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PREFACE:

The prior knowledge base in design and engineering, as with nearly all domains, is extensive. We have been designing and producing a wide range of sophisticated machines and systems for centuries. 

The detailed design of many machine elements and types of machinery has been codified and significant expertise is readily available. Just knowing that someone else has successfully produced a product or system can act as inspiration or provide direction for a similar product or the design of a subsystem that uses associated technology, or needs to have comparable functions. Many attempts have been made at defining design. 

The word can be used as a verb or noun, describing the process and the outcome of design, respectively. Referring to design as a process, it can be considered to include all the activities of market assessment and user requirements, specification, concept generation and idea development, embodiment of details, risk mitigation, consideration of manufacture and production, and implementation. 

Referring to design as a noun, the term is commonly used to describe an artifact such as a vehicle, item of fashion or other product, with the associated features and merits. This may include description or commentary on aesthetic, ergonomic, and technical features. In this book, an inclusive approach to design is used with consideration of a range of functionalities ranging from technical, aesthetic, social, economic, and latent.

 Design is considered to be the process of conceiving, developing, and realizing products, artifacts, processes, systems, services, and experiences with the aim of fulfilling identified or perceived needs or desires typically working within defined or negotiated constraints. Engineering involves significant overlap with design and, indeed, it is often difficult to make a clear distinction.

 A common distinction is the use of quantitative analysis in engineering to aid and inform the development, simulation, testing, and refinement of a system or product. Engineering can thus be considered to be the application of scientific and mathematic principles in combination with professional and domain knowledge, in order to design, develop, and deliver artifacts, products, and systems to realize a societal, commercial, or organization requirement or opportunity.

 Mechanical engineering refers to the use of engineering processes to applications of a mechanical nature, typically involving moving components or energy processes. Mechanical engineering heavily relies on the engineering sciences of thermodynamics and mechanics, often integrated through design, in the development and refinement of a solution for a specific requirement.

 The title for this book comes from the blend of mechanical and design engineering, the latter with its heritage in the on-going collaborations between Imperial College London and the Royal College of Art through the Innovation Design Engineering double masters, of which I have the honor of being joint course director.

 The detailed design of a wide range of machine elements that are commonly used in mechanisms and machines has been the focus of attention of many companies and research groups around the world. Examples of such machine elements include bearings, shafts, gears, belts, chains, clutches, brakes, seals, and springs.

 Many of these are available as stock items or standardized components that are produced by a range of companies, enabling the engineer or designer to focus attention on selection of appropriate stock items and the integration of these within the application of interest, rather than having to repeat the development of previous knowledge.

 For other machine elements such as shafts, some clutches and brakes, and seals, their design can take advantage of prior knowledge and design guidelines. Industry is typically concerned with the development of return for investors, or owners, within their specific product or service sector. 

A wide range of approaches is employed to manage the development and delivery process for new products and systems, or the manufacture and production, and delivery, of artifacts and services. Many models and approaches for the design process are employed in industry and area often bespoke to the particular organization concerned. 

Studies across a range of industries have identified some commonality in approach and a number of models have been proposed as representative of a standardized approach to design, and the management of design. 

A selection of these is presented in Chapter 1, providing an overview of typical approaches to the design process and its management. The objective or quantitative definition of the attributes and requirements for a product, artifact, or system, represents a common activity in design and engineering. 

This enables an assessment of what the design is required to deliver and is often used to monitor the success of a design proposal and in contractual agreements. Two common approaches to specification are introduced in Chapter 2, including the use of product design specification pro-forma tables and quality functional deployment. 

Whether the engineering or design activity involves integration of existing machine elements within a mechanism, or the design of original features and components, in the design of a brand new product or system, ideas are important. 

The development of ideas and the use of a range of creativity tools are introduced in Chapter 3. An overview of the variety of machine elements is introduced in Chapter 4. The design and selection of plain surface bearings and rolling element bearings are considered in

Chapters 5 and 6. Chapter 5 includes an introduction to the wide range of bearing types and presents a selection method for boundary lubricated bearings, as well as a modeling approach for full-film hydrodynamic bearings that can be used to assess the suitability of an initial design proposal. 

The selection of rolling element bearings based on the classical bearing life equation is introduced in Chapter 6 along with a brief consideration of bearing arrangements. Shafts are considered in Chapter 7 with a particular focus on sizing a shaft to limit deflection to adequate limits and assessing dynamic characteristics. 

Gears, critical for transforming speed and torque in transmission systems, are introduced in Chapters 8e11. Chapter 8 provides an overview of a wide range of types of gears and also presents an initial selection procedure for spur gears based on the Lewis formula for bending. The introduction of more comprehensive analysis methods using the American Gear Manufacturer Association (AGMA) equations for bending and contact stress for spur and helical gears, bevel, and worm and wheel gears, is presented in Chapters 9, 10, and 11, respectively. 

The related transmission elements of belts and chains are introduced in Chapter 12, with a particular focus on the selection of belts and chains from stock suppliers using standard selection procedures. Clutches and brakes are introduced in Chapter 13. This chapter includes simple design procedures for single and multiple disk clutches, long- and short-shoe drum brakes, and calliper disk brakes. Seals are used in a wide range of machinery to prevent or limit the flow of fluids between regions in a machine and to exclude dirt or contaminants. 

Chapter 14 provides an overview of the wide range of types of seals and also gives guidance for the sizing of O rings for static and dynamic applications using data from British Standards, as well as modeling methods for assessing the leakage of labyrinth and bush seals. Springs are manufactured by a wide range of world-wide manufacturers and available as both stock items or bespoke designs.

 Chapter 15 introduces the design of a wide range of types of springs, including helical compression, helical extension, helical torsion, leaf, and Belleville springs. A wide range of fastening technologies is available for permanent and semipermanent joining of components. A range of these including threaded fasteners and rivets is introduced in Chapter 16, along with a brief consideration of adhesives, welding, and snap fasteners.

 The selection of wire rope is briefly introduced in Chapter 17. Pneumatic and hydraulic components, the majority available as stock items, are introduced in Chapter 18. Although a component, or process, may have a designated nominal dimension or performance measure, the actual dimension or performance will likely vary within limits of this value. 

Chapter 19 introduces the subject of tolerance with particular consideration of component tolerances for the assembly of cylindrical components, a brief consideration of geometric tolerances, and an introduction to statistical tolerance approaches.

The majority of material presented in this book represents a classic approach to the design and selection of machine elements. A cook-book recipe approach has been adopted for many of these, enabling the rapid development of a proposal for the machine element concerned and its evaluation. It is important to acknowledge the limitations of such an approach as the configuration, or selection, may be far from optimal.

 A typical approach to mitigate against nonoptimal selections is to explore additional selections with variation of a parameter, say a size above and below, or a slightly stronger and weaker material, to see if the outcome is favorable and then follow this lead. In addition, a keen eye on fundamental physics and engineering principles is necessary in the development of any solution or design proposal.

 A considerable quantity of the material in this book has arisen from two editions of my earlier book,Mechanical Design. This new handbook incorporates extensions to the treatment of former chapters on bearings, gears, belts and chains, clutches and brakes, seals, springs, fasteners, and tolerance. 

Specifically for this handbook, new chapters on design, specification, ideation, bevel gears, worm and wheel gears, wire rope, and pneumatics and hydraulics have been developed. The aims of this book are thus to present an overview of the design process and to introduce the technology and selection of a number of specific machine elements that are fundamental to a wide range of mechanical engineering design applications. I hope it is useful to you.