Search Results

Manufacturers of carbureters and ignition devices are called upon to assist in overcoming troubles caused by the inclusion of too many heavy fractions in automobile fuels. So far as completely satisfactory running is concerned, the difficulty of the problem with straight petroleum distillates is caused by the heaviest fraction present in appreciable quantity. The problems are involved in the starting, carburetion, distribution and combustion. An engine is really started only when all its parts have the same temperatures as exist in normal running, and when it accelerates in a normal manner. Two available methods, (a) installing a two-fuel carbureter, using a very volatile fuel to start and warm-up the engine, and (b) heating the engine before cranking by a burner designed to use the heavier fuel, are described and discussed.

Whatever may be the conclusion of business men and engineers as to the fuel problem, dealing with it from the point of view of the engineer as a service man nothing further is needed than that the problem is before us. The paper deals with engine troubles that have been found to demand the greatest amount of attention from farmers. Tractors are not built for or operated by engineers. No quantity production is likely to be attained for some time to come with anything but the commonest forms of cylinder and other features. This judgment is based entirely on the limitations in upkeep knowledge of the average user. The four-cylinder tractor engine seems to be rapidly becoming standard, due to its simplicity and the familiarity of most farmers with this type. Consideration is given, topic by topic, to important parts of the tractor engine and the relation of fuel to difficulties discussed.

THE application of the marine internal-combustion engine to the British ML class of 80-footers and to the American 110-ft. class of submarine chasers, undoubtedly constituted the most important development along this line of automotive work. With a hull form similar to that of an enlarged runabout, driven by a pair of six-cylinder Standard marine engines rated at 220 b.-hp. at 460 r.p.m., the boats of the ML class averaged about 20 knots. A total of 720 boats of this type were built and the class as a whole proved very satisfactory. In the development of the 110-ft. SC class, the requirement of seaworthiness was made of greater importance than speed. Each boat carried three six-cylinder Standard engines identical with those used in the British boats, driving them at about 17 knots. Although rather uncomfortable, as in the case of any small vessel, the 110-ft. boats proved wonderfully successful in heavy weather; about 450 of this class were built. The 220-b.

ANY aggregation of parts assembled to obtain a mechanical result is a series of compromises. The relative importance of the objectives governs the nature of the compromise. The major objectives to be considered in the design of airplane engines are (1) Reliability (2) Small weight per horsepower (3) Economy of fuel and oil consumption (4) Carburetion that permits of easy starting; maximum power through a range of 30 per cent of the speed range; and idling at one-quarter maximum speed without danger of stalling (5) Ability to deliver full power through a small speed range without excessive vibration (6) Complete local cylinder-cooling under conditions of high mean effective pressure (7) Compactness The automobile engine must have (1) Reliability (2) Silence (3) Carburetion that accomplishes proper and even firing in all cylinders under varying throttle conditions, through speeds covering more than 90 per cent of the speed range of the engine.

THE impression that recent aircraft experience should have taught engineers how to revolutionize automobile construction and performance, is not warranted by the facts involved. Aircraft and automobiles both embody powerplants, transmission mechanisms, running gear, bodies and controls, but their functions are entirely different. The controls of an airplane, except in work on the ground, act upon a gas, whereas with an automobile the resistant medium is a relatively solid surface. Similarly, the prime function of the fuselage is strength, weight considerations resulting in paying scant attention to comfort and convenience, which are the first requirements of an automobile body. Aircraft running-gear is designed for landing on special fields, and is not in use the major portion of the time. The running-gear is the backbone of an automobile, in use continuously for support, propulsion and steering; hence its utterly different design.

Modern requirements have already forced the rotative speed of high-duty gas and oil engines to a point where the difficulty of heat-flow control, especially with cast iron cylinders, tends to arrest further progress in this direction. In view of this inherent limitation the art of high-speed engine design can best be advanced, not by continued experimental exploration, but rather by first establishing the basic principles underlying heat-flow effects. The purpose of the present paper is to demonstrate that every internal-combustion engine of given size and type has a safe speed limit and that this can be predetermined upon a rational heat-flow basis. This paper provides an explicit method of procedure, by means of which the design characteristics of a normal gas or oil engine can be critically analyzed for heat-flow effects.

The authors advance for discussion some important problems in the construction of airplanes for military use in this country. The functions of military airplanes designed for strategical and tactical reconnaissance, control of artillery fire and for pursuit are outlined. Problems in construction with reference to the two-propeller system, methods of reducing vibration, application of starting motors, details of the gasoline supply-system, metal construction for airplanes, flexible piping, desirable characteristics of mufflers, shock absorbers, landing gear, fire safety-devices, control of cooling-water temperature, variable camber wings, variable pitch propellers and propeller stresses, are all given consideration. The paper is concluded with suggestions for improvement in design relating to the use of bearing shims, the rigidity of crankcase castings, interchangeability of parts and better detail construction in the oiling, ignition, fuel supply and cooling systems.

The author states as his object a review of what has been done and what must be done to make tractors successful in operating on low-grade fuels, especially kerosene. He takes up in order the four principal methods in common use of applying heat to vaporize kerosene, pointing out the advantages and disadvantages of each method and of its modifications. The author then cites various experiments with different types of carbureters in burning kerosene, drawing at length upon his own experience in this connection. He cites difficulties with gas distribution, manifold condensation, pistons and spark-plugs and points out that carbureter design is inseparable from considerations of tractor engine and manifold design. That better progress has not been made in the past in developing kerosene-burning tractor engines is stated to be largely owing to the fact that there has not been sufficient cooperation between engine and carbureter manufacturers.

The title of this paper fully indicates its scope. The author presents an intimate picture of conditions prevailing at the war front which affect the operation and maintenance of war trucks, and these two factors in turn indicate the trend that design should take. The training of the mechanical transport personnel of the Army is also gone into at some length. The English and American trucks used earlier in the war consisted of about nineteen different makes and forty-two totally different models, resulting in a very serious problem of providing spare parts and maintenance in general. In the British Army transportation comes under an Army Service Corps officer called the Director of Transport and Supplies. At the outbreak of the war these officers had had little mechanical experience, horses being employed principally. In the French Army motor vehicles were used to a greater extent before the war, under the artillery command.

The author outlines methods for producing high-speed engines with high mean effective pressure and gives data resulting from several years' experimental work. He discusses the desirable stroke-bore ratios; valve area, weight, dimensions, location and timing; compression ratios; ignition requirements; and the location and means for operating camshafts and other valve-actuating mechanism. Data are given regarding the best material and dimensions for pistons and the desirable number of rings. The physical characteristics of alloy steel desirable for use in connecting-rods are mentioned. Similar data, including dimensions and factors controlling the construction of the crankshaft and its bearings are included. The relation of the inertia stresses set up by reciprocating parts to those due to the explosion and compression pressure on the piston head is indicated, and the maximum total stress deduced.

The author points out the necessity of obtaining dynamic or running balance of rotating parts, especially in automobile-engine construction. He discusses the manifestations of the lack of static and running balance, such as vibration and high bearing pressures. Formulas are supplied for calculating bending moments and centrifugal forces in a crankshaft that is out of balance. Methods for obtaining static balance are described and the possible conditions existing after static balance is obtained are treated, with especial reference to the existence of one or more couples. Descriptions are given of two representative machines that are used to locate couples and correct for them. The principles of operation are made clear and advantages and disadvantages of each type are brought out fully.

The author discusses in this paper a few of the problems involved in the design of ignition equipment. Some of these problems have been solved and some remain to be solved. The early history of the development of ignition apparatus is traced, reference being made to the vibrating coil type of ignition operated by dry cells or storage batteries, various types of magneto and dual-magneto systems, and combined generator and storage battery systems. The balance of the paper refers more particularly to batteries and ignition proper. The two types of battery ignition, open-circuit and closed-circuit, are described and the current characteristics of each are shown graphically by means of curves. Some of the problems encountered in the development of present battery systems are next considered and such topics as reduction of inertia in the contact-arm, overcoming harmonic vibration, advantages of one-piece cams and the function and design of the condenser are treated in detail.

After a few general introductory remarks the author outlines the operating requirements for tractors, and takes up the matter of the proper sizes of tractors, stated in horsepowers per given number of plows. The use of lower-grade fuels, value of water in the engine, cylinder construction, methods of lubrication and design of drive-wheels are the subjects covered by the balance of the paper.

The author first compares mineral oils with certain other liquids in order to point out clearly certain of their characteristics. He then shows the economic benefits that would result from making more of the crude available for use as fuels. He discusses such topics as cracking methods in use, advantages of dry gas, initial flame propagation, gas producers, hot mixtures, wet mixtures and difficulties of correcting existing engines. He concludes by proposing as a solution of the gasoline problem the more general use of superheated homogeneous fixed dry gases made in vaporizing devices independent of engine cylinders, and outlines means for attaining this end. Performance data covering the use of mixtures of kerosene and gasoline on several cars are included in a table, and several charts throughout the paper illustrate many of the topics discussed.

The author states that the objects of the paper are to define and trace the development of the various processes of carburetion, and to offer such suggestions along these lines as may assist the investigator in developing motorboats, automobiles and self-contained unit motor cars for railway purposes. The surface carburetor is mentioned chiefly as of historic interest. In considering the jet carbureter the author discusses the proportion of gas desired, the effect of the varying inertia of the air and the liquid gasoline and the breaking up of the combustible needed. Following sections review the devices for using kerosene, such as gasoline jet carbureters to which heat is applied, devices of the fixed gas type, the introduction of combustible directly into the cylinder, forcing combustible directly upon a hot surface in the cylinder and devices which raise the combustible to the boiling point.

This paper emphasizes the importance of using standardized testing equipment in order that mental calculations may be avoided in interpreting the reports of other engineers. The situation and environments of the engine-testing plant, cooperation among the men conducting tests, standardized methods of conducting tests, value of venturi meters and testing of accessories are among the subjects discussed in the first part of the paper. The subject of the testing of engine cooling systems is treated at some length, the importance of obtaining operating conditions being emphasized. The paper concludes with two sections covering spark-plug testing and tests for preignition.

This paper first traces the early development of aviation engines in various countries. The six-cylinder Mercedes, V-type twelve-cylinder Renault, and six-cylinder Benz engines are then described in detail and illustrated. Various types of Sunbeam, Curtiss, and Austro-Daimler are also described. The effect of offset crankshafts, as employed on the Benz and Austro-Daimler engines, is illustrated by pressure and inertia diagrams and by textual description. The paper concludes with a section on the requirements as to size of aviation engines, four curves showing the changing conditions which affect the engine size requirements. These curves relate to variations of temperature, air density, engine speed, airplane speed and compression ratio required to compensate for decrease in air density, all as related to varying altitude.

This paper deals only with water-cooled engines, the cooling system being considered as made up of four main units-the water jacket, the circulating system, the radiator and the fan. Water-jacket problems are first considered, followed by a comparison of pump and gravity (thermosyphon) systems of circulation. The next section is devoted to radiator requirements. The balance of the paper relates to the fan. Five curves show graphically the correlations of the various factors of cooling, power consumed, air velocity and volume, engine speed, fan speed, air and water temperatures and the element of time, the results applying to different types and sizes of fans. These curves are of service in the selection of fans for radiator cooling purposes. The classification of fans, fan power consumption and speed, fan belts and pulleys, disadvantages of high fan speed, types of fan bearings, and applications of fans are the subjects next taken up.

The forces necessary to induce and maintain gasoline engine speeds of 3000 r.p.m. or faster, as well as other forces closely associated with high speeds, are numerous. The author has, however, confined his discussion to the three most important groups of forces upon which, in the main, the smooth running and the life of an engine depend. The different component forces were determined in respect to two engines of equal capacity for twenty-four crank positions, uniformly spaced at intervals of 30 degrees, which constitutes two revolutions and one complete cycle in the case of four-stroke cycle engines. Medium-sized six and twelve-cylinder engines were chosen for investigation. Corresponding components were combined as resultant forces and graphically represented in magnitude and direction. Several such characteristic diagrams of the resultant forces acting upon crankpins and main bearings of the two engines investigated are reproduced throughout the paper.