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A DETAILED analysis of the weight-saving possibilities of shaft-turbine installations on helicopters is presented in this paper, which won the 1953 Wright Brothers Medal for its authors. They point out that this weight saving helps to counteract the disadvantage of high fuel consumption. They also discuss helicopter flight characteristics and how they are related to shaft-turbine power characteristics. Finally, they propose some methods of obtaining better matching characteristics between helicopters and shaft-turbines.

THE history of the free-piston and turbine compound engine development is reviewed briefly. After consideration of the status here and abroad, the salient features of the free-piston engine concept are considered. These are mechanical simplicity, compactness, and an excellent torque-speed characteristic, coupled with a fuel economy comparable to the conventional diesel, the modern record holder in this respect. Some prognostications for the future of the development in this country are also presented.

EXPERIMENTAL analyses of residual stresses as related to fatigue properties and to the surface failure known as spalling are discussed in this paper. How those processing operations such as heat-treatment, machining, grinding and straightening contribute the factors causing residual stresses and what are the practical methods of measuring these stresses are also described here.

SOME of the aerodynamic and mechanical problems of jet engines designed for supersonic flight speeds are discussed in this paper. The aerodynamic problems considered include the required range of operation of the compressor, the thermal efficiency of the cycle, the inlet-engine airflow match, and jet nozzle design. Structural difficulties due to high operating pressures and temperatures and the bearing and lube problems arising from high temperatures are also presented.

THE truck engine of the future will be capable of producing more horsepower and will operate at higher rpm, according to Mr. Michell. This means, he said, that new problems will arise in connection with the clutch, transmission, propeller shaft, and rear-axle design. The author discusses some of these problems as far as each of the above parts of the drive line is concerned.

WHY one gets that aching neck and those tired eyes after driving for long stretches is explained in this paper. A brief qualitative study of the motion of the driver and passenger in the front seat of an automobile is given here. The author provides a reasonable explanation for some of the commonly observed kinds of driver fatigue and points the way for some improvement in the dynamic comfort of automobile seats.

MANY rather intriguing claims have been made about reduction of engine friction and increase of power and fuel economy through the use of certain types of motor oils and motor-oil additives. However, this paper shows that engine fuel-consumption measurements to determine the effects of different oils and oil treatments indicate that the only significant property of the engine lubricant relating to engine power, friction, and fuel economy is viscosity. The data also indicate that the “engine viscosities” of some motor oils may be somewhat different from their “laboratory viscosities” as measured in conventional Saybolt or Kinematic viscosimeters.

FATIGUE failure is now one of the most serious hindrances to satisfactory service life for helicopters. To help the industry bring the fatigue failure problem under control, these authors summarize what they have learned from studying 169 fatigue failures that occurred during 58,000 hr of helicopter flying operations. They have classified these failures as being caused by: 1. Design error. 2. Manufacturing error. 3. Field error. They discuss specific examples in each group and what was done to correct the cause of the failure.

SEVERAL factors are involved in the answer to the question, “How do atmospheric conditions affect the ability of a fuel to satisfy the antiknock requirement of automotive engines?” As is well known, an increase in atmospheric temperature increases the octane-number requirement of engines. This paper points out, however, that this causes little change in the road octane-number ratings of commercial fuels. Increasing the absolute humidity has the opposite effect to increasing the temperature and tends to counteract the undesirable effects of changing temperature throughout the various seasons of the year. Increasing the barometric pressure or decreasing the wind velocity both increase the tendency of commercial fuels to knock. Factors indirectly related to weather conditions, such as the coolant or thermostat used in an engine, also affect the knocking tendency of a fuel.

THE new Packard automotive diesel engine is reported to feature reductions in weight and space occupied, while maintaining good life expectancy. It is available in 6-cyl in-line, V8, V12, and V16 models. These models all have a large number of interchangeable parts. They all have the same bore and stroke. According to the authors, noteworthy points of these engines include: 1. Extensive use of aluminum. 2. Turbosupercharging. 3. One-piece cylinder and head assembly. 4. Four valves per cylinder, with stellite seating surfaces on valves and seats in the head.

THE universal positioning seat track is said to be the answer to the problem of providing suitable automotive seating for practically all drivers. It allows each driver to adjust the car seat to the position that best satisfies him. The author points out that providing these adjustments gives a number of advantages, such as: 1. The visibility of the driver can be at a maximum. 2. Each driver of a car can adjust the seat to suit his own individual size-and taste. 3. Less driver fatigue.

HIGHWAY safety-an important problem in the truck and bus industries - is governed by many factors, one of the most important being the human element. This paper describes the Harvard School of Public Health research program concerning the human factor in vehicle design and operation. The project is Sponsored by the Commission on Accidental Trauma of the Armed Forces Epidemiological Board, Department of Defense; the National Association of Automotive Mutual Insurance Companies; the American Trucking Associations, Inc.; and the National Association of Motor Bus Operators. Some items of this investigation include the study of near accidents; detection of the accident repeater; personal adjustment and morale of drivers; human body size and capabilities with relation to controls, instruments, seats, and vision; the effects of temperature, ventilation, noise, and vibration; and desirable safety features to protect the operator if an accident occurs.

STRESS corrosion cracking is a combination of stress and corrosive action that results in individual cracks of a brittle, intergranular nature. The author discusses such failures in compressor rotor blades made of a 12% Cr, type 403 stainless steel. A laboratory technique was worked out for producing similar failures at will. As a result of this study, it was recommended that compressor blades be stress relieved at 950 F. Since this has been done, no further cracking of the blades has been reported. Tests with three alloys in addition to the type 403 showed the former alloys to be superior to 403 in regard to stress corrosion cracking.

RESULTS of the two largest cooperative surveys made in 1951 and 1952 of the antiknock requirements of passenger cars are presented in this paper. Conducted under the auspices of the Coordinating Research Council, data on more than 800 postwar cars are compared with previous surveys and are analyzed for relationship of car design, car age, engine speed, test conditions, test fuel type, make of transmission, and geographical car distribution to octane-number requirements.

THE inherent simplicity of the gas turbine and its well-known success in aircraft applications is leading to its consideration for locomotive use. As a matter of fact, gas turbine locomotives have already found limited use by a few railroads throughout the world. The author discusses these applications and some of the lessons learned from them. He points out that, although the first gas turbine locomotive to be put in service was built in 1941 - the same year that the first commercial diesel locomotive was placed in service -the latter has forged rapidly ahead, so that today the railroads are about 75% dieselized. What, then, has held the gas turbine locomotive back? Mr. McGee points out that two of the most significant factors responsible are: 1. Metallurgical problems - the need for materials capable of withstanding the high temperatures encountered. 2. High fuel consumption.

USE of adhesives to join metal skins to low-density cores results in major weight, manufacturing time, and cost savings, according to the authors. They report here that such sandwich structures have been used in several projects, the most advanced being the B-61A Matador. To achieve a bonded joint between two aluminum sheets or between sheet and core, four generally similar steps are required. The sheet must be cleaned, coated with adhesive, force-dried to remove volatile materials, and finally cured under temperature and pressure. The authors conclude that production adhesive bonding of flat and contoured primary structures, with all its inherent advantages, is now available to the industry.

THE control of residual stresses in automotive cylinder blocks is discussed in this paper. According to the authors, this study was started because a small percentage of castings was being scrapped because of cooling cracks in the valve compartment wall. They discovered that the greatest single factor in inducing trapped stresses in castings is too great a difference in the cooling rates for different portions between 1400 F and 600 F. They also found out that residual tensile stresses can be eliminated in a particular section by keeping its cooling rate at least as fast as that of other significant sections. Moreover, it is possible to move trapped stresses from one section to another by overcooling. They have also developed a method that gives quantitative results that serve as good index values of the trapped stresses present even in complex castings.

INCREASING fuel prices and fuel taxes have forced engine builders to find ways to better engine specific fuel consumption in order to help operators survive the onslaught of increased operating costs. This paper explains how an improved combustion system has yielded up to 15% improvement in fuel consumption. This system was arrived at by analysis of those previous combustion systems which held most promise. The resulting direct-injection open combustion chamber is described here.

COMMERCIALLY available high-temperature brazing alloys, with examples of successful applications for each, are described here. Brazing alloys included are: Nicrobraz, Coast metals alloys, Mond Nickel alloys, Handy & Harman alloys, and Solabraze. Production brazed parts are shown, and details of brazed joints are explained with the aid of photomicrographs. Developments of new high-temperature sheet metal assemblies made possible by brazing techniques are discussed. Particular emphasis is given fabrication of high strength/weight ratio structures. An encouraging future for corrosion-resistant high-temperature brazing is predicted.