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About this book

This book presents the most up-to-date accomplishments in gear design and gear production, detailing theory of gearing and its application. As an enormous number of gears are used in such sectors as automobiles, aerospace, machines, and similar industries, even a very small improvement in the gear design or production, for example a 10 cent savings on each gear, can result in huge of savings in manufacturing, underscoring critical importance of the subject of the book. Giving a solid background in theory together with the latest advances in design and production, the book is ideal for product designers working in numerous industries. The volume also serves as a useful supplement to required texts well for students in mechanical and industrial engineering as it helps establish a scientific foundation to the subject, and facilitates a systematic learning process of gear kinematics, gear geometry, gear design, gear production/finishing operations, and related competencies.

Table of Contents


Chapter 1. Kinematic Foundations of Scientific Classification of Gearing

This section of the book deals with gears and gear pairs. At the beginning, a concept of the “gear vector diagram” is introduced. This concept is extensively employed below aiming the development of a scientific classification of gearing. A concept of a “favorable line of contact” in a gear pair is another mean that is extensively used when developing a scientific classification of gear pairs. These two concepts along with the newly introduced concept of the “generic gear surface”, all together, make the scientific classification of gears and gear pairs possible.
Stephen P. Radzevich

Chapter 2. Theory and Applications Based on S-Gear Geometry

The chapter starts with the theory defining S-gears and their properties and compares S- and involute gears. Most of the text deals with cylindric spur gears. S-gears are defined with the half-symmetric rack profile, which then uniquely defines the path of contact and gears. Reshaping of the gear flanks for external and internal gear pairs is presented here and thermal behavior discussed and compared with the involute gears. Experimental verification of S-gears theory, especially durability and thermal behavior of importance for plastic gears is presented. So, in this chapter a material combination of interest was alloy steel and POM (which was only heat stabilized). The chapter presents some specific information about this. And finally, the planocentric gearbox focused on high-tech industry (e.g., robotics) is presented. The problem is how to achieve required properties. So, all possible analytical tools should be used to minimize backlash and many other parameters which is also presented in the paper.
Gorazd Hlebanja, Miha Erjavec, Matija Hriberšek, Luka Knez, Simon Kulovec

Chapter 3. Kinematic Pairs: Novel Kinds and Classification

This section of the book deals with kinematic pairs, with those observed in gears in particular. The chapter begins with a brief overview of the earlier performed research in the field. Different kinds of kinematic pairs are distinguished, namely, point-contact kinematic pairs, line-contact kinematic pairs, and surface-to-surface-contact kinematic pairs. Contact geometry in kinematic pairs is taken into account aiming more in-detail analysis and the development of scientific classification of kinematic pairs. A novel classification of all possible kinds of kinematic pairs is developed.
Stephen P. Radzevich

Chapter 4. High-Performance Plastic Gears

Plastic gears have been used for decades in a wide variety of applications such as consumer articles or electromechanical actuators in the automotive sector. Plastic specific material properties such as low-density and high-damping characteristics and the possibility of mass production through injection molding are advantageous and contribute to the increasing application of plastic gears. However, the comparatively large differences in material properties compared to steel result in plastic gears mostly being used in low-power drives. In particular, the high-temperature dependency of the material properties and lower strength numbers often represent a challenge for the application of plastic gears.
In most cases, plastic gears are running dry or under starved lubrication. In the context of these operating conditions, the transmission of motion is often of principal importance as the potential to transmit power is limited due to the high level of frictional heat in combination with limited capability for heat removal. The use of a lubricant is required for the transmission of increased power. Grease lubrication offers the possibility of heat dissipation and the reduction of wear. If even higher power is to be transmitted, oil lubrication is required. Operation under oil lubrication separates the tooth flanks from each other and ensures effective dissipation of the heat generated in tooth contact.
Today, VDI 2736 is mainly used for the design and rating of plastic gears. In addition to information on the design of the wheel body and manufacturing of plastic gears, this guideline contains approaches for temperature calculation and load carrying capacity calculation. Due to the high-temperature dependency of the material properties of thermoplastic materials, knowledge of the gear temperature is of essential importance in the design of plastic gears and one of the main steps of the load carrying capacity calculation. VDI 2736 uses the basic principles of the standard DIN 3990 developed for steel gears to calculate the tooth root and tooth flank load capacity. Especially the high deflections under load compared to steel gears are currently not sufficiently considered in VDI 2736. Current research provides new knowledge on the consideration of deflection effects and their influence on the gear load carrying capacity of modern thermoplastic materials and contributes to the optimized design of plastic gears. On the material side, new high-performance plastics are constantly being developed, which further increase the temperature resistance and strength properties required. In addition to widely used materials such as polyacetal and polyamides, polyetheretherketones and other high-performance materials are increasingly being applied. Today, the low availability of standardized strength values represents a challenge for the design of ideally dimensioned components. For this reason, in addition to the investigation of the thermal and tribological operating behavior of plastic gears, the generation of standardized determined strength values is of particular interest.
The following chapter presents an overview of the state of the art and application of plastic gears, introduces existing design and calculation methods for plastic gears, and summarizes some main results of actual research work performed at FZG institute.
C. M. Illenberger, T. Tobie, K. Stahl

Chapter 5. Application of Task-Based Conceptual Design Method for Gear Chamfering Mechanisms

Many objectives of gear design and manufacturing can be considered and resolved by task-based multifunctional conceptual design method developed on the base of long career experience of design and production of numerous custom-made machine tools, innovative hand tools, and other mechanical devices. Requirements of geometrical accuracy and manufacturing efficiency are significant objectives for gear manufacturing technologies and gear chamfering technologies in particular. To satisfy those requirements, the proposed task-based conceptual design methodology is modified and applied in a way to take into account specific needs and features of gear chamfering procedure. The proposed method of conceptual design method can be advantageously pointed out from existing design methodologies by direct consideration of challenged functions at any step of mechanism synthesis, by simultaneous review of several tasks, by similarity and repeatability of analyses and synthesis tools and design cycles, by development and usage of mechanical-functional models, and by quantitative evaluation of different design scenarios. The methodology of creation of gear chamfering mechanisms is serving as an example for extending the scope of application of conceptual, parametric, and analytical resources of the task-based method to the case of surface reproduction technological machines. A concept of multi-degree freedom duplication of different geometrical shapes is the base of methodology for the creation of surface reproduction mechanisms when two parallel chains are providing firstly the geometrical order of surface reproduction and secondly the mechanical set of links necessary for such reproduction. Firstly, an analyzing methodology is applied for consideration and evaluation of various known conceptual diagrams and solutions for the tracking of chamfer surface. Then based on analyses of existing solutions, point and linear models are developed, and, finally, those models are upgraded by additional degrees of freedom and parallel chains to satisfy the remaining challenges and functions. Thus, several design scenarios are created and filtered for evaluation and rejection of not valid solutions. As a result, a series of novel structures are created, and proper manufacturing technology is worked out satisfying different needs of gear chamfering process. The conceptual design phase is commonly preceded by a phase of analyses of existing solutions and proceeded by a phase of parametrical design. Worthy to note that all three procedures are based on the same methodical base which conceptual stage has and hence have the same methodical values and same efficiency in application. An objective of parametric optimization for a type of gear chamfering mechanism is formulated as a requirement of providing a stable surface quality along the involute pattern of gear teeth. Scope of application of the developed methodology of conceptual design is generalized and extended for analyses and synthesis for a class of surface reproduction technological machines. Necessary and clarifying examples are coming to verify the validity and efficiency of task-based conceptual design methodology for surface reproduction and gear chamfering mechanisms.
Hrayr V. Darbinyan

Chapter 6. A Brief Overview of the Evolution of the Scientific Theory of Gearing

This chapter of the book deals with gears, those developed in ancient time, as well as those to be developed in the future. The entire history of evolution of the gear art falls in three periods. These periods of evolution are referred to as (a) the pre-Eulerian period of evolution of the gear art, (b) the time when involute gearing was proposed by Leonhard Euler, and (c) the post-Eulerian period of evolution of the theory of gearing. Principal accomplishments in the field of gearing, and in the theory of gearing in particular, are identified. Each of the accomplishments is associated with the name of the principal contributor of the accomplishment, and then all the accomplishments in the theory of gearing are placed in a chronological order. In this manner, a chart that illustrates the entire evolution of the theory of gearing is constructed. The discussion in this text reveals all the gear scientists who really contributed to the scientific theory of gearing. It is helpful to eliminate numerous of other names, whose contribution is not fundamental by nature.
Stephen P. Radzevich

Chapter 7. Hyperboloid-Type Hobs: Design, Manufacture, and Application

Gears are an important design component of many machines and mechanisms. The most important characteristics of machines and mechanisms, namely their accuracy and smoothness of operation, power density, and so forth, strongly depend on gears. These are the main reasons for the requirements to gears, including but not limited to their accuracy, as well as the productivity of their production, which are permanently growing. In production of gears hobs are used most extensively. High productivity of the gear hobbing process along with the economic performance of the gear generators is the main reason for that. Despite of that, further increase in productivity of the gear hobbing and the gear finishing operations is still required.
Hobs, worm-type shavers, worm-type grinding wheels, and so forth are among the gear cutting tools that are commonly used in gear production. Further analysis and improvements are necessary to succeed in the nowadays gear business. The text below aimed investigation and further improvements in gear cutting tool design, and in production of gears.
Valentyn Nastasenko

Chapter 8. Optimal Selection of the Structural Scheme of Compound Two-Carrier Planetary Gear Trains and Their Parameters

The Torque Method is an easy way for kinematic and power analysis of planetary gear trains, both simple and compound ones. Moreover it gives possibility of optimal choice of a structural scheme (and its parameters) of compound planetary gear trains.
In this chapter most common ways of optimization of planetary gear trains are overviewed. Appropriate optimization criteria of the most common simple planetary gear train (with one external and one internal meshing) are discussed. Multi-objective choice of structural scheme and its parameters of two-carrier planetary gear trains is proposed. Two-carrier planetary gear trains with three and four external shafts are considered. The choice is made between all possible structural schemes of planetary gear trains in question through the torque method.
Dimitar P. Karaivanov, Sanjin Troha

Chapter 9. Development of Gears from the Antiquity to the Present Time

The development of human civilization was made possible by mechanical tools, especially those that served to transmit power. And soon in this development, devices with teeth appeared. Gears were simple wooden aids for many centuries, but the evidences of complex mechanical devices of antiquity exist. Water- and animal-powered devices were used during the Middle Ages. The Renaissance accelerated the development of science and technology. And soon after a steam engine was invented, which supplied more energy as it was possible until then. Later, the combustion engine, the turbines, and electric motors also accelerated the development of mechanical transmissions. Today we find complex mechanical transmissions in industrial plants, in high-performance machine tools and robots, as well as in consumer devices, with increasing demands toward higher loads, lower vibration, lower maintenance, no additional lubrication, etc. So, gears are a crucial part of such devices, and their development far from obsolete. Gear shape, technologies, and materials are being researched and developed to find better solutions.
Jože Hlebanja, Gorazd Hlebanja


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