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Supplementing a “more miles per gallon” movement in 1919, a series of experiments outlined by the S. A. E. Committee on Utilization of Present Fuels was undertaken by the Bureau of Standards, in May, 1920, which included measurements of engine performance under conditions of both steady running and rapid acceleration with different temperatures of the intake charge secured by supplying heated air to the carbureter from a hot-air stove, by maintaining a uniformly heated intake manifold and by using a hot-spot manifold, fuel economy being determined for both part and full-throttle operation. A typical six-cylinder engine was used, having a two-port intake manifold with a minimum length of passage within the cylinder block, an exhaust manifold conveniently located for installing special exhaust openings, rather high peak-load speed and conventional general design.

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.

Two series of tests were made in 1918; one to determine whether the mixture giving best economy and that giving maximum power is a constant quality for all conditions of speed and power output; the other to ascertain what effect changes in the temperature of the fuel-intake system have on the quality of the mixture which gives the maximum power and that which gives best economy. The standard United States ambulance four-cylinder engine was used for these tests, its carbureter having a primary air passage, a primary fuel-jet, an auxiliary air passage with an air-valve and a secondary fuel-jet, the manifold being cast integrally with the cylinder block and a curved riser conducting the fuel mixture from the carbureter to it. The testing methods and fuel consumption measurements are described.

Continued lowering in the grade of fuel obtainable compels automotive engineers to produce engines that will utilize it with maximum economy. The manufacture of Pacific coast engine-distillate with an initial-distillation point of about 240 and an end-point of 480 deg. fahr. was abandoned by the principal oil companies early in 1920. Utilizing this fuel efficiently through its period of declining values forced advance solution of some fuel problems prior to a general lowering of grade of all automotive fuels.

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.

THIS paper describes the various types of radiator installations in use. Tabulated data on several makes of radiation and on successful airplane radiator installations are given. A brief review of laboratory tests is made and the features to be considered in design and manufacture are discussed. The author concludes by cautioning engineers against attempting to base new designs entirely upon experimental data, without comparing the tentative design with existing successful installations.

IN the cooling system for an automobile engine, the water-jacket must be designed to give ample capacity and free flow of the water. It is essential that water-pump capacities and speeds be figured to equal the radiator capacity so as not to retard the flow of water through the radiator and cause hot water to back up into the cylinder; the radiator must always be kept full and still handle the water as fast as the pump carries it. Fan locations are necessarily considered with relation to the radiator and radiator shroud. Fan diameters, blade path and fan speeds should be given thought, in order that the proper volume of air can be handled to carry heat from the engine. The frontal area of the radiator core in square feet per horsepower developed by the engine and several other details which can be worked out by the fan and radiator manufacturers should receive attention. The best possible fan bearings must be used, giving special attention to radial and thrust loads, fan speeds, etc.

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 design of a modification of the Class B Government standardized truck engine is presented, the principal object being a saving in weight without sacrificing either durability or safety factors. The crankcase design is rigid, but the metal is distributed so that the weight will be a minimum. The crankshafts are made of chrome-nickel steel of an elastic limit of 120,000 lb. per sq. in., which further carries out the idea of durability with low weight. The connecting-rod length is slightly more than twice that of the stroke, and this, with light-weight pistons, obviates vibration, without adding weight to the engine on account of increased cylinder height. The flywheel and bell-housing diameters were selected with a view to securing enough flywheel weight for smooth running without increasing the engine weight materially. All-steel supports reduce breakage of arms to a minimum. The manifolds are carefully designed to give economical performance, even with low-grade fuels.

EVERY plow in use should have 10 b.-hp. available. Every tractor engine should deliver continuously at least 33 hp. If the 330-cu. in. engine mentioned were as good as a Liberty airplane engine, it could deliver 57 hp. at 1000 r.p.m. The horsepower actually obtained is as follows: 41.5 in the laboratory 33.0 at the factory 29.0 when burning gasoline 23.0 when burning kerosene 21.0 with poor piston-rings 19.0 with poor spark-plugs 9.5 available at the drawbar The great engineering problem of the future lies between the 57 and the 23 hp. From 19 to 9.5 hp. is the manufacturer's problem. The main difficulties, as outlined by the figures given, lie in the combustion chamber and its ability to dissipate the surplus heat, and in the limitations of fuel. There will be no need for refiners to continue to break up the heavier fuels by processes already so successful, if by ingenuity and good understanding of thermodynamics these can be made to burn in present-day engines.

Few points have aroused such discussion among users and engineers as that of the desirable number of cylinders in an engine. A large part of the work of the author has been in the direction of attaining the same ends as those achieved by the multi-cylinder engine but by different means. He discusses the relations between torque at clutch and number of cylinders and multicylinder engines and uniform torque, the factors governing torque recoil, torque recoil as a function of car weight and engine balance. His conclusion is that the multi-cylinder engine now so widely used exceeds the real requirements and obtains its smoothness of operation at the expense of more desirable qualities. A reduction in car weight would in his opinion enable existing standards of performance to be maintained and even improved by the use of four cylinders for the heavier type, with all that this means in tremendous advantages to the automotive industry and to the user.

The author considers the adaptation of farming implements to the farm tractor the most important engineering problem confronting tractor manufacturers. The problems are intricate in their ramifications, all-inclusive in their scope and fundamental. They can never be solved by theoretical discussion and laboratory tests alone. Extensive field experiments are needed with the machines operated by the farmers themselves. It is the implement which does the work. The mold-board plow and the disk harrow are standard for soil preparation; the oscillating sickle, the reel and the knotter-head for harvesting; the revolving toothed cylinder and the oscillating rack for threshing. Power must be transmitted to these fundamental devices. The automotive tractor fills a place in the farm power field not successfully covered heretofore by any single prime mover.

Efficiency, appearance and comfort will be the catchwords of the car of the future. Extreme simplicity of chassis will be needed to reduce weight and permit the use of substantial sheet-metal fenders, mud-guards and bodies. The center of gravity should be as low as possible consistent with good appearance. For comfort the width and angle of seats will be studied more carefully and the doors will be wider. A new type of spring suspension is coming to the fore, known as the three-point cantilever. Cars adopting it will have a certain wheelbase and a longer spring base. A car equipped with this new mechanism has been driven at 60 m.p.h. in safety and comfort without the use of shock absorbers or snubbers. It is the opinion of the author that this new spring suspension will revolutionize passenger-car construction.

The limit of acceleration has been reached. What may well be considered a maximum for practical service has been secured. The present seven-passenger body is as roomy as could be desired. There should be no need for further increase in size. The author believes the total weight of this large car will be reduced to between 3500 to 4000 lb. To make this reduction without sacrifice of durability greater use must be made of alloy steels and aluminum alloys. The tendency in body design and style is toward smoother lines, fewer breaks and a more graceful contour. The number of closed cars is increasing. There will be a general simplification of detail throughout, better wiring, better lubrication, an increased use of oilless bushings and fewer grease-cups. Brakes and wearing parts will be made more accessible and easier of adjustment. The take-up points for the various adjustments will be placed so that they can be reached with ease.

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.

Whatever may be the conclusion of business men and engineers as to the fuel problem, dealing with it from the point of view of the engineer as a service man nothing further is needed than that the problem is before us. The paper deals with engine troubles that have been found to demand the greatest amount of attention from farmers. Tractors are not built for or operated by engineers. No quantity production is likely to be attained for some time to come with anything but the commonest forms of cylinder and other features. This judgment is based entirely on the limitations in upkeep knowledge of the average user. The four-cylinder tractor engine seems to be rapidly becoming standard, due to its simplicity and the familiarity of most farmers with this type. Consideration is given, topic by topic, to important parts of the tractor engine and the relation of fuel to difficulties discussed.

THE application of the marine internal-combustion engine to the British ML class of 80-footers and to the American 110-ft. class of submarine chasers, undoubtedly constituted the most important development along this line of automotive work. With a hull form similar to that of an enlarged runabout, driven by a pair of six-cylinder Standard marine engines rated at 220 b.-hp. at 460 r.p.m., the boats of the ML class averaged about 20 knots. A total of 720 boats of this type were built and the class as a whole proved very satisfactory. In the development of the 110-ft. SC class, the requirement of seaworthiness was made of greater importance than speed. Each boat carried three six-cylinder Standard engines identical with those used in the British boats, driving them at about 17 knots. Although rather uncomfortable, as in the case of any small vessel, the 110-ft. boats proved wonderfully successful in heavy weather; about 450 of this class were built. The 220-b.

ANY aggregation of parts assembled to obtain a mechanical result is a series of compromises. The relative importance of the objectives governs the nature of the compromise. The major objectives to be considered in the design of airplane engines are (1) Reliability (2) Small weight per horsepower (3) Economy of fuel and oil consumption (4) Carburetion that permits of easy starting; maximum power through a range of 30 per cent of the speed range; and idling at one-quarter maximum speed without danger of stalling (5) Ability to deliver full power through a small speed range without excessive vibration (6) Complete local cylinder-cooling under conditions of high mean effective pressure (7) Compactness The automobile engine must have (1) Reliability (2) Silence (3) Carburetion that accomplishes proper and even firing in all cylinders under varying throttle conditions, through speeds covering more than 90 per cent of the speed range of the engine.

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.