Machine and Mechanisms Introduction to mechanisms and Kinematics 06/06/2022 1
Machine and Mechanisms
Introduction to mechanisms and Kinematics
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KinematicsKinematics
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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Machines and mechanismsMachine
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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Is Engine also a machine
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?
Machines and mechanismsMechanism
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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Wind shield
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.
Loader 4 bar mechanism
Slider crank mechanis
crank & piston
Block feeder
Mechanism terminologyLinkageFrameLinks– rigid bodyJointPrimary joint (full
joint)Revolute joint (pin or
hinge joint)– pure rotation
Sliding joint (piston or prism joint)– linear sliding
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Mechanism terminology cont
Higher-order joint (half joint)Allow rotation and
slidingCam jointGear connection
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Mechanism terminology cont
Simple linkA rigid body contains
only two jointsCrankRocker
Complex linkA rigid body contains
more than two jointsRocker armBellcrank
Point of interestActuator
A power source link
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Kinematic diagrams
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