaces muscular work. In some fields, mechanization includes the use of hand tools. In modern usage, such as in engineering or economics, mechanization implies machinery more complex than hand tools and would not include simple devices such as an un-geared horse or donkey mill. Devices that cause speed changes or changes to or from reciprocating to rotary motion, using means such as gears, pulleys or sheaves and belts, shafts, cams and cranks, usually are considered machines. After electrification, when most small machinery was no longer hand powered, mechanization was synonymous with motorized machines.^[64]

Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provides human operators with machinery to assist them with the muscular requirements of work, automation greatly decreases the need for human sensory and mental requirements as well. Automation plays an increasingly important role in the world economy and in daily experience.

Automata[edit]

An automaton (plural: automata or automatons) is a self-operating machine. The word is sometimes used to describe a robot, more specifically an autonomous robot. A Toy Automaton was patented in 1863.^[65]

Mechanics[edit]

Usher^[66] reports that Hero of Alexandria's treatise on Mechanics focussed on the study of lifting heavy weights. Today mechanics refers to the mathematical analysis of the forces and movement of a mechanical system, and consists of the study of the kinematics and dynamics of these systems.

Dynamics of machines[edit]

The dynamic analysis of machines begins with a rigid-body model to determine reactions at the bearings, at which point the elasticity effects are included. The rigid-body dynamics studies the movement of systems of interconnected bodies under the action of external forces. The assumption that the bodies are rigid, which means that they do not deform under the action of applied forces, simplifies the analysis by reducing the parameters that describe the configuration of the system to the translation and rotation of reference frames attached to each body.^[67][68]

The dynamics of a rigid body system is defined by its equations of motion, which are derived using either Newtons laws of motion or Lagrangian mechanics. The solution of these equations of motion defines how the configuration of the system of rigid bodies changes as a function of time. The formulation and solution of rigid body dynamics is an important tool in the computer simulation of mechanical systems.

Kinematics of machines[edit]

The dynamic analysis of a machine requires the determination of the movement, or kinematics, of its component parts, known as kinematic analysis. The assumption that the system is an assembly of rigid components allows rotational and translational movement to be modeled mathematically as Euclidean, or rigid, transformations. This allows the position, velocity and acceleration of all points in a component to be determined from these properties for a reference point, and the angular position, angular velocity and angular acceleration of the component.

Machine design[edit]

Machine design refers to the procedures and techniques used to address the three phases of a machine's lifecycle:

1. invention, which involves the identification of a need, development of requirements, concept generation, prototype development, manufacturing, and verification testing;
2. performance engineering involves enhancing manufacturing efficiency, reducing service and maintenance demands, adding features and improving effectiveness, and validation testing;
3. recycle is the decommissioning and disposal phase and includes recovery and reuse of materials and components.

See also[edit]

References[edit]

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Further reading[edit]

• Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.). Machinery's Handbook (26th ed.). New York: Industrial Press Inc. ISBN978-0-8311-2635-3.
• Reuleaux, Franz (1876). The Kinematics of Machinery. Trans. and annotated by A. B. W. Kennedy. New York: reprinted by Dover (1963).
• Uicker, J. J.; G. R. Pennock; J. E. Shigley (2003). Theory of Machines and Mechanisms. New York: Oxford University Press.

• Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.). Machinery's Handbook (30th ed.). New York: Industrial Press Inc. ISBN9780831130992.

External links[edit]