"Preface An introduction on a lighter note than is usual for a book of this nature, one that is simple and less academic, is due for a couple of reasons: 1. The text is obviously of a difficult nature (as the foreword note may imply). 2. Renowned scientists have often utilized elementary contexts and examples to introduce complex ideas (Einstein in his Biography of Physics implements the plotting of a mystery as a fil rouge to the illustration of relativity concepts). Along the lines of the above-mentioned scientist, we would follow the same track, not because we or our contributors could ever be compared to the famous scientist, but rather to copy the successful style of many of the great masters of science. Imagine, then, explaining the nature of the book by comparing the text to the notepad of a detective/psychologist involved in a police story. In the background we find a quiet village (the MACHINE) characterized by wellordered operation and ruled by clear laws, rather simple and often appearing even intuitive (natural). The first notes on the pad (Chapter 1 of the book) relate, then, to the coordinated action of a few leading characters who participate in the life of the MACHINE. These we would find to be the MOTOR, the TRANSMISSION, the POWER, the LOAD, the TRANSMISSION RATIO, the FRICTION, and so on. Each of them, as an active citizen, contributes to the operation of the village in full accordance with its laws (the MATHEMATIC EQUATIONS). However, among the citizens hide a few "suspicious characters" who often are unable (because of their nature or because they are urged by outside pressure) to comply precisely with the dictated laws. Sometimes, due to the less predictable behavior of such "suspicious characters," the MACHINE does not function properly"-- Provided by publisher.