Fm Project Report Initial

8/16/2019 Fm Project Report Initial

1/15


2/15

Acknowledgements

“It is not possible to prepare a project report without the

assistance & encouragement of other people. This one is

certainly no exception.”

On the very outset of this project, we would like to extend our

sincere and heartfelt obligation towards all the personages who

have helped us in this endeavor. Without their active guidance,

help, cooperation and encouragement, we would not have made

head way in the project. First and foremost, we would like toexpress our sincere gratitude to our project guide, Prof. r. !ajid

kamran. We were privileged to experience a sustained

enthusiastic and involved interest from his side. "his fuelled our

enthusiasm even further and encouraged us to boldly step into

what was a totally dark and unexplored expanse before us. #e

always fuelled our thoughts to think broad and out of the box. We

would also like to thank our parents, friends and class mates for

their encouragement and all their help at times of need. We would

also like to thank our teachers and other sta$ for their

cooperation in our research.

"hanking you,

#amid %a&a, 'sama (ja& and group


3/15

Abstract

"he major objective of our project is to design a reciprocating arm

and to move the metal piece in to and fro motion and to stop it for

a speci)ed time period at the end of stroke length. "his project isbased on our study of machinery and *uid mechanics. (t is not an

easy task as there are many methods and experiments to do the

same job. +s an engineer our task is to design the thing with

maximum eciency and least cost. "he reciprocating motion

means a motion in which the body moves about a mean position

in to and fro motion. "here are many methods to do the job like

scotch yoke mechanism, rack and pinion mechanism, speci)ed

gear trains, worm and worm wheel mechanism, -uick returnmechanism, slider crank mechanism. "hen there are many other

mechanisms based on motion of *uid like pneumatic arms and

hydraulic arms. "he mechanism we chose was scotch yoke

mechanism to simplify our design.


4/15

ontents/. (ntroduction..........................................................................................................0

/1 Purpose.............................................................................................................0

21 3ack ground......................................................................................................0

41 5ethod of investigation....................................................................................0

61 !cope................................................................................................................7

2. 5ethodology........................................................................................................8

(ntroduction to design................................................................................................ 9

5echanism and 5achine.........................................................................................9

egrees of Freedom and :rubler;s riterion of Plane 5echanism...........................<

!uitable Project esign 5echanisms.......................................................................<ack and pinion............................................................................................../=

!cotch "oke....................................................................................................../=

!cotch "oke with dwell at one end..............................................................//

!cotch yoke with dwell at both ends...........................................................//

#neumatic arm................................................................................................/2

$uick return mechanism.............................................................................../2

%orm and worm wheel................................................................................../4

!elected design...................................................................................................../6

Adantages...................................................................................................... /6

'raw backs...................................................................................................... /6

"ime plan for project................................................................................................ /6


5/15

/=

( Introduction

(.(#urpose "his is an initial report of *uid mechanics project of designing and

manufacturing a reciprocating arm. "his report will cover all the

research and methods of production used to ful)ll the objective.

(.)*ack ground%eciprocating motion >a motion in which a body moves to and fro

about its mean position1 is a very important mechanism and it

had been a permanent source of an engineer;s interest from the

very start. (t is serving engineers well with its di$erent

applications including reciprocating internal combustion engines,

knuckle joints in production molds, and lead screws in lathe

machines, worm and worm wheels to change speed of motion and

many others.

"he basic task looks simple that we just have to move a body in

to and fro motion using any mechanism of our choice. 3ut from

engineering point of view it is not as simple as it seems. First youhave to analy&e your system and it need then you have to collect

data about all the designs currently available. +fter this you need

to make the very important decision of which design you are

going to choose and then come the testing stage if your design

fail at this stage you have to re analy&e all that you have done so

far in the project and that is what we will be doing during the task

assigned to us.

"here are many designs and mechanisms devised to perform

reciprocating motion as discussed earlier as well. !ome of the

designs we considered are Four !top %eciprocating 5otion, One

%otation "wo !troke, and %ack +nd Pinion %eciprocate, %ack +nd

Pinion, !cotch ?oke, !cotch ?oke well at 3oth @nds, am

5echanism with Pause, %otary to Ainear, %eciprocate, "raversing


6/15

/=

#ead !haper, !cotch ?oke with dwell at one end. 3ut to make our

design simple and economical we chose scotch yoke mechanism.

(.+,ethod of inestigation

(n order to make the best product we can. We will study articles,scienti)c journals, watch videos and animations on this topic. "he

complete project will be analy&ed using data available on internet

and in scienti)c papers. !ome other books will also be used to

make references.

(.-!cope(n order to understand the project one must know about its

establishment, working and method of working. We made our

best e$orts in this regard and studied the project from its base.

"he things that interested us were majorly di$erent mechanisms

used to perform reciprocating motion and its wide ranged

applications. "he project will be analy&ed comprehensively and

everything from surface roughness to time of stroke and

mechanism of automating it will be discussed.


7/15

/=

) ,ethodology(n order to understand the problem comprehensively background

study has been done and some of many mechanisms have been

short listed. "hese designs will now be further analy&ed and the

best one will be selected to do the job.

!o far the best design is scotch yoke mechanism but in case of

any problems or design failure other options like -uick return

mechanism, gear trains worm and worm wheel mechanism, slider

crank mechanism will also be analy&ed.

alculations will be done and experiments will be performed in

coming weeks to select and manufacture the best possible

product.

'p till now we have read some research papers and analy&ed

some results of previous experiments performed by other

engineers in the past.


8/15

/=

+ Introduction to design

+.(,echanism and ,achine

(n daily life, we encounter many machines which receive energy

and transform it into useful work. @very machine consists of no. of

parts which moves relative to one another these parts are called

kinematic links or simply links or elements. when these links are

connected together they form pairs. (f the motion of the pair is

completely or successfully constrained >only one type of motion is

allowed1 it is called kinematic pair. Bow if four of more kinematic

pairs are connected in such a way that last link is joined to )rst

link to transmit motion it is called kinematic chain.

+ mechanism is de)ned as a kinematic chain in which one of the

link is )xed. (t may be used to transmit power some kind of

motion or transform motion e.g. engine indicator, type writer etc.

5echanism can be spatial >three plane1 or plane mechanism

>single plane1 no. of planes in which links can move.

+ plane mechanism which consists of four links is called simple

mechanism if the no. of links is greater than four the mechanismis called compound mechanism.

+ mechanism becomes a machine if it is used to transmit power

and work. @xample of use of mechanism as is shown in )gure >/1

below. Figure >a1 is an inversion of slider crank mechanism that is

used in engine to transmit power as shown n )gure >b1

Fig. b) piston and crank Fig. a) inversion of slider

crank


9/15

/=

+.)'egrees of reedom and /rubler0s 1riterion of#lane ,echanism

(n design of mechanisms degrees of freedom is a very important

concept. (n mechanics; degrees of freedom are de)ned as Bo. of

independent motion re-uired to completely de)ned the state of

motion of a body. (n 2 there are three degrees of freedom >one

rotational and two translational1 and in 4 there are six degrees

of freedom, in total, >three rotational and three translational1 for

completely unconstrained motion of bodies.

(n mechanics of machines, OF or mobility or movability of

mechanism is de)ned as Bo. of independent input motion leading

to single useful follower motion. "he degrees of freedom of plane

mechanism is given by Cut&bach criterion.

N =3 (l−1)−2 j−h

e-u./

Where B D no. of OF, A D no. of links, j D no. of lower pairs

>having surface contact1, # D Bo. of higher pairs >having line

contact1.


10/15

/=

For simple plane mechanism with / degree of freedom and no

higher pairs above e-uation becomes

1=3 ( l−1 )−2 j−0

e-u. 2

3 l−2 j−4=0

e-u.4

@-u. 4 is known as :rubler;s criterion for plane mechanisms with

constrained motion. "he simplest possible mechanisms based on

this criterion are slider crank and four bar linkage mechanisms.

+.+!uitable #roject 'esign ,echanisms "o start a detailed discussion on our project we must make clear

to our readers what are we trying to do in this project. First let us

discuss what is reciprocating motion which we are trying to

achieve. +ccording to Wikipedia article available

“Reciprocating motion, also called reciprocation, is a repetitive

up-and-down or back-and-forth linear motion. It is found in a wide

range of mechanisms, including reciprocating engines and

pumps. The two opposite motions that comprise a single

reciprocation ccle are called strokes!.

+ccording to Oxford dictionary

“"#f a part of a machine move backwards and forwards in astraight line.! Aike a reciprocating blade.

"o achieve this motion there are many di$erent mechanism

invented by di$erent scientists with the passage of time the oneswhich are under our discussion are discussed below

+.+.( ack and pinion(t is an assembly pair of two gears one is circular and other is *at

bar with teeth.


11/15

/=

"he circular gear rotates over the *at bar and this causes the

reciprocating motion. "he rack and pinion arrangement is

commonly found in the steering mechanism of cars or other

wheeled, steered vehicles.

+.+.) !cotch "oke "he !cotch ?oke is a mechanism for converting the linear motion

of a slider into rotational motion or viceEversa. "he piston or other

reciprocating part is directly coupled to a sliding yoke with a slot

that engages a pin on the rotating part.

+.+.+ !cotch "oke with dwell at one end(t is a modi)ed form of scotch yoke mechanism. (n this

mechanism the reciprocating part is made to stop for a brief


12/15

/=

period of time at the end of the stroke due to a dwell in scotch as

shown in )gure below.

+.+.- !cotch yoke with dwell at both ends

(t is a further modi)ed form of simple scotch yoke. (n this

mechanism there is dwell at both ends of the scotch and due to

this the reciprocating part stays for a short while at both ends the

mechanism is shown in )gure below


13/15

/=

+.+.2 #neumatic arm(t is a hydraulic arm which does the reciprocating motion due to

the *uid present in it there is simple piston cylinder arrangement

to do the job.

+.+.3 $uick return mechanism "his is also a suitable mechanism to perform reciprocation motion

but has its own limitations

+.+.4 %orm and worm wheel(n this mechanism there is a cylindrical gear known as worm. (t

has tapered threads on it. (t rolls over a circular gear to produce

reciprocating motion. "he assembly is shown in )gure below


14/15

/=

:ears assembly following gear assembly can also be used to

perform the reciprocating motion

+.-!elected design+fter considering our need and analy&ing above given designs we

conclude that the mechanism most suitable for our design is

scotch yoke with dwells at both ends.


15/15

/=

Bow let us tell you some of the advantages and disadvantages of

the mechanism

+.-.( Adantages

#igh tor-ue output with a small cylinder si&e. Fewer moving parts. !moother operation. #igher percentage of the time spent at top dead center

>dwell1 improving engine eciency. (n an engine application, elimination of joint typically served

by a wrist pin, and near elimination of piston skirt and

cylinder scung, as side loading of piston due to sine of

connecting rod angle is eliminated.

Bow some of the draw backs are

+.-.) 'raw backs

%apid wear of the slot in the yoke caused by sliding friction

and high contact pressures. Aesser percentage of the time spent at bottom dead center

reducing blowdown time for two stroke engines.

- Time plan for project

"asks Wee

k /

Week

2

Week

4

Week

6

Week

0

Week

7Aiterature

reviewesign

analysisFabrication

+utomation "esting of

designPresentation

Documents

Fm Project Report Initial