THEORY OF MACHINE (KME-603)
B.Tech Semester VI – Theory Examination (2022–23)
THEORY-OF-MACHINE-KME-603
Theory of Machine is a fundamental mechanical engineering subject that deals with the kinematics and dynamics of machines, focusing on how different machine components move, transmit forces, and perform useful work. The subject bridges the gap between pure mechanics and real machine operation by analyzing mechanisms, gears, cams, governors, flywheels, balancing, gyroscopic effects, brakes, and dynamometers. The question paper is structured to test conceptual clarity, derivation ability, graphical understanding, and numerical problem-solving skills. To score well, answers must be written in clear, descriptive, and logically connected paragraphs, supported by neat sketches, derivations, and correct assumptions wherever required.
SECTION A – BASIC DEFINITIONS AND CORE CONCEPTS
Section A focuses on testing the student’s understanding of fundamental concepts and short theoretical explanations that form the base of the entire subject.
The degree of freedom (DOF) of a mechanism should be explained as the number of independent inputs required to completely define the motion of a mechanism. It indicates whether a mechanism will move freely or remain constrained.
The instantaneous centre of rotation should be explained as the point about which one body appears to rotate relative to another body at a given instant. This concept is extremely important in velocity analysis of mechanisms.
When differentiating between a radial follower and an offset follower, the explanation should focus on the follower line of action relative to the cam center and how offset followers reduce pressure angle and wear.
The law of gearing must be clearly stated and explained as the fundamental condition required to maintain a constant velocity ratio between two meshing gears.
D’Alembert’s principle should be explained as a dynamic equilibrium concept where inertia forces are introduced to convert a dynamic problem into a static one.
The difference between the function of a flywheel and a governor should be explained by highlighting that a flywheel controls speed fluctuation within a cycle, whereas a governor controls speed variation due to load changes.
The concept of hunting of governor should be explained as continuous oscillation of the governor sleeve due to excessive sensitivity.
Hammer blow, dynamometer, and hydrodynamic lubrication should be explained in relation to balancing, power measurement, and lubrication regime respectively, emphasizing their practical importance.
SECTION B – MECHANISMS, GEARS, BRAKES, GOVERNORS & KINEMATICS
Section B evaluates the student’s ability to derive expressions, explain working principles, and solve numerical problems.
The inversions of mechanism must be explained by describing how different mechanisms are obtained by fixing different links of the same kinematic chain. In particular, inversions of the four-bar chain such as crank-rocker and double-crank mechanisms should be explained with examples.
The derivation for the minimum number of teeth to avoid interference must be written step-by-step, explaining the phenomenon of interference in involute gears and how standard proportions help prevent it.
The band and block brake question requires explanation of construction, working principle, and derivation of the relation between tight-side and slack-side tensions, supported by a neat sketch.
Governor numerical problems, especially on the Porter governor, require clear explanation of forces acting on the balls, sleeve movement, effect of friction, and calculation of range of speed, lift, effort, and power.
The derivation of velocity and acceleration of the piston in a reciprocating engine must be explained using kinematic relations, connecting rod geometry, and angular motion of the crank.
SECTION C – NUMERICAL PROBLEMS, CAMS, FLYWHEELS & BALANCING
Section C tests advanced application of theory and numerical problem-solving skills. Answers here must be detailed and methodical.
Velocity analysis problems involving four-bar chains and slider-crank mechanisms require explanation of relative velocity method or analytical approach, clearly stating assumptions and construction steps.
Gear problems involving addendum calculation must explain contact ratio, arc of contact, and involute geometry before proceeding to calculations.
Cam design problems require explanation of follower motion, displacement diagram, base circle, pitch curve, and cam profile construction, especially when offset followers are involved.
Flywheel design problems require understanding of coefficient of fluctuation of energy and speed, turning moment diagrams, and calculation of flywheel mass using radius of gyration.
Governor derivations, such as the height of Watt governor, must be written step-by-step, followed by explanation of inertia governors.
Balancing problems involving multiple masses require explanation of force and couple balancing principles, vector diagrams, and determination of balancing mass.
GYROSCOPIC EFFECTS & DYNAMOMETERS
Gyroscopic problems involving ships and turbines require explanation of gyroscopic couple, angular momentum, and direction of precession, followed by analysis of pitching, rolling, and turning effects.
The hydraulic dynamometer must be explained with its construction, working principle, and advantages in power measurement.
HOW TO WRITE THEORY OF MACHINE ANSWERS IN THE EXAM
In Theory of Machine, never write answers in short bullet points. Always start with a brief introduction of the concept, followed by derivation or explanation, and then numerical application if required. Clearly state assumptions, draw neat diagrams, and explain physical meaning of formulas. Examiners give high weightage to clarity of derivation, logical flow, and conceptual understanding.
