Theory of Machines

1. Machine and Mechanisms
Introduction to mechanisms and
Kinematics
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2. Kinematics
 Kinematics
 It is the study of motion (relative motion of different links), quite apart
from forces which produce that motion. More particularly, kinematics
is the study of position, displacement, rotation, speed, velocity and
acceleration which arise in the design of mechanical system, or
kinematics of machine.
 Kinematic analysis
 Determine
Position, displacement, rotation, speed, velocity, acceleration
 Provide
 Geometry dimensions of the mechanism
 Operation range

 Dynamic analysis
 Power capacity, stability, member load
 Planar mechanism – motion in 2D space
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3. Machines and mechanisms
 Machine
 Oxford dictionary: an apparatus for applying mechanical power,
consisting of a number of interrelated parts each having a
definite function.
 Devices used to alter, transmit, and direct forces to accomplish a
specific objective

Mechanical advantage is sole object of a machine e.g. lathe, shaper,
planer etc.
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5. Machines and mechanisms
 Mechanism
 Mechanical portion of a machine that
has the function of transferring
motion and forces from a power
source to an output
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6. Wind shield

7. Simple Mechanism
Let's make a simple mechanism with similar behavior. Take
some cardboard and make four strips as shown in.
Take 4 pins and assemble them as shown in fig
Now, hold the 6in. strip so it can't move and turn the 3in.
strip. You will see that the 4in. strip oscillates.

8. Loader 4 bar mechanism

9. Slider crank mechanis

10. crank & piston

11. Block feeder

12. Mechanism terminology
 Linkage
 Frame
 Links– rigid body
 Joint
 Primary joint (full joint)
 Revolute joint (pin or hinge
joint)– pure rotation
 Sliding joint (piston or
prism joint)– linear sliding
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13. Mechanism terminology
cont
 Higher-order joint (half
joint)
 Allow rotation and sliding
 Cam joint
 Gear connection
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14. Mechanism terminology
cont
 Simple link
 A rigid body contains only
two joints
 Crank
 Rocker
 Complex link
 A rigid body contains more
than two joints
 Rocker arm
 Bellcrank
 Point of interest
 Actuator
 A power source link
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15. Kinematic
diagrams
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