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In July of 1997, GM will introduce a Police Pursuit Sport Utility to the law enforcement market. The vehicle is based on the popular Chevrolet Tahoe full- size, four-door utility truck that was introduced in 1996. It is shorter than the Suburban and available in only a two-wheel drive version for the Police Pursuit Vehicle (P.P.V.) program. This vehicle replaced the now canceled Chevrolet Caprice, which traditionally had been developed to be a P.P.V. It created a new market niche with its unique size and features. The combination of using proven, existing components and following an aggressive testing schedule allowed GM to develop this unique new product in a 48-week time frame, a relatively short development time for such a challenging program. The GM Truck Group used proven technology on this program.

Operational Deflection Shapes (ODS) analysis has been in existence for more than 20 years, but has been overshadowed by its progenitor, Modal analysis. This paper describes how and why ODS analysis was applied to the development of the GMTG T-series Medium Duty Truck and presents some examples of the results obtained.

Rear end break-away, or skate, is a phenomenon that occurs when live axle equipped vehicles are driven aggressively on rough, winding roads. This paper reviews instrumented dynamic testing of a specially built vehicle. Initial testing linked skate to the tramp oscillation mode of the rear axle. Two variables were evaluated for reducing skate: shock absorber valving and shock absorber placement. The principal conclusion of this work is that although some reductions in skate are possible by adjusting shock absorber valving, optimum control of skate is facilitated by packaging the shock absorbers near the wheels.

SAE research into the ISO 14000 series of standards offers insights into the opinions and attitudes of the experts, U.S. industry leaders and government representatives. A series of focus groups with industry leaders, in-depth interviews and a review of secondary research data, provide a perspective on the ISO 14000 series as it is understood on the eve of acceptance by the international community. This research study, sponsored by SAE, explores reactions to both the early components of the standard (14001 and environmental management systems scheduled to be adopted in the summer of 1996) and those portions of the standard still being developed which relate more specifically to product components and the global standardization of life cycle analysis and eco-labeling.

In the late 1980s engine coolant recycling technologies were developed in response to a temporary but significant increase in the cost of ethylene glycol. Among these technologies was the adaptation of reverse osmosis water desalination processes by Stanadyne Automotive Corp.1 The technical paper describing the reverse osmosis (R/O) technology reports that the process efficiently recovers ethylene glycol and water in a sufficiently pure state to allow its use as a base fluid to reblend into engine coolant. Data generated in standard ASTM bench tests has demonstrated the capability of properly reinhibited R/O recycled engine coolant (ROREC) to comply with the performance requirements of accepted SAE, TMC, ASTM and OEM specifications. The technology has been applied commercially and this paper reports the operating experience of 15 users in Texas and California with diverse service applications. The experience has been very good.

The use of tridem axle groups for heavy commercial trailers was spawned by the Roads and Transportation Association of Canada (RTAC) research of the 1980s and is now commonplace on semi-trailers and B-trains in Canada. The Western Canadian log transportation sector employs a number of industry-specific configurations that are fundamentally different in design and operation to those studied in the RTAC research. Over the last decade, this sector has met the challenge to improve productivity by adding more axles to the trailing system of the traditional 5-axle tractor/pole trailer combination. Although productivity gains were realized with the addition of more trailing axles, both dynamic performance and vehicle mobility were reduced. Where tridem axle groups are used as an alternative to the multi-articulated three and four axle trailer assemblies, dynamic stability is improved and where tridem drive axle groups are used, mobility is also improved.

This paper describes a method for effectively reducing a level of idling vibration in heavy-duty trucks, which has been the point at issue lately. In this method, the vibration level is significantly reduced by using a full vehicle model, which is made by finite elements, and varying parameters to study effects. In order to achieve high accuracy, engine excitation forces calculated from the measured fluctuation in the flywheel angular velocity are input to the model. An effective use of this method in an early development stage has enabled us to reduce development cost and the lead-time.

One of the difficulties in predicting the structural behavior of vehicles such as the full size pickup trucks is the non-linearities involved during the course of the durability events. The current practice in durability and fatigue life prediction of vehicles is to conduct fatigue analysis on the structure using the measured road loads and estimate the fatigue incurred using the in-house and commercially available programs. In this paper the authors attempt to seek a different solution to the durability problem by conducting an upfront non-linear analysis. The results are then compared with the prediction by the fatigue life program in addition to the durability test results obtained on the early prototypes. To conduct the non-linear analysis ABAQUS FEA program is chosen for this investigation and for the linear analysis MSC/NASTRAN is utilized. Subsequently in-house fatigue program is used to predict the fatigue incurred.

A new Sport Handling Suspension has been developed for the 1996 Chevrolet S-Series and GMC Sonoma pickup trucks, which provides a sports-car-like level of handling with an aggressive, lowered appearance in an affordable package while maintaining the truck's payload and trailering capability This paper discusses the process by which the suspension was developed It provides an explanation of how the market opportunity was observed, and how the product concept was tailored to fulfill the market demands The paper also contains a discussion of the history of the sport truck market segment, and a presentation of handling data for a truck with this suspension During the development process, an effort was made to utilize existing components that are shared with other car and truck lines, to help contain tooling and piece costs This enabled the package to be marketed for a very reasonable price The components comprising the system are as follows Specific front and rear springs DeCarbon monotube gas shock absorbers Front and rear stabilizer bars Urethane front and rear jounce bumpers 12 7 1 Steering Gear P235/55R16 Goodyear Eagle GA tires 16x8 aluminum wheels

The wide-spread introduction of performance-based brake testing technology in the United States is imminent. Initial work has been completed by the National Highway Traffic Safety Administration (NHTSA). A subsequent study currently being conducted by U.S. Department of Transportation Federal Highway Administration (FHWA) indicates that the use of this technology by regulatory bodies is likely. The implications for fleet use of performance-based brake testing is two fold. First, immediate economic pay-back can be achieved by incorporating this technology into maintenance practice. Secondly, upon the implementation of performance-based brake testers by regulatory authorities, fleets who have already adopted and understand this technology will have no difficulty complying with new regulations.

An automatically deployed fold-down step has been developed for use on fire apparatus cabs. The step operates pneumatically as the cab doors are opened. This feature optimizes the ergonomics of cab entry while maximizing the interior space available for occupants and equipment.

The use of hydrodynamic transmission with lock-up clutch for a Chinese city bus leads to good fuel economy and ease of operation. Many examples have shown that the microprocessor-based control system used in a vehicle powertrain has the advantage with high control speed over a manual one, but most of the time, its control qualities are poor, especially when outside conditions change. In this paper, a synthetic control method for hydrodynamic transmission for a Chinese city bus is proposed with respect to control qualities of lock-up control. The lock-up control process is divided into two steps, i.e., ‘estimate’ step and ‘fine’ step, so we can apply different control schedules to realize different control demands and get better control qualities.

A newly developed GYB-100 hydrodynamic transmission consisting of DFZFB-323 torque converter with lock-up clutch and power shift gearbox for Chinese city bus has been put into operation. The locking-up process of the torque converter is a transient one, and it will bring great shudder to powertrain and thus reduce the lifespan of the clutch. Measures must be taken to eliminate the shudder. In this paper, the city bus powertrain is supposed to be a concentrated mode, i.e, a spring-mass system having multi-degrees of freedom. From analysis of dynamic characteristics of the lock-up clutch it gives that the friction characteristics of the lock-up clutch are of main importance for avoidance of shudder and the proper control of oil pressure operating the lock-up clutch and oil-filling time will lead to improved friction characteristics. The judgement of quality of the lock-up clutch is presented. Using modern control theory, we get optimal control schedule of the lock-up clutch.

A computer code capable for handling the three-dimensional turbulent flow around the bus was designed. For this study a turbulence model namely the constant viscosity, was considered. A Finite volume technique was used in developing this code. The pressure and velocity distribution around and on the exterior surface of the bus were calculated. These data were used to calculate the drag force and drag coefficient. One-tenth scale model for the Daewoo bus was fabricated from wood. Pressure taps distributed all over the surface of model were used to measure the pressure. By measuring the pressure the drag force and the drag coefficient were calculated. Finally a comparison between the theoretical and experimental results was performed showing a good agreement.

The impact of using system engineering and architecture to solve problems is studied. Information management and electronics technology are evaluated to determine how they can be aided by system engineering. Tools used to do system engineering are described. Issues around the impact of change and use of system engineering are addressed. The increased availability of technology and awareness of the opportunities it presents has caused a surge of interest and use. The technology of electronics in particular has been a subject of this interest. Results of this study show that system engineering can be successfully used to manage change in this industry.

System Engineering is widely recognized as an effective tool for developing complex systems. What is not widely recognized is that it is not just another engineering discipline, but also a structured process for solving any complex problem. The discipline skills required include an understanding of this process and how to modify it to meet the demands of each project. Each company should have a well defined process published as System Engineering Practices. These practices are targeted to the most complex project that can be envisioned, and adapted to meet the needs of each project to which they will be applied.

System engineering is partly concerned with systemic properties of engineered products. Process improvement concerns have shifted attention toward system engineering's process artifacts, road maps, and metrics. This laudable emphasis aims for process improvement, hopefully still connected with obtaining good systems. However, it risks decline in relative attention to system properties of the engineered product. This paper returns to characteristics separating system thinking from other aspects of engineering, and makes explicit those structures often left to intuition. This leads to a specific approach, class and containment hierarchy based meta-architecture, which can explicate and retool the art-even if as process improvement.

The NVT-750, an enhanced redesign of the NVT-650, was developed as a high torque density transaxle suitable for heavy duty front-wheel-drive applications. This transaxle includes the following enhancements: gear durability and attainment of world class gear noise targets, bearing durability combined with increased shaft rigidity, synchronizer durability resulting from improved lubrication flow and optimized synchro design, reverse blockout and durability, high temperature durability with temperature resistant plastics and seal materials, optimized housing and support plate design, and a trimback feature which provides excellent clutching sleeve retention.

The effects of different shot peening parameters on the fatigue life of rear axle hypoid pinion gears were evaluated. Shot hardness, shot size, intensity, shot velocity and prior heat treatment were studied and compared to current production. Metallurgical analysis of the carburized SAE 4320 gears along with residual stress gradient analysis at tooth root fillets were performed. The results showed that significant fatigue life enhancement can be achieved by precision shot peening (directed, air nozzle type) and proper determination and tight tolerance of shot peening process parameters and heat treatment.

The use of a computer-aided design (CAD) system, when properly implemented, dramatically reduces the time required to take new designs to production. The CAD system furthermore improves 1st time quality of the design and tooling, as well as providing automatic documentation of the manufacturing and part design processes. The author describes the development and implementation of a math based system for designing net shape differential gears with all the contact tooling used to make the net shape gear forgings. This system successfully integrates product design, tool design and manufacturing process into a single system.