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STEPS in fatigue design of aircraft lower wing surfaces, as presented here, are: 1. Selecting a structure that permits easy fatigue-crack detection. X-ray inspection of blind areas is suggested. 2. Setting a design quality standard. This is the important stress-concentration factor Kt, which is shown to have a lower practical limit. 3. Choosing a design gross area stress rather than net section stress to give the desired life. The gross area stress is also a better basis than the 1.0g operating stress level for comparing fatigue life in similar aircraft. 4. Step testing to check design quality. This preferred method of fatigue testing is discussed here.

AERATION and cold-temperature starting problems faced by aircraft-engine designers are said to be solved by use of the deaerating cold-weather oil system described in this paper. In this system, all the oil in the tank circulates through the engine rather than the small volume of oil circulated by the conventional system.

THIS paper describes how present size and weight regulations are based on capacities of inadequate highways, or on various arbitrary bridge formulas, or sometimes both. Within a state, contradictory weight limits often are prescribed; and uniformity from state to state is noticeably lacking. Adapting the demand for bigger trucks and trailers for hauling more payload to the various size and weight limitations has resulted in some improvements in truck design. But what are needed are consistent regulations based on logic and fact to encourage designers to produce safer and more efficient vehicles - thus promoting the public interest. As the regulations stand now, Mr. Horine says, they do not benefit the public.

THE Saginaw design of hydraulic steering gear is described in this paper. This gear employs a screw and nut, with a novel system of circulating balls between these two members. The motion of the nut is transmitted to the cross-shaft or pitman shaft by means of rack and sector teeth. Advantages claimed for this design include simplicity and versatility. The loads of the centering springs and even the size and number of reaction plungers can be varied, making the steering “firm” or “soft,” as desired.

RESULTS of an Armour Research Foundation program, promoted by ATA interest in truck exhaust noise problems, are described here. It is shown that exhaust-noise measurements can be made using an octave band analyzer, and values thus obtained agree quite well with listening tests. Highway truck noises are recorded on magnetic tape, which is then fed into the analyzer at leisure. Test-stand measurements, however, give good results only when the exhaust is the main source of truck noise.

A NEW experimental approach for evaluating influence of precombustion reactions on engine knock and some results obtained by this method are described here. Measurements in terms of conventional knock-test units were made of the knocking tendency of a fuel-air mixture previously compressed in a motored engine.

SINCE world war II, integral implements have become increasingly popular. According to the author, this ever-increasing popularity of integral instruments over the corresponding towed type can be attributed to the following factors: 1. Greater maneuverability of tractor and implement combination. 2. Better transporting characteristics of tractor and implement combination. 3. Lower-cost implements. 4. Ease of attachment and control. An implement designer’s viewpoint on tractor hitches and hydraulic systems is presented here. The author hopes that it will help to assure that tractors of the future will have common implement-to-hitch attaching points, so that a tractor may be used with a number of different makes and sizes of integral implements. He also points out that certain performance features are needed to make integral instruments even more popular.

WHAT would happen if an atomic bomb were to explode at noon tomorrow without warning of any kind? Would the automobile turn out to be a death trap for many of us or would it offer as much protection as the ordinary building? Would there be any advantage in having the car turned away from the center of the blast or to having the windows rolled down? Would it be safer to crouch down on the floor of the car at the first sign of an atomic explosion? Would it be safe to enter our cars as soon as the first effects of the explosion have subsided? Would the cars run? It was to find the answers to some of these questions that a group was invited to observe an experiment at the Nevada Proving Ground of the Atomic Energy Commission. This group - which became the SAE-FCDA Advisory Committee - wrote the accompanying report, which tells about the experiment and some of the things that were learned. A. L. Haynes of Ford is chairman of the committee. Other members are: R. B.

THIS paper discusses problems encountered in the Mach number range of 0 to 2 with aircraft having different wing planforms. The delta-wing type is compared to the unswept or straight thin wing. It is concluded that, with the solution to the structural problem having been obtained for the latter wing, the unswept type is superior to the delta type when strictly comparative missions and operating field lengths are considered.

TORQUE converters have many advantages for industrial and commercial vehicles. Some of those listed by the author are: 1. Smooth acceleration. 2. Engine need not be declutched when it is unloaded or idling. 3. More horsepower delivered at low output speeds and during acceleration, compared with conventional transmissions. 4. Operator mistakes of improper gear selection and missing of shifts are reduced to a minimum. 5. Load held to power source at all times. 6. Damping out of engine torsional vibration. 7. Increased life for drive train beyond transmission. 8. Cushioning of shock loads during starting and shifting, and of sudden increases in load.

PREIGNITION, Mr. Heron points out, is an old, if not well-known, disease of Otto-cycle engines. Despite its long history, however, there is much confusion in the terms used to describe it and the other forms of uncontrolled combustion in spark-ignition engines. The author has tried to bring some order out of the confusion by defining the three terms: knock, preignition, and autoignition. He also relates his experiences with destructive, runaway preignition in aircraft engines during World War I. THIS paper and the four that follow, by Melby-Diggs-Sturgis, Hirschler-McCullough-Hall, Williams-Landis, and Winch, constitute the complete Symposium on Preignition that was presented at the 1953 SAE Summer Meeting. Discussion of all papers is published at the end of the last paper in the group, by Winch.

COMBUSTION-chamber deposits are the primary cause of preignition. This preignition may be silent or it may be manifested by a variety of engine noises ranging from light pings to violent explosions. Its occurrence, according to these authors, is favored by changes in engine operating conditions that result in the development of higher pressures and temperatures during compression, or that cause an increase in the concentration of oxygen available to support the combustion of carbonaceous material. Thus, increased compression ratio, supercharging, operation with retarded spark timing, and the combustion of lean mixtures are likely to increase the tendency for the occurrence of preignition. Some hydrocarbons have a greater tendency to be ignited by hot deposit particles than others. Preflame reactions of the fuel tend to sensitize it to ignition. Under certain conditions, the effect of these preflame reactions can be minimized by tetraethyl lead.

STUDIES of cars on the road show that both fuel and lubricant characteristics affect the occurrence of autoignition. For instance it is indicated that autoignition can be eliminated by increasing the fuel antiknock quality, although the Research octane number required may vary slightly depending on fuel composition. Limited evidence is also presented to indicate that aromatic constituents of gasoline are somewhat less effective in suppressing autoignition than are paraffin hydrocarbons. In addition, it is shown that differences in autoignition tendency are observed when different fuels and lubricants are used during the deposit buildup period. In one series of tests a difference of seven octane numbers was observed between autoignition tendencies resulting from operation with different lubricants.

DEPOSIT-induced ignition (the erratic ignition of the fuel-air mixture by combustion chamber deposits) is one of the problems hindering the development of higher compression, more efficient engines. Deposit-induced ignition results in uncontrolled combustion, which often is followed by knock. In some modern engines, the suppression of knock originating through this mechanism may require higher fuel antiknock quality than that required to suppress ordinary knock. Fuel composition and volatility have been found to affect the amount of deposit ignition. Reduction in fuel end point reduces deposit ignition. Among individual leaded hydrocarbons, aromatics produce by far the most deposit ignition, but the differences among full-boiling gasoline stocks of similar volatility do not appear to be related to their hydrocarbon-type proportions. Engine operating conditions favorable to carbon formation tend to increase deposit ignition and magnify differences among fuels.

PROPER lighting of slow-moving farm vehicles-a necessity when these vehicles travel the highways at night-was the problem tackled by the SAE Tractor and Implement Safety Light Subcommittee and a corresponding FEI committee. Among the results of their work, which is reported in this paper, are: 1. A standard breakaway connector for the tractor and implement lighting system. 2. A telescoping staff lamp that can be extended to the left, when needed for safety, to show the left-hand end of an implement. 3. Changes in the Uniform Act Regulating Traffic on Highways to permit use of such a staff lamp. 4. A lamp with an extension cord for use where a staff lamp is not long enough. 5. A proposed standard bracket for holding the extension-cord lamp.

PROGRESS made in the development of man-made fibers is precipitating a revolution in the design of automobile upholstery fabrics, according to the author. In various combinations with each other, with the older manmade fibers, and with natural fibers, they are capable of producing fabrics of increased decorative value together with a serviceability heretofore unthought of. The author discusses the properties of some of these synthetics. He points out that none of them can be called the universal fiber. Each has individual characteristics of outstanding merit, but not one of them alone is suitable, for one reason or another, to all textile applications. On the other hand, combinations of these fibers yield properties not possessed by the individual fibers themselves.