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This paper explains how structural properties of radial and bias ply truck tires affect tire and vehicle performance. The author concludes that a knowledgeable evaluation of the pros and cons of both bias and radial ply truck tires be based on individual operational evaluations and the compromise of tire characteristics which best satisfy needs. Neither radial nor bias ply truck tires can be generalized as the superior choice since each type has areas of superiority.

A simple method based on bevameter soil values enables the engineer to evaluate the motion resistance of a pneumatic tire, in the given soil, and to perform parametric analyses of design and performance. The parameters measured include, besides soil parameters, the following characteristics of the tire: width, diameter, inflation pressure, carcass stiffness, and load. An inexpensive electronic desk calculator assures accuracy of prediction that is more than satisfactory.

This paper discusses equipment and procedures required to retread radial tires, emphasizing truck tires; reviews retreading process for conventional tires; and notes changes required for radials. In exploring the most extensive problem, inability to properly contract and expand radials to provide curing pressure, the paper indicates the need for an elastic matrix and supports use of precured tread systems.

A mobile test station has demonstrated its effectiveness in measuring straight-ahead traction coefficients of truck tires. This system - incorporated into a modified trailer-tractor combination - is designed to test the entire range of light-truck and heavy-truck tires now in production. The tire carriage assembly is installed in the center of the flat-bed trailer. The tire is hydraulically loaded to the ground through an opening in the bed. To ensure reasonably valid tire-traction data, the system is designed to minimize variations in such test parameters as load, brake line pressure, vehicle speed, and tire orientation. The mobility of the system makes it possible to test tires on various types of road surfaces, thus providing a complete spectrum of surface coefficients for both wet and dry conditions.

Tire traction test data has shown empirically that peak skid number dry pavement traction performance of bias ply tires is inversely proportional to the dynamic instantaneous tire load and is a function of inflation pressure. A modification to classical braking theory, which assumes constant traction coefficients at the tire-road interface, is therefore required to obtain maximum theoretical unlocked wheel vehicle deceleration. Optimum brake proportioning between front and rear axles is dictated by the maximum braking force which, with respect to each axle, can be generated at the tire-road interface. The inclusion of peak traction coefficient normal load sensitivity significantly modifies classical theory and changes the selection of brake force balance required to attain maximum theoretical deceleration capability. The importance of the effects of tire traction load sensitivity on the requirements of FMVSS 105-75 is discussed in this paper.

Ten sets of tires with nine different off-road tread patterns were tested on a paved surface using a towed, instrumented trailer to measure their cornering characteristics (wet and dry) and their braking performance (wet, full skid). The data obtained and a method for rank ordering are presented.

In recent years, significant advances have been made in analysis and testing of vehicle frames. In particular, sophisticated finite element techniques have been developed that enable the designer to predict and evaluate frame design from the drawing board stage. However, most applications of this technology have, until very recently, been aimed at evaluating static response of the frame to certain “program” loads. This paper describes applications of an approach that considers interaction between the frame and remaining vehicle components (suspension-power train-body structure) during dynamic loading of the entire vehicle. Techniques and applications of dynamic frame modeling are presented, including discussions of open section beam modeling, cutouts, joint flexibilities, and attachment considerations.

A mobile dynamometer has been constructed for measurement of the longitudinal force/slip characteristics of truck tires. The application of this apparatus in testing of a preliminary sample of tires has indicated that the shear force production properties of truck tires differ in many respects from the corresponding behavior of passenger car tires. These differences are discussed in terms of shear force sensitivity to a number of operating variables. The inadequacy of current semi-empirical tire models in representing truck tire traction is noted.

A comprehensive structural performance standard for school bus superstructures is being developed by a special task force on school bus safety organized by the School Bus Manufacturers Institute. This paper presents a progress report on the standard. Included is a review of the main features: the basic philosophy that the bus body must be capable of safe, controlled energy absorption in the event of a crash; the establishment of a statically equivalent test through the use of energy absorption as a simulation parameter; and detailed specifications for simulated crash modes. As a specific example, the rollover simulation test specification is presented in its entirety and a critical assessment is provided.

This paper outlines several specifications for heavy-duty truck wiring, especially wire and harness assemblies, and low-tension electrical wire. Emphasized are avoidance of substandard wiring and components, identification of circuits, grounding techniques, and construction. It is noted that improved specifications will result in reduced maintenance costs.

Obtaining and maintaining a stratified charge in a practical engine is a difficult problem. Consequently, many approaches have been proposed and reported in the scientific and patent literature. In attempting to assess the most profitable approach for future development work, it is important to group together similar approaches so that one can study their performance as a group. Making such a classification has the additional advantage of helping to standardize terminology used by different investigators. With this thought in mind, a literature study was made and a proposed classification chart prepared for the different engine combustion systems reported in the literature. For the sake of completeness, the finally proposed classification chart includes homogeneous combustion engines as well as heterogeneous combustion engines. Because of their similarity of combustion, rotary engines such as the Wankel engine are considered as “reciprocating” although gas turbines are not included.

A new concept in school bus body construction, the Wayne Lifeguard bus, provides solutions to specific problems cited by critics of school bus safety. This report chronicles development of the Lifeguard bus from conception through production and compares it with traditionally built buses.

In this paper, the experimental results concerning the effect of the geometrical and operating factors of the CVCC engine on NOx emission, taking into consideration the fuel economy, are described with respect to a specific engine configuration, and they are compared with the results calculated by means of the mixture formation model. Furthermore the relationship between the NOx emission level and specific fuel consumption has been explained, and then it has been shown that the controlled combustion obtained with the CVCC engine is very effective for eliminating fuel economy penalty and reducing emissions.

Vehicle systems utilizing a stratified charge engine have been evaluated for their emission potential. They have shown the ability to meet the 2.0 gm/mi NOx emission standard without EGR at low mileage, but require some form of aftertreatment device to simultaneously achieve emission levels of 0.41 gm/mi HC and 3.4 gm/mi CO. The system hardware required in conjunction with the stratified charge engine is described.

This paper describes the major electrical characteristics of the automotive power supply system. It is a compilation of existing data and new information that will be helpful to both the electrical component and electronic assembly designers. Previously available battery/alternator data is organized to be useful to the designer. New dynamic information on battery impedance is displayed along with “cogging” transients, regulation limits and load dump characteristics.

The engineer's traditional task of finding the best, most economical solution to technical problems becomes vastly more demanding in a time of energy and materials scarcity. Adaptability, flexibility, and quick access to suitable alternatives will acquire new significance in the next decade. Conservation measures, such as recycling, remanufacturing, and design for production and operational efficiency will increasingly figure in the development of transportation products. Beyond these and other changes in design emphasis lies a rising clamor for engineering accountability. Product liability legislation, many costly court decisions, and increased governmental regulation of many aspects of design all indicate growing public concern with the consequences of new technology. The trend toward establishing agencies for technology assessment will allow the engineer to participate in the evaluation of his designs in terms of their long-term social and economic impacts.

This paper presents the various features and operational properties of a two-dimensional mathematical model of crash victim motions. The earliest forms of this model can be traced to the early 1960s. Developmental work on two-dimensional models then continued both within the automotive industry and in independent organizations such as the Highway Safety Research Institute (HSRI). The most recent product of this activity is the MVMA two-dimensional mathematical crash victim simulation developed at HSRI for the Motor Vehicle Manufacturers Association. The features of this model include: 1. An eight mass representation of the human body where contact between the crash victim and the vehicle is represented in terms of independent force-deformation properties of the victim and the vehicle. 2. An extensible multi-joint neck and a realistically flexible shoulder joint. 3. A real-line representation of the vehicle interior or exterior where shape is given as a network of points. 4.

Development progress of the direct injected Stratified Charge Rotary engine program at Curtiss-Wright is detailed. Basic configurations are described and compared to both reciprocating stratified charge engines and the carbureted Rotary engine. Data and theoretical analyses are presented for progressive developments from initial feasibility testing in 1962 through current configurations now on test. It is concluded that the Stratified Charge Rotary Engine research efforts to date have demonstrated potential for an efficient, lightweight, compact, economic powerplant capable of broad range operations justifying further research efforts.

Improvements in cost or performance of an order of magnitude are occurring in the technology available to make small computers. This is occurring both in the processing unit with the microprocessor, and in the memories supporting the processor. As cost/performance is improved, the computer can be dedicated to more mundane tasks, such as carburetor control, while already being used in traffic light control. This development, permitting the use of arbitrarily large amounts of intelligence at low cost makes electronics capable of performing control functions formerly done with mechanical or hydraulic systems.

Whether we like it or not, increased usage of automotive electronics is going to focus attention on a class of components which may have little glamour or exotic appeal, but which will assume a role of vital and critical importance in tomorrow's automobile-the electrical connector. Though we may think of them as simple hardware, electrical connectors and interconnecting devices have reached a surprisingly high level of sophistication. This paper reviews the basic physics of electric contacts, with the objective of demonstrating how an understanding of the fundamental phenomena governing the behavior of electric contacts can be useful not only to designers and manufacturers, but also to users of electrical connectors.