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The paper is devoted more especially to enclosed body construction, with the object of creating a closer relation between the chassis and the body designer, from the viewpoint of an automotive body constructor. After enumerating what are probably the most important materials that enter into enclosed-body construction, inclusive of glue, the author outlines what constitutes the proper seasoning of wood, this being very important because very little all-metal or steel construction has been developed as yet for enclosed bodies, owing to the fact that many parts are required that necessitate using wood. Chassis deflection is discussed in its relation to enclosed-body construction and an outline is presented of body-construction development in general. The author believes that body construction will not be changed radically until either the basic type of design or shape is transformed or there is a firmer foundation to build upon.

Statistics taken from a report made by the Department of Agriculture regarding the number and size of farms in the United States indicate that approximately 2,580,000 farms are available as a market for the isolated gas-electric lighting plant. The common types of lighting plant are classified in three groups, each of which is subdivided into three classes, and these are illustrated, described and discussed. The characteristics of the ideal farm lighting-plant are enumerated and discussed as a preface to a somewhat lengthy consideration of the factors that influence the design of the component parts, which are grouped as pertaining to the engine, the generator, the switchboard and the battery. Storage batteries are still considered the weakest part of the isolated plant and they are specially commented upon. The author emphasizes that much still remains to be accomplished as regards the stability of design, reliability and economy of the isolated plant.

The author first considers the style and arrangement of the seats, the position of the rear axle as affecting the rear kick-up in the chassis frame, and the position of the rear wheels as determining the distance from the back of the front seat to a point where the curve of the rear fender cuts across the top edge of the chassis frame. The location of the driver's seat and of the steering-wheel are next considered, the discussion then passing to the requirements that affect the height of the body, the width of the rear seat, and the general shape. The evolution of the windshield is reviewed and present practice stated. Structural changes are then considered in relation to the artistic requirements, as regards the various effects obtained by varying the size or location of such details as windows, doors, moldings, panels, pillars, belt lines, etc., and the general lines necessary to produce an effect in keeping with the character of the car.

The two broad divisions of aluminum pistons from a thermal standpoint are those designed to conduct the heat from the head into the skirt and thence into the cylinder walls, and those designed to partly insulate the skirt from the heat of the piston head. Pistons of the first type seem logical for heavy-duty engines; those of the second type are better suited for passenger-car engines. The objections of wear, piston slap, excessive oil consumption and crankcase dilution are stated as being the same for aluminum as for cast-iron pistons; and these statements are amplified. Piston slap is next considered and, as this can be overcome by using proper clearance, pistons of the second design tend to make this condition easier to meet. Many tests show that when too much oil is thrown into the cylinder bores, tight-fitting pistons and special rings will not completely overcome excessive oil consumption.

The author advocates the use of the fragile aluminum crankcase as a spacer, running crankshaft bearing bolts clear through the crankcase and the cylinder base, so tieing the bearings firmly to the castiron cylinder-block and using the through-bolts also as holding-down studs for the cylinders. The results of experiments on six-cylinder engines with reference to the satisfactory utilization of engine fuel now on the market are then presented. The problem is how to carry the fuel mixture in a proper gaseous state from the carbureter into the cylinder without having the fuel deposited out meanwhile. The power developed at engine speeds of 400 to 2800 r.p.m., with and without hot air applied to the carbureter, is tabulated, the proper location of the intake manifold is discussed, and the necessary features of a satisfactory engine to utilize present-day fuel are summarized.

The author proposes to determine what features of spark-plug construction cause preignition and how this preignition manifests itself. To this end observed conditions on an Hispano-Suiza aviation engine following 4 hr. of an intended 6-hr. run are reported, with supplementary tests and observations. This resulted in experiments made to determine the cause of preignition, using spark-plugs constructed so that different features of their design were exaggerated. Illustrations of these plugs are shown and the results obtained from their tests are described. The different observed peculiarities are then stated, analyzed and compared with normal spark-plug performance. The experiments serve as a means of identification of special forms of preignition and as an indication of the abnormally high temperatures to which valves and combustion-chamber walls are thus subjected.

Shortly after the armistice, the author witnessed the surrender of the German submarine fleet and subsequently inspected 40 of the 170 submarines first surrendered. He also inspected 185 submarines in Germany. Practically all the engines were of the Machinenfabrik Ausburg-Nürnburg four-cycle Diesel type, of 300, 550, 1200 and 1750 hp. There were but five Krupp two-cycle engines. Brief comment is made regarding the design of these engines. The author, who supervised the dismantling of the German submarine U-117 at the Philadelphia Navy Yard, gives a detailed description of its engines, which were of the 1200-hp. type. This includes comments regarding materials, design details, valve mechanism, starting and reversing gear, lubrication, cooling and accuracy of workmanship. The air-compression system and some of its auxiliaries are outlined.

The annual report covering transportation by the largest British air-transport company laid particular emphasis upon the greater value of the faster machines in its service. Granted that efficient loads can be carried, the expense, trouble and danger of the airplane are justified only when a load is carried at far greater speed than by any other means. A reasonable conclusion seems to be that we can judge the progress made in aviation largely by the increased speed attainable. It is interesting and possibly very valuable therefore to inquire into the relations of power and resistance as applied to small racing machines with aircraft engines that are available.

A tendency exists in most shops to assume that brazed joints cannot be successfully heat-treated. As a consequence, many fittings used in aircraft work and assembled by brazing smaller parts together are finished and installed without being heat-treated after the brazing operation. This practice causes parts to be used that not only do not develop the available strength of the material, but which are in some cases, under internal stress due to the heating in the brazing operation. Recent experiments made at the Naval Aircraft Factory show that the assumption mentioned is entirely erroneous. The author considers this matter with a view to specifying the use of steels and brazing spelters which will permit the subsequent or perhaps the simultaneous heat-treatment of the parts.

The paper defines properties that describe the performance of a radiator; states the effects on these properties of external conditions such as flying speed, atmospheric conditions and position of the radiator on the airplane; enumerates the effects of various features of design of the radiator core; and compares methods that have been proposed for controlling the cooling capacity at altitudes. Empirical equations and constants are given, wherever warranted by the information available.

The free, resilient, self-expanding, one-piece piston-ring is a product of strictly modern times. It belongs to the internal-combustion engine principally, although it is applicable to steam engines, air-compressors and pumps. Its present high state of perfection has been made possible only by the first-class material now available and the use of machine tools of precision. The author outlines the history of the gradual evolution of the modern piston-ring from the former piston-packing, giving illustrations, shows and comments upon the early types of steam pistons and then discusses piston-ring design. Piston-ring friction, the difficulties of producing rings that fit the cylinder perfectly and the shape of rings necessary to obtain approximately uniform radial pressure against the cylinder wall are considered at some length and illustrated by diagrams.

The author presents the practical side of the body designer's work and refers to him as being between the office and the shop, the one who stands in the way of the impatient man that wants action without preparation. The development of the body designer and body designing is reviewed and the position and duties of the designer are stated at some length. The design factors are considered in detail and the making and utilization of wax models are described, followed by a lengthy consideration of curved-surface bodies, wood body frames, style and body types. The fittings and minor design details are discussed and future designs predicted from present indications. The author explains the body designing business in detail to refute the suspicion that the working methods of body designers are different from those employed by the other members of an engineering force because body designing is different and distinct from the other branches of motor-car engineering work.

It has long been recognized that, in automotive engines, particularly those of six or more cylinders, excessive vibration is apt to occur despite all precautions taken in balancing; and that this is because the engine impulses coincide at certain speeds with the torsional period of the crankshaft, or rate at which it naturally twists and untwists about some point or points as nodes. Very serious vibration occurred in the main engines for the United States submarines S 4 to S 9, which are required to complete five specified non-stop shop tests and an investigation was made of which the author reports the findings in detail, illustrated with photographs and charts.

Iron ranks first of all the metals; copper, lead and zinc come fairly close together in tonnage; tin ranks next; and aluminum is fifth of the non-ferrous metals. The place of aluminum in the automotive industry is shown in a diagram and another brings out the production of copper and aluminum, both receiving comment. The metallography of aluminum alloys is discussed in some detail, as well as the phenomena of growth and aging, charts and photomicrographs being shown and commented upon. The effect of alloying on physical properties is treated in a similar manner in considerable detail and a comparison of aluminum with other metals follows. Forging alloys are described and some miscellaneous aluminum-alloy forged parts are pictured. The advantages of forging alloys are enumerated and many of their present uses specified; other contemplated uses for the newest alloy are for cast disc-wheels for passenger cars, differential carriers and cast rear-axle housings.

The best weight for a tractor of given horsepower must be a compromise based upon a mean of the many conditions to be encountered by a given machine or by different machines of the same model. While the weight logically will bear some relation to the drawbar pull, the latter in turn depends upon tractor speed. The next item is weight distribution, which requires the utmost skill of the designer; this is elaborated and diagrams are shown of tractors operating in comparatively firm and in soft ground, ascending a grade and when the drive-wheels are mired. The four-wheel-drive tractor requires a modification of the foregoing analysis and the diagrams are applied to afford a similar analysis for this type. The author's conclusion is that, while careful engineering will make the light-weight tractor of conventional type stable under most conditions, there is a possibility that any future trend toward lighter machines will open the field to other types.

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.

Although aluminum is the most abundant metal in the earth's crust, it was not until the early eighties that means were discovered for reducing it from its ores in such quantities and at such cost as to make it a commercial possibility. The world immediately began to find uses for this material. Two groups developed; one, assuming for aluminum properties that it did not possess, thought that it would in time replace all other metals; the other, which, reacting from the first-mentioned view due to failures and disappointments, thought it had little use. It was afterward realized that much research was necessary to make aluminum a really commercial metal. One of the main aims of the automobile engineer is to obtain lightness combined with proper strength. The paper deals with decreasing the weight of automobiles by more extended use of aluminum alloys. The physical properties of aluminum are described in considerable detail and its varied uses are enumerated.

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.