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After noting that the early development of the automobile industry took place at a time when gasoline was a drug on the market, this paper reviews the cycle of operations of a standard gasoline engine in order to point out its limitations and the possibilities of utilizing a less volatile fuel than gasoline and of securing lower consumptions of fuels of all kinds. Compression and expansion limitations and the reduction of mean effective pressures at light loads are considered. Disadvantages of throttling control are pointed out, citing as a parallel example the trend of steam engine design away from this means of control. The author then outlines the advantageous features of the improved Diesel engine design, and by means of curves shows the great fuel economy of this type as compared with gasoline engines. He concludes by defining “the ideal tractor engine.”

The author describes in a general way the three classes of battleplanes-the fighting, the reconnaisance and the bombing machines-and outlines the service for which each type is best fitted. The tests of engines and airplanes, prior to acceptance for the French Army, are cited. Among the difficulties of construction, those relating to the plane itself are relatively less serious than those relating to the engine. The greatest difficulty is to secure a reliable engine weighing only about 2 lb. per hp. The qualities of rotary and fixed-type engines are compared. The paper is concluded with a few remarks about aviators and mechanics and the relation of one to the other. The author has reserved some of his most interesting observations for the discussion, in which he describes vividly some actual airplane attacks and refers to night flying and night landing, concluding with suggestions as to “what America must do.”

Starting with the statement that command of the air in warfare rests largely with the side that produces the best single-seater fighter, the author proceeds to outline some of the problems confronting the designer of fighting airplanes, and particularly the smaller ones. Considering better performance and better fighting qualities as the main desiderata, the author discusses means of obtaining them by: (1) increasing the horsepower-weight ratio; (2) decreasing the wing or structure resistances; (3) devising a new arrangement of the supporting planes, with regard to the position of pilot or crew, or by a combination of the above. Considerable space is devoted to methods of decreasing wing resistance, principally by employing low-resistance aerofoils, and the shaping of wing tips is also referred to.

The author calls attention to the unreliability of the magnetic compass when used for aerial navigation and to the possible development of the gyroscopic compass for this purpose. He then explains how the drift of an airplane in flight makes it difficult to follow with accuracy a given course devoid of landmarks, unless an accurate drift indicator using the principle of the stroboscope is available. The development of such an instrument is then described, as are also means for synchronizing it with the compass. The use of the automatic synchronized instrument in flight over land is outlined, and its application to flight over water is described in considerable detail. Rules for aerial navigation over water, observation as to movement of wave crest and determination of wind velocity and direction are considered in their relation to the use of the instrument.

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, 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.

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 author first considers the size of farm on which tractors can be used profitably. Confining his remarks to certain of the central and north central states, he points out the fact that there is a strong tendency for farms from 20 to 100 acres to be combined with others to make units of a more efficient size for the application of modern farming methods. Farms from 100 to 500 acres, representing 65 per cent of the total farm acreage, are the greatest users of tractors. Farms over 500 acres contain 25 per cent of the farm land, and also represent an important tractor market. Efficient sizes of tractors are next treated; three and four-plow sizes are generally preferred. Belt work, representing 50 per cent of a typical tractor's work, and other special duties performed by the tractor are next referred to.

The author describes a number of detailed developments that took place during the working out of a line of worm-driven trucks. The details of front axle and steering parts are dealt with at length, the reasons for the final constructions being clearly explained and the constructions themselves well illustrated. Details concerning difficulty with the Hotchkiss type of drive on heavy trucks, troubles with drive-shafts and lubrication of the worm wheel are all covered thoroughly; spring-shackle construction and lubrication, radiator and hood mounting come in for detailed attention and the question of governors is interestingly covered. Brief reference is made to the influence of unsprung weight, the differences between truck and pleasure car practice in this respect being pointed out.

Inasmuch as horses cannot meet the demand for increased farm power, the tractor must come at once. So far the supply of tractors has been entirely inadequate to meet the demand. The author specifiies some of the problems that confront designers of farm tractors. To make the tractor immediately available for farm work, it must be adaptable to practically all of the existing types of horse-drawn implements, besides furnishing belt power for a wide variety of present power-driven farm machinery. In designing tractors it must be remembered that the horse is a very flexible unit, capable of a wide variation in power output. Designing a tractor to furnish the necessary power for the majority of farm conditions, requires an intimate knowledge of crops, soils and farm management. These must be analyzed carefully so as to make the machine have as wide a range of usefulness as possible.