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The uniqueness of heavy and medium duty vehicle powertrain design, compared to that of passenger cars, is two fold: vast variations exist from vehicle to vehicle because of mission requirements, and powertrain components are sourced from a diverse group of suppliers. Vehicle powertrain design involves selection of the appropriate major components, such as the engine, clutch, transmission, driveline, and axle. At this design stage the main focus is on power matching, to ensure that the vehicle's performance meets specifications of gradability, maximum speed, acceleration, fuel economy, and emissions[1, 2, 3, 4 and 5]. The general practice also demands that the durability of the drivetrain components for the intended vocation or application be verified. Equally important but often neglected in the design phase is the system's NVH (Noise Vibration and Harshness) performance, such as torsional vibration, U-joint excitation, and gear rattle.

To validate the integrity of a commercial vehicle's exhaust system's structural design is a challenging job. An integrated approach to use both simulation/modeling and hardware testing must be employed to reduce product development cost. In addition to the considerations of the geometry and configuration specs of 70-90 parts and joints as well as material's thermal and mechanical property data in model development, representative loading must be used. For base excitation type of loading, such as the one experienced by the vehicle's exhaust system, one must decide whether to conduct the time domain transient analysis or frequency domain random vibration analysis. Although both methods are well known, few discussions can be found in the literature regarding their effective use in the framework of product design and development. Based on our study, the random vibration method should be used first for identifying high stress locations in the system and for design optimization.

Powertrain torsional vibration has become a subject of increasing concern for the heavy duty truck industry in recent years. This is due in part to truck and diesel engine developments, and to drivetrain system trends. A computer simulation is an effective tool in analyzing this problem. A powertrain vibration analysis program has been developed by the authors. It has been used extensively in the evaluation and optimization of powertrain system performance. In this paper, first the heavy duty powertrain is characterized as a vibrating system. Its natural frequencies, mode shapes and frequency response characteristics are reviewed. Second, the theory of torsional vibration and its application in the simulation are described. The drivetrain is described as a discreet model. An undamped modal analysis is given as an eigenvalue problem.

Nowadays, developing web (World Wide Web) engineering is considered to be a top priority task in many companies. A corporate web information center with broad coverage to support a company's worldwide engineering activities can make the product development and customer support more efficient. First, the archived, readily available product information, knowledge database, and user friendly engineering tools can ease up the more ever demanding engineering jobs. Second, the convenient information storage, retrieval systems and hyperlinks on the web should ensure effective communications among engineers, customers, and suppliers. However, without in-depth planning, the full benefits of web engineering cannot be realized. To be effective, other companion engineering programs must also be instated. This paper reviews the experience we have gained in utilizing web engineering for product development and customer support.

In recent years, several transit agencies have tested buses equipped with hybrid powertrain systems. It has been reported that hybrid powertrains have significant advantages over conventional diesel engine systems, in the area of emissions and fuel economy performance. Presented in this paper are engineering issues and suggestions from an auto component supplier point of view in the design of such a powertrain system. The particular system being considered consists of a downsized diesel engine, a generator, a battery package, two identical AC induction motors, and gearbox systems for the left and right driven wheels. The assembly is supported by an H-shaped suspension sub-structure uniquely designed to achieve the “ultra-low floor” configuration. Our discussion covers the system performance, as well as the durability issues. In particular, the presentation focuses on the durability and the design layout of the gearbox and suspension substructure.

The uniqueness and challenge of heavy and medium duty vehicle manufacturing is that the vehicle&s subsystems and major components are procured from different suppliers. As a consequence, engineering task coordination for total vehicle performance optimization is required even if the intended design modification is only on one component. In the case of suspension design, related subsystems such as the drive axle, driveline, brake system, steering system, and engine mounts should all be included for review. The related potential problems for study fall into three categories, namely: function, durability, and NVH. The effective approach in addressing all these issues early in the design stage is through computer modeling and dynamic system simulation of the suspension system and related subsystems.

Welding has been used extensively in automotive components design due to its flexibility to be applied in manufacturing, high structural strength and low cost. To improve fuel economy and reduce material cost, weight reduction by optimized structural design has been a high priority in auto industry. In the majority of heavy duty vehicle's chassis components design, the ability to predict the mechanical performance of welded joints is the key to success of structural optimization. FEA (finite element analysis) has been used in the industry to analyze welded parts. However, mesh sensitivity and material properties have been major issues due to geometry irregularity, metallurgical degradation of the base material, and inherent residual stress associated with welded joints. An approach, equilibrium-equivalent structural stress method, led by Battelle and through several joint industrial projects (JIP), has been developed.