SIMPLE MECHANISMS By Dr Ruby Mishra KIIT Deemed to be University
SYLLABUS:Simple Mechanism CLASSIFICATION OF LINKS AND PAIRS KIEMATIC CHAINS DEGREES OF FREEDOM GRUBLER’S CRITERION FOR PLANE MECHAN'ISM KUTZBACH MODIFICATION ON GRUBLER’S CRITERION FOUR BAR MECHANISM AND ITS INVERSION GRASHOF’S LAW SINGLE SLIDER CRANK CHAIN AND ITS INVERSIONS DOUBLE SLIDER CRANK CHAIN AND ITS INVERSION TEXT BOOK: Theory of Machines: By S S Ratan REFERENCE BOOKS: Theory of Mechanism and Machines: Sharma and Purohit
Mechanisms and Machines Generally it is desired during the construction of a machine to transfer and transform motion available in one form to another form. Some cases of available input motion and desired output motion can be enlisted as below: AVAILABLE INPUT MOTION Continuous Rotation DESIRED OUTPUT MOTION Rectilinear Motion Rectilinear Motion Continuous Rotation Continuous Rotation To-and-fro Oscillation To-and-fro Oscillation Continuous Rotation A mechanism is a combination of a number of bodies assembled in such a way that motion of one causes a constrained and predictable motion to the others. A machine is a mechanism or a combination of mechanisms which apart from transferring and transforming motion and forces, also converts the available mechanical energy into some kind of desired work. If all the points of a mechanism move in parallel planes, then it is defined as a plane mechanism. If all the points do not move in parallel planes then it is called spatial mechanism.
Mechanisms …(Contd..) In a Lathe the input motion is available in the form of uniform rotational motion of the shaft of the driving electric motor. This motion has to be transferred to two different locations, i.e., to the Head stock to provide motion to the job and also to the tool post to provide motion to the cutting tool. RIGID AND RESISTANT BODIES A mechanism consists of a number of individual components which can be said to be “ RIGID” ideally, but practically they can be appropriately called as “RESISTANT BODIES” A body is said to be rigid if under the action of forces, it does not suffer any distortion, i.e., distance between any two points on the body remains constant. A belt behaves as a resistant body under tensile forces in belt drive applications. Similarly a fluid may also behave as a Resistant body under compressive forces during their application in Hydraulic press etc. A body is said to be resistant if it can transmit motion in a specified direction without undergoing much deformation.