Distinguished Figures in Mechanism and Machine Science: Their
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KOM DIGITAL NOTES.Pdf
DIGITAL NOTES Kinematics of Machinery R18A0307 B.Tech –II – I DEPARTMENT OF MECHANICAL ENGINEERING MALLA REDDY COLLEGE OF ENGINEERING & TECHNOLOGY (An Autonomous Institution – UGC, Govt.of India) Recognizes under 2(f) and 12(B) of UGC ACT 1956 (Affiliated to JNTUH, Hyderabad, Approved by AICTE –Accredited by NBA & NAAC-“A” Grade-ISO 9001:2015 Certified) MALLA REDDY COLLEGE OF ENGINEERING & TECHNOLOGY Department Of Mechanical Engineering,MRCET. COURSE OBJECTIVES: Understand the fundamentals of the theory of kinematics and dynamics of machines. Understand techniques for studying motion of machines and their components. Use computer software packages in modern design of machines. UNIT – I Mechanisms : Elements or Links , Classification, Rigid Link, flexible and fluid link, Types of kinematic pairs , sliding, turning, rolling, screw and spherical pairs lower and higher pairs, closed and open pairs, constrained motion, completely, partially or successfully constrained and incompletely constrained . Machines : Mechanism and machines, classification of machines, kinematic chain , inversion of mechanism, inversion of mechanism , inversions of quadric cycle, chain , single and double slider crank chains. UNIT – II Straight Line Motion Mechanisms: Exact and approximate copiers and generated types Peaucellier, Hart and Scott Russul Grasshopper Watt T. Chebicheff and Robert Mechanisms and straight line motion, Pantograph. Steering Mechanisms: Conditions for correct steering Davis Steering gear, Ackermans steering gear velocity ratio. Hooke’s Joint: Single and double Hookes joint Universial coupling application problems. UNIT – III Kinematics: Velocity and acceleration - Motion of link in machine - Determination of Velocity and acceleration diagrams - Graphical method - Application of relative velocity method four bar chain. Analysis of Mechanisms: Analysis of slider crank chain for displacement, velocity and acceleration of slider - Acceleration diagram for a given mechanism, Kleins construction, Coriolis acceleration, determination of Coriolis component of acceleration. -
Design, Fabrication and Analysis of Four Bar Walking Machine Based on Chebyshev’S Parallel Motion Mechanism
European International Journal of Science and Technology Vol. 3 No. 8 October, 2014 Design, Fabrication and Analysis of Four Bar Walking Machine Based on Chebyshev’s Parallel Motion Mechanism K. Manickavelan, Balkeshwar Singh*, N. Sellappan Mechanical & Industrial Engineering Section Salalah College of Technology, Salalah, Sultanate of Oman *Corresponding Email: [email protected] Abstract A mechanism is the heart of a machine. Machines are mechanical devices used to accomplish work. Since ancient time, mechanisms and machines have been used to reduce human effort. They have entered and impacted almost all aspects of human society since the industrial revolution. It is the mechanical portion of machine that has the function of transferring motion and forces from a power source to an output. This research paper involves the design, synthesis and fabrication of a four bar link kinematic walking machine. These kinematic walking machines have four-legged that can walk on any surface. It is an arrangement of six linkages that are powered together by a single motor. The rotation is transferred by chain drive to the links. This device is analogous to a four-legged such as an animal. The motor can either be powered by mains or a battery. The kinematic walking machine comprises four legs that move simultaneously to provide motion. Each of these four linkages are made of a four bar mechanism. This mechanism is based on the Chebyshev’s parallel motion. The Chebyshev linkage is a mechanical linkage that converts rotational motion to approximate motion. His equation defines the dimensions and relations of the links. Four driving links have 90° angular difference. -
Straight Line Linkages
Straight line linkages Straight line linkages Generation of straight line motion using linkage mechanisms has always been a common requirement in machine design practice. Although exact straight line cannot be generated using simple mechanisms though some simple mechanisms are designed such that they can produce approximate straight lines for short range of motion. These approximate straight line mechanisms has important applications in machine design (robotics etc.). Perfect straight lines can also be generated using linkage mechanisms but those are relatively complex mechanisms. There are two classes of straight line mechanisms • Approximate straight line linkages • Exact straight line linkages – Watt's linkage – Scott Russell linkage – Hoekens linkage – Peaucellier–Lipkin linkage – Chebyshev linkage – Sarrus linkage – Roberts Mechanism – Hart's A-frame – Grasshopper mechanism – Hart's invensor – Evans mechanism – Quadruplanar-Inversor Straight line linkages Watt's linkage Roberts mechanisms Peaucellier–Lipkin linkage Chebyshev linkage Source: lecture Massachusetts Institute of Technology (2010) Straight line linkages Approximate straight line linkages – Watt's linkage – Hoekens linkage – Chebyshev linkage – Roberts Mechanism – Grasshopper mechanism – Evans mechanism Straight line linkages Watt's linkage / Watt's Parallel Motion Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt in which the central moving point of the linkage is constrained to travel on an approximation to a straight line. It was described in Watt's patent specification of 1784 for the Watt steam engine. It is also used in automobile suspensions, allowing the axle of a vehicle to travel vertically while preventing sideways motion. Hand-drawn diagram by James Watt (1808) in a letter to his son, describing how he arrived at the design. -
1. Basics and Kinematics of Mechanism 2. Cam and Follower 3
Machines and mechanisms Contents: 1. Basics and Kinematics of Mechanism 2. Cam and Follower 3. Governor 4. Gear and Gear Train 5. Inertia Force Analysis Basics and Kinematics Mechanism: 1. A rigid body possesses _____ degrees of freedom. a. One b. Two c. Four d. Six 2. Which of the following is an open pair? a. Journal bearing b. Ball and Socket joint c. Leave screw and nut d. None of the above 3. Which of the following is a higher pair? a. Turning pair b. Screw pair c. Belt and pulley d. None of the above 4. A higher pair has__________. a. Point contact b. Surface contact c. No contact d. None of the above 5. In a ball bearing, ball and bearing forms a a. Turning pair b. Rolling pair c. Screw pair d. Spherical pair 6 . Which of the following is an inversion of Single slider crank chain? a. Beam engine b. Rotary engine c. Oldham’s coupling d. Elliptical trammel 7. ________ is an inversion of Double slider crank chain. a. Coupling rod of a locomotive b. Scotch yoke mechanism c. Hand pump d. Reciprocating engine 8. A ball and a socket forms a a. Turning pair b. Rolling pair c. Screw pair d. Spherical pair 9. The Kutzbach criterion for determining the number of degrees of freedom (n) is (where l = number of links, j = number of joints and h = number of higher pairs) a. n = 3(L-1)-2j-h b. n = 2(l-1)-2j-h c. n = 3(l-1)-3j-h d. -
A Bulleted/Pictorial History of Mechanisms and Machines
A Bulleted/Pictorial History of Mechanisms and Machines Dr. Robert L. Williams II, Professor Mechanical Engineering, Ohio University © 2021 Dr. Bob Productions [email protected] www.ohio.edu/mechanical-faculty/williams South-Pointing Chariot, 240 CE China i0.wp.com/cdn.makezine.com/uploads/2013/02/10319906.jpg Hieropolis Sawmill, Third Century CE (Asia Minor, First Slider-Crank Mechanism) en.wikipedia.org/wiki/Hierapolis_sawmill 2 Mechanisms and Machines History, Dr. Bob Table of Contents PROLOGUE .............................................................................................................................................. 3 1. MACHINES AND MECHANISMS ................................................................................................... 4 2. CONCEPTS RELATED TO MACHINES AND MECHANISMS ................................................. 8 3. IMPORTANT DEVELOPERS OF MECHANISM SCIENCE AND ENGINEERING ............. 10 4. LINKAGES, GEARS, AND CAM-FOLLOWER MECHANISMS ............................................. 14 5. SOME SPECIFIC MACHINE AND MECHANISM INVENTIONS IN HISTORY .................. 25 6. IMPORTANT PERSONS IN THE HISTORY OF MECHANISMS ........................................... 38 7. DEFINITIONS ................................................................................................................................... 44 REFERENCES ........................................................................................................................................ 46 © 2021 Dr. Bob Productions 3 -
Copyrighted Material
CH01 06/29/2015 15:7:34 Page 1 1 Introductory Concepts 1.1 Introduction to Machines 1.1.1 Brief History of Machines In our modern world, we are surrounded by machines, and they have become an integral part of our daily lives. We know that high-tech machines of today were not always in existence, but it is hard to imagine what it would be like without them because our lives would be drastically different. It is difficult to say when the first machine was developed. Knowledge of very early machines comes from archeology, but this work is difficult. The difficulty is partly due to the fact that it is rare to discover intact machines, but it is more common to discover early machine components. Over time machines developed from very crude to extremely elaborate, and often that development moved in parallel with the development of human culture. In the very early years, machine development was difficult and slow. Sometimes advance- ments in technology were driven by military needs, and other times advancements were required for survival. Primitive man devised simple tools made of wood, stone, or bone that were essential for survival. Machines were developed to produce fire, and simple mechanisms were developed to trap animals for food. Numerous machines from different cultures were also developed to extract water. Archimedes (287–212 BC) developed a method for water extraction using a spiral screw, such as the one illustrated in Figure 1.1. Machines such as levers and inclined planes were used by the Egyptians to build numerous monuments such as the pyramids. -
Approximate Straight Line Linkages – Watt's Linkage – Hoekens Linkage – Chebyshev Linkage – Roberts Mechanism
Mechanism Design Straight line linkages Straight line linkages Generation of straight line motion using linkage mechanisms has always been a common requirement in machine design practice. Although exact straight line cannot be generated using simple mechanisms though some simple mechanisms are designed such that they can produce approximate straight lines for short range of motion. These approximate straight line mechanisms has important applications in machine design. These mechanisms were used extensively in classical machines such as steam engines. Perfect straight lines can also be generated using linkage mechanisms but those are relatively complex mechanisms. Straight line linkages There are two classes of straight line mechanisms • Approximate straight line linkages – Watt's linkage – Hoekens linkage – Chebyshev linkage – Roberts Mechanism • Exact straight line linkages – Sarrus linkage – Peaucellier–Lipkin linkage – Hart's A-frame Straight line linkages Watt's linkage Roberts mechanisms Chebyshev linkage Peaucellier–Lipkin linkage Source: Eugene S. Ferguson: KINEMATICS OF MECHANISMS FROM THE TIME OF WATT (1962) A. B. Kempe, HOW TO DRAW A STRAIGHT LINE (1877) Straight line linkages Watt's linkage Roberts mechanisms Peaucellier–Lipkin linkage Chebyshev linkage Source: lecture Massachusetts Institute of Technology (2010) Straight line linkages Watt's linkage / Watt's Parallel Motion Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt in which the central moving point of the linkage is constrained to travel on an approximation to a straight line. It was described in Watt's patent specification of 1784 for the Watt steam engine. It is also used in automobile suspensions, allowing the axle of a vehicle to travel vertically while preventing sideways motion.