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THIS paper describes the important factors that must be considered in a study of engine power loss due to combustion-chamber deposits. Dafa are presented to show the effects of fuel composition, sulfur and lead concentration, and lubricant composition, engine design, and operating conditions on deposit power loss. The influence of engine operating conditions existent during the accumulation of deposits, and the importance of the engine conditions selected to evaluate the magnitude of the deposit power loss are illustrated. It is indicated that deposits cause power loss by thermal and physical restriction of the intake charge, and by reduction of thermal efficiency. It is concluded that differences in effect among the majority of commercial fuels and lubricants are probably small although relatively large differences may exist in certain critical engine applications. The engine operating conditions under which the deposits are accumulated are a major factor in deposit power loss.

ALL-HYDRAULIC buses, with power-operated control devices and auxiliaries, are now operating in three American cities, and winning a favorable response from passengers and drivers, as well as from maintenance mechanics, according to the author. He describes the new design features of these buses, their complete hydraulic power actuation, and explains how it is accomplished. Although power steering appeals to drivers, and dependable efficient operation of the hydraulic system makes the bus desirable from the purchaser’s point of view, the author believes that eventual savings in maintenance costs will be the factor which will place the all-hydraulic buses in a preferable position. He also points out certain features which can be advantageously incorporated in trucks at the present time. But he agrees that the situation in regard to trucks presents complexities that will not arise in relation to buses, which have a concentrated radius of operation and more unified service facilities.

BECAUSE of its effect on oil consumption and power, piston-ring and cylinder-wall wear has been made the subject of special research tests conducted by the four authors of this paper. They used the Oak Ridge facilities now available to industry, and secured radioactivated piston rings for installation in the test equipment. As the rings wear, the wear debris is picked up by the lubricating oil. The amount of iron from the activated ring that is present in the oil at any given time may readily be determined with a Geiger counter. The results discussed are classified under three broad divisions: the effect of operating conditions, lubrication, and fuel on engine wear.

THIS paper presents the latest findings in a 30-year study by GMC Research Laboratories, seeking the cause and prevention of knock in automotive and aircraft engines. The authors made a series of single-cylinder engine studies in which engine firing conditions were directly observed and recorded on supersensitive instruments through a transparent quartz window in the engine cylinder head. This enabled them to duplicate in the laboratory certain conditions in highway driving. They also secured visible confirmation of how various fuels and fuel blends behave in the critical precombustion process, during the phase when the fuel’s antiknock quality is put to test.

THE design and application of tractor bevel gears is covered in this paper. The authors discuss the problems involved, under the following headings: 1. Basic bevel-gear systems in use, based upon the method of cutting. 2. Method of calculation and selection of factors determining the static and maximum tensile stresses. 3. Summary of static and maximum tensile stresses, and fatigue life analysis. 4. Materials and heat-treatment.

SINCE the evidence shows that the wear of materials is closely related to the elastic limit of strain, the author proposes a new concept as a practical measure of this property. He introduces the term “modell,” which he defines as the Brinell hardness multiplied by 106 and divided by the elastic modulus. Modell, the author says, gives an indication of the depth of penetration that a metal can tolerate without exceeding its elastic limit. As materials with high modell values have, in general, good wearing qualities, the author discusses the possibilities for increasing the modell values for engineering materials.

A NUMBER of aircraft are now being designed, or are actually flying, with auxiliary power systems utilizing the expansion of air bled from the compressors of main propulsion gas turbines. These include systems which heat the bleed air through the agency of a combustion chamber on the auxiliary power motor. The design requirements for machinery of this class are very unusual, and are believed to be unique in the field of turbine engineering. These factors are particularly prominent with respect to range of gas supply conditions and control characteristics. The influence of these factors on practical design requirements is discussed in this paper. Emphasis is placed on the comparative advantages and limitations of turbine systems with these characteristics in view.

IN this paper the authors present results of their study of precombustion reactions - which are chemical changes occurring in the fuel-air mixture ahead of the flame front - based on thermodynamic analysis of engine data. A single-cylinder, knock-test engine, operated at a fixed compression ratio, was used in conjunction with balanced pressure equipment for obtaining experimental data. The thermodynamic analysis showed that simplification in computation of the heat of precombustion reactions would be possible if ignition timing were retarded, so that the normal flame would be initiated after completion of the precombustion reaction. Therefore, tests were run both at normal ignition timing and with retarded spark. Another series of tests were made to determine the effects of precombustion reactions on the power developed by the engine.

THE author discusses the following phases of superchargers for reciprocating internal-combustion engines: 1. Adaptation of the supercharger to engine requirements. 2. Details of the more important superchargers, such as the rotary, radial (centrifugal) and axial superchargers, and exhaust gas turbosuperchargers. 3. Effects of superchargers on engine performance. 4. Details on a few typical examples of supercharged industrial engines, such as the Caterpillar diesels for heavy earthmoving equipment and the Daimler-Benz 800-hp engine for fast trains; and superchargers, such as the Brown-Boveri and the M.A.N. products.

DEMONSTRATING the versatility of the hemi-U spherical or spherical segment combustion chamber, a series of carefully controlled tests has been completed in connection with experimental engine developments, as described by the author of this paper. Using regularly available fuels, or stimulated with super fuels, the engines showed power outputs far greater than the previous designs. The author points out that identical test engines, differing only in combustion-chamber design and valve layouts, showed that a hemispherical head design had a thermal efficiency equal to one full compression ratio better than the next best design, the conventional overhead valve type. The new engine, which develops more than 180 actual horsepower in the production version, using only nonpremium grades of fuel, is expected to respond to whatever demands may be made upon it when the anticipated quality fuels of the future become available.

CONCERN about possible future military operations in arctic regions has led to the development of winterized hydraulic equipment which can be operated in subzero climates. In this paper the authors present a diagnosis of complex arctic operations together with a record of typical accomplishemnts to date. The ultimate objective is to have all powered equipment capable of starting and operating in temperatures down to -25 F. Primary technical problems center around the over-designing of all adjustable devices so that they can be handled by operators wearing heavy mittens. Under extreme cold conditions gloves cannot be removed for even an instant, nor can fingers be permitted to come into direct contact with cold metal.

THE first part of this paper is devoted to pictures of some of the present-day types of, power-steering units. These are followed by pictures of several of the pumps that have been developed for these power-steering units. The remainder of the paper covers: 1. Vehicles equipped with power steering. 2. Le Tourneau electrical power steering. 3. Accessories and hydraulic fluids.

A NEW system for measuring accurately the air consumption of single-cylinder test engines is described in this paper by two engineers who have sought to eliminate errors resulting from the pulsating airflow caused by piston movement and the opening of the intake valve. The new technique utilizes the principle of critical or sonic flow of gas through a convergent nozzle to measure air consumption to an accuracy of 1% under all operating conditions, as compared with errors of as much as 20% resulting from the use of conventional orifice meters. In addition the new system makes possible the maintenance of constant inlet air pressure, temperature, and humidity, independent of prevailing atmospheric conditions, whereas the conventional system fails to isolate the engine’s “breathing” from vagaries of atmospheric conditions. The new technique is not needed for multicylinder engines inasmuch as they produce a “steady state” of airflow through conventional orifice meters.