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Brakes have three functions: (a) maintaining a car at rest, (b) reducing the speed of a vehicle or bringing it to a stop and (c) holding a vehicle to a constant speed on a descending grade. The kinetic energy of a moving vehicle is directly proportional to the weight of the vehicle and to the square of its speed. The amount of heat produced in the braking surfaces of a vehicle descending a given grade for a given distance will be the same whether the speed be high or low, but the rate of heat production will vary inversely as the speed. In addition to the retarding effect of the braking system a braking effect is constantly present that depends on the tractive resistance of the vehicle at various speeds and on the engine itself. Wind resistance and the resistance of the engine when the throttle is closed also produce retarding effects that assist in the work of braking.

Since the road-service tests of the four special fuels supplied by the Research Department, made under 1922 summer-weather conditions, gave results that were deemed inconclusive, arrangements were made for a repetition of both series of tests under the winter-weather conditions of 1923 to determine whether the relative fuel mileages for different fuels are dependent on the temperature at which car operation is conducted. The paper is a report upon the results obtained. Four fuels that bore a relation to those used in the 1922 summer tests were specified and means adopted whereby knowledge of their quality was concealed from the drivers, special emphasis being placed on crankcase-oil dilution and on the performance as reflected by the drivers' comments.

Although the proper timing of the spark is as essential as the spark itself and the electrical and mechanical devices for producing the spark have been many, little attention has been given to the study of spark-advance. An error in timing of ± 20 deg. in a low-compression engine, or of ± 15 deg. in most other engines, has been shown experimentally to cause a loss of 10 per cent from the best power and economy, provided other conditions remained the same. Hand or semi-automatic control can average hardly closer than ± 15 deg. to the correct advance because the speed and the load combinations are constantly changing on the road. Two important phases mark the spark-advance problem.

The author discusses commercial-airplane design in general terms, considering the subject under the main divisions of economy, safety, speed and comfort. Under economy, mention is made of possible reductions of first cost by designing for long life and reliability, the effect of the former on the depreciation allowance being obviously advantageous. Airplane size is debated also, the trend of progress being seemingly toward the giant airplane. Safety is stated to be dependent upon reliability, structural strength, stability, control, fire prevention and reduction of risk of injury to passengers in the event of a crash. Minimizing the results of a crash is considered suggestively. Speed is governed almost solely by the ratio of wing loading to power loading; hence, speed will always be kept as low as possible without loss of business to competing transportation enterprises. Included among desirable measures to secure comfort are adequate ventilation and the elimination of noise.

The author discusses the factors that must be considered in solving the transportation problems and then describes the operation of the English-railway cartage-system in some detail under the two main divisions of delivery and collection. An important feature of the system is that of the control afforded by locating a controller, or dispatcher, in a central office and holding him responsible for the movements of the carmen, or drivers. The details of this control are explained. The field for the motor truck in railway-terminal service is outlined and a presentation is made of the merits and demerits of unit containers, together with an illustrated description of the English “fiats,” or demountable bodies. Other subjects treated include cartage costs, tonnage hauled, unified control of cartage and expressions of opinion quoted from numerous English trade organizations.

Detroit Section Paper - Since a gear is a product of the cutting tool, the gear-cutting machine and the operator, it can be no more accurate than the combined accuracy of these fundamental factors. All gear manufacturers aim to eliminate split bearings, high and low bearings, flats and other inaccuracies in tooth contour, because a gear having teeth the contours of which comply with the geometrical laws underlying its construction is by far the most satisfactory. Illustrations are presented to convey an understanding of the geometrical principles involved, together with other illustrations of testing instruments and comments thereon. The application of these instruments is termed quality control, which is discussed in some detail under the headings of hob control, machine control and gear control.

The author states briefly the phenomenal growth of taxicab usage and consequent demand for this type of motor vehicle, mentioned the differences in body requirements for taxicabs as compared with those of passenger cars, and describes the methods used to secure durability in taxicab-body construction to discount the severe service to which the body is subjected. Tabular data are presented and comments made regarding the woods that are suitable for body framework, and the methods of joining frame members and reinforcing frame joints are outlined. The desirable types of roof and the factors that influence design are discussed at some length, illustrations being presented also, and minor considerations, such as types of hardware, dash and instrument-boards, are included. A brief summary states present conditions, and a bibliographical list is appended of informative publications relating to the subject.

Since the authors presented a paper on this subject that included the test results of only three fuels, the number of fuels investigated has been increased to 14 and several improvements have been made in the method relating to the manner of the preparation of the equilibrium solution and in the apparatus used for the measurement of vapor-pressures. In addition to describing these improvements, the present paper includes data on the fuels; a series of empirical curves from which it is possible to determine, aided by the data from the distillation curve, the dew-points of non-aromatic hydrocarbon fuel; a table showing a comparison of the more important properties of the fuels; and definite evidence that the 85-per cent point is the best single measure of the effective volatility of a motor-fuel, from a standpoint of distribution and crankcase-oil dilution.

In the case of the internal-combustion engine, where virtually every separate portion of explosive mixture behaves differently, the usual thermodynamic interpretations of the pressure-volume indicator-card, as applied to steam engineering, have little value. In internal combustion, the pressure-volume diagram is of value only as an expression for the product of the force exerted upon the piston-top times the distance through which the piston moves. The paper (Indiana Section) begins with the fundamental phenomena and develops from them a diagram such that each fuel-mixture particle can be properly exposed for analysis during the process of combustion. This is termed the pressure-volume-quantity card, and it is described in detail and illustrated. An extended consideration of its surfaces follows, inclusive of mathematical analysis.

The author describes a series of road service-tests, made on stock cars driven by their usual drivers when using fuel of specified grades, to determine the effect of any changes in the fuel volatility on the gasoline mileage for the respective make of car, as part of a general research program undertaken jointly by the automotive and the petroleum industries. The object was to determine the best fuel as regards volatility, from the general economic standpoint, and what grade of fuel would afford the maximum car-mileage per barrel of crude oil consumed. Factors influencing the selection of cars used are enumerated and the fuels tested are discussed, together with general comment and a description of the test procedure. The results are tabulated and commented upon at some length, inclusive of descriptions of the methods. A summary of the results is presented in the form of conclusions that are stated in four specific divisions.

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.

Grouping the influences that are retarding the development of aviation into five specified divisions, the author, who took a prominent part in the development of the Liberty engine and other wartime aviation activities of the Government, discusses each one, in the order of its importance, in an effort to point out the limitations that exist as differentiated from misconceived non-existent limitations and to indicate remedial measures stimulative to a provident trend and vigorous growth of aviation. The subjects of adequate landing-fields, the real and imaginary dangers of flying, single and multi-engine airplanes, passenger comfort and commercial considerations are treated at some length, prefatory to an outline of the trend of airplane design and an enumeration of powerplant requirements.

After indicating the line of development since November, 1918, toward making the internal-combustion engine better adapted to aircraft service, the successful application of the supercharger to improve engine performance at great altitude is described and the over-dimensioned and over-compressioned engine also is discussed as a means toward that end. The use of anti-knock compounds to permit the use of high compression-ratios at small altitudes without knocking is commented upon and engine size is considered for both airplane and dirigible service. Further review includes air-cooling experiments in reference to the air-cooled radial engine, refinement of aviation-engine details, and improvements in aircraft powerplant parts and fuel-supply systems. For commercial aviation, powerplant reliability and low cost are stated as essentials. Illustrations are presented of the supercharger and of the engines and sylphon fuel-pump mentioned.

As a result of the general policy of the Motor Transport Corps to standardize the materials used for automotive vehicles for Army Service, in cooperation with the Bureau of Standards, the Society of Automotive Engineers and the automotive industry, the Bureau of Standards has been engaged for some time in developing a standard method for testing brake-linings. While the work is not complete, much information has been gained. This paper reports the progress of the work. The equipment developed and the methods used for both main and supplementary tests are described. Information is given regarding the coefficient of friction, as influenced by various factors. The endurance test, showing the comparative behavior of linings under conditions similar to those of severe service, is believed to be satisfactory as developed. Further work is necessary before recommending the conditions for the other test, intended to determine the relative endurance under ordinary or light service.

The dimensions of automobile-body seats receive consideration with regard to the features that are conducive to comfort. A diagram is presented upon which the dimensions treated are indicated, and a tabulation of seat dimensions of 12 representative cars is included. Comments are made upon the factors influencing seat dimensions, as well as recommendations regarding the different desirable dimensions. The considerations are inclusive of cushion height, depth and slope, leg-room and head-room, upholstery shape and softness of trimming, foot-rest and other control-element locations, factors influencing entrance and egress provisions, seat widths and advisable front and rear-compartment heights. The author recommends the standardization of a range of locations for the different control elements.

The nature of flame propagation in an automobile engine cylinder has, for some time, been the subject of much discussion and speculation. However, very little experimental work has been done on flame movement in closed cylinders with a view to applying the knowledge directly to the internal-combustion engine. It has become recognized that knocking is one great difficulty which attends the use of the higher-boiling paraffin hydrocarbons, such as kerosene, and that knocking is one of the major difficulties to be overcome in designing higher-compression and hence more efficient engines. It was desirable, therefore, to determine, if possible, the nature and cause of the so-called fuel knock in an internal-combustion engine. The work described in this paper was undertaken to determine the characteristic flame movement of these various fuels and the physical and chemical properties which influence this flame propagation.

Automobile body building derives its origin from carriage body building, which was highly developed before automobiles were thought of. The introduction of automobile bodies fitted to a metal frame changed body builders' rules and calculations. The influence of the metal frame is discussed briefly and the limiting sizes of body members are considered also. According to the ideas expressed, the weight of bodies can be reduced if the metal frame is designed so as to support the weight of the passengers and the body. The dead-weight also can be reduced if the frame is built in proportion to the amount of weight carried, the number of passengers and the style of bodies being considered. But in the construction of enclosed bodies, as in sedans, coaches and broughams, very little weight can be saved if stability, durability and lasting quality are to be retained.

The data given in this paper were obtained from an investigation by the Bureau of Mines in cooperation with the New York and New Jersey State Bridge and Tunnel Commissioners to determine the average amount and composition of the exhaust gases from motor vehicles under operating conditions similar to those that will prevail in the Hudson River Vehicular Tunnel. A comprehensive set of road tests upon 101 motor vehicles including representative types of passenger cars and trucks was conducted, covering both winter and summer operating conditions. The cars tested were taken at random from those offered by private individuals, corporations and automobile dealers, and the tests were made without any change in carbureter or other adjustments. The results can therefore be taken as representative of motor vehicles as they are actually being operated on the streets at the various speeds and on grades that will prevail in the tunnel.

Stating that it is conceded by engineers that weight reduction is desirable economically but that it is not unusual to find that weight reduction is looked upon as incompatible with reliability and road-holding properties, the author outlines briefly the normal weight-distribution in an automotive vehicle and gives a short analysis of the power required to drive it having in mind the necessity of reducing the absolute friction-loss. The use of aluminum for various parts is debated, especially those in which reliability is distinctly a function of lightness and not of weight such as engine pistons, and the application is made general to cover all parts of an automobile in which the stresses are determined by road shocks and speed. The trend of design in general and recent research in particular are stated to be along the lines of weight reduction without any sacrifice of essentials.

The author describes the type, size and general characteristics of the engines with which the German submarines were equipped at the time of the surrender, after having personally inspected 183 of them at that time, and then presents the general details of construction of these engines, inclusive of comments thereon. The maneuvering gear for such engines receives lengthy consideration and the reliability of engines of this type is commented upon in some detail, the author having confirmed his opinion that the German submarine engine is extremely reliable. One of the controlling factors in the design is that the Germans had investigated steel casting to the point where the successful production of steel castings was an ordinary process, and the author believes this to have been largely responsible for the success of the German submarine engine.