In machine design or design of machine elements we study about the design of individual components of machinery like shafts, keys, belts, bolts, gears, etc. In mechanical system design we means that how these components are going to work in collaboration, reliability of the system when different components work together. This book includes design of conveyors for material handling systems (belt conveyors), design of multispeed gearbox for machine tools, design of I.C. engine components and optimum design. It also includes the design of pressure vessels used in mechanical systems. This book provides a systematic exposition of the basic concepts and techniques involved in design of mechanical systems. Our hope is that this book, through its careful explanations of concepts, practical examples and figures bridges the gap between knowledge and proper application of that knowledge.