Preface

Dear Colleagues,

This document has been prepared for the Asyncrhronous learning of the mechanisms. It is based on third edition of the “Mechanisms” book that was published in 1999 which was developed from course lectures on “Mechanisms” given to mechanical engineering students at the Middle East Technical University starting from 1974. After 20 years since its first publication, over five thousand copies sold (in addition to an unknown number of photocopies made) and being out of print for the last seven years, I was not planning to prepare the third edition of the book for a number of reasons. However, within the last two years, I had the time and courage to rewrite most parts of the book.

As any other teaching material, learning is up to the student. Effort must be shown so that the material shown can be of any use.

There has been numerous changes in computation facilities and in mechanical engineering education over the last two decades both at METU and abroad. For the one thing, what used to be a mainframe computation has become a simple calculation in a personal computer. Engineers who had to write their own program using FORTRAN and then interpret a bunch of number outputs now can use specific or general package programs with excellent graphic capabilities. During the eighties and nineties robots, and numerically controlled systems have changed the way we look at mechanical engineering. Still the old science (or technology, or art) of mechanisms has its utmost importance in machine design, although the tools of the design and products to be designed have changed. To disseminate the knowledge, contrary to the belief of some people, even at the age of the Internet, books are essential tools.

In Chapters 1 and 2 an effort has been made to orient the student with the systems that are going to be discussed. The topological characteristics of mechanisms including the type of joints, degree of freedom of mechanisms and enumeration of mechanisms are given. Only in this chapter spatial mechanisms are included to make the student familiar with all the mechanisms he may see in practice.

Chapter 3, 4 and 5 is devoted to the kinematic analysis of planar mechanisms. Displacement, velocity and acceleration analysis using graphical and analytical methods are shown. Unified approach is used between different methods based on the vector loop equations. Examples are shown using general purpose programs such as AutoCAD©, EXCEL©or MathCAD©. One can as well utilize any other drawing package or spread sheet or mathematics programs such as CADkey©, Lotus© or MATLAB©. Use of package programs such as Working Model©, ADAMS©or the like were not encouraged since these programs are specifically designed for the kinematic and dynamic analysis of mechanisms. Although these programs are excellent tools for professional engineers, their value in learning the basic concepts in these fields is questionable.

Chapter 6 deals with linear mechanical systems- gear trains. In Chapter 7 simple mechanisms that are most often encountered in practice are discussed in more detail. The characteristics of four-bar, slider-crank and inverted slider-crank mechanisms are given. For the four-bar and slider-crank mechanism design for dead centers problem is treated analytically. The coupler point curve and related theorems are explained. Straight line motion generation by means of slider-crank and swinging-block mechanism is discussed.

Chapter 8 is on cams. The nomenclature, motion curves and the cam design is explained in detail both graphically and analytically

Many thanks are due to the colleagues Dr. Kemal Ider, Dr. Kemal Özgören, Dr. Resit Soylu and Dr. Turgut Tümer and to the assistants Miss. Burcu Söylemez and Mr. A. Serdar Sezen who have proofread the draft copy. The contributions of all the assistants who helped in giving this course and all the students who have taken this course over the last 25 years are greatly appreciated.

The web pages were prepared by Mr Özgür Ekici. Mr Ahmet Serdar Sezen has prepared some of the Flash® animations but more than that, I am grateful to him for teaching me how to use this program. The support given by Enformatics Institute and its director Prof. Dr. Neşe Yalabık is greatly appreciated.

Eres Söylemez

August 2001, Ankara