Theory of Machines: Unit V: Balancing and Vibration

Balancing and Vibration

Learning Objectives, Introduction

A machine has many moving parts. Some machines have rotating motion and some of them have reciprocating motion.

Unit: V

Balancing and Vibration

Chapter 12: Balancing of Rotating Masses

Chapter 13: Balancing of Reciprocating Masses

Chapter 14: Free Vibrations

Chapter 15: Force Vibrations

Chapter: 12

Balancing of Rotating Masses

Learning Objectives

While reading and after studying this chapter, you will be able to:

Understand the importance of balancing in machines.

Distinguish static balance with dynamic balance using appropriate examples.

State conditions for the complete balancing of rotating masses.

Describe the balancing of several rotating masses in the same plane.

Explain how the different masses rotating in different planes are balanced.

SYLLABUS

Balancing single rotating mass - Balancing of several coplanar rotating masses - Static and dynamic balancing - Balancing of several masses rotating in different planes.

INTRODUCTION

A machine has many moving parts. Some machines have rotating motion and some of them have reciprocating motion. If these moving parts are not in complete balance, inertia forces are set up which may cause excessive noise, vibration, wear and tear of the system. 

Thus, balancing is the process of designing or modifying machinery so that the unbalance is reduced to an acceptable level and if possible is eliminated entirely.

When a particle or mass moving in a circular path, it experiences a centripetal force acting radially inwards. An equal and opposite force acting radially outwards on the axis of rotation and is known as centrifugal force. This is a disturbing force, and its magnitude remains constant but the direction changes with the rotation of the mass.

The centrifugal disturbing force, FC = m ω2 r

where

m = Mass of the rotating component in kg,

ω = Angular velocity of the component in rad/s = 2πN/60,

N = Speed of the component in rpm., and

r = Distance of C.G. of mass from the axis of rotation in metres.

In fact, due to modern trend of development of high speed machines and vehicles, the problem of balancing becomes greater importance for mechanical engineers. This type of unbalance problem is very common in steam turbine rotors, engine crankshafts, rotary compressors, centrifugal pumps, etc.

1. Types of Balancing

Study of the problem of balancing can be divided into two classes:

1. Balancing of rotating masses, and

2. Balancing of reciprocating masses.

In this chapter the balancing of rotating parts of machines are considered.

Theory of Machines: Unit V: Balancing and Vibration : Tag: : Learning Objectives, Introduction - Balancing and Vibration


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ME3491 4th semester Mechanical Dept | 2021 Regulation | 4th Semester Mechanical Dept 2021 Regulation