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The authors outline some of the problems that confront the automobile engineer today, showing how the demand for better performance and economy and the ever-increasing cost of volatile fuels has emphasized the necessity for thorough engineering work in the successful automobile manufacturing plant. Believing that the accurate analysis of the heat distribution in a modern automobile engine will be of great value, the authors describe a comprehensive test, made under their direction, of such an engine. This test includes measurements of the brake horsepower, friction horsepower, fuel consumption and heat losses to jackets, exhaust and cooling air. The engine tested was inclosed in a hood, similar to that used on the car in normal service and an air blast was directed through this hood at speeds approximating those at which the engine would drive a car with a given gear ratio.

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, from a first-hand study of this engine in the laboratory of Professor Junkers, traces the progress of the developmental work, and discusses the methods of operating the engine, its present status, its application to airplanes, trucks and tractors, details of marine and stationary types, fuel, advantages of and objections to the double-piston construction, and describes at some length the various parts entering into the construction of this type of engine. In conclusion, he summarizes the fundamental advantages of the Junkers engine.

The author first mentions hot-tube ignition, which preceded the spark-plug, then the low-tension type of make-and-break ignition, following with the development of spark-plugs. He compares the conical and petticoat types of porcelain and discusses at some length the insulating materials used in spark-plugs, such as porcelain, mica, steatite, glass and quartz. In this connection he covers the composition of the material, its dielectric strength, carbon-absorbing ability, heat-conductivity, mechanical characteristics, and the difficulties of glazing. Under the heading of general design of spark-plugs the author takes up such points as assembly of insulator and center electrode, electrodes, gaskets, and separable and integral plugs.

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.

The efficiency of the automobile engine, as operated on the Otto cycle, is thought by the author to be too low, and he therefore suggests a method of improving it. He considers the various losses by which heat is dissipated in internal-combustion engines and finds that the best opportunity for increasing thermal efficiency is by an increased expansion of the charge. The author suggests that this expansion be carried 50 per cent further than is ordinarily done. In order to obtain higher efficiency at part load, the suggestion is made that instead of throttling the mixture, the admission valves be closed earlier. In case the expansion is 50 per cent longer than the induction stroke and the cut-off takes place earlier as the load becomes lighter, it will be necessary to vary the fuel opening inversely with the air induced. It is suggested that the fuel valve and cut-off lever be connected together and operated by the accelerator pedal or hand lever on the steering wheel.

After a brief consideration of airplane-engine practice in France, England and Germany, the author outlines the problems encountered in designing a twelve-cylinder aviation engine. He explains at some length the difficulties in determining the connection between propeller and engine and shows why valve-in-head location was chosen. Such features of engine design as the mounting of carbureter and exhaust pipes, methods of fuel and lubricant supply and details involved in selecting the lighting, starting and ignition equipment are considered.

The paper opens with a number of quotations from publications issued by the Army War College and showing the bearing of motor transport on a proper military policy for the United States. The author then describes two experimental trips recently made by motor-truck owners near New York in an effort to determine proper motor-transport operating conditions. A statistical summary is given for these two experimental trips. The Army War College has issued in compliance with instructions of the Secretary of War a “Statement of a Proper Military Policy for the United States,” supplemented by a number of pamphlets dealing with particular features of this military policy in considerable detail. In many of these supplementary pamphlets there appears a considerable amount of material bearing upon the subject of motor transport and from them the brief quotations in the following paragraphs are taken.

The author outlines the constructions that have performed cially that four-cylinder engines carried under a hood are the most satisfactory. The defects revealed by war service are given in considerable detail, the author finding that all of the trucks used had developed some weak point. Radiators and springs are specified as a general source of trouble. The author outlines a number of operating troubles developed under the existing conditions of operation and gives examples of the way these have been remedied. Considerable attention is paid to the methods of operating trucks away from made roads. The methods of fitting chains to the wheels, and the use of caterpillar attachments are described. Dimensions are given for bodies and a number of suggestions made as to their proper construction.

The question as to whether a part should be made or bought is one that must be settled by the individual maker according to the value of his product, the nature of the part, his capital available for manufacturing purposes and the price at which his product is sold. The author describes the practice followed by some of the large companies, showing that in spite of their being quantity producers, they have found it desirable to buy a number of important parts. Certain parts are rarely made by automobile manufacturers, either because they can be bought more cheaply or because the machinery to produce them is intricate. The author sums up the problem by stating that a manufacturer makes the unit on account of not getting deliveries or because he does not get a fair price from the parts maker or an article good enough to satisfy his conditions. In order to give individuality to the product, the car maker often produces certain parts, such as the engine, himself.

The author considers the effects of velocity variation on the operation of a car and states that this variation is absorbed mainly by the flywheel. A formula is given for calculating the pressure on universal bearings. Various methods of protecting and lubricating joints are described. A number of European types of joints are illustrated. A much larger number of types of joints are used abroad in-asmuch as each maker usually makes his own design instead of purchasing it from a specialist as is the usual practice in this country. In conclusion the paper describes types of joints using flexible material, such as leather or spring steel.

The author outlines in a general way the relation of car performance to modern engine development. He considers particularly weight reduction and torque performance of high-speed engines, giving the undesirable characteristics attending the increased torque range gained by higher speed. He next discusses the relation of torque to total car weight, to acceleration and to hill-climbing ability and suggests a method of determining the value of a car in terms of its performance ability. The author holds incorrect those systems in which the amount of lubrication is in proportion to speed only; and in which oil for crankshaft and crankpin bearings must cool as well as lubricate them. He shows a system designed to solve these oiling problems. Static, running and distortion balance of a rotating mass are defined by the author, who shows how they apply to a large number of types of crankshafts.

The author gives a brief review of developments during the past year in the construction of aeroplanes, particularly as affected by the European War. He takes as an example the Renault twelve-cylinder engine, citing the respects in which the present differs from previous models. Such factors as the changes in cooling systems, method of drive, valve construction and starting devices are considered. The requirements of aeroplane engines, such as constant service, high speeds (of aeroplanes) and stream-line form of engines and radiators, are outlined. Propeller requirements are dealt with at length, curves being given by which the efficiency and diameter of the propeller can be obtained. In conclusion a number of different engine installations are illustrated and compared.

In this paper the author gives the results of an investigation of coarse crystallization. This investigation was carried out with commercial materials such as cold-drawn wire, hot and cold-rolled sheet, strip steel, cold-drawn tube and cold-pressings. The results of other investigations are briefly outlined. Coarse crystallization, or grain-growth, it is stated, is due to the action of a limited amount of strain, exceeding the elastic limit, followed by annealing within certain temperature ranges. The experimental work which led to this conclusion is explained in detail in the paper. The effect of forging, cold-drawing, cold-rolling and cold-pressing was determined with commercial materials. Some study was made of the effect of carbon on grain-growth and of the effect of coarse crystallization on the physical properties. In the discussion of commercial materials special reference is made to those used in motor car construction.

The author starts with the development of the pneumatic tire since its invention by Dunlop in 1888, and proceeds to show why several different types of tire construction are now in use. The merits of the three types of tires, namely, the clincher, straight-side and quick detachable, are discussed as regards energy consumption, traction, total mileage, cost-per-tire-mile, cushioning effect, reliability, ease of applying and service. The conclusions brought out show principally the advantages of the straight-side tire. Statistics are offered to show the trend of the rim situation, and it is pointed out that it is just a question of time when the quick detachable clincher will cease to survive. It had a legitimate place during the development stage, but with the developed straight-side tires giving entire satisfaction, the author holds that there is no excuse for continuing the quick detachable clincher type.

The author has selected fourteen automobiles on which to make a study of the factors of safety used in their design. He considers specifically the front axles, front-wheel spindles, propeller-shafts, clutch-shafts, transmission drive-shafts and rear-axle drive-shafts. The method of calculating the stresses is outlined; compositions of the steels used are given; and complete data are presented showing the factors of safety of the various parts, together with the intermediate figures used in obtaining the factors.