Transmission error is a measure of the positioning accuracy of a gear system. This has been widely documented in gearing for many years as the source of problems in noise and vibration. It is a result of errors in the contact conditions which affect the driven gear with respect to the rotation of the driver gear. This research aims to present a better understanding of the basic kinematics of worm gear systems by identifying the significant influences which determine the contact conditions. A literature review of existing theory is described which determines the major areas considered in worm gear contact analysis. Formulae are derived which quantify the effect of component parameter variation on contact. An investigation of the design, manufacture, and operating processes is recorded which identifies error sources relative to the theoretical contact condition. A computer program is developed which calculates contact characteristics such as worm and wheel component form, transmission error and contact marking pattern for a given design including any contact error sources. Computer calculations are validated by comparing direct measurements of these characteristics from several manufactured gear sets with synthesised results produced using the design information, machine settings and error sources detected during production. The behaviour of these gear sets during operation under a torque load has been investigated experimentally. Measured transmission error data from a test rig is used to develop a basic model of worm gear deformation under load. This model has been added to the computer program to improve and extend the analysis capability. The test rig has also been used to investigate the effect of initial wear on contact characteristics. The good correlation between calculated and experimental results shows that the characteristics of a worm gear set can be predicted once all elements of the design and manufacture are known. The results also validate the software as a useful design tool for academic and industrial applications. Important conclusions are drawn on design techniques, the manufacturing process, and the effects of operating under load. Further areas of investigation are identified which offer future research an opportunity to expand upon these conclusions.

An aircraft in low-level flight experiences a large increase in lift and a marked reduction in drag, compared with flight at altitude. This phenomenon is termed the 'wing-in-ground' effect. In these circumstances a region of high pressure is created beneath the aerofoil, and a pressure difference is set up between its upper and lower surfaces. A pressure difference is not permitted at the trailing edge and therefore a mechanism must exist, which allows the pressures above and below to adjust themselves to produce a continuous pressure field in the wake. It is the study of this mechanism and its role in the aerodynamics of low-level flight that forms the basis of our investigation

Marketers are faced with informed and highly complex consumers. The consumer market is becoming more competitive and more difficult to predict as consumers make purchase decisions in their everyday life. An ongoing need exists for information and an examination of purchasing behaviour for marketers to succeed in their pursuit of business endeavours. This study examines the influence of selected variables on motor vehicle-related purchasing behaviour. Five independent variables, namely branding, price, promotion, safety features and colour were investigated and the dependent variable (purchasing behaviour) was examined. In doing so, various stages which consumers undergo when making purchasing decisions were discussed. These stages were outlined as need recognition, information search, and evaluation of alternatives, purchase and post-purchase behaviour. The primary research objective of this study was to determine the influence of selected variables on motor vehicle-related purchasing behaviour. In order to achieve the objectives of the study, an empirical investigation was undertaken. The quantitative (positivistic) paradigm was used in this study, as the aim was to test the hypotheses and conceptualmodel of the study using statistical analysis. In gathering primary data, 192 self-administered questionnaires were issued to respondents for completion by means of convenience and quota non-probability sampling. Upon completion of all the questionnaires, data was analysed in order to arrive at the conclusions regarding the research questions. The empirical findings and analysis followed a systematic and statistical process, where exploratory factor analysis using target rotation was used to test the validity of the measuring instrument. Cronbach alpha correlation coefficients were used to confirm the reliability of the measuring instrument, while multiple regression analysis was carried out to test the hypothesised relationships between the independent variables and the dependent variable of the study. ANOVA was applied to determine differences in the demographic characteristics of respondents. The main findings on the validity and reliability of the measuring instrument proved to be statistically satisfactory. The main findings which emerged from the multiple regression analysis suggested that price and colour had statistically significant influence on motor vehicle-related purchasing behaviour. Findings revealed that branding, promotion and safety conditions had no significant effects on motor vehicle related purchasing behaviour. Accordingly, the hypotheses for price and colour were accepted and those for branding, promotion and safety conditions were rejected. Therefore according to respondents, price and colour of a motor vehicle are the most important considerations when undertaking purchasing decisions regarding motor vehicles. Additionally, the empirical investigation revealed that significant differences exist between age groups of respondents, meaning that different age groups of respondents had different perceptions and opinions with regard to their purchasing patterns relating to price. Furthermore, significant differences were also found between male and female respondents in terms of price and colour, meaning that the two genders had different perceptions and opinions with regard to their purchasing patterns in these areas. The empirical findings of this study are relevant for motor vehicle retailers and original equipment manufacturers, as the findings provide important information regarding the influence of selected variables on motor vehicle-related purchasing behaviour. Secondly the findings of this study contribute to the body of knowledge regarding purchasing behaviour.

Bolted connections where used from the beginning of vehicle construction for joining two or more parts. The reliability of bolted connections is still a major problem. The objective of this research thesis is focused on an advanced monitoring system for bolted connections in vehicle construction. A mechanical “vibrating test bench”, which was developed by the aeronautical engineer Mr. Junkers, is being adapted, to suite the requirements of the automotive industry. It is designed according to DIN 65151 standards. The bolted connection is tightened to a specific torque to achieve the required preload forces and then exposed to an oscillating elastic shear force. The preload force and their loss are measured in relation to the number of load cycles. The ideal locking mechanism would be, if no settling occurs. Realistic in practice is the remaining of a sufficient preload force which doesn’t decry with time. The aim of this thesis is, to gain knowledge that will assist in the future control of the bolt locking procedure. The test bench can be used to verify the clamping capability of a bolted connection. With the dynamic computer-aided test system it will also be possible to test critical bolted joints and their safety, which reduces the probability of costly product recalls, or even severe cases of failure.

The automotive industry is under expanding legislative pressure to decrease vehicle weight in order to enhance fuel efficiency; and to improve crash performance as well. For this purpose, hot rolled FB590 is a high strength steel (HSS) which can be used in automotive chassis and suspension applications. A major problem affecting mainly car underbodies is the effect of corrosion, often nucleating at sites where stone chipping has damaged protective coatings. Therefore, car components are frequently exposed to aggressive environments as a consequence of aqueous salts from the street coming into contact with affected and unprotected steel. This circumstance significantly decreases both the life and the appearance of the influenced parts, and may result in compromised structural strength leading to catastrophic failure. The main aim of this research is to further the understanding of the effects of simulated operational environments. Fatigue tests were initially carried out on mild steel under tensile loading and two severity-levels of corrosion as preliminary tests. Then a comprehensive programme of fatigue tests was performed on FB590 and its welds under bending and tensile loading and covering the range of environmental conditions experienced in automotive applications. There is no available data for FB590 in terms of fatigue performance in various environments and under bending and tensile loading as well. Additional techniques such as surface profilometry, scanning electron microscopy and so on were added to support the findings. The other aim was to monitor fatigue tests using a combination of Acoustic Emission (AE) and Digital Image Correlation (DIC) to identify the damage mechanisms that occur during failure although there had been limited research in this area. The combination of AE and DIC can provide much useful information to help to distinguish the different AE signals originating from various possible failure mechanisms such as plastic deformation, delamination of corrosion products or DIC paint and crack initiation and propagation. This might be utilized for an effective and powerful approach to monitoring multiple failure mechanisms; this has significant applications in automotive chassis testing. This information can provide a very valuable tool for the purpose of assessing material for automotive designers, which can then be used to decide on appropriate safety factors to avoid over-designing products and in order to ensure reliability and robustness of new products. In addition, the steel industry can also benefit from this research, as these findings can assist in enhancing the products and diminishing the effects of these environments on structural integrity.

The Anti-lock Braking System (ABS) is one of the most important safety features in modern vehicles. It is a device integrating complicated electronic systems, hydraulic systems and mechanical components. It is possible to produce faults in these systems due to extreme vehicle operating conditions, which may lead to the failure of the ABS. However, there has not been an effective mechanism available in current operation and service facilities, which allows the performance of the ABS to be checked on-board or at a service base. This research therefore aims to investigate and develop approaches which allow the ABS systems to be monitored in different ways. As the ABS is a highly integrated system, conventional monitoring methods cannot be applied to it directly. The primary objective of this research is to develop a condition monitoring model for a typical ABS system under different conditions and then to monitor the dynamic characteristics and performance of the ABS according to simulation and experimental results. The Rapid Control Prototype (RCP) technique is used by applying dSpace MicroAutoBoxII on the ABS controller. A full mathematical model has been developed to simulate the ABS system under different conditions and seeded fault conditions. This results in a full understanding of the characteristics of measurable variables such as wheel velocity and vehicle velocity. This work has led to the conclusion that a model-based condition monitoring approach is the method with the most potential for the monitoring of the ABS systems. To overcome inevitable measurement noise and model uncertainties, a Kalman filter (KF) has been designed and evaluated through both simulation data and experimental results. This has been found to have acceptable performance and has subsequently been incorporated into the model-based condition monitoring system. The performance of the model-based condition monitoring system has been evaluated using an ABS test system. The ABS test rig consists of the basic ABS components and also the dSpace MicroAutoBoxII components, together with NI data acquisition equipment. The ABS test rig developed in this research is highly flexible to allow experimental investigations under different fault conditions with different severities. It has demonstrated that the monitoring system can reliably detect different possible faults in the ABS such as speed sensor failure, solenoid valve sticking or stuck, hydraulic fluid leakage and pump efficiency loss. All these faults occur with high possibility according to a systematic failure mode analysis based on that of similar components. Obviously, there is still considerable work which needs to be carried out to adopt this system in industry. For example, interfaces to integrate this new system into existing vehicle electronics should be investigated. In addition, specific fault conditions from different vehicle manufacturers should be simulated to tailor the system to specific vehicles specifically.

The stringent emission laws, the depletion of petroleum reserves and the relation of fuels with politics have forced the world to find alternatives to fossil fuels. Biodiesel is one of the biofuels which is renewable and environmentally friendly and can be used in diesel engines with little or no modifications. For the last two decades, many researchers have reported extensive work on the performance and emission characteristics of engines running with biodiesel during steady state operation. However, there are numbers of knowledge gaps that have been identified which include limited information on biodiesel physio-chemical properties and their effects on combustion behaviour and performance and emission characteristics of the engine. In this study after an exhaustive literature review, the following four research areas have been identified and investigated extensively using available numerical and experimental means. The initial focus was to investigate the most important properties of biodiesel such as density, viscosity and lower heating value using experimental and numerical techniques. The effects of biodiesel blend content on the physical properties were analysed. For each property, prediction models were developed and compared with current models available in literature. New density and viscosity prediction models were developed by considering the combined effect of biodiesel content and temperature. All the empirical models have showed a fair degree of accuracy in estimating the physical properties of biodiesel in comparison to the experimental results. Finally, the effects of density and viscosity on the fuel supply system were investigated. This system includes the fuel filter, fuel pump and the engine combustion chamber in which air-fuel mixing behaviour was studied numerically. These models can be used to understand the effects of changes in the physical properties of the fuel on the fuel supply system. In addition, the fuel supply system analysis can be carried out during the design stage of fuel pump, fuel filter and injection system. The second research objective was the investigation into a CI engine’s combustion characteristics as well as performance and emissions characteristics under both the steady and transient conditions when fuelled with biodiesel blends. The effects of biodiesel content on the CI engine’s in-cylinder pressure, brake specific fuel consumption, thermal efficiency and emissions (CO2, NOx, CO, THC) were evaluated based on experimental results. It has been seen that the CI engine running with the biodiesel resulted in acceptable engine performance as well as reduction in main emissions (except NOx). Following this study, a detailed analysis on the transient performance and emission output of the CI engine has been carried out. During this analysis, the emission changing rate is investigated during speed transient and torque transition stages. Further to this, a transient emission prediction model has been developed using associated steady and transient emission data. The model has been shown to predict the transient emission reasonably accurately. The third research objective was to develop a method for on-line measurement of NOx emission. For this purpose the in-cylinder pressure generated within a CI engine has been measured experimentally along with mass air flow and these parameters have been used in the development of a NOx prediction model. This model has been validated using experimental data obtained from a NOx emission analyzer. The predicted data obtained from NOx prediction model has been compared with measured data and has shown that the deviation is within acceptable range. The final research objective was to develop a simple, reliable and low-cost novel method to reduce the NOx emission of the CI engine when using biodiesel blends. A potential solution to this problem has been found to be in the form of direct water injection which has shown to be capable to reduce NOx emission. Using a water injection technique, the performance and emission(NOx and CO) characteristics of a CI engine fuelled with biodiesel has been investigated at varying water injection flow rates. Intake manifold water injection reduces NOx emission by up to 40% over the entire operating range without compromising the performance characteristics of the CI engine

No description available.

The aim of this thesis is to describe the motor vehicle taxation in the Member States of the European Union. The thesis is divided into three sub- chapters. The first chapter describes the historical development of the laws of the Member States of the European Union in the field of vehicle taxation. This chapter also describes types of charges, which may be subject to motor vehicles. This chapter ends with the introduction of EURO emission standards and their impact on motor vehicle taxation. The second chapter is devoted to the collection of road tax in the Czech Republic and its beneficiaries, the State Transport Infrastructure Fund. The third chapter discusses the issue of motor vehicle taxation in individual member countries of the European Union, including specific taxes in individual states, their structures and their revenues.

This paper investigates a number of psychological factors that influence the South African Black middle class to engage in bandwagon consumption when purchasing luxury motor vehicles. The South African Black middle class has been receiving attention in consumer markets, especially from luxury brand houses looking at emerging markets for growth. This study was designed to measure the impact of the self-concept, susceptibility to normative influence, propensity to seek status and the need for uniqueness on the propensity to engage in bandwagon consumption behaviour. An online survey of 184 people identified as Black middle class, provided the data which was analysed using the PLS Structural Equation Modelling (SEM) technique. The results of the model confirmed the presence of bandwagon luxury motor vehicle consumption among this market segment. It was also found that the bandwagon consumption behaviour occurs in spite of the self-concept and need for uniqueness. Status consumption and susceptibility to normative influence were confirmed as antecedents to the bandwagon consumption. / Dissertation (MBA)--University of Pretoria, 2014. / zkgibs2015 / Gordon Institute of Business Science (GIBS) / Unrestricted