Fundamentals of Machine Design: Philosophy, Types, and Key Considerations

[Music] welcome to this course on design of machine

elements you know today we are going to give you the introductory lecture on design philosophy that is the lecture

number one now before starting this particular course

let me tell you a few words that this course is primarily an elementary level course on the

design and for this course the prerequisite is only you can say the

ideas what you have already gathered from the basic course on strength of material and Engineering

mechanics the knowledge of these two courses what you have already covered I suppose we will be enough to follow this

course and once again welcoming you to this course let us proceed for the lecture number one on

design philosophy firstly what we understand by the

design or what we are going to do in the design course or what will our objective to take and design as a

whole let us have some discussion onto it so first of all if you look onto this

board you can see we have given three points basic concept of design in

general concept of machine design and their types factors to be considered in

machine design so all these three points are you can say an overall idea that which will

give us an guideline to follow a machine design or design of machine elements as as a

whole now you can just see that design is essentially

a decision making process and we can see that for every problem we need to design a

solution and so that if we combine together then what is happening that design is to

formulate a plan to satisfy a particular need and to create something with a physical

reality so just looking through the just the three

points at what I have just told you let us have uh ideas that what is being meant by this three typical

points it is a decision making process the most vital part of a design is a decision making process and it

everything is boted on the decision so one designer should be a good

decision maker that is one of the primary objectives in the design now once again you have seen that

what we have been talking about that every problem for every problem we need to have a

solution that is what is being meant to that one in the typical type of design or

whatever you find out in your practical day-to-day life when you face a problem then you have to solve it you may not be

knowing many things for the problem that what you will do you will try to solve your

problem building up your ideas onto the existing methodologies or existing whatever you are having in

hand you cannot simply sit idle looking for the fact that I will gather all the knowledge

everything and then I will give a solution that is not a a very good design concept the idea is that the

world will go on running but you have to give some solution which is

feasible which is applicable and which will be used in the mankind yes of course you can have

continuous changes over that continuous modification over that but some something you have to give so with the

existing knowledge whatever you are having the tools in your hand make a decision and that decision is what is a

primary objective of a machine design that means what we once again if we try to formulate the enter idea then

what we can say just have a look once again that design is to formulate a plan to satisfy a particular

need and to create something with a physical reality now I suppose you have

understood that what I have just main to say about this design ideas that means the concept or whatever you say that why

the decision making is important let us go for another example say we take up a example of design of a

chair is a very common thing you have seen in everyday's life a design of that same

chair the responsibility is given to you then what you should look into the fact here the factors need to be

considered comes out to be like something like this the purpose for which the chair is to to be

designed whether the chair is to be designed for a grownup person or a child material for the chair strength and cost

need to be determined Aesthetics of the designed chair

so let us take up those points one by one first of all the factors to be considered is the for what the chair is

required is is it a easy chair is it a chair used for study purpose is it a chair used in restaur or dining

tables so one has to know that means one has to define the problem so you know what is a for the chair is being made if

it is an easy chair then you understand that its back rests its hand rests will be designed accordingly

and if it is an restora chair hand rests may not be there because the size of the chair should not be that

big and it has to fit within the small tables at the same time is the chair

required for an old person or a child then you understand that depending upon the the situations your chair

design also changes the size will change okay the color look will might be changing that will come down later on in

this design of chair now again you know normally the material of the chair is

wooden well you can have the chair made of aluminium you can make the chair of RW iron which are very

nowadays so where it comes and consideration is aluminium wood or rot iron is not the problem the problem is

that the material or the problem in the sense what I mean to say the thinking in the line should be like

this the material should withstand the load of the person sitting on the chair whether he's an old person or an

child here the material selections is one of the very primary thing in the design

aspect first of all the material should as I told you should take up the load that means it should not

fail another thing is that it should not be too costly another thing that by making The

Chair by that material the chair should not be too heavy so that it cannot be carried from one place to another place

easily hence we can see that in the design just simply for consideration of the chair one has to think of these

things that failure that means material selection should be such that it should not

fail it should not be too costly and it should not be also heavy too so this is one of the aspects of the

material you can understand in a in any other designs this is also a requirement now you can see that we have

been discussing about that aesthetic sense now what is the aesthetic sense you understand that means just four legs

one back rest suppose you have designed a chair Simply Having four legs one back

rest and one hand rest without any shape or not looking very you know very attractive now the word attractive is a

relative matter I I understand but overall you have to look into the fact that means what is the fact that overall

how the people's mind are there what we understand what is beauty what is the color

concept which colors are being preferred by old man which colors are being preferred by

children which color suits in the restora which color suits in a how home dining hall or which color suits in the

seminar Hall of an Institute so there comes an Aesthetics part in designing the same chair what we

have been talking about similarly another aspect of the design

of chair has not been pointed out over here is also the ergonomics you understand the ergonomics

of a chair means it has to have a standard height it has to be having a standard width or depth whatever we call

or in other words in short I may say that the dimensions of the chair has to be like that that it can suppose you

have designed for an old man then it can accommodate an average variety of old man in general means a person having an

height of say 5 ft should not feel uncomfortable at the same time a person having an height of 6 ft also should not

also be comfortable in the similar manner so somewhere you have to put the ergonomics into account if I can say

roughly you measure all the chairs you will be finding out that in general the study chairs or the restora chairs will

have a height of around say 18 in 16 to 18 in in general all the reading tables study tables if you try to find out the

heights then you will be finding out that it will be in the vicinity of 30 in so this is an ergonomic aspect that if

it is like that you will be feeling comfortable while working so you can just see in this

particular example we have taken up so many aspects just simply a design of a chair has to be thought very carefully

looking into some of the ideas just which came into my mind right now

however if you have a if you go through a more thinking process you should add more to what I have said so that the

design is good your decision comes out to be much better than the what the decision I have taken so so this is one

of the aspects of what I was just considering in the design of chair so what we understand as a whole

that 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 so every Walk of Life in each and every Walk of Life it is a problem is a

design you are designing continuously are designing your mother at home is cooking

she is designing she is designing new recipes and her decision of course we know is very good so you relish the

foods so that is a design so every day we have the problems and we need to solve

it you go to the market you are you want to buy some copies pencils that's a design that's a

decision making which one will be better to suit you suit your requirement that is also a

design however once we see that almost everyone is involved in design we get an overall

idea is that that what we mean by Design so once again the design

of the basic concepts of design comes into the factor is the decision making every stage of

design consideration of this different factors to draw certain conclusions leading to an Optimum design Market

survey to read people's mind study of existing nors all this taken together you can see

all this taken together consider are again reiterated reiterated in decision making every stage of design means you

take this one think of over go to again and decision making procedure once you are finalized all

these ideas together then you come to an conclusion again the same decision making which is the basic basis of the

design and that is what what we call the basis concept of design you understand a bad decision leads to a bad design and a

bad product that is what is the gist of taking a bad decision as you have seen here see for example you can see uh

there are there could be two cars available in the market of of course of the same size same range are doing the

more or less the same type of work so do you think that one is bad another is good D both are doing nicely

in the market both are being used by the people so what is what the situation is coming out to be some decision was there

that both the designers for the cars have thought of taken the decision and then they have optimized

the design and given a shape to their ideas now one of the important factor in their design or the decision making what

I've just shown you is a market survey that is also another category of an design we'll be just looking after a

few minutes that type of designs are very much dependent on Market survey people's

mind that is also very useful in decision making once you have taking a decision

then re rest is relatively easy suppose you have chosen that for this category of car my engine size will be such that

it is creating a 60 BHP whatsoever may be the other cars available in the market that is also

60bp theirs is also 60 BP yours design also 60 BP it doesn't matter you have taken a decision and you have launched

your product and they have taken a decision they have launched your product both are going

parallell now the difference may be there in their salability because someone might have

taken a better decision while implementing the design looking into people's

mind and looking and read the people's mind for one of them could be better so his

car might be selling little fairly than the other one so all this leads to a single point

what I trying to say is the repeatedly I'm telling the design is and decision making again we look to the other

one is that the design discipline so design may be of different products and with present specialization and

knowledge Bank we have a long list of design disciplines say to pick a few ship

design clothing fashion design which is very common in today's life you can see process design building design bridge

design and many more and lastly we concentrate on our machine design or design of machine

elements as the code suggests anyway the overall call it as a machine design now you have seen so

many disciplines of the design every field whatever has been shown in the slide are based upon

certain knowledges acquired by the people in that particular discipline and they have taken some

decisions from their knowledge of their discipline and are designing in and are designing the required products in their

specialization say cloth design so they know they know the people's mind the similar manner what has been discussed

there's no point in repeating and uh from that people are doing the cloth design someone is doing

the ship design now here we are for the machine design so what we understand by the

machine design now just to know about machine design one has to know what is

machine first of all one has to know what is machine let us look onto a definition of a machine as a

whole so as I have given over here is uh idea of the definition of machine machine is defined 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

now here can see that we have defined in this second paragraph the machines can receive mechanical energy and modify it

so that a specific task is carried out so you see that the machine definition lies in the

fact that we are in general we are getting an some sort of energy at the input

device and then we are getting some useful mechanical works in the particular

process the Transformations are being done by various machine Elements which are put together in a

combination in a coherent manner in such a way that one machine element responds nicely with the other res machine

element and thereby creating the ultimate effect in the terms of some mechanical work done in

general so that is what we understand as a machine

now so what we understand once again just you can look at that particular slide

where it has been given in the form of a picture which says a modification transformation of energy that is what I

told you utilize the machine elements so that means this machine elements are is our primary Duty which has to be

designed so machine design involves primarily designing machine elements so that they may transmit the forces and

perform their task successfully so this energy what you get you use some machine elements and then

you and this machine elements will give you the output in terms of mechanical work

done now that is the idea of the machine design as it is being written here so

before we go to this particular aspects of machine design once again uh let us have a look at

something else now we can see that

here here you can see a person riding a cycle so we can think of that he is

giving some sort of energy and just take look at this one if you are giving some sort of energy and

you can see the pedal which is transforming the energy

to give you a rotation of the cycle and that is his that is the output work he is getting that means this is one

machine design problem here what you are getting that the energy or mechanical energy being transformed to another form

of mechanical energy and as far as the design is concerned what you will be getting that you have to design the

pedal you have to design the chain sprocket Arrangement you have designed the wheel you have to design the be

rings so that your specific problem of moving a person through a machine which rotates

and moves onto the road well this is what user problem which in one term we call as an

bicycle so this is one example of what we can say a mechanical energy is being transformed to a mechanical

energy so this is a simple situation all of you know and SE all our machine

elements here you can see a aircraft this aircraft was used in 1971 in Bangladesh

War so this is also a machine and primarily this machine runs on F Aviation fill so the aviation fil

is being used utilized primarily to give you a mechanical output in terms of flying the

aircraft this one you can see is a locomotive engine nowadays is not in

operation however it has got very interesting machine elements so that we will come to see so here also

you are using uh combustion coal combustion to make a steam just cold combustion to make a steam and that

steam you know through a steam chest it is giving an reciprocating motion to a piston Arrangement and that piston while

reciprocating giving a circular motion you can see very carefully that this piston coming out these are the lings

which creating the reciprocating motion to a circular motion in the wheel these are all what you can see the machine

machine element okay so have a we have a look onto this one so this is another example

that all the machine is being and see a sinkunas coordination what was just telling that

this machine element is coordinate coordinating with this machine element and gradually you are getting one from

one form of the energy I'm just pointing out this form of energy because this is I this I suppose that is a steam energy

we are getting and then we are getting a mechanical work output in forms of rotation of the wheels those these are

the different machine elements so the enter one is a machine however these are machine elements so that was shown in

the definition that how we can what is the idea or what is the definition of the machine as a

whole so just have a very quick look onto that one yes it's a closer look at the

machine elements well here you can see uh

car of the same ideas that means you are using an Fel to drive a car and these are some of

the internal components of the car so you understand that this

is the your filter this is a battery for giving you the this is a source of power and uh some few more

we can see well this is a very close look this a I think it is from the back side and

is a radiator and uh so and so

forth all the other component this is the main engine well just missed it okay this is this is the this is the portion

where we have we have seen the engine you have Al seen earlier a closer looks to some other

units this is an bail drive you can see here this is a bail drive it is a mechanical drive and uh so this this

machine is also built up up so many machine elements so once again we can see how nicely the machine elements are

being synchronized to perform a operation and that enter one we call as an machine and you are going to design

such machine elements and put it together to form a machine well once again this is

the filters oil filters there a close look at the back battery see here is an

arrangement where you can see a rotary uh yes see a rotary motion is being giving an reciprocating motion

see this is the the inner crank is giving an rotary motion and outer side see this is the slot onto which

this bar is moving and this is another link which is actually rotating this link as you can see in the figure it's

need not to be described all the things here is the LA machine what you can you have

seen in our Workshop this is a machine and interestingly at this moment the specimen it is making or the job it is

making is a specimen for tensile tensile test okay specimen for tensile

test so this is this particular Le is driving power and electrical power so the

transformation of electrical energy to a mechanical form so these are few of the machine

elements that what we have seen so that gives you

the idea okay so we have seen once again just quickly look at the

board I mean this one machine design involves primarily designing machine element so that they may transmit the

forces and perform their task successfully so after looking at this particular video clips now you got the

idea that means what what we meant by Machine elements while it is transmitting the forces to perform the

dusk successfully what are the successful task we have seen a bicycle Aeroplane car

Etc so this is the concept of the machine as a whole and we are now clear what we are going to

design so once we see that we are defined that our

job that what we are going to design that is a design of machine elements now we come down to the idea that are types

of design what are the types of design we can see one is an Adaptive

design another is developmental design and another one we call as an new design so these are the types of design one can

think of let us have have a quick look at what we mean by these terms adaptive design developmental design and new

design now adaptive design is based on existing design standard products or systems are adopted for a new

application conveyor builds control systems of machines and mechanisms or Hol systems are some of the examples

very existing Design Systems are adapted for a particular use so basic thing is that let us uh discuss on this

particular point that what do we mean by adaptive design now so adaptive design is just we have

seen the definition something is available you put it together and let it

perform SE Duty it's an Adaptive design see you have got a pump purchased you want to run the

pump to lift water you require to rotate I mean run the pump how you

run the pump obviously if you're having an electrical power with you let us assume you have an electrical power with

you so you utilize an electrical primover now this electrical primover has to be attached to the Palm

shaft shaft so that the Palm shaft rotates it rotates the impar and your purpose of lifting water is being

satisfied in this particular case how you are joining these two ideas I mean how you are transmitting the

power it could be directly coupled so you have to design a couple we'll be learning later on how to design a couple

or you have seen a bail drive just now what we have seen in the car in the video clip so similar a bail Drive is

required to run the pump so you can do in either way either you use an coupling or you use a bail

drive now interestingly the pump the motor the belt or the coupling everything is available it's

standardized so what you do you just put it together together to solve your purpose although the designs of examples

of conveyor build H systems Etc are given over here I'm giving you another example just what I have seated right

now this is what we call as an Adaptive design the next one in the line is the developmental

design now this developmental design is something that a existing design is being is is there and you are going on

developing or modifying the design so new model of a card is a typical example of a developmental

design at the very I mean uh that on stop this my this lecture I was telling that you have to give a solution

to the world you have given it later on you thought that moment the decision what

was you have taken was Cor correct but it could have been better if I have considered certain other aspects there

is an ample opportunity to do that and that is what we understand as a developmental design so you go on

developing the design and get a newer and newer and better and better products the last one is a new

design let's have a look into this one this type of design is an entirely new one but based on existing scientific

principle that means you are not creating any Innovations okay it is given later no scientific invention is

involved but requires creative thinking to solve a problem examples of this type of

design May uh include a small vehicle for transportation of Main and material on board a ship or in

a desert some research activity may be necessary so what we understand by the

new design that is uh the product is not available in the market

but there is an possibility that if you can look or if you can design a something like that it might helpful to

the mankind as a whole people as a whole like that so you go on thinking give some

innovative ideas and for which you are not creating a

Newton's law mean a new invention but what is EXA exactly you are having in your hand and the

tools you are utilizing that however whether your ideas are crystallizing or not you can have some

tests on models you can make some research activities and that is where you have

seen the scope of R&S in the industries and many other places so here is the idea of the new design

something which is not exactly existing you can think of that one with available ideas

knowledges and your Innovative thinking and some research activities so this is what we understand by new

design now we can see the design when we classify the types of design design

based on methodologies earlier we talked about what could be the types of designs and

this is what is the method based designs means what are the methods by which we do a design

problem here you can see we have given three such sets of ideas one is rational design another is

empirical design and another one is the third one is industrial

design let us have a look once again that what we understand by these three terminologies namely rational design

empirical design and Industrial design rational design based on determining the stresses

and strin of components and thereby deciding their

Dimensions what it is meant by the standard design methodologies or overall

what you have learned so far in your earlier strength of material I can I can say that is one of

the examples of a rational design how you know the you know stress is how much stress is defined by um load divide

dived by the area so you have some load onto a say a circular

rod and then having an cross-sectional area say a so you know that P ided by a is a stress

generated now you do a tensile test for that material find out its yeld Point means the point where the material is

going to fail say this value is Sigma the value is Sigma so Sigma equals

to so if we look into this one then we find that

um what we understand that is

this excuse me so we what I just trying to say Sigma equals to

P ided by area so what you you understand is that if you know the

load if you know the design strength or the material property so area comes out to be P / by Sigma this is your

design that means what should be the cross-sectional area you can immediately tell provided you know the material

property so that is what we are uh trying to say about this that based on it this is the

one yes this is the based on the deter I mean uh this is the rational design slide uh sorry uh it's went to other

slides anyway now come down to the indust design industrial design is based on Industrial considerations and Norms

that is the market survey external look production facilities low cost use of existing standard products this we have

already discussed earlier in some other form that while designing a C Market survey people's mind what should be the

external look which people want more okay what could be the production facilities that will make my uh product

cheaper all these considerations are the what we understand by industrial design of course this

design is based on existing standard products no doubt but you have to have an extensive knowledge Bas for all these

ideas of the market production facilities new developments in Production

Technologies and the primarily the cost Factor so these are all what we understand by the industrial

design now the another one the last one is an empirical Design This is based on empirical formula which in turn is based

on experience and experiments here is an typical example what we can say

right when we tighten a knot on a bol the force exerted or the stresses induced uh is very difficult to you know

find out that is exactly but experience shows that the tightening Force may be given by P equal to 248 D where D is the

Bold diameter in millimet and P is the applied force in kg here is surprisingly there is no

mathematical backing of this equation but it is based on observations and experience so what we find that this one

the empirical design is purely based on the experience of the people experience of the

designers similarly like this in our later course you will be finding out uh there are so many other empirical

relations developed from the experiments and from the exper I mean the experiences of the people of the

designers which we call as an empirical design now one of the most important thing also

comes into picture is the factors to be considered in machine design what device or mechanism to be

used okay to decide the relative arrangement of the constituent elements material forces on the elements

size shape and space requirement weight of the product the method of manufacturing the

components and their assembly how will it operate reliability and safety aspects

inspectability maintenance cost and asset atic of the design

products so all these points what has been written over here let us have a quick

recapitulation in somehow or other this has been spelled in this lecture at the earlier stages but now let us look into

in a categorically first of all what device or mechanism to be used this is a very

important aspect because a same work can be carried out by two different type of mechanisms so here comes a decision

making that which mechanism to be adopted of course this which mechanism to be adopted for a better

performance as I have told you earlier Here Comes again the same old Factor the decision

making however uh the mechanism and thinking of the mechanisms as a whole is a knowledge based means what I

mean to say that you should have an idea of the what are the different types of mechanism

available next comes the material we had a long discussion on this particular material while considering the example

of chair now this m material selection has become uh one of the uh one of the research areas you can say almost the

metallurgists are day by day every day they are giving new materials new developments the reason you know why

suppose you want to fly an aeroplane your material should be such that it should withstand the strength at the

same time it should be quite light the entire machine should be light so that you have a lesser Force to you require

and lesser power to fly the machine in air next comes the ideas of the shape size and space requirements and

forces on the elements weight of the product

and these situations are also to be described so we can understand that material

we have discussed force on the elements there could be various types of force that comes into

picture and this forces could be either a static type of force or it could be a dynamic Force as

such so what we understand is that the next one comes out to be the

size size is one factor that one has to also consider

very carefully you understand the size shape and space

requirement are again interconnected with material force on the elements means

these are all interconnected suppose you you have a material of lest strength your sizes

increases okay that means choice of material gives you the idea of the size either oversiz or under

size another thing is that if you are designing a machine element and following certain standards

then what happens you know that the design a size what you get from your calculation you will use a next size so

that it comes out to be within the standard sizes a machine what has been

designed depends where you are going to use so obviously the space requirement comes into picture that we can

intuitively understand what it is that weight of the product of course is very much required to be considered because

it determines some the cost onto the product particularly so material cost is an tremendous I mean uh one thing one

should keep in your mind mind the method of manufacturing the components and their assembly that is

also very important in the sense that you can use an various procedures we'll be discussing like costing forging

Machining which one will give you the same situation is the economics uh better machine economics comes up the

first and how your design uh will be withstanding the strength Etc of course you can take up the method manufacturing

methodologies depending upon the component but anyway which gives you a better B batch production which gives

you u a material behavior in a better way so all these things are dependent onto the

Manufacturing Technologies how will it operate the operation should be very smooth just

you press a button or entire system starts nowadays we find in so many

machines well uh that may not be that simple but still you want has to keep it in your mind reliability and safety

aspects this is one of the situation which has to be taken care of now what is reliability it is basically

a probability that machine will not fail in its life duration now this requires that you have to be very careful that

how much wear is taking place where the forces taking place onto the machine elements how it is taking machine on the

machine elements so that none of the safety Norms are being violated so that is what is the reliability so all safety

are ects starting from environment to design strength as a whole should be taken

up to make a machine reliable inspectability that means you have to check the machine time to time

so the machine assembly should be such that you should not have a difficulty in inspectability of the

machine maintenance cost and Aesthetics of the design products are the this last three

points have been to be discussed however maintenance is indirectly related to reliability and

safety aspects the more and more you have the maintenance proper maintenance then uh some more rather your

reliability and safety aspects will of course increase in this matter cost and

Aesthetics we have already discussed in the in this lecture at the earlier case while we are talking about

the chair and so what we can just very quickly

recapitulate the ideas what we have learned in this lecture overall we have learned that

machine is a combination of several machine elements arranged to work together as a whole to accomplish

specific purposes machine design involves designing the elements and arranging them optimally to obtain some

useful works this is what we understand by the machine and machine design as a whole the steps to be followed by a

designer as such machine design requires a thorough knowledge of engineering science in its totality along with a

clear decision making capability every designer follows his own methodology based on experience and

Analysis that we all know next the main steps to be followed in general are Define the

problem first you have to be understanding the problem make preliminary design decisions which

repeatedly I have told this decision is a very important factor make design sketches carry out design analysis and

optimization design the elements for strength and durability prepare documentations to be followed

for manufacturer the reliability in machine design that this one is the reliability

of a designed machine is concerned with the proper functioning of the elements and the Machine as a whole so that the

machine does not fail in use within its designed life overall safe design Approach at

every stage of the design is needed this is the reliability in machine design is a very important

factor so with this we end the lecture on design philosophy thank you [Music]

the [Music]