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Structural attenuation of a running diesel engine measured by a new technique showed a constant value regardless of engine speeds. It was verified by this result that structural attenuation is a physical quantity unique to the structure of each engine and, therefore, a good indicator for evaluation of low noise engine structure. In addition, a hydraulic excitation test rig was devised to measure structural attenuation directly and to make effective use of it for noise reduction. Based on the accurate measurements by the excitation test rig, modal analysis and system simulation were conducted for implementation of countermeasures against noise.

A new oval test track will be designed, constructed and operated in a manner that will successfully pull-together representatives from virtually all of the key interests in dealing with the challenging issues of highway pavement and truck durability. With construction scheduled to begin in the Summer of 1998 and completion scheduled for late 1998 or early 1999, the mission and commitment for this venture is to pull-together the people from several state DOTs, respective universities, and, of vital importance, the truck manufacturing industry. Results from these tests, over a period of a few years, will provide answers that not only greatly improve performance of hot mix asphalt pavements in all state DOTs, but also efficiently and productively address issues of durability and wear performance of medium / heavy duty trucks and key components.

The new generation of air disc brakes developed by PERROT is suitable for Heavy Goods Vehicles (HGVs) from classes 4 to 8. Their design, construction and function is described in this paper. In addition, it is explained in which way the brakes are tested and proven on the different test rigs and in the vehicle.

Leaf springs must be regarded as safety components of a vehicle which failures can cause severe accidents. They have to fulfill various functions as a spring element and for guiding the axles and are also responsible for driving comfort. Therefore, the durability approval must be carried out under representative service-like loading, which take into account complex leaf deformations in operational usage. In this paper the influencing parameters for the durability approval of leaf spring suspensions are discussed and the test rig and the standardized test program SPRILOS (SPRIng LOad Sequence) for the durability approval are described.

The durability approval of truck axles is performed on proving grounds with well defined road characteristics as well as in laboratory test facilities simulating these loading conditions. These proof out tests are supposed to reproduce within a reasonable time the customer usage conditions which are expected during the life of a vehicle taking into account the large scatter of service. The programs and requirements are based on extensive measurements as well as long term experience. However, the development of vehicles for specific mission profiles as well as the introduction of components from new light weight material and innovative manufacturing technologies with different durability properties, requires procedures for the evaluation of the programs themselves. Within this paper the procedure of a comparative damage evaluation of test track and laboratory test programs with respect to an appropriated mission profile is demonstrated as example on a truck axle.

The design of wheel hubs must be based on stresses generated under customer usage through operational loads acting on the wheel. Therefore, the service loading conditions must be taken into account as well as the generated stresses and the hub fatigue properties. In this paper the decisive parameters for design and durability - operational loads, fatigue properties, which depend on material and manufacturing technology, and design - are discussed and the procedure for an optimum light-weight design is treated. Finally, the test procedure for durability approval, the corresponding test facility, the test programs and requirements, and some typical test results are presented.

Air spring systems are increasingly used on suspensions for commercial vehicles. To prove their durability a reliable test procedure is necessary: to be applied already in the development stage to be used to qualify individual air spring manufacturers and to assure manufacturing quality. In this paper the test procedure, the test facility and some test results are presented. In the test facility the air spring is mounted on a fixture and is loaded by a servohydraulic actuator. The mounting of the air spring allows to simulate all operational deformations, being decisive for the durability. Based on the extensive measurements on proving ground and public roads the test program was worked out. The test program includes besides the loading and deformations during driving also kneeling operations as well as high and low temperatures. The accelerated laboratory tests deliver results which correspond to the existing experience at the service usage.

The active and passive safety of a vehicle is composed of several features, which have a very important role in engineering a coach or a bus. The demand for a safe travel urged the bus industry to develope certain methods, through which a better quality and safer coach can be realized. The main areas of this problem are harmonization among brake and steering systems, wheel suspension, arrangement of the driver's compartment in order to improve the ride characteristics and a detailed structural analysis of the whole skeleton /body/. The analysis to be presented introduces a part of the whole development and engineering work at Ikarus Body- and Coach Building Works, and shows certain correlations among parameters determining the safety of a vehicle. The analysing method to be dicussed is suitable for computer programs and has been proved by tests carried out at laboratory and test tracks, mainly in Hungary.

This paper describes a Heavy Truck Round Robin Brake Test involving three test vehicles at ten different proving grounds. The purpose of the program was to evaluate the practicality and repeatability of the test procedure proposed by the ABS Test Procedure Task Force of the Heavy Truck Subcommittee of the Motor Vehicle Safety Research Advisory Committee to NHTSA and to compare surface friction characteristics of dry high Mu and wet low Mu (coal tar emulsion sealed) test surfaces at different proving grounds.

An indoor climate controlled high speed flat bed tyre test facility has been developed primarily for testing on ice. High friction tests are also possible. Braking and steering characteristics of heavy truck and car tyres can be measured. The facility has a stationary test wheel rig that rotates 90 degrees and a 55 m long moving steel track. The maximum speed is 40 km/h. Motions and wheel load are operated by computer controlled hydraulic actuators. Results from heavy truck tyre measurements on ice and dry steel show good correlation with vehicle tests. Passenger car tyres have also been successfully tested.

Frequency domain testing has had limited use in the past for durability evaluations of automotive components. Recent advances and new perspectives now make it a viable option. Using frequency domain testing for components, test times can be greatly reduced, resulting in considerable savings of time, money, and resources. Quality can be built into the component, thus making real-time subsystem and full vehicle testing and development more meaningful. Time domain testing historically started with block cycle histogram tests. Improved capabilities of computers, controllers, math procedures, and algorithms have led to real time simulation in the laboratory. Real time simulation is a time domain technique for duplicating real world environments using computer controlled multi-axial load inputs. It contains all phase information as in the recorded proving ground data. However, normal equipment limitations prevent the operation at higher frequencies.

Emissions from heavy-duty diesel vehicles have come under increased scrutiny with passage of the U.S. Clean Air Act Amendments of 1990. Methanol (M100) is seen as an important option for operators of transit fleets given the fuel's liquid nature and relative availability. This paper presents the results of a 36-month demonstration of a fleet of six methanol-powered transit buses equipped with DDC 6V-92TA engines. The engines were delivered in 1991 and were the first batch of Detroit Diesel engines certified to meet 1991 clean air standards. A similarly equipped control fleet of six diesel buses was tracked simultaneously. This paper includes an evaluation of bus operating data and emissions. Data such as fuel and oil consumption were collected along with a complete list of maintenance actions on both fleets. Chassis dynamometer emissions testing was carried out by Environment Canada at their River Road (Ottawa) test facility.

For commercial vehicles the availability of the truck has become increasingly important to the owner. Unexpected stops and visits to workshops are expensive nuisances not least if caused by some minor faults. The cab comfort and the vehicle response are fundamental to the driver. The accessibility and fault localizing are principal to the mechanic. The safety and the environmental impact are scrutinized by the authorities. The adaptability are vital to the dealers. The climate capability is needed to global presence and to long distance transports. Light weight structural solution permits heavy pay-loads. Low total usage cost is a must to be competitive. Advanced technology is implemented into the truck at increasing rate to satisfy all the aspects above. Quality has become the key issue to reach for the high standard demanded.

The objective was derivation of a tire braking/cornering force model based on only a few standard tests, so that elaborate testing of all possible combinations of lateral and longitudinal forces could be avoided Such a model would be particularly useful for truck and bus tires because testing large tires is expensive and appropriate testing facilities are rare The required model can be derived from the concept of the slip circle (not a friction force circle) Using the slip circle concept, all tire forces at any cornering/braking combination can be predicted from the results of only two basic tests -- a free-rolling cornering test and straight-line braking test The slip circle concept has been incorporated into a subroutine called the COMBINATOR -- a piece of public domain software sponsored by SAE Cooperative Research This paper discusses the Slip Circle Model, introduces the COMBINATOR, and demonstrates effectiveness by comparison of modeling results and experimental data

The objective of this paper is to demonstrate the use of computer modeling and simulation as an effective analytical tool which can be integrated with representative data from user duty cycles and validated against response data measured on a vehicle. Computer modeling is an increasingly important design tool, but the necessity of real-world test data is often overlooked. This paper will present an example of the process, using the Logistics Vehicle System Replacement (LVSR). The project uses real-world proving ground data as inputs to the vehicle model, as well as instrumented vehicle test data to validate outputs of the vehicle model.

Radian Inc, working in partnership with the U. S. Army National Automotive Center, has been designing and developing a Thermal Imaging Inspection Station (TIIS) for assessing and diagnosing the condition of truck tires and other components of vehicles in a real-time operational environment. Recently, multiple failures of M939 truck tires (14.00R20, Load Range J, manufactured by both Michelin and Goodyear) have been reported, and the U. S. Army Tank-Automotive and Armaments Command (TACOM) contracted with Radian to participate in a tire-testing program, using the TIIS at the TACOM tire-testing lab and in field tests, in hopes of determining the cause of these failures. Tires that failed on the tire dynamometer demonstrated similar problems to tires that failed in field operations. Thermal images recorded in the lab and in the field under similar conditions were highly comparable.

As a response to the continuing demand for lower weight and improved driver comfort, Hendrickson Truck Suspension Systems has designed and developed an innovative front steer axle and air suspension module for a 5.5 tonne (12,000 lbs.) axle rating. A system for a 6.7 tonne (14,600 lbs.) axle rating is under development. The suspension is a steel spring and air spring load-sharing system, offering roll stability and handling better than any on highway mechanical system while giving superior ride characteristics. In addition to the suspension, the module features an efficient fabricated steel steer axle and clamp group. The clamp group provides progressive support to the vertical legs of the axle housing with increasing bolt torque, thus maintaining the structural integrity of the box section axle. The complete system is significantly lighter in weight than competitive spring and forged axle suspensions and is designed for minimal maintenance.

Lincoln Composites has conducted research to reduce cost and weight of all-composite NGV fuel containers. This research was conducted in cooperation with Battelle and others under GRI funding. Heavy tow carbon fiber was investigated as a means of reducing material cost. Advantex® glass fiber was evaluated as a replacement for conventional E-glass. Changes to the dome contour reduced fiber stresses due to bending. Other design and manufacturing issues were addressed. The design was finalized and passed all required NGV2 qualification tests, which were conducted by Powertech Labs. The overall program goals for cost and weight were achieved.

Recent advancements in three-dimensional digital terrain mapping and vehicle simulation technology present an opportunity to introduce “real-world feedback” early in the design process. Designers of suspension, braking, steering and safety systems can evaluate and optimize designs using computer simulation of a vehicle on the digital proving ground (DPG). A range of possible design behaviors can be identified and analyzed prior to expensive prototyping and testing. Even a series of specific test maneuvers may be evaluated prior to actual testing to ensure safety of the driver and prototype vehicle. As a result, the design process is more efficient and the use of the actual proving ground is more cost effective. This paper presents an overview of the use of the digital proving ground for vehicle design evaluation. Several examples of digital proving ground tests will be discussed.

The Hybrid Electric Transit Bus (HETB) was dubbed “Space Bus” by the technicians of the Cleveland Regional Transit Authority because of NASA involvement. Developed as a proof of concept test bed, the HETB has proven the use of ultra-capacitors as a viable energy storage device. In the process, a cost-effective engineered hybrid drive system was also developed. The HETB made its debut at the 1997 SAE Truck and Bus Conference in Cleveland. After the show, the HETB was prepared to complete the first round of proving ground testing under the scrutiny of NASA scientists.