ME- 212 F KINEMATICS OF MACHINES LAB LTP - - 2 Sessional : 25 Marks Practical : 25 Marks Total : 50 Marks Duration of Exam : 3 Hrs. List of Experiments : 1. To study various types of Kinematic links, pairs, chains and Mechanisms. 2. To study inversions of 4 Bar Mechanisms, Single and double slider crank mechanisms. 3. To plot slider displacement, velocity and acceleration against crank rotation for single slider crank mechanism. 4. To find coefficient of friction between belt and pulley. 5. To study various type of cam and follower arrangements. 6. To plot follower displacement vs cam rotation for various Cam Follower systems. 7. To generate spur gear involute tooth profile using simulated gear shaping process. 8. To study various types of gears – Helical , cross helical worm, bevel gear. 9. To study various types of gear trains – simple, compound, reverted, epicyclic and differential. 10. To find co-efficient of friction between belt and pulley. 11. To study the working of Screw Jack and determine its efficiency. 12. Create various types of linkage mechanism in CAD and simulate for motion outputs and study the relevant effects. 13. Creation of various joints like revolute, planes, spherical, cam follower and study the degree of freedom and motion patterns available. 14. To design a cam profile by using the requirement graph using on-line engineering handbook and verify the same using a 3D mechanism on CAD. Note : 1. At least Ten experiments are to be performed in the Semester. 2. At least eight experiments should be performed from the above list. However these experiments should include experiments at Sr. No. 12, 13 and 14. Remaining two experiments may either be performed from the above list or as designed & set by the concerned institution as per the scope of the syllabus.
EXPERIMENT No. 1 AIM: - To study various types of kinematics links, pairs, chains & Mechanisms. APPARATUS USED: - Kinematics links, pairs, chains & Mechanisms. ( Kinematic Pair Board) THEORY: What is Kinematics? Kinematics is the study of motion (position, velocity, acceleration). What is Kinetics? Kinetics is the study of effect of forces on moving bodies. Kinematic Link: A link is defined as a member or a combination of members of a mechanism connecting other members and having relative motion between them. The link may consist of one or more resistant bodies. A link may be called as kinematic link or element. Eg: Reciprocating steam engine. Classification of kinematic link is binary, ternary and quaternary Joint: A connection between two links that allows motion between the links. The motion allowed may be rotational (revolute joint), translational (sliding or prismatic joint), or a combination of the two (roll-slide joint). Kinematic pair: Kinematic pair is a joint of two links having relative motion between them. The types of kinematic pair are classified according to • Nature of contact ( lower pair, Higher pair) • Nature of mechanical contact ( Closed pair, unclosed pair) • Nature of relative motion ( Sliding pair, turning pair, rolling pair, screw pair, spherical pair) Kinematic chain:
When the kinematic pairs are coupled in such a way that the last link is joined to the first link to transmit definite motion it is called a kinematic chain. Eg: The crank shaft of an engine forms a kinematic pair with the bearings which are fixed in a pair, the connecting rod with the crank forms a second kinematic pair, the piston with the connecting rod forms a third pair and the piston with the cylinder forms the fourth pair. The total combination of these links is a kinematic chain. Eg: Lawn mover Here, we had to check whether the given link is a kinematic chain We can use two formulas 1. l = 2p-4 2. j= (3/2)l – 2 Mechanism: If motion of any of the movable links results in definite motions of the others the linkage is known as mechanism Machine: When a mechanism is required to transmit power or to do some particular type of work it then becomes a machine. Degrees of Freedom: It is defined as the number of input parameters which must be independently controlled in order to bring the mechanism in to useful engineering purposes. It is also defined as the number of independent relative motions, both translational and rotational, a pair can have. Degrees of freedom = 6 – no. of restraints. To find the number of degrees of freedom for a plane mechanism we have Grubler’s equation F = 3 (n – 1) – 2 j1 – j2 F = Mobility or number of degrees of freedom n = Number of links including frame j1 = Joints with single (one) degree of freedom J2 = Joints with two degrees of freedom F > 0, results in a mechanism with ‘F’ degrees of freedom F = 0, results in a statically determinate structure F < 0, results in a statically indeterminate structure. CONCLUSION: Hence the study of various types of kinematics links, pairs, chains & Mechanisms is completed.
EXPERIMENT No. 2 AIM: - To study inversions of 4 Bar Mechanisms, Single & double slider crank mechanisms. APPARATUS USED: - Single slider crank mechanism & double slider crank mechanism. THEORY: FOUR BAR MECHANISM: - A four bar link mechanism or linkage is the most fundamental of the plane kinematics linkages. Basically it consists of four rigid links which are connected in the form of a quadrilateral by four pin joints. ➢ ➢ ➢ ➢ INVERSIONS OF SINGLE SLIDER–CRANK CHAIN :Different mechanisms obtained by fixing different links of a kinematics chain are known as its inversions. A slider – crank chain has the following inversions :First inversion (i.e; Reciprocating engine and compressor) Second inversion (i.e., Whitworth quick return mechanism and Rotary engine) Third inversion (i.e., Oscillating cylinder engine and crank & slotted – lever mechanism) Fourth inversion (Hand pump) INVERSIONS OF DOUBLE-SLIDER CRANK-CHAIN: A four-bar chain having two turning and two sliding pairs such that two pairs of the same kind are adjacent is known as a double-slider-crank chain. The following are its inversions: ➢ First inversion (i.e., Elliptical trammel) ➢ Second inversion (i.e., Scotch yoke) ➢ Third inversion (i.e., Actual Oldham’s coupling) PROCEDURE: Reciprocating engine mechanism: In the first inversion, the link 1 i.e., the cylinder and the frame is kept fixed. The fig below shows a reciprocating engine.