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Technical Paper

Emission Comparison of DDC 6V-92TA on Alcohol Fuels

1990-10-01
902234
The Detroit Diesel 6V-92TA engine has been redesigned to run on alcohol fuels to meet 1991 urban bus emission standards. A prototype engine was tested over the EPA transient procedure, using mixtures of methanol, ethanol (with and without water), gasoline, and ignition enhancer. Regulated and selected unregulated emissions were measured. Organic material hydrocarbon equivalent (OMHCE) emissions were significantly above the hydrocarbon emission standard; however, emissions of CO and NO, were below the 1991 emission standards for the fuel combinations used. Particulate emissions were close to the 1991 urban bus emission standard for some configurations. The method used for calculating OMHCE emissions when ethanol was used is also given.
Technical Paper

Influence of Lube Oil Filter Performance on Engine Wear in City Buses

1990-10-01
902238
Past work suggests that finer filtration of engine lubricating oil reduces wear caused by abrasive particles. However, field data confirming this is limited. Filters were tested in the laboratory to establish micron ratings and in the field to relate filtration and wear. Field tests were conducted on city buses powered by Detroit Diesel 6V92 engines. Oil analysis was used as an indicator of engine wear and as the basis for comparing different filtration systems. Used oil was analyzed for particle size distribution, wear metal concentration and oxidation. Lower particle concentrations resulted when finer full-flow oil filters were used. Further reductions in particle concentrations resulted from the addition of bypass filters to the filtration systems. Corresponding decreases in engine wear metals accompanied reductions in particle concentrations.
Technical Paper

Unitized Radial Shaft Seals for Engine Applications

1990-10-01
902237
Today's engines for trucks and buses impose stringent requirements for a sealing system. This report lists the criteria the sealing system must meet and discusses the basic problems that need to be solved in the development of a Cassette Seal (unitized shaft seal). Based on actual designs, this report will explain the basic construction and will discuss the function and capabilities of this sealing system.
Technical Paper

A New Approach to Control the Regeneration Process In Wire Mesh Traps

1990-10-01
902236
The proposed wire mesh particulate trap employs a radical design for controlling the regeneration process. A prototype for a 6.2 L diesel engine was designed, built and tested to demonstrate performance characteristics and to correlate with an analytical evaluation. Presented in this paper is the first round of test data achieved thus far. Regeneration is initiated by an electric heating element embedded in the wire mesh, and a single butterfly valve controls the division of flow between the wire mesh and bypass channels. The trap design relies on oxygen in the exhaust gases for regeneration and employs a closed-loop control logic to limit the maximum temperature during regeneration. Test results indicate an ability to achieve high collection efficiencies at low pressure drops and a controlled regeneration process. Work continues to explore the regeneration characteristics under variable engine operating conditions.
Technical Paper

The GM 3500 HD Its Design & Development

1990-10-01
902242
The GM 3500 HD is a new class 4 truck being introduced this fall. Complementing GM's successful introduction of the 11,000 lb and 12,000 lb cab/chassis in 1990, this truck will have a GVW rating of up to 15,000 lbs. The design and development of this truck began in late 1987 and utilized selected common parts from GM's light duty pickup truck and commercial forward control chassis. Several features unique to the class 4 market were incorporated for increased customer satisfaction. Among these are low loading heights, three cab/axle offerings, large brakes, increased cooling, and large frame sections with straight flat rails behind the cab. A description of the vehicle features and how the design evolved and developed will be detailed. In addition, significant performance criteria that were met or exceeded will be summarized to establish the high level of vehicle performance achieved.
Technical Paper

Drivetrain Optimized Mercedes-Benz Vans with an Environmentally Improved Diesel Engine Concept and Aerodynamically Formed Design Features

1990-10-01
902243
The Mercedes-Benz van range T1 was upgraded in 1989 according to market analysis. In this van range, performance, lower engine speed and greater fuel economy as well as other user-friendly and environment-protecting factors have led to a further optimization of all important commercial vehicle-specific criteria like economy, safety and environmental compatibility.
Technical Paper

Zero Wear Analysis of an Injector Coupling

1990-10-01
902239
The coupling is an integral part of the Cummins CELECT electronically controlled injector. Excessive wear was observed on early designs of the coupling and coupling bore. The coupling wear was caused by a high stress concentration and excessive side loading of the coupling as it slid against the coupling bore. The zero wear theory was used to develop a coupling design where the maximum wear depth does not exceed half the peak to peak surface finish (zero wear) over the life of the engine. The side load exerted on the coupling was compared with the calculated contact pressure for zero wear. The undesirable effects of a square edge stress concentration are discussed in the zero wear model. The physical effects of the sharp edge and chamfered coupling edge are reported, but not analyzed in this paper. Three different coupling designs were investigated by applying the zero wear concept.
Technical Paper

Utility Vehicle Weight Problems and Design Considerations

1990-10-01
902241
Today the utility industry can choose from the widest variety of truck mounted equipment and chassis than ever before available. The increasing complexity of today's utility work vehicles and their regulatory environment requires increased emphasis on, and understanding of, how to predict and prevent vehicle weight distribution problems, and the design considerations which must be applied in order to provide a safe, legal, and successful complete truck assembly.
Technical Paper

New Developments in Drum Brake Analysis

1990-10-01
902249
This paper outlines the extension of the “GAPFRIC” concept to model in three dimensions the frictional interface between brake linings and drum of an S-cam operated pivoted abutment type of leading and trailing shoe brake assembly. The approach incorporates an accurate representation of the brake itself to include such features as drum stiffness and its mounting face. The brake shoe representations include the actual web and platform thus eliminating the need for shoe stiffness approximations to a curved beam of uniform section as used in previous 2D work. Analyses have been completed to investigate how the combined axial and circumferential distortions, within a brake, influence the temperature and interfacial pressure distributions and consequent brake performance. Consideration is given to the significance of shoe and drum stiffness and the effects of different lining moduli are illustrated.
Technical Paper

Truck Brake Block Swell, Growth, and Thermal Instability

1990-10-01
902248
All friction materials swell. That is, they temporarily increase in thickness with an increase in temperature. Brake block swell is usually greatest the first time the brake heats them above 150°C (about 300°F). Block growth also involves a change of thickness from heating. But growth is permanent. It is determined by measurements taken at ambient temperature, before and after the block is heated. This paper introduces and defines several types of truck brake block thermal instability, and describes their effects on brake performance. Methods to measure thermal instability of brake blocks are described. Data are presented for several original equipment manufacturer (OEM) and aftermarket brake blocks. Information is given on the ways truck brake block thermal instabilities may affect brake performance and durability. Through better awareness and understanding of these thermal effects, better brake performance can be achieved with OEM and replacement brake blocks.
Technical Paper

Suspension Bracket Design

1990-10-01
902246
Integrity of bolted joints is one of the most important issues faced by engineers designing a new vehicle. The work reported here summarizes efforts to develop a rear leaf spring attachment to a frame bracket. The job was done while trying to resolve incidents of joint loosening in a prototype truck. It was found that the bolt holding the joint together was underutilized due to the bracket being overly stiff and due to reinforcement placement. This article considers compression-tension loads in the joint, defines efficiency of the bracket, describes related laboratory and proving ground tests and gives recommendations for the design of similar joints. The recommendations could be used for design of any joint containing a rubber bushing with an inner sleeve clamped in a bracket with a bolt including the following suspension components: upper and lower control arms, shock absorbers, suspension links, etc.
Technical Paper

Designing a Radial Tire for MPV's

1990-10-01
902245
The increased popularity of MPV's (multi-purpose vehicles such as light trucks, passenger vans, and utility vehicles) during the 1980's has created an expanding vehicle market segment. These vehicles operate under a wide range of inflation and loading conditions which require all-season and off-road performance. Through the use of high technology computer-aided engineering (CAE) tools and testing methods, unique MPT (multi-purpose tire) concepts have been developed which reduce trade-offs and optimize overall tire performance.
Technical Paper

A Multi-Axle Steering System for Straight Trucks

1990-10-01
902258
A multi-axle (four-wheel) steering system for trucks and other commercial vehicles is described. The benefits of multi-axle steering and several examples of existing approaches are discussed. This leads to a set of defined goals for the subject design. The resultant design is described on a component and operational basis. Test results are analyzed to judge system performance. Finally, a discussion of concerns related to reducing the prototype to a manufacturable system is made.
Technical Paper

Development of a Medium-Duty Truck with a Mechanical Linkage Type Four-Wheel Steering System

1990-10-01
902257
In complying with a customer demand for improving low-speed maneuverability of commercial vehicles in narrow streets, a medium-duty truck with a mechanical linkage type four-wheel steering system with a hydraulic assist and a steering lock device is developed. A mode select gearbox allows a driver to select one of three rear-wheel steering modes; 2WS, same-phase 4WS, and opposite-phase 4WS. The steering lock device is locked during 2WS operation for preventing rear-wheel steering. An electronic control system is applied for easier mode selection, synchronization of locking and unlocking the steering lock device with a mode select operation, and vehicle speed limitation during 4WS operation. We made efforts particularly to suppress vehicle yaw motion when the vehicle is running in the same-phase 4WS mode. Several innovative new mechanisms are incorporated on this vehicle. This paper deals with these mechanisms and these functions.
Technical Paper

Switch Technologies for Heavy Duty Trucks

1990-10-01
902254
Throughout the 90's there will be continuous progress in switch technology applicable to heavy duty commercial vehicles such as trucks, buses, off-highway construction, agricultural, in many ways similar to that applied to passenger cars. Visibility, recognition of function, ease of function, location and consistence of operation will be principal areas of concern with the foremost being safety and longevity of service. That portion of the switch behind the dash panel also becomes increasingly important as space becomes more valuable. Major changes will occur both to the switches themselves as well as the method used for the signals such switches transmit.
Technical Paper

Extended Service 16.5 Inch Brake Design for Heavy Commercial Vehicles

1990-10-01
902250
Combined improvements in cam and shoe design, friction material formulation, and control of service hardware can produce a significant increase in life of a standard 16.5 inch diameter, cam actuated brake. Modifications of the cam and shoe permit the addition of usable lining volume. Optimum lining wear characteristics can be chosen from a number of evolving non-asbestos friction material formulas. Optimum shoe geometry and replacement linings are possible through control of service components.
Technical Paper

Performace Comparison of HFC-134a and CFC-12 in a Heavy Truck Air Conditioning System

1990-10-01
902261
This paper reviews vehicular wind tunnel tests performed on a heavy truck air conditioning system utilizing refrigerants HFC-134a and CFC-12 with various condensers. Refrigerant type was found to have little effect on system temperatures but considerable effect on system pressures. Condenser design was able to compensate for the increased pressures induced by HFC-134a. Condenser design also affected refrigerant charge weights of both refrigerants. Refrigerant charge weights are important today because of limited supplies of CFCs, and will be important in the future when more costly HFC-134a becomes the standard refrigerant. Structural durability of the compact, lightweight PF® condenser was found to be acceptable for heavy truck applications. REVISIONS RECENTLY MADE to the Montreal Protocol by its signatory nations have shortened the timetable for phaseout of ozone-depleting compounds.
Technical Paper

Application of Electronic Controls to On-Off Fan Drives and Air Conditioning Systems

1990-10-01
902260
The application of electronic controls to on-off fan drives and air conditioning systems offers improved operating efficiencies, extended component life, easier troubleshooting and reduced maintenance costs for trucks and buses. This paper describes the differences between the traditional control systems which rely on mechanical temperature and pressure switches and recently developed control systems which incorporate the use of electronic logic circuitry. A recently introduced on-off fan drive control system is discussed in detail. Also described is an advanced air conditioning control system currently being field tested.
Technical Paper

Fuel Tank Heat Shield Design

1990-10-01
902259
The placement and design of heat shields is a critical step in the design of todays vehicles. Computer modeling of heat shield configurations can help to optimize shielding performance while minimizing their size and cost. In this paper an attempt was made to determine the most effective shielding arrangement between the exhaust system and the fuel tank. It has been determined through numerical experimentation that vehicles equipped with plastic fuel tanks should have tank shields installed as a first preference over exhaust shielding in most practical applications.
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