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The adoption of the present system of feeding a number of cylinders in succession through a common intake manifold was based upon the idea that the fuel mixture would consist of air impregnated or carbureted with hydrocarbon vapor, but if the original designers of internal-combustion engines had supposed that the fuel would not be vaporized, existing instead as a more or less fine spray in suspension in the incoming air, it is doubtful that they would have had the courage to construct an engine with this type of fuel intake. That present fuel does not readily change to hydrocarbon vapor in the intake manifold is indicated by tables of vapor density of the different paraffin series of hydrocarbon compounds.

A large number of tests were made in the altitude laboratory of the Bureau of Standards, using aircraft engines. The complete analysis of these tests was conducted under the direction of the Powerplants Committee of the National Advisory Committee for Aeronautics. Many of the engines were of the same make, differing in compression ratio or dimensions. The testing program included determinations of the brake-horsepower at various speeds and altitudes, or air densities, and the friction power, or the power required to operate the engine with no fuel or ignition at various speeds and air densities, with normal operating conditions of oil, water and the like. Some tests included determination of the effect of change of mixture ratio and of air temperature, and of different oils. The difficulties caused by the necessity of using indirect methods to ascertain the effect of various factors are outlined. The test analyses and curves are presented.

The first car credited by the author as being equipped with two or more direct drives is the Sizaire-Naudin, in 1905. The transmissions of this car and of one embodying similar principles of gearing, brought out in 1909, are described and illustrated by diagrams. After the Sizaire-Naudin, the next double direct-drive transmission was the Pleukharp transmission axle, made in 1906, although the real ancestor of the present double-drive rear axles is the 1906 Pilain transmission; both are described and illustrated. Other early American and foreign forms are commented upon and diagrammed, including the Austin design, believed by the author to be the first to use a two-speed axle of the simplest and lightest possible type to provide two direct drives in connection with a separate gearset to give additional forward speeds and the reverse. Modern two-speed axles are reviewed, with critical comment and diagrams, and considerable discussion of gear ratios is included.

An analysis of japanning practice as a systematized industrial operation is presented as the result of an investigation. The nature of japans is discussed and an outline given of how the apparently contradictory requirements that japans must be weatherproof, somewhat flexible, sufficiently thick to be lasting, possess enough hardness to prevent excessive scratching under ordinary service conditions and take on a brilliant finish, can be fulfilled in an ordinary industrial plant without undue expenditure, so as to accomplish the original and primary objects of applying a finish to metal parts to prevent them from too great deterioration and supply a pleasing appearance to the finished product. Adequate provision for securing a uniform product is essential. The details of this are discussed. Three ways of applying japan are explained. The considerations involved in cleaning the metal and baking japan are enumerated at some length and the methods are described.

For many years plywood has been used for such automobile parts as roofs and dash and instrument-boards, but it was not until the closing of the European war that the extent to which this material was used in automobile construction greatly increased. The sudden requirement of airplanes created a large demand for plywood which would withstand the severest weather conditions. Glues were perfected that enabled plywood to withstand 8 hr. of boiling or 10 days of soaking in water without separation of the plies. Plywood as an engineering material is discussed. It is then compared in considerable detail with ordinary boards and also with metals and pulp boards, statistics and illustrations being given. The molding of plywood is considered with especial reference to employing plywood for surfaces having compound curvatures, and the limiting factors in the use of plywood for this purpose are mentioned.

After stressing the importance of transportation, the possible uses of the motor truck are considered. The increased cushioning and traction obtained from pneumatic truck tires accomplish faster transportation, economy of operation, less depreciation of fragile load, easier riding, less depreciation of roads and lighter-weight trucks. These six advantages are then discussed separately and various data to substantiate the claims made are presented. Following detailed consideration of transportation and operation economies, and depreciation of loads and roads, the practicability of pneumatic tires is elaborated, and wheels, rims and tire-accessory questions are studied. The four main factors bearing upon truck design for pneumatic tires are stated and discussed; emergency equipment for tire repair is outlined and a new six-wheel pneumatic-tired truck is described.

The discussion is largely in regard to the ability of a truck to deliver merchandise economically under a given set of external conditions. The matter of truck tire equipment is reviewed in the light of recent experiences of many operators and service men. The general functions of tires, securing traction, cushioning the mechanism and the load and protecting the road, are elaborated and six primary and seven secondary reasons given for the use of pneumatic tires on trucks within the debatable field of 1½ to 3½-ton capacity. The deciding factors in tire choice, those affecting time and those affecting cost, are stated and commented upon, the discussion next being focused on how tires affect these factors. Considerations relating to both truck and tire repairs are then reviewed.

The farm tractor is finding itself among the most essential of mechanical agricultural devices; the industry is young, and controlling basic factors of design are not yet completely crystallized, nor has research had its proper share in the development. Some further factors of the author's earlier article on tractor plowing speeds2 are discussed in this paper. The earlier article dealt chiefly with plowing data on the assumption that there was delivered at the drawbar of the tractor a constant horsepower. This paper starts with a normal condition of a constant engine power which is to be delivered to the crankshaft under governor control for any of the travel speeds analyzed. The tractor is considered as powered by a given brake-horsepower engine, this power being transmitted through sets of gears in which the net bearing and gear efficiency is taken to be 73 per cent.

In view of the inestimable services in the development of standardized transportation rendered to the Army by the Society of Automotive Engineers, particularly during the war, the author believes it important that the Society be acquainted with the intentions and policies of the War Department regarding the engineering development of motor transportation from the viewpoint of the problems and needs of the American Army. The fundamentals of the policies on motor transportation of February, 1919, as approved by the Chief of Staff, are stated and the subsequent changes discussed in some detail. Standardization of chassis as favored by the Army receives specific and lengthy consideration and the Government standardized trucks are commented upon. The standardization of body design and parts specifications are discussed in some detail. It is the policy of the Motor Transport Corps to maintain a thoroughly adequate and efficient engineering branch, which is now operative.

The undisputed economy of the Diesel-type engine using heavy fuel oil is recognized, as no other power-generating unit of today shows better thermal efficiency. It is the result of the direct application of fuel in working cylinders. Transmission processes, such as the burning of fuel under a boiler to produce a working agent which must be carried to the prime mover, are less economical. The various factors which enter into a comparison between steam and heavy-oil installations are illustrated. The subject is treated in a more or less elementary manner. The diagrams and sketches are intended to explain the working principles of such examples of two and four-cycle engines as are now in actual operation in cargo ships, these being of the single-acting type. Double-acting and opposed-piston-type engines have been built and are being tried out. The working processes of two-cycle and four-cycle engines are illustrated and described in some detail, inclusive of critical comment.

Emphasizing the necessity of persuading fuel manufacturers to improve the suitability of internal-combustion engine fuel by the mixture of other materials with petroleum distillates, and realizing that efficiency is also dependent upon improved engine design, the author then states that results easily obtainable in the simplest forms of automotive engine when using fuel volatile at fairly low temperatures, must be considered in working out a future automotive fuel policy. The alternatives to this as they appear in the light of present knowledge are then stated, including design considerations. The principles that should be followed to obtain as good results as possible with heavy fuel in the conventional type of engine are then described. These include considerations of valve-timing and fuel distribution. Valve-timing should assist correct distribution, especially at the lower engine speeds.

DURING the first two years of the war the author conducted in England experimental work for the British Government on the engine he describes. After brief mention of V-type water-cooled engines and the general situation as regards revolving air-cooled and radial water-cooled types, the discussion is narrowed to two distinct designs of fixed radial air-cooled engine, both of which have been tried out and seen some service. The fundamentals in which fixed radial air-cooled engines give promise of excelling are weight of powerplant per horsepower, the fuselage mounting and space required being duly considered; reliability and durability; fuel and oil consumed per horsepower-hour; streamline mounting, with armor, if desired; quick detachability of powerplant; accessibility, and freedom from certain inherent difficulties peculiar to water-cooled engines.

THE Navy Department established the Naval Aircraft Factory (a) to assure a part, at least, of its aircraft supply; (b) to obtain cost data for the Department's guidance in dealing with private manufacturers, and (c) to have under its own control a factory capable of producing experimental work. The history of this development is given in some detail, including statistics of size, valuations and output.

SOME practical examples of correct as well as of incorrect methods of designing are studied, using a motor vehicle for illustration. The mechanism of such a vehicle should be very simple, and the elimination of certain links and members here and there may become more or less desirable. It is essential to know how much this will burden other members, and what strengthening or even redesigning may become necessary. It has been proposed to eliminate the torque and radius-rods. By formulas and drawings the author shows how complex the problem is and the various changes that must follow such an attempt. A vehicle must have much stiffer springs if the torque rod is to be eliminated. This inevitably leads to a study of springs and of the influences of brakes. A vehicle can be operated at somewhat higher speed with a torque-rod.

The author discusses the different types of material used in the production of the Liberty engine, the physical properties of the finished parts and the heat-treatments used in making them, applying the information as set forth to the automobile, truck and tractor industries. Under their several heads the different engine pans are discussed with close attention to details. Chemical analyses are given for each part and approved heat-treating temperatures are indicated. Quenching, direct and indirect, water and oil cooling, hard spots, warpage, scaling and hair-line seams are treated. The advantages and disadvantages of the Izod impact test are stated briefly.

Naval aircraft are distinctively American types. Only one foreign seaplane was copied by the United States during the war, and when finally put into production it resembled the British prototype in externals only. While the Navy does a large part of its own designing and building through a corps of naval constructors, its theory of manufacture is to assemble parts procured from separate makers, and private design and construction are encouraged by contracting with builders. Available talent both in and out of the service and the facilities of parts makers, the new materials developed during the war and organized engineering which drove the entire process toward speedy results were appropriated by the Navy. The NC flying boat is typical of U. S. Navy practice. In the same way the dirigible C-5 is a purely American type. The development of really large flying craft before 1917 was held back because no suitable engine had been designed. When the 350-hp.

A new type of automotive engine should be the quest of all designing engineers. Investigation has revealed the fact that 68 per cent of all tractor engine troubles occur in magnetos, spark-plugs and carbureters, the accessories of the present-day automotive engine. Four-fifths of the fuel energy supplied is regularly wasted, yet the fuel is a liquid meeting severe requirements of volatility, etc., and is already becoming scarce and costly. In an airplane, fuel is carried by engine power. In ocean-going cargo vessels it increases available revenue space. It is at once clear that for purely practical reasons the question of fuel economy, no less than the question of the nature of the fuel, becomes momentous. What fuel will do is entirely a question of what process it is put through in the engine; in what way combustion is turned into power.

The development of the Motor Transport Corps is outlined; the number of motor vehicles for one army at war strength and the number for the proposed peace-strength army with increased motorization are specified and the disposal of surplus motor vehicles is discussed. The problem of keeping uptodate the motor vehicles in service is stated and the cooperation of automotive engineers is requested. The vexatious unsolved problem of spare parts is stressed and solutions are suggested. The question of peace-time training and matters relating to the motor transport reserve are considered in some detail. The motor transport personnel required on a war basis and for a proposed peace army of 509,000 men is enumerated, as well as that of the motor transport reserve corps and the national guard required to bring the proposed peace-time army to war strength.

The engine-fuel situation has changed almost overnight. Oil-consuming activities have taken on an accelerated expansion and the situation has shifted from excess supply to a position where demand is assuming the lead and is seeking a supply. A gasoline stringency, accompanied presumably by a marked rise in price, is a prospect to be anticipated. The production of gasoline is increasing more rapidly than the production of its raw material, crude petroleum. The available supply of the latter is very limited in view of the size of the demand. As a direct result of the situation, gasoline is changing in character and becoming progressively less volatile. The low thermal efficiency of the prevailing type of automotive apparatus contributes strongly to the demand for gasoline as engine fuel and has a bearing upon the quantity and the price of this specialized fuel.

Iron rust is caused by electrolytic action between the various constituents of iron or steel in the presence of moisture and impurities. It is a continuous process; a coating of rust does not protect the metal underneath. The principal requirements of a rust-prevention process as applied to automobiles, aircraft and other machined and hardened parts are that it (1) Prevent rusting under normal use (2) Prevent the spreading of rust (3) Make no change in dimensions or fits (4) Make no alterations in physical properties (5) Be permanent for the life of the part (6) Be easy and quick of application (7) Be commercially practicable as to cost Of the most familiar rust-proofing processes, the cold, the hot and the high-temperature, the last is eliminated by requirements (3) and (4), while the cold processes and also japanning are eliminated by (2), (3) and (5). There remain three hot processes, the Parker, the Coslett and the Guerini.