JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisites

Basic principles of mechanics

Course Overview: Mechanical devices are designed to have mobility to perform certain functions. The theory behind the study of KOM leads us to design machines by understanding the relationship between the geometry and the movement of various parts of machine. This course will provide the knowledge on how to analyze the motions of mechanisms and design mechanisms to give required movement. This includes relative motion analysis and design of gears, gear trains, cams, linkages and steering gears by simultaneous graphical and analytical analysis of position, velocity, and acceleration of links in a machine.

Course Objective

The objectives of the course are to enable the student;

• 1. To understand the basic principles of kinematics and the related terminology of machines.
• 2. Discriminate mobility; enumerate links and joints in the mechanisms.
• 3. Formulate the concept of analysis of different mechanisms.
• 4. To understand the working of various straight line mechanisms, gears, gear trains, steering gear mechanisms, cams, and Hooke’s joint.
• 5. Analyze a mechanism for displacement, velocity, and acceleration of links in a machine.

Course Outcomes

On successful completion of the course, the student will be able to

• 1. Be familiar with different machine elements which accomplish similar results.
• 2. Calculate mobility and enumerate rigid links and types of joints in mechanisms.
• 3. Able to create a schematic drawing of real world mechanisms.
• 4. Able to conduct a complete translational and rotational mechanism for the velocity and acceleration analysis.
• 5. Able to design mechanisms of basic cam systems for different machinery.

UNIT - I

Mechanisms: Elements or Links – Classification – Rigid Link, flexible and fluid link – Types of kinematics pairs –Types of constrained motion-kinetic chain-. Mechanism-machine- Structure - inversions of mechanism – inversions of quadric cycle chain, single and double slider crank chains, Mechanical Advantage - Grubler’s Criterion.

UNIT - II

Kinematics: Velocity and acceleration – Motion of link in machine – Determination of Velocity and acceleration – Graphical method – Application of relative velocity method. Plane Motion of Body: Instantaneous center of rotation- centrodes and axodes – Three centers in line theorem – Graphical determination of instantaneous center, determination of

angular velocity of points and links by instantaneous center method. Kliens construction - Coriolis acceleration - determination of Coriolis component of acceleration. Analysis of Mechanisms: Analysis of slider crank chain for displacement- velocity and acceleration of slider – Acceleration diagram for a given mechanism.

UNIT - III

Straight-Line Motion Mechanisms: Exact and approximate copied and generated types – Peaucellier - Hart - Scott Russel – Grasshopper – Watt -Tchebicheff’s and Robert Mechanism – Pantographs. Steering Gears: Conditions for correct steering – Davis Steering gear, Ackerman’s steering gear. Hooke’s Joint: Single and double Hooke’s joint –velocity ratio – application – problems.

UNIT - IV

Cams: Definitions of cam and followers – their uses – Types of followers and cams – Terminology – Types of follower motion - Uniform velocity, Simple harmonic motion and uniform acceleration and retardation. Maximum velocity and maximum acceleration during outward and return strokes in the above 3 cases. Analysis of Motion of Followers: Tangent cam with Roller follower – circular arc cam with straight, concave and convex flanks.

UNIT - V

Higher Pair: Friction wheels and toothed gears – types – law of gearing, condition for constant velocity ratio for transmission of motion – velocity of sliding Forms of teeth, cycloidal and involutes profiles – phenomena of interferences – Methods of interference. Condition for minimum number of teeth to avoid interference – expressions for arc of contact and path of contact of Pinion & Gear and Pinion & Rack Arrangements– Introduction to Helical – Bevel and worm gearing Gear Trains: Introduction – Types – Simple – compound and reverted gear trains – Epicyclic gear train. Methods of finding train value or velocity ratio of Epicyclic gear trains. Selection of gear box - Differential gear for an automobile

TEXT BOOKS:

• 1. Theory of Machines and Mechanisms/JOSEPH E. SHIGLEY/Oxford/3 rd Edition/International Edition
• 2. Theory of Machines / Thomas Bevan/Pearson/3 rd Edition

REFERENCE BOOKS:

• 1. Theory of Mechanism and Machines /Jagdish Lal/Metropolitan Book Company
• 2. Theory of Machines /S. S. Rattan / Tata McGraw Hill Publishers.
• 3. Kinematics & Dynamics Of machinery/Norton/TMH
• 4. Theory of Machines / Sadhu Singh / Pearson.
• 5. Mechanism and Machine Theory / JS Rao and RV Duggipati / New Age
• 6. Theory of Machines by / R.K. Bansal (Lakshmi Publications).