Design philosophy - Module 1 Fundamentals of machine design Lesson 1 Notes | EduRev

: Design philosophy - Module 1 Fundamentals of machine design Lesson 1 Notes | EduRev

 Page 1


 
 
 
 
 
 
 
 
Module  
1 
Fundamentals of 
machine design 
 
Version 2 ME, IIT Kharagpur 
Page 2


 
 
 
 
 
 
 
 
Module  
1 
Fundamentals of 
machine design 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Lesson  
1 
Design philosophy 
 
Version 2 ME, IIT Kharagpur 
Page 3


 
 
 
 
 
 
 
 
Module  
1 
Fundamentals of 
machine design 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Lesson  
1 
Design philosophy 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
 
• Basic concept of design in general. 
• Concept of machine design and their types. 
• Factors to be considered in machine design. 
 
 
1.1.1 Introduction 
Design is essentially a decision-making process. If we have a problem, we need 
to design a solution. In other words, to design is to formulate a plan to satisfy a 
particular need and to create something with a physical reality. Consider for an 
example, design of a chair. A number of factors need be considered first: 
(a) The purpose for which the chair is to be designed such as whether it is to 
be used as an easy chair, an office chair or to accompany a dining table. 
(b) Whether the chair is to be designed for a grown up person or a child. 
(c) Material for the chair, its strength and cost need to be determined. 
(d) Finally, the aesthetics of the designed chair. 
Almost everyone is involved in design, in one way or the other, in our daily lives 
because problems are posed and they need to be solved. 
 
1.1.2  Basic concept of machine design 
Decision making comes in every stage of design. Consider two cars of different 
makes. They may both be reasonable cars and serve the same purpose but the 
designs are different. The designers consider different factors and come to 
certain conclusions leading to an optimum design. Market survey gives an 
indication of what people want. Existing norms play an important role. Once a 
critical decision is made, the rest of the design features follow. For example, 
Version 2 ME, IIT Kharagpur 
Page 4


 
 
 
 
 
 
 
 
Module  
1 
Fundamentals of 
machine design 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Lesson  
1 
Design philosophy 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
 
• Basic concept of design in general. 
• Concept of machine design and their types. 
• Factors to be considered in machine design. 
 
 
1.1.1 Introduction 
Design is essentially a decision-making process. If we have a problem, we need 
to design a solution. In other words, to design is to formulate a plan to satisfy a 
particular need and to create something with a physical reality. Consider for an 
example, design of a chair. A number of factors need be considered first: 
(a) The purpose for which the chair is to be designed such as whether it is to 
be used as an easy chair, an office chair or to accompany a dining table. 
(b) Whether the chair is to be designed for a grown up person or a child. 
(c) Material for the chair, its strength and cost need to be determined. 
(d) Finally, the aesthetics of the designed chair. 
Almost everyone is involved in design, in one way or the other, in our daily lives 
because problems are posed and they need to be solved. 
 
1.1.2  Basic concept of machine design 
Decision making comes in every stage of design. Consider two cars of different 
makes. They may both be reasonable cars and serve the same purpose but the 
designs are different. The designers consider different factors and come to 
certain conclusions leading to an optimum design. Market survey gives an 
indication of what people want. Existing norms play an important role. Once a 
critical decision is made, the rest of the design features follow. For example, 
Version 2 ME, IIT Kharagpur 
once we decide the engine capacity, the shape and size, then the subsequent 
course of the design would follow. A bad decision leads to a bad design and a 
bad product. 
Design may be for different products and with the present specialization and 
knowledge bank, we have a long list of design disciplines e.g. ship design, 
building design, process design, bridge design, clothing or fashion design and so 
on. 
Here we are concerned with machine design. We now define a machine as a 
combination of resisting bodies with successfully constrained relative motions 
which is used to transform other forms of energy into mechanical energy or 
transmit and modify available energy to do some useful work. If it converts heat 
into mechanical energy we then call it a heat engine. This is illustrated in figure-
1.1.2.1. 
 
Q
1
Q
2
W pdv =
?
 
ANIMATE 
 
 
 
 
1.1.2.1A- Conversion of heat to mechanical energy in a piston cylinder 
arrangement. 
 
In many cases however, the machines receive mechanical energy and modify it 
so that a specific task is carried out, for example a hoist, a bicycle or a hand-
winch. 
This modification or transformation of energy requires a number of machine 
elements, some small and some large. Machine design involves primarily 
designing these elements so that they may transmit the forces safely and 
perform their task successfully. Consider the following simple mechanisms: 
(a) Hand winch  (b) Small press operated by a power screw.. 
Version 2 ME, IIT Kharagpur 
Page 5


 
 
 
 
 
 
 
 
Module  
1 
Fundamentals of 
machine design 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Lesson  
1 
Design philosophy 
 
Version 2 ME, IIT Kharagpur 
 
 
 
 
 
Instructional Objectives 
 
At the end of this lesson, the students should have the knowledge of 
 
• Basic concept of design in general. 
• Concept of machine design and their types. 
• Factors to be considered in machine design. 
 
 
1.1.1 Introduction 
Design is essentially a decision-making process. If we have a problem, we need 
to design a solution. In other words, to design is to formulate a plan to satisfy a 
particular need and to create something with a physical reality. Consider for an 
example, design of a chair. A number of factors need be considered first: 
(a) The purpose for which the chair is to be designed such as whether it is to 
be used as an easy chair, an office chair or to accompany a dining table. 
(b) Whether the chair is to be designed for a grown up person or a child. 
(c) Material for the chair, its strength and cost need to be determined. 
(d) Finally, the aesthetics of the designed chair. 
Almost everyone is involved in design, in one way or the other, in our daily lives 
because problems are posed and they need to be solved. 
 
1.1.2  Basic concept of machine design 
Decision making comes in every stage of design. Consider two cars of different 
makes. They may both be reasonable cars and serve the same purpose but the 
designs are different. The designers consider different factors and come to 
certain conclusions leading to an optimum design. Market survey gives an 
indication of what people want. Existing norms play an important role. Once a 
critical decision is made, the rest of the design features follow. For example, 
Version 2 ME, IIT Kharagpur 
once we decide the engine capacity, the shape and size, then the subsequent 
course of the design would follow. A bad decision leads to a bad design and a 
bad product. 
Design may be for different products and with the present specialization and 
knowledge bank, we have a long list of design disciplines e.g. ship design, 
building design, process design, bridge design, clothing or fashion design and so 
on. 
Here we are concerned with machine design. We now define a machine as a 
combination of resisting bodies with successfully constrained relative motions 
which is used to transform other forms of energy into mechanical energy or 
transmit and modify available energy to do some useful work. If it converts heat 
into mechanical energy we then call it a heat engine. This is illustrated in figure-
1.1.2.1. 
 
Q
1
Q
2
W pdv =
?
 
ANIMATE 
 
 
 
 
1.1.2.1A- Conversion of heat to mechanical energy in a piston cylinder 
arrangement. 
 
In many cases however, the machines receive mechanical energy and modify it 
so that a specific task is carried out, for example a hoist, a bicycle or a hand-
winch. 
This modification or transformation of energy requires a number of machine 
elements, some small and some large. Machine design involves primarily 
designing these elements so that they may transmit the forces safely and 
perform their task successfully. Consider the following simple mechanisms: 
(a) Hand winch  (b) Small press operated by a power screw.. 
Version 2 ME, IIT Kharagpur 
In each one of these mechanisms some useful work is being obtained with  
certain combinations of a number of machine parts. Designing these 
mechanisms would involve firstly designing these elements and then assembling 
them in order. 
    
 
  
CLIPPING
 
                                           1.1.2.1V  Introduction to machine design 
 
1.1.3  Types of design  
There may be several types of design such as  
Adaptive design  
This is based on existing design, for example, standard products or systems 
adopted for a new application. Conveyor belts, control system of machines and 
mechanisms or haulage systems are some of the examples where existing 
design systems are adapted for a particular use. 
Developmental design 
Here we start with an existing design but finally a modified design is obtained. A 
new model of a car is a typical example of a developmental design . 
New design 
This type of design is an entirely new one but based on existing scientific 
principles. No scientific invention is involved but requires creative thinking to 
solve a problem. Examples of this type of design may include designing a small 
vehicle for transportation of men and material on board a ship or in a desert. 
Some research activity may be necessary.  
1.1.4  Types of design based on methods 
Rational design 
This is based on determining the stresses and strains of components and 
thereby deciding their dimensions. 
Version 2 ME, IIT Kharagpur 
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