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A radically new approach to the design of bearings demonstrated feasibility in a U.S. Army SBIR1 program. It was first applied to universal joints on the HMMWV (High Mobility Multipurpose Wheeled Vehicle) in order to maximize the concept's performance benefits and optimize vehicle cost savings. The program2 was one of five recipients of the U.S. Army's 1995 SBIR Phase II Quality Awards. The concept has been issued three patents3. This paper presents the theory and documents HMMWV field test results in the successful development of a new universal joint with bearings that eliminate field lubrication and provide a major reduction in maintenance.

A generalized theoretical model of tire cornering properties is presented in steady state condition with lateral deflection of tread and complex deformation of carcass under consideration. The model is suitable for full range of vertical load and slip angle. Six parameters are defined to represent the characteristics of tire stiffness, contact pressure distribution and carcass deformation. The model is validated against test data. Some simplified models, e.g. brush model, HSRI model when longitudinal force is zero, Fiala model etc., can be derived as some specific cases of this model. The analytic model provides a sound foundation for semi-empirical expression and gains insight into study of vehicle system dynamics.

Based on the tire cornering properties in steady state condition, a theoretical model of non-steady state tire cornering properties (NSSTCP) with small lateral inputs is presented. The outputs of the model are lateral force and aligning moment, while the inputs are yaw angle and lateral displacement (or turn slip and slip angle). The deformation characteristics of contact patch are analyzed in non-steady state condition. The flexibility of tread and that of carcass are both taken into account. The deformation of carcass is assumed to compose of translating part, bending part and twisting part. The tests of NSSTCP including pure yaw motion and pure lateral motion are realized with step inputs of yaw angle and slip angle respectively and test data is then transformed into frequency domain. The model is validated through comparing the computational results with test frequency response.

The detailed analysis of the tire loading and the subsequent deformations under operational driving conditions is of great importance for the basic investigation of the functionability as well as for the input and verification of the computer simulation of tires. Such data are also required for the definition of mission profiles as well as for the derivation of programs for the durability approval. The principles for the measurement of global tire deformations by spring loaded deflection transducers arranged in-between the tire crown and the rim are described. By combination of those sensors with wheel force transducers the determined tire deformations are referred to the actual service loading conditions. The sensors and transducers are described and examples of field measurement on heavy truck tires under distinguished driving conditions are presented.

Performance measures such as static roll stability, rearward amplification and load transfer ratio are a means to assess the engineering performance of heavy vehicles and to support truck size and weight policy decisions. It was expected that, for a particular vehicle configuration, there would be some degree of correlation between the various performance attributes. For example, a relatively high static roll stability may be associated with a relatively low load transfer ratio, at least within a particular vehicle configuration. In terms of developing performance measures such correlations are of great significance because (i) the number of performance attributes requiring specification may be reduced and (ii) potential conflicts between performance criteria in different attributes may be avoided. This type of analysis has not been carried out before, and requires a large database of performance numerics in order to determine relationships between each of the performance attributes.

The objective of this paper is to describe a Class 8 heavy truck that the Virginia Tech Center for Transportation Research has modified and instrumented for use in evaluating Intelligent Transportation Systems (ITS) technologies. The truck is capable of recording a variety of data, both electronic and video, in real-time from a suite of sensors and cameras that have been inconspicuously mounted on the tractor. The tractor, trailer, and instrumentation package enable Virginia Tech to conduct commercial vehicle ITS research related to safety and human factors, and advanced vehicle control systems (AVCS). This paper will describe the instrumentation package, and address both general and specific types of research that can be performed using this truck.

Steady state non-linear cornering properties, giving the lateral slip to force characteristics of individual axles as result are determined from experimental data. The handling diagram of the vehicle combination facilitates an examination of any unstable steady state yaw response. The method offers a viable alternative to the traditional constant radius test. Axle data is derived using the bicycle model via measurements taken during handling manoeuvring while the magic tire formula is used for adaptation of measured axle data into mathematical representation. The results of axle data evaluation, using a semi-trailer combination, manoeuvring over high friction surface conditions are presented.

This paper describes an economical rear obstacle detection system that eliminates the tractor to trailer cable connection using infrared (IR) wireless communication. The Trailer Subsystem operates whenever power is applied to the trailer from the J560 power connector. The subsystem transmits Obstacle Detection information to the tractor via an IR transmitter. The Tractor Subsystem is activated when the vehicle is put in reverse. Thus the entire system is active only when the vehicle is backing. During operation this subsystem receives and decodes the transmitted signal from the trailer and determines what, if any, warnings should be given the operator.

Research is currently being undertaken to develop improved suspensions for Combat Support Vehicles (CSV's). Part of this work focuses on the feasibility of using intelligent suspensions to continuously optimise the vehicles performance as the operating environment changes. For an intelligent suspension to be effective in this case, it should enable increased vehicle speed from an improvement in ride performance whilst not detracting from vehicle safety or handling performance. This paper investigates the power consumption of a CSV vehicle with a slow-active suspension. From the power consumption it is possible to estimate the extra fuel consumption and reduction in vehicle top speed. The power consumption was evaluated for a set of representative terrain profiles and vehicle speeds, demonstrating the trade off between suspension power consumption and ride performance improvement.

A government, industry, and university cooperative is developing an advanced hybrid electric city transit bus. Goals of this effort include doubling the fuel economy compared to current buses and reducing emissions to one-tenth of current EPA standards. Unique aspects of the vehicle's power system include the use of ultra-capacitors as an energy storage system, and a planned natural gas fueled turbogenerator developed from a small jet engine. Power from both the generator and energy storage system is provided to a variable speed electric motor attached to the rear axle. At over 15000 kg gross weight, this is the largest vehicle of its kind ever built using ultra-capacitor energy storage. This paper describes the overall power system architecture, the evolution of the control strategy, and its performance over industry standard drive cycles.

Natural Gas engines are viewed as an alternative to diesel power in the quest to reduce heavy duty vehicle emissions in polluted urban areas. In particular, it is acknowledged that natural gas has the potential to reduce the inventory of particulate matter, and this has encouraged the use of natural gas engines in transit bus applications. Extensive data on natural gas and diesel bus emissions have been gathered using two Transportable Heavy Duty Vehicle Emissions Testing Laboratories, that employ chassis dynamometers to simulate bus inertia and road load. Most of the natural gas buses tested prior to 1997 were powered by Cummins L-10 engines, which were lean-burn and employed a mechanical mixer for fuel introduction. The Central Business District (CBD) cycle was used as the test schedule.

Through the clean air act and other various federal and state legislation, fleets are facing greater pressures to use alternate fuels. This is not because alternate fuels are so desireable, but that they are potentially the fuels, used with recent engine developments, which can meet the future emission standards of the E.P.A.. These alternates are: liquified natural gas, compressed natural gas, methanol and ethanol. Currently there is no national or local publically available infrastructure system for the distribution of these fuels. Despite the weakness in the infrastructure system, alternate fuel usage seems certain to grow in the future. This paper will outline two micro-tests conducted in Chicago using biodiesel as an alternate fuel for in-service motorcoaches. This was an exploratory investigation to determine the effects of the fuel on the engine, the performance characteristics and the infrastructure requirements needed to use this fuel.

Shock absorber tuning has become an important part in today's ride development of commercial vehicles. With dampers conventionally only capable of one damping characteristic for different operating conditions (load, speed, road) this is leading to a compromise in ride quality and safety. This paper describes the benefits of two different intelligent damping control systems for trucks, buses and trailers. The shock absorbers are controlled either electronically or pneumatically. Results are presented showing that with such a system, ride safety and comfort, cargo protection and road friendliness will be improved.

A prototype active cab suspension has been built and evaluated. As the system uses low bandwidth valves and is powered by the existing power steering system, it is perhaps a good example of expected performance from a production active control system. System architecture is described. The control system is presented, and system performance is reported.

The lead battery industry's proactive approach to working with state and federal regulators on environmental regulatory and legislative issues has proven to be a successful tool in producing a high recycling rate for lead-acid batteries. The reverse distribution system set up by the battery industry to collect and recycle lead-acid batteries alleviates the concerns raised by governmental agencies and environmental groups over how the batteries are handled. Not only does the industry benefit from better public relations as a result of their commitment to ensure a high recycling rate, it also provides a reliable source of recyclable materials necessary to operate battery recycling facilities.

According to the recent trend of high speed and heavy load in truck & bus services, supplemental brake systems are highly desired to obtain safety, easy operation, and economical advantages such as longer lining life. To meet such requirements, a compact eddy current brake system (ECB retarder) using powerful permanent Nd-Fe-B magnets has been designed, manufactured, and supplied to market. This paper reports the basic idea, construction design, and material selection of new ECB retarders. Using the derivation from Maxwell equations, the retardation force was obtained, and the design was made based on the obtained principle.

Austempered Ductile Iron (A.D.I.) is an engineering material gaining wide acceptance by designers of Automobile Components, Agricultural Equipment, Railroad Parts, Mining Tools, Transportation Equipment, and General Machinery. A.D.I, has a unique microstructure which enables it to display remarkable mechanical properties for a low manufacturing cost. The A.D.I. technology involves two processes: A) A good quality ductile casting, free of shrinkage voids and eutectic carbides, with closely controlled chemistry and graphitic nodule count. B) An austempenng heat treatment cycle which consists of austenitizing and an isothermal quench. The success of austempered ductile iron as an engineering material lies in its unique after heat treatment microstructure which consists of acicular ferrite mixed with high carbon stable austenite. Due to the differences between the metallurgies of cast iron and steel, this structure does not occur in commonly used steels.

It is the intent of this technical paper to inform tapered roller bearing producers and manufacturers of axle nuts about the results of recent research dealing with wheel bearing preload axial pressures. A testing program was conceived and perfected in the interest of correlating internal tapered roller bearing axial load pressures with the clamping forces introduced by tightening axle nut systems. Using the information presented in this technical paper, it will be possible for all manufacturers of wheel end components to develop appropriate installation instructions for their proprietary products. These instructions would be suitable for original OEM assemblies or during retrofit operations.

Modem power steering systems for heavy trucks are available with a variety of hydraulic valve options. Two of these options, port design and torsion bar spring rate, directly influence vehicle handling characteristics. This study focuses on the effects of steering torque requirements and valve response on steering activity, which contributes directly to driver fatigue. A test was performed measuring steering torque and steering position at highway driving conditions to compare long term steering effort and corrections with different valve options. The findings indicate lowered effort in power steering systems does not increase steering corrections, if accompanied by increased valve responsiveness.

This paper will review the current truck and bus steering column technology and marketplace in Europe. European specifications, norms and customer driven performance criteria are discussed. New technical solutions coming onto the market place are creating increasing diversity in techniques applied to steering column design and these are examined. An overview presentation of the Pailton Engineering past and current product and some of their development ideas looks at the two markets, truck and bus, separately. The concept of pedestal floor mounted and bulkhead mounted steering columns is considered. Mechanical clamping and air unclamping are explained and the use of electrically adjustable columns in trucks and buses is discussed. The concept of steering systems engineering to include the steering column as a vital integrated member in a steering system instead of a single stand alone item is discussed.