THEORY OF MACHINES-I
Course Objectives
1. Understand the basic concepts of machines and mechanisms.
2. Understand/ compute the velocity and acceleration diagrams of all basic mechanisms.
3. Draw velocity and acceleration diagrams of basic link mechanism.
4. Understand turning moment and crank effort diagram.
5. Understand the types of lower pairs.
6. Understand the types of cam & follower.
7. Understand the types of drives such as: belts, ropes and chains.
8. Derive the relationship between tension on tight and slack sides of belts and HP transmitted by the belt.
9. Understand different types of brakes and dynamometers.
10. Applied different formulae to compute problems on brakes.
11. Understand the functions, types and characteristics of governors.
12. Apply the theory of governors to solve numerical problems.
Detailed Contents
1. Basic Concept of machines: link mechanism kinematic pair and chain, principles of inversion, inversion of a four bar chain, slider-crank-chain, double slider-crankchain and their inversions, kinematic pairs, Graphical (relative velocity vector and instantaneous center methods) and Analytical methods for finding: Displacement, velocity, and acceleration of mechanisms (including Corliolis components).
2. Lower Pairs: Universal joint, calculation of maximum torque, steering mechanisms including Ackerman and Davis approximate steering mechanism, engine indicator, Pentograph, Straight line mechanisms
3. Belts, Ropes and Chains : Material, types of drives, idle pulley, intermediate or counter shaft pulley, angle and right angle drive, quarter turn drive, velocity ratio, crowning shaft pulley, loose and fast pulley, stepped or cone pulleys, ratio of tension on tight and slack sided of belts, HP transmitted by belts including consideration of creep and slip, centrifugal tensions and its effect on HP transmitted. Use of gravity, idle, flat, V-belts and rope materials. Length of belt, rope and chain drives, type and cone type.
4. Cams: Types of cams and follower, definitions of terms connected with cams, displacement velocity and acceleration diagrams for cam followers. Analytical and Graphical design of cam profiles with various motions (SHM, uniform acceleration and retardation, cycloidal). Analysis of follower motion for circular convex, tangent cam profiles. Calculation of pressure angle.
5. Friction Devices: Concepts of frictions and wear related to bearing and clutches. Types of brakes, principle of function of brakes of various types. Braking of front and rear tyres of a vehicle, Problems to determine braking capacity, Types of dynamometers,(absorption, transmission).
6. Flywheels: Turning moment and crank effort diagrams for reciprocating machines Fluctuations of speed, coefficient of fluctuation of speed and energy, Determination of flywheel mass and dimensions for engines and Punching Machines
7. Governors : Function, types and characteristics of governors, Watt, Porter and Proell governor. Hartnell and Willson-Hartnell, spring loaded governors. Simple numerical problems on these governors. Sensitivity, stability, isochronisms and hunting of governors. Governor effort and power controlling force curve, effect of sleeve friction.