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AFTERCOOLING, coupled with higher pressure turbocharging can increase vehicle engine output. The author thinks that it is possible to anticipate diesel engines being run with compressors supplying air at pressure ratios higher than 2/1. Density ratio is the most important consideration in increasing pressure ratio, since the engine's output is dependent upon weight rather than volume of air supplied. Because the density of the compressed air is dependent upon its temperature at any pressure level, cooling the air after compression results in density increases. This paper describes various methods of after-cooling which increase engine output and fuel economy.

Statistical measures of whole-body vibration from ambulation are shown to be higher than those from operation of earthmoving machinery and significantly higher than published guidelines for human exposure to whole-body vibration. The inconsistency of human response to low level vibration of technological origin as compared to human imperceptiveness to high level vibration from ambulation is discussed.

THIS authors sees a need, in the near future, for commercial vehicles with engines of 1000 to 1200 hp - powerplants that yield high outputs but require limited space. He sees an immediate need for more and more horsepower per cubic inch of piston displacement and per unit of space for the engine. He directs attention to six design potentials which may supply the answer: (1) the gas turbine; (2) supercharging; (3) aircooled diesels; (4) higher engine speeds; (5) 2-stroke diesel improvement; (6) compound engines. He also links the future development of the internal-combustion engine with basic improvement of components through simplification, calling for the elimination of extraneous gadgetry.

Modern data acquisition methods combined with new testing and analysis techniques are revolutionizing product design and development. Detailed analysis of recorded vehicle drive-line data has given today's engineer new insights into drive-line dynamics. This paper discusses how vehicles can be analyzed as a series of torsional springs and inertia masses. A two axle, 300 hp, 15 cu yd earthmoving tractor scraper (model 621) is used to illustrate significant factors. Main emphasis is on drive-line resonant torsional vibrations and shock loading. Diesel engines as torsional vibration exciters and transmission clutches as the major shock load producers are covered in some detail. How analog computers can effectively be used to facilitate vehicle development is briefly discussed.

A new 2-ring piston package has been developed which has proven successful in internal combustion engines. The need for a compact piston arrangement is discussed along with the steps followed to arrive at excellent oil economy. The paper presents other advantages related to cost savings, lower wear, and reduced engine friction. The paper discusses applications of the compact piston package along with its advantages in designing compact engines.

The effect of altitude on the performance of two turbocharged prechamber diesel engines and one direct-injection diesel engine has been studied in a test cell. One prechamber engine was tested at altitudes up to 16,000 ft. The data from these tests are presented and compared with performance at standard conditions. Using the data, an analytical method of predicting the performance of turbocharged diesel engines at altitude has been developed. An iterative computer program, using part-load data taken at standard conditions, is used for the prediction. Comparison is made with the simulated altitude data and with other calculation methods.

The causes of turbine blade excitation are described, and the factors that influence amplitudes of vibration are discussed. Blade rotation in an asymmetrical pressure field produces a periodic force on the blade. Harmonics of this periodic force excite the blades at their natural frequencies. Gas disturbances created by nozzle vanes also can excite the blades. Amplitudes are affected by the type of exhaust system combined with the type of turbine housing, turbine housing design, engine speed, vane design, and any local gas disturbance or condition that creates asymmetrical gas flow through the turbine housing.

After reviewing the present state of diesel engine design art as applied to vehicle applications, the paper analyzes future application requirements and outlines possible paths of engine development. In general, future requirements demand engines of higher output, lighter weight, better fuel economy, and smoke-free operation. A better understanding of vehicle load demands and careful matching of engine and drive-line will be required. Reference to extensive recent research developments shows that the diesel engine industry will be prepared to meet this challenge to provide the customer the best possible engine in terms of return on his investment.

The Cushion Hitch is a unique application of vibration absorber theory to a self-propelled tractor-scraper. The scraper mass is utilized as a damper for suppressing predominate bouncing motions of the tractor unit. A more comfortable and safer operator ride, with increased productivity, results from the Cushion Hitch application. This paper describes development of the early prototype design as well as the final production version. Particular emphasis is given to both the hydraulic and the structural characteristics of the system.

A report on a detailed evaluation of cylinder pressure measurement was made in 1967 by the author. At the beginning of that paper, the primary importance of cylinder pressure measurement was pointed out. Pressure is the means by which work is extracted from the gases; the cycle is known only to the extent that this work function ∫PdV is known. At the end of that paper, it was concluded that cylinder pressure could be measured accurately enough to determine imep and that complete electronic determination of imep was needed. A system for determining imep electronically with excellent accuracy has been developed and has been in use for several years. This paper describes the Caterpillar indicated mean effective pressure (imep) meter and gives a sample of the information it can provide.

Fatigue failure of machine components subjected to high contact pressures is rapidly becoming recognized as a serious design limitation. Confusion has resulted from grouping three distinct types of contact fatigue failure under the term “pitting” A Geared Roller Test Machine is described that reproduced each of the three modes of failure. The stress-life relationships obtained for rollers tested under conditions of rolling plus sliding correlated well with actual gear performance. The sensitivity of the test to changes in material, micorstructure, and processing variables is demonstrated.

THIS paper presents results which will answer many of the problems facing an engine manufacturer in the selection of the most suitable types and sizes of superchargers to use with a line of engines. Although performance curves of production model diesels are available, decisions are still needed in choosing peak supercharging pressures, drive means, and size and effectiveness of intercoolers, if any. The author describes the use of a typical model to determine response to variation in intake and exhaust conditions, resulting in data which will assist in evaluating engine potentials with any system of supercharging. Thus, supercharger selection for a particular line of engines is aided by knowledge of engine characteristics as a second-stage compressor.

Chromatographic analysis of diesel exhaust indicates a number of low molecular weight hydrocarbons, below C6. Using reactivity index as a criterion, much of the diesel exhaust reactivity can be attributed to ethylene and propylene caused by the thermal decomposition of the fuel. Hydrocarbons in the C4-C7 range, including high relative reactivity olefins, are generally low in volume concentration and therefore contribute little to the overall exhaust reactivity. Hydrocarbons, in terms of parts per million carbon above C7 are low in present diesel engine designs, so individual volume concentrations are generally fractional parts per million. Reactivity per horsepower-hour from diesel engine exhaust is less than that from the one small industrial gasoline engine tested by the heavy-duty truck diesel engine cycle.

TESTS on two series of diesel engines were run. The first group, consisting of four engines, had the stroke changed only, while the second group had the stroke/bore ratio changed and the displacement held constant. Results of the tests indicate that the longer stroke engines had more power, higher torque, and lower fuel consumption. Friction was high for the short-stroke engines at low speeds and for the longest stroke engine at high speeds. Theoretical analysis indicates that the optimum stroke/bore ratio for best performance may vary as the compression ratio and bore diameter are changed.

A system has been developed that provides real-time measurement of heavy-duty diesel engine particulates emitted during the EPA transient emission test cycle. This is accomplished by measuring the opacity of the exhaust/air mixture in an EPA type dilution tunnel with a light extinction opacity meter. Simultaneously, the temperature in the dilution tunnel is measured, and the ratio of the dilution tunnel temperature to a standard temperature is used to correct the opacity signal to standard conditions. The outstanding features of the system are that it produces a continuous record of when particulates were generated during the 20-minute transient cycle and that particulate cycle results are available immediately upon completion of the transient cycle without the requirement of conditioning and weighing filters. Results to date indicate correlation of the opacity-particulate monitor measured particulates to gravimetrically determined particulates to be within 10% for specific engines.

TRACTORS operate in a wide range of conditions, from desert to swamp. At all times, the final-drive seals must keep the oil in and the dirt out. In this paper, the authors discuss the latest developments in seal design and the resulting improvements in performance. Efficient performance of a tractor final-drive seal depends upon a number of factors, including: bellows and bellows-boot operation, seal load and area, seal material, wear washer, and gasket structures.

Analytic modeling and analog computer simulation techniques are presented for determining power train transient responses excited by clutch-actuated gear shifts. A method for describing the dynamics of a transmission arrangement having several clutches and interconnected planetary gear sets is considered in detail. Simulation model testing is directed toward optimizing system design parameters and evaluating power train component capability and vehicle shift-feel. Data reduction techniques applied to model responses of torque and speed will yield appropriate spectrums representative of simulated work cycle. The spectrum data are used to predict hours of life for gears, bearings, and driveshafts, according to cumulative fatigue damage theory.

This paper traces the development of lubricants for Diesel engine and heavy duty service from the time the mobile Diesel became a production entity in this country. Beginning with a background of lubricants found acceptable for large Diesel engines in marine and stationary service, the trend in the supply of lubricants in subsequent automotive practices in the early 1930's led to difficulties in ring sticking, bearing corrosion and cylinder scuffing in the moderate speed, heavy duty engine seeking commercial favor at that time. The attempts to solve these problems, both as to engine improvements and lubricant selection, are reviewed historically. The logical development of additive oils followed the pattern of alloy steel achievements.

The requirements for cylinder pressure measurement for mechanical load, imep, and cycle analysis are developed. Methods for determining errors in transducers are presented, and the results are shown. The tests include passage error, hysteresis, nonlinearity, mounting strains, thermal strain, and twist in the crankshaft. Theories are developed to predict errors due to time or phase delay, passage, and thermal strain. The theory of the balanced pressure indicator is developed and the minimum delay and pressure error are calculated. Read-out systems are evaluated. Areas needing improvement are pointed out and specifications for the ideal pressure transducer are presented.

Advance in earthmoving technology has made necessary a corresponding advance in cutting edge technology. In adopting the concepts of matching the cutting edge to the machine, or possibly the job requirements of the machine, in rare instances it is found that the cutting edges employed in the 1930's and 1940's are satisfactory; however, in general, the increase in horsepower and carrying capacity of earthmoving machinery has necessitated a vast increase in the strength and wear properties of the cutting edge. The development of these properties, based on academic, laboratory, and field precepts, has advanced hand-in-hand with machine developments.