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A method of predicting highway truck/tractor component lives based on warranty data is provided. This method incorporates computer modeling techniques into standard reliability analysis procedures to facilitate Reliability Estimation and Failure Prediction. Specifically, published truck/tractor usage data provided the basis for the computer modeling, and Weibull Distribution Analysis methods were utilized for Reliability Estimation. General considerations in the development of the computer model, and specific suggestions for the application of the method to vehicle applications other than highway truck/tractors are provided.

Well defined design criteria and extensive testing are necessary to develop a reliable agricultural vehicle monitoring and information system.

A refined method for determining true ground speed has been developed which is particularly applicable to agricultural and off-highway equipment. The radar sensor provides a conditioned output signal whose frequency is directly proportional to true ground speed. Applications include precise vehicle speed display, transmission control, wheel slip control, and agricultural equipment control for planting, spraying, harvesting, etc. Advantages include increased farm productivity, maximized crop yield, reduced fuel consumption etc. The radar sensor can interface with on-board microprocessor based equipment for controlling farm implements with greater accuracy and at higher vehicle speeds than previously possible. The radar sensor described is readily adaptable to most tractors, easy to install and service, extremely rugged, and environmentally secure.

This paper considers alternative methods for measuring the true ground speed of tractor vehicles as a means for controlling wheel slip to improve traction efficiency and reduce vehicle and tire wear. Test data are presented on the slip of both driven and undriven wheels for a tractor operating under various speed, load, and soil conditions. Data from a “fifth wheel” operating on smoothed and compacted soil behind a draft sled also is included. Vehicle speed determined from the speed of undriven wheels as well as vehicle speed derived from driven (slipping) wheels using a number of data processing strategies is not sufficiently accurate for either vehicle monitoring or closed loop control. The errors of single and dual beam doppler radar speed sensors caused by vehicle motion are analyzed. Single beam radar systems are shown to operate with an accuracy acceptable for operator control using signal integration times greater than approximately one second.

A need to improve agricultural tractor productivity and in-field fuel economy has prompted the development of a new power shift transmission for John Deere Tractors. With all 15 forward speeds power shiftable under load, the operator can achieve and maintain an optimum match between implement load and tractor power for maximum fuel efficiency with little effort. Shift control, torsional vibration isolation, increased efficiency, and mechanical front wheel drive capability are vital parts of this new design.

Attempts to improve fuel efficiency of farm tractors motivated the development and application of viscous fan drives to agricultural tractors. Early drives on tractors performed in an on-off fashion similar to drives widely used in on-highway trucks and passenger cars. Due to the high engine power and slow moving operational modes of farm equipment, a drive which continuously modulated output speed as a function of cooling requirements was desired. A design was generated and applied to agricultural tractors. Resulting vehicle performance improvements include reduced fuel consumption, reduced operational noise, and reduced engine warm-up time.

A Vehicle-Engine-Cooling (VEC) system computer simulation model was used to study the transient performance of control devices and their temperature settings on oil, coolant and cab temperatures. The truck used in the study was an International Harvester COF-9670 cab over chassis heavy-duty vehicle equipped with a standard cab heater, a Cummins NTC-350 diesel engine with a McCord radiator and standard cooling system components and aftercooler. Input data from several portions of a Columbus to Bloomington, Indiana route were used from the Vehicle Mission Simulation (VMS) program to determine engine and vehicle operating conditions for the VEC system computer simulation model. The control devices investigated were the standard thermostat, the Kysor fan-clutch and shutter system. The effect of shutterstat location on shutter performance along with thermostat, shutter and fan activation temperature settings were investigated for ambient temperatures of 32, 85 and 100°F.

A computer simulation program was developed to simulate the thermal responses of an on-highway, heavy duty diesel powered truck in transient operation for evaluation of cooling system performance. Mathematical models of the engine, heat exchangers, lubricating oil system, thermal control sensors (thermostat and shutterstat), auxiliary components, and the cab were formulated and calibrated to laboratory experimental data. The component models were assembled into the vehicle engine cooling system model and used to predict air-to-boil temperatures. The model has the capability to predict real time coolant, oil and cab temperatures using vehicle simulation input data over various routes.

Application of electronics to agricultural and construction vehicles is shown to be motivated by two basic needs — increased productivity and improved protection. Increases in productivity include gains in both machine performance and operator efficiency. Improved protection includes prevention of expensive machinery failures and more effective safety systems to protect the operator. Reasons for needed improvements in productivity and protection are first described, then several examples are given of current electronic systems used in both agricultural and construction equipment. Finally, future electronic systems are considered and many examples of anticipated next-generation agricultural and construction developments are detailed.

Electronic devices have been making rapid inroads in automotive products over the past five years. Gains that have been seen in the passenger car segment will naturally extend to the truck and bus markets. For this extension to be successful, the special needs of the truck and bus customers must be met. This paper summarizes the market segmentation of this industry, surveys currently available electronic products, and indicates probable direction for future developments. The opportunity is present, the technology is ready, and the challenge is to carry out the application of electronic technology judiciously providing the customer with value for his dollar and making him more competitive in an increasingly competitive business environment.

Most bus, truck and off-highway vehicle automatic transmissions today have hydraulic controls similar to the type used on automobile transmissions. Because the number of transmission applications is increasing rapidly and customer demands for improved vehicle performance, greater durability and better reliability are growing, present hydraulic controls are being pushed to their capacity. Overall transmission performance can be improved by replacing hydraulic controls with electrohydraulic controls which incorporate microcomputer-based electronics for intelligence, but continue to employ hydraulics for power to apply the clutches in the transmission. Important benefits available with a microcomputer-based controls system include: shift point optimization, improved shift point accuracy, transmission-application customization, mechanical linkage elimination, improved fuel economy, and overall powertrain optimization.

Several factors (changing operator skills, changing legislation, and changing technology among others) are creating the need for improved vehicle diagnostic systems. There are many difficulties in designing good diagnostic systems that incorporate the optimum compromise between effectiveness in locating a fault, and test hardware overhead. Before such a compromise can be arrived at, it is necessary to move away from the add-on approach to diagnostic hardware, and treat failure detection, isolation, and repair as a total system that pulls together vehicle, dealer, and factory capabilities.

The use of electronic instruments on International Harvester agricultural equipment to monitor critical machine performance is a reality today. The first section of the paper provides a synopsis of the instrumentation systems currently available. The second section describes some of the display and transducer requirements needed for the future. The last section describes some of the unique environmental requirements for on-board agricultural equipment instrumentation systems.

A combination of subscale wind tunnel model tests and full-scale coast-down and highway fuel consumption tests have been conducted on baseline and low-drag tractor-trailer configurations. Fuel savings calculated for the low-drag configuration, based on the model drag data or the full-scale drag data, correlate quite well with fuel savings obtained from over-the-road tests at highway speeds. Sub-scale drag tests for flow-vane and boattail devices provided drag reductions of about 48 percent and 15 percent, respectively, for bus- or motor-home-type vehicles. Full-scale boattail drag data are also presented.

Contemporary wind tunnel test techniques used to determine the aerodynamic drag of model trucks are reviewed. The effect of drag coefficient changes are evaluated in terms of reductions in fuel consumption and several comparisons are made between wind tunnel predictions and road measurement. The drag reductions and fuel consumption reductions presently available and those expected from future aerodynamic modifications are examined, based on wind tunnel experience.

The problem of evaluating the fuel savings effectiveness of a truck aerodynamic drag reducing device in an over-the-road test is considered. The sensitivity of a vehicle's fuel consumption rate to factors other than the drag reduction produced by a device is discussed to illustrate potential sources of error. Evaluations of typical performances of several different drag reducing designs demonstrate how effectiveness varies as a function of the design of a device and the short-term and the long-term wind conditions under which it operates. Current SAE over-the-road test procedures are discussed in terms of the correlation between the test result and the probable long-term final savings produced by a device. Results from several fleet experiments are reviewed to illustrate differences in fuel savings results as functions of the drag reduction potential of the vehicle, the design of the device, the test conditions, the test technique employed, and the method of data interpretation.

Worldwide interest in secondary braking systems on buses and trucks is increasing. The causes of this interest are the needs to extend service brake life and to help meet upgraded European braking standards. To satisfy this demand, Detroit Diesel Allison has developed an integral output retarder for the Allison MT600 transmission with future adaptability to the V730 and HT740 transmissions. This retarder provides sustained high power absorption at high output speeds as well as braking capability down to very low output speeds. The unique configuration of the Allison retarder includes both friction clutch and hydraulic retardation. Development of the retarder required combining these two methods through use of a control system which provides quick response leading to smooth braking and suitable operator controllability.

A digital signal processing method is employed to generate mobility functions and acoustic transfer functions. The acoustic transfer function is defined as the sound pressure level per unit force at the cab mount. Peaks in the driving point mobility function) measured at the cab mount locations, correlate with peaks in the acoustic transfer function. These functions were evaluated in the frequency range 50–1000 Hz where truck interior noise is strongly influenced by structural vibration. Reducing the mobility leads to a reduction in the acoustic transfer function. A method for evaluating bracket structural changes was determined and some general design guidelines established for the reduction of truck interior noise.

In order to react to continuing changes in the nature of journeys made using urban buses, it is suggested that bus design should be viewed in the context of the whole journey. Each journey has a number of features; including the person who makes it, its purpose, the stages of the journey, the common elements of each stage, and the custom and practice it reflects. Examples are taken to show how each feature affects bus design, and a number of areas for significant design innovation are identified.

Bus remanufacturing has grown into a nationally recognized field in transit industry. Complete restoration of critical structural components is very important for its sound growth. Structural parts are examined to reveal their deterioration in unexposed areas. Road call data is compared to analyze the performance of remanufactured buses. Development of a positive scope of work and quantification of contractor evaluation criteria are discussed.