kom unit 1 ppt
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April 11, 2023 1Kinematics of Machinery - Unit - I
KINEMATICS OF KINEMATICS OF MECHINERYMECHINERY
April 11, 2023 2Kinematics of Machinery - Unit - I
KINEMATICS OF MECHINERYKINEMATICS OF MECHINERY
Unit – I-Basics of MechanismUnit – I-Basics of MechanismUnit – II – KinematicsUnit – II – KinematicsUnit – III – CamsUnit – III – CamsUnit – IV – GearsUnit – IV – GearsUnit – V - FrictionUnit – V - Friction
April 11, 2023 3Kinematics of Machinery - Unit - I
Unit – I-Basics of MechanismUnit – I-Basics of Mechanism
1.Terminologies1.TerminologiesMachineMachineMechanismMechanismKinematic PairKinematic PairLinksLinksKinematic ChainKinematic Chain
2.DOF2.DOFKutzhback Kutzhback EquationEquationGrubler EquationGrubler Equation
3.Grashoff Law3.Grashoff Law4.Mechanism4.Mechanism
Four BarFour BarSingle-Slider CrankSingle-Slider CrankDouble-SliderDouble-Slider
5.Inversion of 5.Inversion of MechanismMechanism
6.Mechanical 6.Mechanical AdvantageAdvantage
7.Transmission Angle7.Transmission Angle8.Design of Mechanism8.Design of Mechanism
April 11, 2023 4Kinematics of Machinery - Unit - I
MECHANISMMECHANISM
Mechanism – Part of a machine, which Mechanism – Part of a machine, which transmit motion and power from input point to transmit motion and power from input point to output pointoutput point
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April 11, 2023 6Kinematics of Machinery - Unit - I
Example for MechanismExample for Mechanism
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Example for MechanismExample for Mechanism
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PLANAR MECHANISMSPLANAR MECHANISMS
When all the links of a mechanism have plane When all the links of a mechanism have plane motion, it is called as a planar mechanism. All motion, it is called as a planar mechanism. All the links in a planar mechanism move in the links in a planar mechanism move in planes parallel to the reference plane.planes parallel to the reference plane.
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MACHINEMACHINE
A machine is a mechanism or collection of A machine is a mechanism or collection of mechanisms, which transmit force from the mechanisms, which transmit force from the source of power to the resistance to be source of power to the resistance to be overcome. overcome.
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Though all machines are mechanisms, all Though all machines are mechanisms, all mechanisms are not machinesmechanisms are not machines
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KINEMATICSKINEMATICS
April 11, 2023 12Kinematics of Machinery - Unit - I
RELEVANCE OF KINEMATIC RELEVANCE OF KINEMATIC STUDYSTUDY
Motion requirementsMotion requirements Design requirementsDesign requirements
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MOTIONMOTION STUDYSTUDY
Study of position, displacement, velocity and Study of position, displacement, velocity and acceleration of different elements of acceleration of different elements of mechanismmechanism
Given input Desired output Given input Desired output
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Motion requirementMotion requirement
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DESIGN REQUIREMENTSDESIGN REQUIREMENTS
Design: determination of shape and sizeDesign: determination of shape and size
1.1. Requires knowledge of materialRequires knowledge of material
2.2. Requires knowledge of stressRequires knowledge of stress
Requires knowledge of load actingRequires knowledge of load acting
(i) static load(i) static load
(ii) dynamic/inertia load(ii) dynamic/inertia load
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DYNAMIC/INERTIA LOADDYNAMIC/INERTIA LOAD
Inertia load require accelerationInertia load require acceleration
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LINK OR ELEMENTLINK OR ELEMENT
Any body (normally rigid) which has motion Any body (normally rigid) which has motion relative to anotherrelative to another
Binary linkBinary link Ternary linkTernary link Quaternary linkQuaternary link
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Examples of rigid linksExamples of rigid links
April 11, 2023 22Kinematics of Machinery - Unit - I
PAIRING ELEMENTSPAIRING ELEMENTS
Pairing elements: Pairing elements: the geometrical forms by which two the geometrical forms by which two members of a mechanism are joined together, so that the members of a mechanism are joined together, so that the
relative motion between these two is consistentrelative motion between these two is consistent. . Such a pair of Such a pair of links is called links is called Kinematic PairKinematic Pair..
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PAIRING ELEMENTSPAIRING ELEMENTS
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PAIRING ELEMENTSPAIRING ELEMENTS
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KINEMATIC PAIRSKINEMATIC PAIRS
A mechanism has been defined as a combination so A mechanism has been defined as a combination so connected that each moves with respect to each other. connected that each moves with respect to each other. A clue to the behavior lies in in the nature of A clue to the behavior lies in in the nature of connections, known as kinetic pairs.connections, known as kinetic pairs.The degree of freedom of a kinetic pair is given by The degree of freedom of a kinetic pair is given by the number independent coordinates required to the number independent coordinates required to completely specify the relative movement.completely specify the relative movement.
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TYPES OF KINEMATIC PAIRSTYPES OF KINEMATIC PAIRS
Based on nature of contact Based on nature of contact between elementsbetween elements
(i) (i) Lower pairLower pair : The joint : The joint by which two members are by which two members are connected has surface connected has surface contact. A pair is said to be a contact. A pair is said to be a lower pair when the lower pair when the connection between two connection between two elements are through the elements are through the area of contact. Its 6 types area of contact. Its 6 types are are
Revolute(Or)TurningPairRevolute(Or)TurningPair
Prismatic(Or)SlidingPairPrismatic(Or)SlidingPair
Screw(Or)HelicalPairScrew(Or)HelicalPair
CylindricalPairCylindricalPair
Spherical(Or)GlobularPairSpherical(Or)GlobularPair
Flat(or)PlanarPairFlat(or)PlanarPair
April 11, 2023 30Kinematics of Machinery - Unit - I
(ii) Higher pair:(ii) Higher pair: The contact between the The contact between the
pairing elements takes place at a point or along pairing elements takes place at a point or along a line. a line.
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Based on relative motion between pairing elementsBased on relative motion between pairing elements
(a) Siding pair [DOF = 1](a) Siding pair [DOF = 1]
(b) Turning pair (revolute pair)(b) Turning pair (revolute pair)
[DOF = 1][DOF = 1]
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Based on relative motion between pairing Based on relative motion between pairing elementselements
(c) Cylindrical pair(c) Cylindrical pair [DOF = 2][DOF = 2]
(d) Rolling pair(d) Rolling pair
[DOF = 1][DOF = 1]
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Based on relative motion between pairing Based on relative motion between pairing elementselements
(e) Spherical pair [DOF = 3](e) Spherical pair [DOF = 3]
(f) Helical pair or screw pair [DOF = 1](f) Helical pair or screw pair [DOF = 1]
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Based on the nature of mechanical constraintBased on the nature of mechanical constraint
(a) Closed pair(a) Closed pair
(b) Unclosed or force closed pair(b) Unclosed or force closed pair
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CONSTRAINED MOTIONCONSTRAINED MOTION
one element has got only one definite motion one element has got only one definite motion relative to the other relative to the other
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(a) Completely constrained motion(a) Completely constrained motion
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(b) Successfully constrained motion(b) Successfully constrained motion
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(c) Incompletely constrained motion(c) Incompletely constrained motion
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KINEMATIC CHAINKINEMATIC CHAIN
Group of links either joined together or Group of links either joined together or arranged in a manner that permits them to arranged in a manner that permits them to move relative to one another. move relative to one another.
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Kinematic ChainKinematic Chain
Relation between Links, Pairs and JointsRelation between Links, Pairs and JointsL=2P-4L=2P-4J=(3/2) L – 2J=(3/2) L – 2L => No of LinksL => No of LinksP => No of PairsP => No of PairsJ => No of JointsJ => No of JointsL.H.S > R.H.S => Locked chainL.H.S > R.H.S => Locked chainL.H.S = R.H.S => Constrained Kinematic ChainL.H.S = R.H.S => Constrained Kinematic ChainL.H.S < R.H.S => Unconstrained Kinematic L.H.S < R.H.S => Unconstrained Kinematic
ChainChain
April 11, 2023 41Kinematics of Machinery - Unit - I
LOCKED CHAIN (Or) LOCKED CHAIN (Or) STRUCTURESTRUCTURE
Links connected in such a way that no relative Links connected in such a way that no relative motion is possible. motion is possible.
L=3, J=3, P=3L=3, J=3, P=3 L.H.S>R.H.SL.H.S>R.H.S
April 11, 2023 42Kinematics of Machinery - Unit - I
Kinematic Chain MechanismKinematic Chain Mechanism
Slider crank and four bar mechanismsSlider crank and four bar mechanisms
L=4, J=4, P=4L=4, J=4, P=4
L.H.S=R.H.SL.H.S=R.H.S
April 11, 2023 43Kinematics of Machinery - Unit - I
Working of slider crank Working of slider crank mechanismmechanism
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Unconstrained kinematic Unconstrained kinematic chainchain
L=5,P=5,J=5 L=5,P=5,J=5
L.H.S < R.H.S L.H.S < R.H.S
April 11, 2023 45Kinematics of Machinery - Unit - I
DEGREES OF FREEDOM DEGREES OF FREEDOM (DOF):(DOF):
It is the number of independent coordinates required to It is the number of independent coordinates required to
describe the position of a body.describe the position of a body.
April 11, 2023 46Kinematics of Machinery - Unit - I
Degrees of freedom/mobility of Degrees of freedom/mobility of a mechanisma mechanism
It is the number of inputs (number of It is the number of inputs (number of independent coordinates) required to describe independent coordinates) required to describe the configuration or position of all the links of the configuration or position of all the links of the mechanism, with respect to the fixed link the mechanism, with respect to the fixed link at any given instant. at any given instant.
April 11, 2023 47Kinematics of Machinery - Unit - I
GRUBLER’S CRITERIONGRUBLER’S CRITERION Number of degrees of freedom of a mechanism is given by Number of degrees of freedom of a mechanism is given by
F = 3(n-1)-2l-h. Where,F = 3(n-1)-2l-h. Where, F = Degrees of freedomF = Degrees of freedom n = Number of links in the mechanism.n = Number of links in the mechanism. l = Number of lower pairs, which is obtained by counting the l = Number of lower pairs, which is obtained by counting the
number of joints. If more than two links are joined together at any number of joints. If more than two links are joined together at any point, then, one additional lower pair is to be considered for every point, then, one additional lower pair is to be considered for every additional link.additional link.
h = Number of higher pairsh = Number of higher pairs
April 11, 2023 48Kinematics of Machinery - Unit - I
Examples - DOFExamples - DOF
F = 3(n-1)-2l-hF = 3(n-1)-2l-h Here, n = 4, l = 4 & h = 0.Here, n = 4, l = 4 & h = 0. F = 3(4-1)-2(4) = 1F = 3(4-1)-2(4) = 1 I.e., one input to any one link I.e., one input to any one link
will result in definite motion will result in definite motion of all the links.of all the links.
April 11, 2023 49Kinematics of Machinery - Unit - I
Examples - DOFExamples - DOF F = 3(n-1)-2l-hF = 3(n-1)-2l-h Here, n = 5, l = 5 and h = 0.Here, n = 5, l = 5 and h = 0. F = 3(5-1)-2(5) = 2F = 3(5-1)-2(5) = 2 I.e., two inputs to any two links are I.e., two inputs to any two links are
required to yield definite motions in required to yield definite motions in all the links.all the links.
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Examples - DOFExamples - DOF
F = 3(n-1)-2l-hF = 3(n-1)-2l-h Here, n = 6, l = 7 and h = 0.Here, n = 6, l = 7 and h = 0. F = 3(6-1)-2(7) = 1F = 3(6-1)-2(7) = 1 I.e., one input to any one link will result in I.e., one input to any one link will result in
definite motion of all the links. definite motion of all the links.
April 11, 2023 51Kinematics of Machinery - Unit - I
Examples - DOFExamples - DOF
F = 3(n-1)-2l-hF = 3(n-1)-2l-h Here, n = 6, l = 7 (at the intersection of Here, n = 6, l = 7 (at the intersection of
2, 3 and 4, two lower pairs are to be 2, 3 and 4, two lower pairs are to be considered) and h = 0.considered) and h = 0.
F = 3(6-1)-2(7) = 1F = 3(6-1)-2(7) = 1
April 11, 2023 52Kinematics of Machinery - Unit - I
Examples - DOFExamples - DOF
F = 3(n-1)-2l-hF = 3(n-1)-2l-h Here, n = 11, l = 15 (two lower Here, n = 11, l = 15 (two lower
pairs at the intersection of pairs at the intersection of 3, 4, 3, 4, 66; ; 2, 4, 52, 4, 5; ; 5, 7, 85, 7, 8; ; 8, 10, 118, 10, 11) and ) and h = 0.h = 0.
F = 3(11-1)-2(15) = 0 F = 3(11-1)-2(15) = 0
April 11, 2023 53Kinematics of Machinery - Unit - I
Examples - DOFExamples - DOF
(a)(a)F = 3(n-1)-2l-hF = 3(n-1)-2l-hHere, n = 4, l = 5 and h = 0.Here, n = 4, l = 5 and h = 0.F = 3(4-1)-2(5) = -1F = 3(4-1)-2(5) = -1I.e., it is a structureI.e., it is a structure
(b)(b)F = 3(n-1)-2l-hF = 3(n-1)-2l-hHere, n = 3, l = 2 and h = 1.Here, n = 3, l = 2 and h = 1.F = 3(3-1)-2(2)-1 = 1F = 3(3-1)-2(2)-1 = 1
(c)(c)F = 3(n-1)-2l-hF = 3(n-1)-2l-hHere, n = 3, l = 2 and h = 1.Here, n = 3, l = 2 and h = 1.F = 3(3-1)-2(2)-1 = 1F = 3(3-1)-2(2)-1 = 1
April 11, 2023 54Kinematics of Machinery - Unit - I
Determining DOF and PairsDetermining DOF and Pairs
NNbb=No of Binary =No of Binary LinksLinks
NNtt=No of Ternary =No of Ternary LinksLinks
NNoo=No of Other =No of Other LinksLinks
N=Total No of N=Total No of LinksLinks
L=No of LoopsL=No of Loops
P=No of PairsP=No of Pairs M=Mobility or M=Mobility or
DOFDOF
P=N+L-1P=N+L-1
M=N-(2L+1)M=N-(2L+1)
April 11, 2023 55Kinematics of Machinery - Unit - I
Determining DOF and PairsDetermining DOF and Pairs
P=N+L-1P=N+L-1
M=N-(2L+1)M=N-(2L+1)
NNbb = 4,N = 4,Ntt=2, N=2, N00=0=0
N=6, L=2N=6, L=2
Sol:Sol:
P=6+2-1=7P=6+2-1=7
M=6-(2x2 +1)=1M=6-(2x2 +1)=1
April 11, 2023 56Kinematics of Machinery - Unit - I
Determining DOF and PairsDetermining DOF and Pairs
P=N+L-1P=N+L-1
M=N-(2L+1)M=N-(2L+1)
NNbb = 5,N = 5,Ntt=1, N=1, N00=0=0
N=6, L=2N=6, L=2
Sol:Sol:
P=6+2-1=7P=6+2-1=7
M=6-(2x2 +1)=1M=6-(2x2 +1)=1
April 11, 2023 57Kinematics of Machinery - Unit - I
Determining DOF and PairsDetermining DOF and Pairs
P=N+L-1P=N+L-1
M=N-(2L+1)M=N-(2L+1)
NNbb = 9,N = 9,Ntt=0, N=0, N00 =2=2
N=11, L=5N=11, L=5
Sol:Sol:
P=11+5-1=15P=11+5-1=15
M=11-(2x5 +1)=0M=11-(2x5 +1)=0
April 11, 2023 58Kinematics of Machinery - Unit - I
Grashoff LawGrashoff Law
The sum of the The sum of the shortest and shortest and longest link length longest link length should not exceed should not exceed the sum of the the sum of the other two link other two link lengths.lengths.
s+l < p+qs+l < p+q
(e.x) (1+2) < (3+4)(e.x) (1+2) < (3+4)
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INVERSIONS OF INVERSIONS OF MECHANISMMECHANISM
A mechanism is one in which one of the links of a kinematic A mechanism is one in which one of the links of a kinematic chain is fixed. Different mechanisms can be obtained by fixing chain is fixed. Different mechanisms can be obtained by fixing different links of the same kinematic chain. These are called as different links of the same kinematic chain. These are called as inversions of the mechanism. inversions of the mechanism.
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INVERSIONS OF MECHANISMINVERSIONS OF MECHANISM
1.Four Bar Chain1.Four Bar Chain
2.Single Slider Crank2.Single Slider Crank
3.Double Slider Crank3.Double Slider Crank
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1. FOUR BAR CHAIN1. FOUR BAR CHAIN
(link 1) frame(link 1) frame (link 2) crank(link 2) crank (link 3) coupler (link 3) coupler (link 4) rocker (link 4) rocker
April 11, 2023 65Kinematics of Machinery - Unit - I
INVERSIONS OF FOUR BAR INVERSIONS OF FOUR BAR CHAINCHAIN
Fix link 1& 3. Crank-rocker Fix link 1& 3. Crank-rocker
or Crank-Leveror Crank-Lever
mechanism mechanism
Fix link 2. Drag link Fix link 2. Drag link
or Double Crank or Double Crank
mechanism mechanism
Fix link 4. Double rocker Fix link 4. Double rocker
mechanismmechanism
Pantograph Pantograph
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APPLICATIONAPPLICATIONlink-1 fixed-link-1 fixed-
CRANK-ROCKER CRANK-ROCKER MECHANISMMECHANISM OSCILLATORY OSCILLATORY
MOTIONMOTION
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CRANK-ROCKER CRANK-ROCKER MECHANISMMECHANISM
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Link 2 Fixed- DRAG LINK Link 2 Fixed- DRAG LINK MECHANISMMECHANISM
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Locomotive Wheel - DOUBLE Locomotive Wheel - DOUBLE CRANK MECHANISMCRANK MECHANISM
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2.SLIDER CRANK CHAIN2.SLIDER CRANK CHAINLink1=GroundLink1=GroundLink2=CrankLink2=Crank
Link3=ConnectingRod Link3=ConnectingRod Link4=SliderLink4=Slider
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lnversions of slider crank lnversions of slider crank chainchain
(a)(a) crank fixed (b) connecting rod fixed (c) slider fixedcrank fixed (b) connecting rod fixed (c) slider fixed
Link 2 fixedLink 2 fixed Link 3 fixed Link 3 fixed Link 4 fixed Link 4 fixed
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ApplicationApplicationInversion II – Link 2 Crank Inversion II – Link 2 Crank
fixed fixed Whitworth quick return motion Whitworth quick return motion
mechanismmechanism
2
1
2
2
ˆ
ˆ
BoB
BoB
urnstrokeTimeforret
wardstrokeTimeforfor
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Quick return motion mechanismsQuick return motion mechanisms
Drag link mechanismDrag link mechanism
12
21
ˆ
ˆ
BAB
BAB
urnstrokeTimeforret
wardstrokeTimeforfor
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Rotary engine– II inversion of slider crank Rotary engine– II inversion of slider crank mechanism. (crank fixed)mechanism. (crank fixed)
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ApplicationApplicationInversion III -Link 3 Connecting rod Inversion III -Link 3 Connecting rod
fixed fixed Crank and slotted lever quick return Crank and slotted lever quick return
mechanismmechanism
2
1
2
2
ˆ
ˆ
BoB
BoB
urnstrokeTimeforret
wardstrokeTimeforfor
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Crank and slotted lever quick return Crank and slotted lever quick return motion mechanismmotion mechanism
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Crank and slotted lever quick return Crank and slotted lever quick return motion mechanismmotion mechanism
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Application of Crank and slotted lever Application of Crank and slotted lever quick return motion mechanismquick return motion mechanism
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Oscillating cylinder engine–III inversion of Oscillating cylinder engine–III inversion of slider crank mechanism (connecting rod fixed)slider crank mechanism (connecting rod fixed)
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ApplicationApplicationInversion IV – Link 4 Slider fixed Inversion IV – Link 4 Slider fixed
Pendulum pump or bull enginePendulum pump or bull engine
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3. DOUBLE SLIDER CRANK 3. DOUBLE SLIDER CRANK CHAINCHAIN
It is a kinematic chain consisting of two It is a kinematic chain consisting of two turning pairs and two sliding pairs. turning pairs and two sliding pairs.
Link 1 Frame Link 1 Frame
Link 2 Slider -ILink 2 Slider -I
Link 3 CouplerLink 3 Coupler
Link 4 Slider - IILink 4 Slider - II
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Inversion I – Frame FixedInversion I – Frame FixedDouble slider crank mechanismDouble slider crank mechanism
1sincos 22
22
p
y
q
x
1sincos 22
22
p
y
q
x
Elliptical trammelAC = p and BC = q, then, x = q.cosθ and y = p.sinθ.Rearranging,
April 11, 2023 83Kinematics of Machinery - Unit - I
Inversion II – Slider - I FixedInversion II – Slider - I Fixed SCOTCH –YOKE MECHANISMSCOTCH –YOKE MECHANISM Turning pairs –1&2, 2&3; Sliding pairs – 3&4, Turning pairs –1&2, 2&3; Sliding pairs – 3&4, 4&1 4&1
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Inversion III – Coupler FixedInversion III – Coupler Fixed OLDHAM COUPLINGOLDHAM COUPLING
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Other MechanismsOther Mechanisms1.Straight line motion 1.Straight line motion
mechanismsmechanismsCondition for perfect steeringCondition for perfect steering
Locus of pt.C Locus of pt.C will be a will be a straight line, ┴ to AE if, straight line, ┴ to AE if,
is constant.is constant.
Proof:Proof:
ACAB
..,
.
constACifABconstAE
constbutADAD
ACABAE
AE
AB
AC
AD
ABDAEC
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1.a) Peaucellier mechanism1.a) Peaucellier mechanism
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1.b) Robert’s mechanism1.b) Robert’s mechanism
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1.c) Pantograph1.c) Pantograph
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2.Indexing Mechanism2.Indexing Mechanism
Geneva wheel mechanismGeneva wheel mechanism
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3.Ratchets and Escapements3.Ratchets and Escapements
Ratchet and pawl mechanismRatchet and pawl mechanism
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Application of Ratchet Pawl Application of Ratchet Pawl mechanismmechanism
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4. 4. Toggle mechanismToggle mechanism
Considering the Considering the equilibrium condition of equilibrium condition of slider 6, slider 6,
For small angles of For small angles of αα, F is , F is much smaller than P.much smaller than P.
tan2
2tan
PFP
F
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5.Hooke’s joint5.Hooke’s joint
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Hooke’s jointHooke’s joint
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6.Steering gear mechanism6.Steering gear mechanism
Condition for perfect steeringCondition for perfect steering
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Ackermann steering gear Ackermann steering gear mechanismmechanism
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Mechanical Mechanical AdvantageAdvantage Mechanical Mechanical
Advantage of the Advantage of the Mechanism at Mechanism at angle a2 = 0angle a2 = 000 or or 18018000
Extreme position Extreme position of the linkage is of the linkage is known as toggle known as toggle positions.positions.
April 11, 2023 98Kinematics of Machinery - Unit - I
Transmission Transmission AngleAngleθθ = a1=Crank Angle = a1=Crank Angle
γγ = a2 =Angle between = a2 =Angle between crank and Coupler crank and Coupler
μμ = a3 =Transmission = a3 =Transmission angleangle
Cosine LawCosine Law
aa22 + d + d2 2 -2ad cos -2ad cos θθ = =
bb22 + c + c22 -2 bc cos -2 bc cos μμ
Where a=AD, b=CD,Where a=AD, b=CD,
c=BC, d=ABc=BC, d=AB
Determine Determine μμ..
April 11, 2023 99Kinematics of Machinery - Unit - I
Design of Design of MechanismMechanism 1.Slider – Crank 1.Slider – Crank
MechanismMechanismLink Lengths, Stroke Link Lengths, Stroke Length, Crank Angle Length, Crank Angle specified. specified.
2.Offset Quick Return 2.Offset Quick Return MechanismMechanismLink Lengths, Stroke Link Lengths, Stroke Length, Crank Angle, Length, Crank Angle, Time Ratio specified.Time Ratio specified.
3.Four Bar Mechanism – 3.Four Bar Mechanism – Crank Rocker MechanismCrank Rocker MechanismLink Lengths and Rocker Link Lengths and Rocker angle Specified.angle Specified.
April 11, 2023 100Kinematics of Machinery - Unit - I
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