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For many years, the primary consideration for determining motor gasoline volatility specifications has been good car performance, i.e., fast start-ups, freedom from vapor lock, and good driveability. Now, for late-model cars, there is a new consideration for volatility control. This is exhaust emissions. Fuel volatility has been found to have a significant effect on the exhaust emissions of many late-model vehicles. A decrease of 5 psi RVP from current levels increased exhaust CO an average of 28% at 70°F and 22% at 30°F in a group of eleven cars. Exhaust hydrocarbons were increased an average of about 5% at both temperatures. Now, before lowering fuel volatility, it is important to consider the effect the change will have on exhaust emissions as well as car performance.

Automotive friction materials are composites containing three kinds of components: an organic binder, fiber for reinforcement, and property modifiers. At low braking temperatures, the wear rate of the friction materials is controlled primarily by abrasive and adhesive mechanisms. At higher braking temperatures, the wear rate increases exponentially with increasing temperature due to thermal degradation of the binder and other components, and the exponential wear rate is frequently accompanied by brake fade. Thus, one method of reducing thermal wear and fade tendency is to lower the temperature at the rotor/friction material interface. Since the rate of heat transfer from the interface is mostly dependent upon the conductive and convective modes, a rotor of high thermal conductivity will have a significant advantage over a rotor of low conductivity, if the heat capacity remains the same.

This paper presents the findings of the second year of a planned three-year program to investigate the hydrocarbon losses sustained during the refueling of passenger cars. The magnitude and frequency of occurrence of spills by type of spill were estimated from observations of refueling operations during a five-city, four-season field survey. The magnitude of the average observed loss due to spills was 10.6 g and the probability of a spill loss was 0.329. The average spill loss was 3.5 g per refueling operation or 0.3 g/gal of dispensed gasoline. Measurements of displaced hydrocarbon losses were made under controlled conditions during a laboratory study conducted in the Scott all-weather room. A regression analysis of these data yielded a model which estimates the displaced hydrocarbon loss as a function of dispensed fuel temperature, displaced vapor temperature, and the Reid vapor pressure of the fuel.

The A-weighted sound level accounts for the bulk (but not all) of the jury's reaction to the sound of trucks coasting on a variety of tires. A component of the jury's reaction is related by the study to the manner in which the sound decays after the vehicle passes the point of observation. This component also appears to depend strongly on the characteristics of the sound. The jury's reaction shows two forms of distortion: end-of-scale compression and temporal drift. The analysis attempts to account for these factors and to see beyond them into the jury's basis for reacting.

The SAE Truck Tire Noise Subcommittee, as a part of its efforts toward writing a measurement and evaluation procedure, conducted an experimental test program for relating objective and subjective assessments of truck tire noise. The program comprised a series of designed experiments involving 6 trucks, 18 sets of tires, and 5 vehicle operating modes. The test runs were presented in random fashion to a jury situated alongside a highway. The subjective noisiness ratings and the A-weighted sound levels obtained verified the design objectives of the experiment and, further, correlated well with each other.

A noise standard is acceptable only if it isolates the area of concern (tire sounds), correlates to human response, and is repeatable, easily understood, and economically feasible. With these goals attained, the SAE Subcommittee on Truck Tire Noise proposes their recommendations on “Sound Level of Highway Truck Tires-Recommended Practice SAE XJ57.” Part I of this paper contains the final draft of the test procedure that the Subcommittee has proposed to SAE committees as a recommendation. Part II explains and supports the Subcommittee's decisions for the recommended specification.

The nature of the sound produced by running truck tires is primarily due to the tread pattern design. At 50 mph the sound consists of a fundamental in the frequency range 300-400 Hz and of several higher harmonics. Each of these harmonics, including the fundamental, may consist of several separate frequencies; however, the spread of these frequencies is less than one-third octave. The singing, persistent sound produced by certain tire designs is shown to be associated with the level of the higher harmonics, particularly the third and fourth.

The A-weighted sound-level measurements of truck tire sounds are dependent on a number of variables. These parameters, in general, include vehicle speed, load, inflation pressure, tread wear, test surface, tread pattern, distance from the microphone to sound source, time, number of tires used on the vehicle, tire size and type, etc. These parameters are individually considered and their effects on the A-weighted sound level measurements of truck tire sounds are discussed in this paper.

A conceptual framework has been developed for investigating the generation of sound by tires. Recent measurements have quantified some of the characteristics of truck tire sounds. The characteristics that have been measured include the peak A-weighted sound level and its dependence on the tread pattern, speed, and deflection of the tire; the effect of the road surface on tire sound levels; and the spectral distribution of tire sounds. These characteristics are discussed in terms of the mechanisms of tire sound generation.

As highway development programs brought increased truck traffic through formerly isolated communities, public sensitivity to truck tire noise increased significantly. Industry was alert to the possible consequences of social and legal pressures and acted in concert to set up standards for noise control and for establishing criteria by which to measure annoyance levels. Work by several leading associations provided a starting point for investigations by the SAE Truck Tire Noise Subcommittee. The Subcommittee's efforts resulted in formulation of a tire testing procedure and a consolidation of requirements to be incorporated into a proposed standard. This paper reviews the objectives and approaches of the Subcommittee and serves as an introduction to the accompanying papers.

A computer model of a tractor-semitrailer is developed which extends that given by Mikulcik in SAE 710045 (Ref. 10 of paper). The extended model allows translation, yaw, roll, and pitch of both tractor and semitrailer. Lateral and fore-and-aft weight transfer is displayed. Wheel dynamics are included, and effects of wheel slip, slip angle, vehicle speed, and tire load are used in the calculation of the tire forces. The vehicle is maneuvered by a simulated driver who specifies the front-wheel steer angle and the brake torques. The ability of the model to accurately describe a real vehicle is studied by using the model to simulate a full-scale experimental test. The model is also used to study two types of proportional braking for a tractor-semitrailer executing a large-radius turn on a wet asphalt track.

This paper reviews the procedures and experience of the Army in applying the prototyping concept to the development of aircraft capable of satisfying the stringent requirements for man and equipment mobility. The concept has produced the objectives of early determination of design feasibility and production of least-cost airmobiles with a high degree of capability. Present and past programs are reviewed.

This paper discusses the Dynamometer System of Accurate, Unambiguous Readouts (Dinosaur), a new system used in the performance testing of engines at John Deere. Readouts are digital, and data are in engineering units; thus, the engineer supervising the test can make decisions regarding the conduct of the test while there is still time to modify the test program. Testing time is reduced as the operator need not perform calculations, data conversions, etc. Test setup and teardown time is minimized by checking all instrumentation transducers for proper operation prior to the test at which time a bulkhead system with quick-disconnect connectors is utilized. Among the subjects discussed are the operation and design of Dinosaur, the method of digital computation, and the use of a new programmable-cascadable frequency divider.

Aircraft wheels and brakes are significant maintenance cost items on transport airplanes. Cost can be minimized by adequate design criteria for original equipment and modernization of existing equipment through the incorporation of new technology. The four parties key to the minimization of operational costs of wheels and brakes are the Federal Aviation Admin. (FAA), the airframe manufacturer, the supplier, and the user. This paper deals with how each of these parties can contribute to this effort.

This paper presents considerations in formulating test requirements for public ground transportation programs. Ground transportation systems are categorized by function, speed, subsystem characteristics, etc., in order to aid in establishing requirements of test engineering technology, test laboratories, and test facilities. Current LTV public transportation programs are used to exemplify the general test requirements of systems proposed to fill the current and projected needs of society.

This paper describes a hoist dynamometer capable of reproducing field conditions for the purpose of providing comparative data on friction materials used on band brakes and clutches by the crane and hoist industry. Performance qualities essential to the braking system are recorded for both automatic and manual operation. The dynamometer enables the testing to be performed under controlled conditions which can be both repetitive and reproducible.

The recently announced Model 225 Excavator is Caterpillar Tractor Co.'s initial entry into the hydraulic excavator market. The development program for this machine was designed, from the beginning, to achieve a machine well suited not only to the United States but to overseas markets. Major features of the vehicle, and how these features were affected by unique aspects of the development program, are discussed.

High-pressure hydraulic systems (operating at pressures of 3500 psi or greater) are replacing mechanical systems with smaller and more reliable machines. This paper discusses the existing limitations of the technology of high-pressure hydraulics, as well as the advantages of systems working at pressures in the area of 5000 psi. An analysis is made of a hydraulic circuit and its components, including the reservoir, pump, valves, motor, cylinders, hoses, and fluid.

A new model of a turbocharged direct-injection diesel engine has been developed to meet present and near-future power needs for heavy-duty trucks. This paper gives a full description of the new V8 design with special emphasis on the turbocharging system including exhaust manifold arrangement and valve timing. It also covers other design features, such as Scania's unique oil filtering system, the durable cylinder head sealing arrangement, and the accessory drive. Finally, the paper deals with aspects of the development and testing program that was undertaken to attain an economic and virtually smoke-free diesel engine of high durability and reliability.

Over the past several years, the Army has become increasingly aware of the disastrous effect of solid particle contamination on the life and efficiency of fluid power system components. Something must be done to give a more reliable, quicker, and more accurate check on the system condition at any given time. In July 1971, the Army Mobility Equipment Command acquired a prototype portable automatic particle counter for use on fluid power systems. This battery-operated counter connects directly to the vehicle or test stand at a fixed, predetermined test point, eliminating the need for sample containers and simplifying the test procedures. Connection, analysis, and disconnection takes less than 5 min. The portable counter has been used on a number of vehicles with verification samples being taken and checked by Oklahoma State University. Results to date have encouraged the Mobility Equipment Command to continue with the field verification program.