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A SURVEY of 30 typical bus operating companies was made by the author to get a representative opinion regarding the accessibility of present-day buses for servicing and maintenance. After pointing out the large number of complaints about inaccessibility that these companies had, he discusses their needs under the following classification: 1. Accessibility for nightly service operations. 2. Accessibility for scheduled inspection, testing, and adjustment work. 3. Accessibility for removal of complete units. 4. Accessibility within major units themselves.

AN ANALYSIS has been made of the performance of basic, reheat, regenerative, and regenerative-plus-reheat turboprop engines for flight speeds of 200-600 mph, altitudes of 0-50,000 ft, and turbine inlet temperatures of 2000-2500 R, and a range of compressor pressure ratios of 6-42. The effects of flight and engine design conditions on fuel consumption, power per unit engine frontal area, power per pound of engine weight, and airplane range are compared for several types of turboprop engine.

THE development of engines with higher compression ratios and those having valves in the head has meant that the minimum performance requirements of present-day distributor and coil type ignition systems are being approached. The authors of this paper have closely examined the ignition system as a whole to determine if these new demands can be met without appreciably increasing the primary current. The authors suggest that, if the reserve energy of ignition coils could be used more effectively, we could reduce its value and use the excess energy to charge the secondary circuit to a higher voltage without affecting total reliability.

A SET of curves has been developed that makes it possible to determine the maximum permissible spark-plug gap that can be fired by voltages transmitted through this critical region, the spark-plug barrel. The investigation that led to the development of these curves consisted of the following steps: 1. To determine a satisfactory way to simulate engine operating conditions in trie laboratory, this to consist of a correlation of spark-plug bomb pressures to various conditions of engine power. 2. To determine the sparking voltages required to fire various gaps at the different bomb pressures corresponding to various engine power configurations. 3. To determine experimentally the breakdown voltage for various spark-plug barrel configurations at different altitudes and to express this relationship analytically.

THIS paper describes the line of reasoning on which automotive stress analysis is based. It concerns itself primarily with operational stresses in the chassis proper and only in a limited way with aspects of engine and transmission design. The author tries to show that the automotive method does not rely on trial and error alone, and is tailored to the product and its service.

IN this Horning Memorial Lecture, Dr. Barnard shows that gasoline has played a major role in the development of the automobile from a noisy, odorous, temperamental vehicle to the dependable, highly engineered mechanism of today. (Dr. Barnard received the Horning Memorial Medal for 1949.) He goes on to show how the development of the gasoline itself-by means of cracking processes, improvements in octane number and the like - contributed to the overall success of the gasoline automobile.

THIS study was undertaken, the authors say, to chart the probable trends in motor fuel volatility for the next 5-10 years. They also outline the field in which research and development work may have to be undertaken by the automotive and petroleum industries in the same period. The factors that will affect fuel volatility are discussed and the probable volatility trends estimated. The effects of both present military mobilization and an all-out military emergency on fuel volatility are estimated.

AID for the fleet operator is contained in this paper, which presents basic information to help him get the best from his fuel, whether he uses gasoline or diesel fuel, from his lubricating oil, whether he uses the regular or heavy duty, and from his gear lubricants.

THE four types of hydraulic control systems developed by the farm machine industry to cover the various applications required by the farmer of today are reviewed here. The author explains the terms used to describe these controls and discusses the principal parts of the mechanisms, which afford the many varied operations in the field.

PROPER stability and performance analyses of a hydraulic servomechanism, such as may be used for an aircraft control-surface power-boost system, require a knowledge of system constants. Important among these constants are the hydraulic damping or resistance factors for basic hydraulic system components. Theoretical and experimental investigations have been combined in the determination of resistance factors for straight metal tubes, tubing bends, flexible hoses, and fittings. The effects of pertinent system parameters on the resistance factors have been investigated.

THE increasing interest now being exhibited in the influence of residual stresses on the life and service performance of machine parts prompted the present investigation. Actually, the author is concerned here only with the thermal and transformation stresses that are developed in some heat-treating operations. Further, he discusses only the macroscopic type of stresses, that is, those that are distributed over the part as a whole, rather than the micro-stresses, which occur within a single grain or between several grains.

THE use of ignition quality improver additives has been under active laboratory investigation since the early 1930’s, but economic and fuel availability considerations have not been such as to foster their commercial application. The Navy has, however, conducted evaluation tests of many of the additives that have been made available for testing over the past 15 years. A large number of compounds of various types have been found to be effective in raising the cetane number of diesel fuels. Many of the additives lose their effectiveness, however, when blended with diesel fuel and stored under certain conditions. The results of laboratory engine tests have shown that certain additives do not materially increase piston-ring wear or engine deposits outside the piston-ring belt but show a tendency to cause ring sticking.

THE gas turbine fuel control situation is in a state of confusion, the author feels, because of such factors as the newness of gas turbine development, the lack of comparative evaluation tests on controls, and the lack of time for the results of field experience to become generally known among administrative personnel. After analyzing the present status and discussing the functional requirements of jet controls, Mr. Mock considers the following questions: 1. Is the fuel control part of the control of the engine or of the airplane? 2. What are some of the special difficulties of the jet control engineer in meeting military needs? 3. Who should supervise the selection and adaptation of a fuel control for a given jet engine and airplane?

MANY of the automotive differentials that have been developed since the first one was built in 1827 are described here. The ideal differential would distribute torque equally to the two driven wheels being differentiated, under any condition of relative motion as dictated by ground speed. At the same time it would never permit torque to be applied to any one wheel in excess of the available traction without causing both wheels to slip simultaneously. The complete answer to this problem has not yet been found and, the authors admit, may be what we are looking for is a mechanical or electronic brain to do the job.

THE 1949 octane-number requirement survey conducted by CRC indicated that: 1. Maximum octane-number requirements based on Research numbers of commercial fuels were 1-2 units higher than those based on primary reference fuels. 2. Blends of diisobutylene, isooctane, and n heptane, matching the commercial fuels in Motor and Research octane numbers, followed the commercial fuels closely in antiknock behavior. 3. About 50% of the customers’ cars knocked on the fuel found in the gasoline tanks. 4. The spread in octane-number requirements of engines, which manufacturers consider representative of their production, was almost as great as that found among cars in service.

IN this presentation the author shows that: 1. There is a place for the turbine in highway freight hauling operations-subject to certain limitations. 2. The turbine engine is not yet proved. 3. It has not reached its maximum in performance and development. 4. It is not yet available for installation and (we guess) the cost will not be prohibitive.

DATA on gasoline consumption and travel time of commercial vehicles are of considerable use to the operators and manufacturers of trucks and to the public officials who administer the highway facilities. Thus, industry and government decided to cooperate in a program designed to obtain information about these factors. This paper summarizes the results of the study, placing particular emphasis on the basic relations established, the application of the results, and the preliminary trends for the gasoline and time economy of commercial vehicles.

TIRE and tube expenses take a large part of the commercial vehicle maintenance dollar. In fact, for 1948 they amounted to 26% of total maintenance costs. It is for this reason that anything that can be done to keep tire and tube expenses down will quickly pay for itself - and much more. The author discusses two general ways in which tire and tube costs can be-and are being - reduced: 1. By improvements in the tires and tubes themselves, such as: puncture sealing tubes, new tread design, and wide-base rims. 2. By taking care of the tires during their active life, such as: by avoiding driving over foreign material that can be picked up by the tires, by removing such material as is picked up as quickly as possible, by reducing overloads, by avoiding operating conditions that cause slippage between tires and the road