The paper is intended to familiarize automotive engineers with the general subject of spectroscopy, by pointing out the various methods that can be employed to determine the actual instantaneous pressures obtained in normal combustion, the temperature-time card of the internal-combustion engine and the progress of the chemical reactions involved in normal and abnormal combustion. The subject of spectroscopy is outlined and explained, illustrations are presented of different types of spectra, and spectroscopes and their principles are discussed. The remainder of the paper is devoted to an outline of what the spectroscope can reveal about the nature of combustion.
The author describes the research work on the internal-combustion engine done recently in his laboratory in England, and presents his deductions therefrom, based upon an analysis of the evidence he has obtained to date. Fuels are discussed at length under three specific headings, many tabular data being included and commented upon, and the calculation of thermal efficiency described. Mean volatility and detonation are discussed and the author's present views regarding turbulence are stated, this being followed by a brief summary of the conclusions reached by Mr. Tizard, a colleague of the author, following recent investigations. The influence of the nature of the fuel upon detonation is presented, a lengthy discussion of the subject of stratification being given under three specific divisions, inclusive of comment upon the benefits derived from using weak fuel-mixtures.
The paper is an exposition of the theoretical analysis made by the author of the experimental work of Woodbury, Canby and Lewis, on the Nature of Flame Movement in a Closed Cylinder, the results of which were published in THE TRANSACTIONS for the first half of 1921. No experimental evidence is presented by the author that has not been derived previously by other investigators. The relation of pressure to flame travel is derived first, the relation of mass burned is considered and a displacement diagram constructed, described and analyzed. The break of the flame-front curve, called the “point of arrest,” enters prominently into the discussion and computations; the pressure in the flame-front is studied; the reaction-velocities are calculated; and general comments are made.
Believing that it is one of the functions of the purely scientific man to direct engineering attention to practical possibilities that will be of use in solving important problems, the author outlines the history of the photographic recording apparatus he describes later in detail and comments upon its general features that are of advantage in engineering practice, with illustrations, inclusive of the use that is made of the string galvanometer. The subject of indicators for high-speed engines is discussed in general terms introductory to a full and detailed description of how this automatic photographic recording apparatus can be used to overcome difficulties that pertain to ordinary indicator-diagrams taken on the internal-combustion engine by former methods. A further use of this apparatus is in anti-knock research and its recent usage for this purpose is described and illustrated.
Stating that present internal-combustion engine fuel is too low in volatility for economical use and that this is the cause of engine-maintenance troubles, the authors believe that, since it is not possible to obtain the more volatile grades in sufficient quantity, the only hope of remedying this condition is to learn how to use the heavy fuel, and that the most promising method of doing this lies in the effective use of heat. As the experimental data regarding the best temperature at which to maintain the metal in a hot-spot manifold and the range of temperatures available in the exhaust gases are meager, the authors experimented in the Purdue University laboratory to secure additional data. They present a summary of the results.
After pointing out that although kerosene costs less than gasoline at the present time and is a cheaper fuel for the farmer to use, the author states that if the industry continues to construct tractors designed to use kerosene as fuel it will not be long before the cost of it is the same as that of gasoline. He argues that automotive engines should be designed to run on any liquid fuel and gives figures on the available supply of petroleum products and distillates in the world at the present time. The requirements laid down by the Government for gasoline are mentioned and it is stated that it is not possible for the oil industry to supply generally to the trade a gasoline meeting the recently adopted Government specifications which the author considers are very lenient.
The various methods employed to measure detonation or fuel knock in an internal-combustion engine, such as the listening indicator, temperature and bouncing-pin, are discussed and the reasons all but the last cannot be employed to give satisfactory indications of the detonation tendencies of fuels are given. The bouncing-pin method, which is a combination of the indicator developed by the author and the apparatus designed by Dr. H. C. Dickinson at the Bureau of Standards, is illustrated and described. In this method the evolution of gas from an electrolytic cell containing sulphuric acid and distilled water measures the bouncing-pin fluctuations in a given period of time. The accuracy of this method of comparison is brought out in a table. The qualities that a standard fuel must possess are explained and the objections to a special gasoline are pointed out.
The many improvements effected in gasoline-engine construction during the war for airplane, heavy truck, tractor and tank usage have done much toward making the gasoline-driven rail motor-car a practical possibility today. The gasoline-electric cars built by the General Electric Co. are mentioned and light rail motor-car construction is discussed in general terms. Reliability and low maintenance cost are commented upon briefly, and the requirements of service for rail motor-cars are outlined.
While investigating the sources and causes of noise in automobiles during an extensive connection with one of the largest automobile companies, the authors recorded their experiences in the shop in the form of notes. Some of these are offered with a view to stimulating the discussion of the subject and with the hope that additional information will be brought out by an exchange of ideas, particularly on the problem of eliminating gear-noises. In many cases they found that noise was caused by failure to allow sufficient clearance for an adequate oil-film. And it was noted frequently that when one noise had been located and silenced another appeared that had not been apparent before. The topics that have been considered include the running-in of brake-bands, engine knocks, oil-pump gear-noise and that of gears in general, the clearances of ball bearings, backlash, and rear-axle bevel-gears.
After pointing out that the publication of articles in the trade and technical journals, to the effect that very considerable weight-reductions in motor-truck construction with consequent savings in gasoline and tires are possible, works an injustice to the motor-truck industry and is misleading, the author outlines some of the reasons why such weight-reductions are very difficult to effect, as well as the possibilities of standardizing axle details. The use of aluminum to effect weight-reduction is commented upon and the various advantages claimed for metal wheels are mentioned. In the latter connection the author points out that, while these claims may be true, they are unsupported by reliable data. The greater part of the paper is devoted to an account of a series of tests conducted by a large coal company to determine the relative merits of wood and metal wheels on its trucks.
The author enumerates the distinctive features of buses designed for city, for inter-city and for country service and comments upon them, presenting illustrations of these types of bus. Steam and electric motive power are discussed and the chassis components for bus service are considered in some detail. The general types of bus body are treated, together with the influences of climatic conditions and local preferences. Comfort and convenience factors are discussed at some length and the problems of heating, lighting and ventilation are given constructive attention. Fare-collection devices and methods are commented upon, and the State and local legal regulations are referred to in connection with their effect upon bus operation. Illustrations are included and a table showing condensed specifications for city buses is presented.
The rail motor-cars now used by the New York, New Haven & Hartford Railroad are illustrated and commented upon, and statistical data regarding their operation are presented. The features mentioned include engine type and size, transmission system, gear-ratio, double end-control, engine cooling, heating by utilizing exhaust gases and exclusion of exhaust-gas fumes from the car interior. A table gives revenue data.
In the paper an attempt is made to answer the broader phases of the questions: What constitutes a bus? and In what respects does a bus differ from other classes of automotive equipment? by establishing the principles on which the design and operation of motorbuses should be based. The treatment of the subject is in the main impersonal, although specific references to the practice of the Fifth Avenue Coach Co. and illustrations of its equipment are made to emphasize the points brought out. The questions of the unwisdom of overloading, rates of fare and the service requirements are discussed briefly as a preface to the paper proper. The factors controlling bus design are stated to be (a) safety, (b) comfort and convenience of the public and (c) minimum operating cost. The various subdivisions of each are commented on in some detail, and numerous illustrations and tabular data supplement the text.
After pointing out that the operating temperature is a vital factor in the life of a pneumatic truck-tire, the author outlines an investigation that was conducted at the plant of the Goodyear Tire & Rubber Co. This sought to determine (a) the best means of measing tire temperatures; (b) the temperature effect of inflation-pressure, load, long runs, frequency of stops, and the sizes of the rim and the tire; (c) the temperature of various designs of tire; and (d) some suitable means of reducing large-tire temperatures. The main reason for the rise in the temperature of a tire is stated to be the generation of heat resulting from rapid flexing; and the various factors having to do with this generation of heat and its dissipation to the atmosphere are listed. The laboratory testing-machine and the methods and apparatus employed to measure the temperatures are described.
Metropolitan-New England Sections Paper - The loss of power due to the friction of the various parts of the chassis has been carefully and elaborately investigated by a dynamometer, the dual purpose being the determination of the amount of internal frictional resistance of the front or rear wheels and the measurement of the power that can be delivered at the rear wheels with the concomitant rate of fuel consumption. The rolling-friction due to the resistance of the wheels as a whole is taken up first and afterward the separate resistances of the tires, bearings and transmission are studied under varying conditions of inflation-pressure and load. The five frictional resistances that were chosen as giving the most useful information are those of the front tires, the rear tires, the front bearings, the rear bearings and the engine.