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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.

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.

Vibrations of several kinds can occur in crankshafts, but the principal ones are transverse and torsional; the paper deals entirely with the latter. A simple case of torsional vibration is considered first and the principles are applied to the torsional vibration of a shaft, the argument being carried forward at some length. A discussion of critical speeds follows and this is supplemented by a lengthy mathematical analysis, inclusive of diagrams. Calculations were made to determine the period of the shafting of United States submarines S4 to S13 and these are described. The three cases investigated include the charging condition when the engine is driving the dynamo, the after clutch being disconnected; the surface condition, when the engine drives the propeller; and the submerged condition, when the motors drive the propeller, the forward clutch being disconnected. Calculations were made also with a Sperry magnetic clutch substituted for the usual flywheel and clutch.

Ignition is discussed in a broad and non-technical way. The definition of the word ignition should be broad enough to include the complete functioning of the ignition apparatus, beginning from the point where mechanical energy is absorbed to generate current and ending with the completion of the working stroke of the engine. The ignition system includes the mechanical drive to the magneto or generator and the task imposed on the system is by no means completed when a spark has passed over the gap of the spark-plug. Ignition means the complete burning of the charge of gas in the cylinder at top dead-center, at the time the working stroke of the piston commences. The means employed to accomplish this result is the ignition system. In the present-day type of gasoline engine a spark produced by high-voltage electricity is almost universally used for ignition. This high-voltage electricity is produced by a transformer.

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.

The automotive industry was considered a mechanical one until fuel difficulties caused a realization that the internal-combustion engine is only a piece of apparatus for the effective utilization of chemistry. The only great cloud on the horizon of the automotive industry today is the fuel problem, one way to dispel it being to increase the supply and the other to make the automotive device do what it has been designed to do. The author reviews the production of oil and of automotive apparatus, considers the available fuels and states the two distinct parts of the fuel problem as being first carburetion and distribution, external to the engine and one of purely physical relationship, and, second, the combustion of fuel inside the engine cylinder. The subjects of regulating combustion by additions to the fuel, the chemistry of fuels and the burning of heavy fuels are discussed at length.

A brief outline of the elementary principles of the operation of jump-spark ignition systems is given preliminarily to the discussion of the advantages of battery-type systems, and four vital elements in a jump-spark ignition system are stated. A diagram is shown and explained of an hydraulic analogy, followed by a discussion of oscillating voltage and oscillograms of what occurs in the primary circuit of an ignition system when the secondary is disconnected. The subjects of spark-plug gaps and current values receive considerable attention and similar treatment is accorded magneto speeds and spark polarity, numerous oscillograms accompanying the text. The effects of magneto and of battery ignition on engine power are stated and commented upon and this is followed by a lengthy comparison of battery and magneto ignition, illustrated with charts.

A discussion of the advantages of magneto ignition resolves itself into a comparison of magneto and battery-ignition systems, resembling early discussions of the relative merits of the direct and the alternating-current electric systems; both are in existence and fulfilling their respective parts. After stating that ignition is closely related to carburetion and generalizing on the subject of ignition, the author discusses the fundamentals of ignition systems at length, presenting numerous diagrams, and passes to somewhat detailed consideration of comparative spark values, using illustrations. Storage batteries and auxiliary devices receive due attention next and numerous characteristic curves of battery and magneto ignition are shown. Impulse couplings are advantageous in starting large truck and tractor engines, which generally use magnetos; these are described.

The author views in perspective some facts from a purely scientific standpoint, and then shows their application to problems of the automotive industry. After reviewing the present facilities for measurement and the ability to make measurements of distances both infinitely small and large, as an aid toward a proper conception of the ultimate structure of matter, he applies this scientific knowledge in the direction of a solution of the fuel problem, which is a fundamental one because it involves the limitation of a natural resource. From 1918 and 1919 statistics, the amount of gasoline produced was something like 20 to 25 per cent of the crude oil pumped; 8 to 10 per cent is kerosene and 50 per cent is gas and fuel oil and a residue carrying lubricating oil, paraffin and carbon. Kerosene demand and production are practically fixed quantities; gasoline demands are increasing.

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.

The development of the supercharger for aircraft engines has led to the possibility of hitherto unheard-of speed of transportation. An analysis of a definite case is presented to show the different aspects of the problem in a practical form, with a view toward determining what can reasonably be expected. An attempt is also made to arrive at a knowledge of the elements involved whose improvement will effect the greatest gain. The supercharger overcomes the deficiency of the ordinary gas engine's serious loss of power at great altitudes, due to its inability to obtain sufficient oxygen for the combustion of a normal charge of gas which, in an engine of conventional design, is essential to the development of its maximum output.

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 paper surveys the economic and engineering aspects of the automotive industry, so that engineers can align themselves with its future development. Better performance and longer life due to improved design and materials distinguish the 1920 car from its predecessors. One of the healthiest signs in the industry is the uniform determination of practically every manufacturer to improve the quality of his product. The designer has been forced to extend himself in getting the highest possible output from the smallest possible units. This trend is very noticeable. Conditions relating to prices, the return to peace-time production, the potential demand for cars and the present supply, and the probable improvements in cars are then reviewed, the thought then passing to a somewhat detailed discussion of detachable-head engines.

In investigating the forces that tend to break up and destroy roads, the most destructive of these being that of impact, the United States Bureau of Public Roads devised a method of receiving the impact of a truck on a small copper cylinder and determining its amount by measuring the deformation of the cylinder. The impact values are largely dependent upon the type and construction of the truck. Unsprung weights have a great influence upon the impact value of the blow on the road surface and a reverse influence upon the body of the truck; these effects are in two different directions. The present aim of the Bureau is to investigate this impact and the effect of the unsprung weight on the road. Most of the tests have been made on solid tires, a few have been made on worn solid tires and some on pneumatic tires. The Bureau intends to elaborate all of these tests, including different types of pneumatic tire, different unsprung weights and special wheels, such as cushion or spring wheels.

From a laboratory examination of the controlling relationships between carburetion and engine performance still in progress, the general conclusions so far reached include fuel metering characteristics, the physical structure of the charge, fuel combustion factors and details of engine design and manufacture. In every throttle-controlled engine, the variation in fuel metering for best utilization is inversely functional with the relative loading and with the compression ratio, but the nature of the fuel leaves these general relationships undisturbed. The physical structure of the charge influences largely the net engine performance and the order of variation of the best metering with change in load. Perfect homogeneity in the charge is theoretically desirable but entails losses in performance.

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.