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THE automotive industry is developing without due regard to the fuel situation. This situation is an integral part of the automotive field and should not be left out of account. Owing to the pressure of automotive demand, the supply of engine fuel is changing in character and price, with danger of precipitant alterations; there arises in consequence a fuel problem which cannot be adequately solved without the active participation of the automotive industry.

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.

THE track-laying type of vehicle is, of course, old. The emergency which brought the modern “tank” into existence was the menace of the machine-gun. The tank is simply a device that can approach closely and destroy the gun or its crew. It is fundamentally a man killer, and its strongest points are speed and mobility. It is now an indispensable arm of the military service. The writer gives a rapid résumé of the fantastic period in design, the early work done on heavy armored cars and the reasons for concentrating on the track-laying type of vehicle. The American type of track was adopted as a foundation and from this and around it France, England and the United States have developed the tanks known through successful use in the war. The British are to be credited with producing the first practical fighting machine of this type. France has two types of machine, one mechanically driven and the other with electric drive, both small.

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.

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 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.

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.

The authors first define the elementary conditions governing combustion efficiency, dividing these conditions into three main classes. They next compare engines operating on constant volume, constant temperature and constant pressure cycles, dealing specifically with the Otto, Diesel and semi-Diesel types. The main part of the paper is devoted to an outline of the constant pressure cycle, analyzing its advantages as compared with the merits of the constant volume cycle now used in internal-combustion engines. The paper is concluded with a detail description of a proposed constant pressure engine.

CORRELATION OF BENDING STRENGTH AND ERRORS OF HELICAL GEAR has not been clarified sufficiently even now. As the investigation by using only experimental method is not sufficient and so the analytical method of obtaining gear bending strength has been developed by one of the authors. Hence, the correlation of bending strength and errors, especially in the aspect of the direction of pressure angle error and tooth trace error, is clarified by this analytical method which was verified by some experiments. And by further investigations, it is confirmed that the helical gear is tougher against the negative pressure angle error, and the fine module gear is sensitive against the errors.