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Development of a Speed Modulated Accessory Drive System for Transit Buses

Automotive Consultants Inc-Richard A. Tarkir
Tandem Engrg.-Gordon W. R. Taylor
Published 1989-11-01 by SAE International in United States
The paper describes the design of a new accessory drive system suitable for transit and highway buses. In a transit bus environment, the accessories consume more power than the drive energy up to about 65 Km/h. The new system provides a constant speed drive for the accessories allowing for more efficient operation and downsizing of the components. The use of the system also allows greater layout flexibility of components for the engine compartment designer. The system makes use of a mass produced automotive continuously variable transmission from Van Doorne Transmissions in Holland.An analysis of the power requirements, description of the installation layout and analysis of the component downsizing potential is presented. Description of the modifications to the basic automotive transmission is also provided.
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Design of a Regenerative Braking System for City Buses

Indian Institute of Technology Madras, India-G. V. N. Rayudu
The University of Toledo Toledo, OH-Satish C. Reddy
Published 1989-11-01 by SAE International in United States
In this paper a design of a regenerative braking system for use in city buses is proposed. This system consists of a fixed displacement hydraulic pump/motor unit and a hydro-pneumatic storage accumulator which is linked to the conventional transmission of a city bus. The use of a fixed displacement hydraulic pump instead of a variable displacement pump used in existing designs allows for a very significant reduction in cost at a small sacrifice in performance. A driving pattern was constructed using data collected from actual city bus routes in the city of Madras, India. The vehicle used to model the regenerative braking system was an Ashok Leyland Comet city bus. Computer simulations show that this system has the potential of providing considerable fuel savings while significantly reducing the level of exhaust emissions.
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Preliminary Evaluation of a Porous Metal Diesel Particulate Filter

Compix Enterprises, Inc. Latham, NY-L. R. Lefkowitz
Drexel University Philadelphia, PA-S. H. Brock, R. J. Tidona, N. P. Cernansky
Published 1989-11-01 by SAE International in United States
Because diesel engines operate on an efficient thermodynamic cycle at a low economic cost, their particulate pollution has been tolerated. However, the Environmental Protection Agency is now setting more stringent particulate emission standards to be met by all diesel-powered vehicles. One candidate system to meet the new EPA requirements is a continuously regenerative porous metal trap oxidizer device. A test program was initiated to evaluate the design and performance of this diesel particulate filter (DPF) on a single-cylinder diesel engine. This DPF is comprised of a rotating porous metal filter element driven by a variable speed electric motor, a heater element for filter regeneration, a nozzle for controlling the particulate deposit pattern on the filter element, a scraping device to insure proper filter regeneration, and a stainless steel housing. A 20-micrometer powder metal element and a 21-micrometer fiber metal element were tested. Collection efficiences in the 70 to 80 percent range were obtained for the optimum combination of heating and scraping for the 20-micrometer powder metal element at a pressure drop across the DPF of…
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Heavy Vehicle Braking - U.S. versus Europe

Vehicle Research and Test Center East Liberty, OH-Richard W. Radlinski
Published 1989-11-01 by SAE International in United States
Differences in regulations and design philosophies have brought about the development of significantly different hardware in the braking systems of U.S. and European heavy vehicles. In the service braking system, for example, European heavy vehicles generally have larger front brakes than their U.S. counterparts, and they are usually equipped with load-sensing brake proportioning valves (not used on U.S. vehicles). Emergency brake systems and parking brake systems are also different. This paper discusses those differences that have a significant impact on safety-related performance and presents the results of recent tests that were run to compare the braking performance of a U.S. five-axle tractor semitrailer combination to a European vehicle of the same basic size, weight and axle configuration in various simulated accident avoidance maneuvers.
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Electronic Transfer Case for 1990 Aerostar Electronic Four Wheel Drive

Dana Corporation-Wes Dick
Ford Motor Company-John Richardson
Published 1989-11-01 by SAE International in United States
A transfer case was designed to utilize electronic control. It has a planetary interaxle differential for proportional torque split. An electromagnetic clutch is applied across the differential to enhance mobility when road coefficients allow single wheel or single axle traction loss. The need for clutch actuation is monitored by an electronic module and sensor system, that detects abnormal amounts of differentiation in the interaxle unit. Clutch actuation is signaled and controlled by the module, which is also electrically connected to the rear axle ABS brake system to eliminate any possible simultaneous function compatibility issues.System emphasis is on foul weather mobility when negotiating highway and secondary roads. The family vehicle market was targeted and performance parameters were adjusted toward mobility and driver confidence to complete a given trip.
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Engine-Independent Heaters in Heavy Duty Applications: The European Experience

Espar Products. Inc.-Les Shepard
Published 1989-11-01 by SAE International in United States
The European transportation industry has a relatively long and varied experience with the use of engine-independent heaters for diesel engines. Because of strict anti-idling laws, high fuel cost, and union mandates relating to driver comfort, heaters are widely used to pre-heat engines and to maintain heat in cabs and cargo areas without idling. This presentation will cover representative heater designs and installations for heavy duty vehicles in various climates, and statistical data on the resulting fuel economies and reduction of noise, emissions, and engine wear. For example, heaters have been found to substantially reduce winter idling; this not only reduces fuel consumption and pollution, but also decreases engine wear. Aside from the economic advantages of this technology, it enables compliance with legislation common in Europe which curtails idling.
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Layout of Braking System and Influence on Handling under Consideration of European Braking Standards

IVECO Magirus AG Ulm, West Germany-F. Uffelmann
Published 1989-11-01 by SAE International in United States
The different applications of trucks (short-, medium-, long distance haulage, construction site) lead to very different requirements to be met by the brake systems. Concerning transmission the air braking system has great advantages for trucks and has therefore prevailed. On the other hand the design of the brake system must consider the regulations. In Europe common regulations concerning braking systems have been brought out since 1972 and have superseded formerly national standards. So the set up of the braking system mainly with regard to the brake balance is dealt with under consideration of the european braking standards. The influence of braking on handling is very important. Therefore the behaviour of a truck and a tractor/semitrailer is discussed for braking in a straight line and in a turn.
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Tires, Pressures and Pavements

Michelin Technical Services-Randall B. Clark
Published 1989-11-01 by SAE International in United States
All vehicle inputs to pavement are transmitted through tires. An understanding of pavement damage, therefore, requires an understanding of the role of the tire. This paper presents basic tire mechanics and discusses tire to pavement contact stresses. Determining the pavement damage potential of various tire/load/pressure combinations is of particular interest to pavement designers. In the past, attention has been focused on the load and pressure of particular tires without regard to their utilization. Herein is presented a new concept which incorporates the frequency of use of tires of interest since pavement damage is cumulative and results from multiple passes. It is logical then to focus attention on the most widely used highway tires, many of which are running overinflated. Specialty tires do not generate as many pavement cycles and, therefore, may not be detrimental to pavements even though they may require higher inflation pressures. Thus, proper tire pressure selection of widely used tires could tend to benefit pavements. Air pressure selection is explained with emphasis on matching pressure to the maximum service load. The advantages…
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Heavy Duty, Large Single Plate Diaphragm Spring, Dry Clutches

Eaton Valeo Clutch Corporation-J. J. (John) Willyard
Published 1989-11-01 by SAE International in United States
The typical heavy duty European truck clutch (large single plate, diaphragm spring type) has many functional advantages compared to the typical heavy duty North American truck clutch (twin plate, coil spring type).Design comparisons, installation measurements, drive evaluations, laboratory tests, fleet tests and theoretical analyses are used to demonstrate the following advantages:
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Increased Safety and Improved Comfort Thanks to Electronic Systems for Bus and Truck Applications

Robert Bosch GmbH-Reiner Emig, Heinz Decker
Published 1989-11-01 by SAE International in United States
Electronic systems have been used in commercial vehicles for quite a few years now. At the start, this primarily related to consumer electronics equipment (car radio and CB radio), but, since the late 70s, electronic control systems have also been used for a wide variety of applications in commercial vehicles. This development went hand in hand with the development of digital microcontrollers. It was only when such powerful electronic circuits were developed that it was possible to implement complex control tasks at feasible cost with adequately compact design. Nowadays, an extremely wide variety of systems is offered for the engine, suspension, brakes, comfort and entertainment.
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