Search Results

Improvement in airframe structural efficiency through the utilization of unique and minimum weight concepts is a primary applied engineering objective for the hypersonic environment. The essential elements for hypersonic structures criteria are temperature environment, low load intensities, room temperature load conditions, structural stability, minimum gage material requirements, material producibility, reusability, nonoptimum factors, and vehicle configuration compatibility. A comparison of thermal structural concepts indicates that the hot load-carrying structure is the leading candidate for a typical M8 hypersonic cruise vehicle wing and fuselage application.

Preliminary selection of basic materials for flight vehicles is based on Mach number-altitude orientation, which includes turbulent flow to laminar flow location and effects. Structural weights and materials as a function of temperature are presented for both protected and unprotected primary structures. Design considerations and material selections for other pertinent items such as inlets, nose cones, leading edges, and transparencies are also considered.

The large difference between the total numbers of manned and unmanned spacecraft and their respective missions is discussed. The environmental and functional requirements having different effects on the two spacecraft types are described. The materials characteristics involved in those requirements and the resulting typical configurations are reviewed. It is concluded that vibration and pressurized gas containment have the outstanding influence on spacecraft structural systems. It is noted that new structural factors of safety have not been derived on the basis of any rational consideration of the design conditions for stability or pressure critical structure.

Mariner IV and the Lunar Excursion Module (LEM) are compared to explore the question “Does man's presence make any difference in space vehicle structures?” The environment, mission requirements, and subsystem interfaces are examined to determine the extent to which they affect the space vehicle structure and to see which elements are influenced by the presence of man. The author concludes from the comparison that man is a unique payload for a space vehicle and, consequently, his presence strongly influences the payload structure. The rest of the space vehicle structure is primarily influenced by size requirements and by mission duration.

The aerospace changing aerothermodynamic environment from subsonic to supersonic to hypersonic flight velocity has brought the cost environment to the foreground. The increasing performance demands for lightweight structure and the resulting increase in airframe cost are discussed. The influence of material and fabrication costs on the desired efficient structural concepts of a supersonic wing box cover are evaluated. The solid-state diffusion bonding process is presented as a potential fabrication solution to achieving the desired minimum weight structure at low airframe cost.

This paper presents a technique for assessing the influence of configuration geometry, size, and mass on the dynamics of hovering vehicles. First, the equations of motion for small perturbations from hover are discussed and certain derivatives removed or simplified from considerations of symmetry. The remaining derivatives are then related to configuration geometry, size, and mass by simple momentum theory. The accuracy of this theory is examined by comparing test results on ducted fan and free propeller configurations. The rather limited experimental data agree with the momentum theory for ducted fan configurations, provided flow separations are not important. The effects of mass and size are separated from the effects of geometry by introducing a nondimensional system of stability derivatives. It is shown how these nondimensional derivatives can be used to predict the effects of changing the mass or size of a configuration of given geometry.

There is a trend toward growing row crops in narrower row spacings that affects the design of harvesting equipment; in particular combines used for harvesting corn. As the rows become narrower the headers are made larger to harvest a greater number of rows with each pass through the field. Larger headers can influence the balance, hydraulic system, wheel tread, tire size, and power requirements of the machine.

Stability is an important consideration in the operation of a three-point hitch control system. The equations are developed and stability evaluated by the Nyquist criterion for an actual system. The general solution for transfer functions is eliminated; instead, the equations that describe the system are written in matrix form. Digital computer solutions of the matrix written in complex numbers provide data points for the Nyquist diagram.

The nomenclature and fundamental theory for servomechanism analysis are covered in this paper. Included are the mathematics, block diagram representations, analysis of steady-state and transient response, and analysis of stability. Sufficient details are given to permit the reader to understand basic works in the field.

Many improvements have been made during the past 5 years in the design of the human work space on off-highway vehicles. Some of the possible effects of the severe environment encountered on tractors are pointed out in this paper. This article emphasizes that engineers who design the controls and human work space on off-highway vehicles should work as a team with medical doctors and industrial psychologists. Some explanations are given as to why the human work space on tractors has not received an adequate share of engineering design effort. Several suggestions for the improvement of the human work space are made: There should be more supervision of noise, better vibration insulation, addition of automatic safety controls, use of air conditioned cabs, addition of power safety controls, use of air conditioned cabs, addition of power meters and wheel slip meters.

High performance power trains used in current off-highway rubber tire haulage equipment are important to the increased work capability of these machines. Successive innovations and refinements accomplished during the past 50 years to reach the present state of development are reviewed. Advantages obtained during this evolution are noted, and some evaluation is made of contemporary drive means. From this background of achievement, attention is focused on opportunities for further advancements in power trains for such wheeled transport vehicles.

Narrow-row spacing (30, 20 and 15 inches) of corn and soybeans a newly developing farm practice, aimed at increasing yields, affects tractor design and usage. Problem areas include tires, rear wheel tread, rear axles and rear axle housings.

The work tool machines that are discussed are those that have been used to shape the face of the earth and can broadly be described as earthmoving machines. The paper then traces the evolution of drive systems for track-type tractors, motor graders, and loaders (track and wheel), with particular emphasis placed on matching drive systems to the vehicle so that the final result is a useful work tool machine that can be used efficiently in its intended work cycle. Finally, a survey is made of the various drive systems offered by industry today, together with predictions of future drive systems.

A study of driving conditions in the central Los Angeles area has led to the formulation of a new chassis dynamometer test cycle for exhaust emissions testing. A single vehicle was used to develop a street route representing a variety of morning peak hour commute trips. A cycle was then compared against the street route with seven vehicles of varying size to assess the validity of the cycle in terms of mode pattern and exhaust emissions.

Octane number requirement studies were made with eight late-model passenger cars to evaluate effects of temperature, humidity, and altitude. Primary reference fuels and 1965 CRC full-boiling reference fuels were used. Temperature and humidity tests were made on a chassis dynamometer at sea level, while effect of barometric pressure was studied on the road at altitudes up to 6000 ft. Regression analysis was used to study the correlation between changes in octane number requirement and changes in temperature and humidity. These correlations were linear and varied among the cars. The average changes in ONR were somewhat smaller, but in fair agreement with those reported in the literature. The altitude effect also varied among cars tested and was generally nonlinear. On the average, the effect of barometric pressure from sea level to 3000 ft was smaller than concluded from earlier studies; from 3000-6000 ft, the pressure effect was larger.

Emission tests on 404 1966-model cars with exhaust controls in public use confirm that the vehicle manufacturers have done a good job of building cars with low emissions. However, field data on emissions higher than proving-ground results and some deterioration of emissions with mileage, indicate that more effort is needed on emission control in the field.

A new series of multifunctional gasoline additives has been developed with the objective of improving overall engine cleanliness in addition to performing the normal functions associated with these additives. Both dynamometer and field test data are presented to show the improvement in engine cleanliness derived from the use of such products. These include information on overall sludge deposits, valve tulip deposits, and PCV function.

The production of pollutants and an increasing need for pollution management are an inevitable concomitant of a society with a high standard of living. The automotive diesel engine is used more than any other type of engine for transporting freight over highways. Two kinds of pollution to be considered with regard to the diesel engine are the dark exhaust smoke and odor, of which the public is quite cognizant, and the less obvious but possibly toxic carbon monoxide, oxides of nitrogen, unburned hydrocarbons, and trace compounds of other toxic materials. This paper discusses sampling, measurement techniques, and established standards for exhaust smoke and odor. Examination of diesel exhaust shows it to be less offensive in terms of harmful effects than the invisible exhaust from other types of engines. The major problem is exhaust color and odor.

The California legislature, engine manufacturers, fleet operators, and enforcement agencies have pursued an active program of diesel smoke reduction since 1939. This program has resulted in creditably low smoke levels. While diesels do not contribute substantially to total community air pollution problems, the public complains about the bad appearance of diesel smoke. There are many fruitful approaches for fleet operators to reduce diesel smoke, including more strict maintenance, fuel additive, driver indoctrination, and engine derating. Fleets in the Los Angeles area have achieved excellent smoke reduction by these methods and, at the same time, maintain clean, first-class, economical operations. Two of these fleets are analyzed in this report.

The impact of the Californian regulations on Europe, and their applicability to European conditions, is considered with particular reference to the diesel engine. In Europe photochemical smog is scarcely a problem; the toxic effect of carbon monoxide is the greater hazard. The emission by diesel engines of this and other toxic gases is low, but the exhaust smoke emission may be objectionable. Theories of smoke formation in combustion are considered, and methods of smoke measurement are described, including their shortcomings. The present position of European antismoke legislation is outlined, and characteristics of the diesel engine controlling smoke emission are examined. Finally, the performance of antismoke fuel additives, which may allow uprating of 10-15%, and the problems associated with their use, are described.