The document discusses kinematic concepts related to mechanisms and machines. It defines kinematic links, pairs, chains and their types. It describes mechanisms as kinematic chains with one fixed link and machines as mechanisms that transmit power or do work. The document discusses degrees of freedom of spatial and planar mechanisms using mobility formulas. It also covers Grashof's law for four-bar chains and examples of single slider crank inversions including the beam engine, locomotive coupling rod, and Watt's indicator mechanism.

1. Last Updated on:
Mechanics
Jigar.vaghela@darshan.ac.in
8866110641
Engineering Concepts
23-10-2019
Prof. Jigar J. Vaghela

2. 2Concepts Darshan Institute of Engineering & Technology, Rajkot
Introduction
Mechanics
Static Dynamics
Kinetics Kinematics

3. 3Concepts Darshan Institute of Engineering & Technology, Rajkot
Kinematic Link: Each part of a mechanism, which moves relative to
some other part.
It may consist several parts.
Links
Kinematic
Link
Rigid link
Flexible
link
Fluid link
Resistive link*

4. 4Concepts Darshan Institute of Engineering & Technology, Rajkot
The two links or elements of a machine, when in contact with each
other, are said to form a pair.
Kinematic Pair

5. 5Concepts Darshan Institute of Engineering & Technology, Rajkot
Kinematic
Pair
Lower Pair
Higher pair
Square shaft in
square hole
Cam and Follower

6. 6Concepts Darshan Institute of Engineering & Technology, Rajkot
A kinematic chain may be defined as a combination of kinematic
pairs, joined in such a way that each link forms a part of two pairs
and the relative motion between the links or elements is completely
or successfully constrained.
Kinematic Chain
Types of Joints in Kinematic Chain
Binary joint Ternary Joint Quaternary Joint

7. 7Concepts Darshan Institute of Engineering & Technology, Rajkot
When one of the links of a kinematic chain is fixed, the chain is
known as mechanism.
A mechanism with four links is known as simple mechanism.
A mechanism with more than four links is known as compound
mechanism.
Mechanism

8. 8Concepts Darshan Institute of Engineering & Technology, Rajkot
When a mechanism is transmit power or do some particular type of
work, it then becomes a machine
Machine
Mechanism Machine Structure

9. 9Concepts Darshan Institute of Engineering & Technology, Rajkot
Types of Constrained Motions
Completely Constrained Motion Incompletely Constrained Motion
Successfully Constrained Motion

10. 10Concepts Darshan Institute of Engineering & Technology, Rajkot
Myth: Number of possible motion of any mechanism.
Truth: Number of independent possible motion of any mechanism.
Definition: “It is the number of independent coordinates required to
describe the position of a body.”
Degrees of Freedom (DOF) / Mobility

11. 11Concepts Darshan Institute of Engineering & Technology, Rajkot
Question: How many DOF can be possible for any mechanism.
Myth: There can be only six no. DOF possible.
Truth: Max. DOF for any mechanism can be Infinite but only six type
of DOF is possible.
DOF

12. 12Concepts Darshan Institute of Engineering & Technology, Rajkot
DOF of a spatial Mechanisms
DOF= 6(N-1) - 5P1 - 4P2 - 3P3 - 2P4 - P5
N=Total Number of links in a mechanism.
P1=Number of Pairs having one degree of freedom
P2=Number of Pairs having two degree of freedom and so on
DOF of Planar Mechanism
DOF= 3(N-1) - 2P1 - P2
DOF

13. 13Concepts Darshan Institute of Engineering & Technology, Rajkot
Redundant link is the one, whose presence doesn't make any
difference in the mechanism.
Redundant link
Find DOF

14. 14Concepts Darshan Institute of Engineering & Technology, Rajkot
Grashof law
Four bar chain
Drag Link Crank & Rocker Rocker-Rocker Parallelogram

15. 15Concepts Darshan Institute of Engineering & Technology, Rajkot
Beam engine (crank and lever mechanism)
Inversions of Four Bar Chain

16. 16Concepts Darshan Institute of Engineering & Technology, Rajkot
Coupling rod of a locomotive (Double crank mechanism)
Cont.

17. 17Concepts Darshan Institute of Engineering & Technology, Rajkot
Watt’s indicator mechanism (Double lever mechanism)
It’s also known as straight line mechanism
Cont.

18. 18Concepts Darshan Institute of Engineering & Technology, Rajkot
Inversions of Single Slider Crank Chain

19. 19Concepts Darshan Institute of Engineering & Technology, Rajkot
Pendulum pump or Bull engine
Cont.
Fixing the cylinder or link 4 (i.e. sliding pair).

20. 20Concepts Darshan Institute of Engineering & Technology, Rajkot
Oscillating cylinder engine
Cont.
Connecting rod (link 3) forming the turning
pair is fixed

21. 21Concepts Darshan Institute of Engineering & Technology, Rajkot
Rotary internal combustion engine or Gnome engine
Cont.
Crank (link 2) is fixed

22. 22Concepts Darshan Institute of Engineering & Technology, Rajkot
Crank and slotted lever quick return motion mechanism
Cont.
Link AC (i.e. link 3) forming the turning pair
is fixed.

23. Jigar J. Vaghela
THANK YOU
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Jigar.vaghela@darshan.ac.in