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THE SATISFACTORY maintenance of motorcoaches probably has been the subject of more extensive discussion and study than has any other phase of fleet operation, in the author's opinion. Effective economical maintenance has a large influence on net profit, but the maintenance of motorcoaches is merely one phase of operation and, while it influences the other phases, it likewise is influenced by them. Cooperation is the most important factor contributing to successful maintenance, but the author remarks the difficulty of segregating any part of the organization which can be considered solely responsible. He asks where the maintenance organization begins and where it ends, and answers that it seems necessary to include the office, operating, garage and shop divisions and even the selling division. Each division must know something of the work of the other divisions and how its work fits in with that of the general organization.

THIS paper describes the use of the gyro-accelerometer, an instrument capable of recording angular velocity, angular acceleration and the total angle turned. The design and development of this instrument came as a result of research into the riding-quality of automobiles, which work demonstrated the necessity of measuring angular motions in a moving car under road conditions, a task that was impossible to accomplish with the equipment that was then available. To avoid taking a great number of readings and obtain a basis of comparison, a standard test, consisting of driving a car over a special bump at different speeds and plotting curves of the resulting angular quantities as given by the gyro-accelerometer, was devised. This test is known as the standard-bump test, and the values of maximum angular acceleration obtained at different speeds are evidently closely related to riding-quality.

FIRST reviewing briefly the history of molded brake-lining, the author states that the introduction of molded lining has, until recently, met with considerable opposition. After the first volume-production adoption in 1924, there were no further adoptions of the strictly molded types in production until 1927, when the trend in brake design seemed to change suddenly from the external type to the internal type of brake. The present movement toward the use of molded brake-lining was brought about through the inability of woven lining to meet the exacting demands of some of the newer types of internal brake. In the author's opinion, the molded type of lining has more nearly fulfilled the present requirement of internal brakes than has any other type. He states that at least seven different brands of molded lining are now on the market, and that three of them are in large-volume production.

CONSTRUCTIVE criticism of automobile bodies as now built is given herein, based on experience gained in driving five-passenger sedan cars of many makes a total distance of nearly 10,000,000 miles in one year in tests at the General Motors Proving Ground. The fault finding, although humorously exaggerated, will be valuable if taken seriously, as it gives to all body designers and builders the benefit of testing experience that few companies are in a position to gain at first hand. The author treats his subject from the viewpoint of the abstract customer; that is, the automobile-purchasing public as a whole and as represened by the imaginary average man, who is assumed to have average stature and body structure and to drive all the different makes of car. Thus he is assumed to change from one to another make frequently, instead of becoming used to only one or two cars.

THIS paper is an attack on the usual system of front suspension of an automobile and a proposal to substitute independently sprung front wheels for the conventional assembly of wheels, rigid axle and semi-elliptical springs. Mounting of the front wheels on a solid axle is a survival of horse-drawn-vehicle days which the author asserts is so unsatisfactory from the standpoint of rational mechanics that it should long ago have become a memory in the automotive industry. To the complex action and reactions of the axle, oscillating between the springs and the tires, and of the wheels, with their gyroscopic effects, are attributed the phenomena of shimmy and wabble that have become so disconcerting and even dangerous since the advent of low-pressure tires and front-wheel brakes. The origins of the various abnormal vibrations are analyzed, the effects of damping and of friction are discussed, and the part played by the conventional steering-gear and steering connections is considered.

AN effort is made to determine the essentials of an ideal shock-absorber and to describe the types that approach or depart from this ideal. Mathematical analysis is not used, but judgment is based on the experience of the author with various types. The requirements of a satisfactory shock-absorber are defined and the methods used by the author in culling out certain shock-absorbers that fail to meet these requirements are outlined. By means of a machine based on the principle, of a steam-engine indicator, the energy required to move a shock-absorber throughout its cycle at varying speeds is measured and charts are obtained. When these charts are compared with a characteristic shape of diagram of a shock-absorber found from repeated trials on the road to give the most satisfactory riding, the merits or shortcomings of any other shock-absorber can be deduced from the difference in shape.

A STUDY of the effect of supercharging on the performance of the engines of passenger-cars showed that the power increase varied from 35 per cent at 1000 r.p.m. to 59 per cent at 3000 r.p.m., with a maximum supercharging pressure of only 6.5 lb. per sq. in. In acceleration tests made at the General Motors Proving Ground of two cars of similar model, one equipped with a supercharged engine and the other with a high-compression engine, the supercharged car accelerated from 5 to 25 m.p.h. in 5 sec.; the unsupercharged car, in 10 sec. From 15 to 50 m.p.h. the supercharged car accelerated in 12.7 sec.; the unsupercharged car, in 21.0 sec. On an 11-per cent grade up which the cars were started at 10 m.p.h., the speed of the supercharged car was 40 m.p.h. at the top; that of the unsupercharged car was 18 m.p.h. These and other results of the tests are portrayed by curves.

Layout, facilities and activities relating to making road-tests of motor vehicles at the 1125-acre proving grounds of the General Motors Corporation near Detroit, this tract being designed to provide a place where road conditions are suitable for obtaining data that can be interpreted accurately, compared with similar data and used constructively, are outlined and illustrated. Adequate facilities are provided and ideal road-conditions have been established so that motor-vehicle tests involving endurance, speed, acceleration, hill climbing, riding-quality and other comparative tests can be made. Conditions are such that tests can be repeated from day to day, thus compensating for the variations of the weather and other factors. Complete and conclusive tests can be carried out readily and promptly, and the results are free from guesses and personal opinions. The speed track is 20 ft. wide and nearly 4 miles long. Traffic is in one direction, clockwise.

A heavy high-speed vehicle, such as a modern motor-coach, combines weight and speed, requires frequent brake-applications and necessitates the dissipation of an increased quantity of heat. As it weighs about four times as much as a passenger car approximately four times the braking-effort is required; consequently four times as much pedal-pressure must be exerted. To supplement the driver's muscular equipment, some outside force, such as compressed air, the vacuum of the intake-manifold or the inertia of the moving vehicle, must be utilized. The author limits his present discussion to the use of the last-named force which he terms the use of “self-actuation,” and also to its application to the rigid-shoe type of internal wheel-brake. Through mathematical analysis he determines the effect of self-actuation measured in terms of the increase or decrease of the cam pressure required to sustain the same normal pressure before and after an outside torque has been applied to the brake drum.

After quoting statistics that show the alarming increase in thefts of automobiles and analyzing numerous conditions under which automobiles are stolen, the authors discuss locks as theft retardants, saying that the providing and the improvement of locks has always been man's method of seeking security from thieves and comes in naturally for first consideration as the normal course to pursue in working toward adequate theft prevention. The present identification systems in use are mentioned, together with their features of advantage and disadvantage, and numerous practices that owners and drivers can adopt which tend to minimize theft are cited. The early forms of locking device are outlined and statistics are included which show the percentage of cars actually locked when they are equipped with a locking device.

After defining hypoid-gears and outlining their action, together with their general characteristics and advantages, the authors compare them specifically with spiral-bevel gears and follow this with a description of how the axis of the pinion is offset from the axis of the gear and how the direction of the offset determines whether the spiral is right-handed or left-handed. Considering pitch-lines, details of the mesh between a crown-gear and an offset pinion are presented, since this constitutes a special case of hypoid-gearing, and the application of these principles to a pair consisting of a pinion and a tapered gear is discussed. The rate of endwise sliding, the proper ratio of gear-diameters, tooth loads and tooth profiles are other phases treated specifically, and computations of surface stresses by the Hertz formulas, with special reference first to a comparison between helical teeth and straight teeth, and then with reference to hypoid-gears, are outlined.

Progress in the development of automotive worm-gearing is interestingly outlined. Previously tO 1912, American experience had been limited almost exclusively to the industrial form, generally of the single-thread type. Introduction of the motor truck required a worm for the final-drive but one having entirely different characteristics from that of the industrial gear. Experience in designing these was lacking, however, as was also the special machinery to produce them. In 1913, machinery was imported from England and since that time development has been rapid. First efforts were devoted to simplifying the design of the axle as a whole, studying the problem of getting lubricant to the bearings, heat-treating the parts, and improving the materials of construction.

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 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.

After pointing out that the general question of weight reduction is no exception to the fallacies that seem to have beset the development of the automobile from its earliest days, the author outlines briefly the problem confronting the automobile designer. The influence of the weight of the reciprocating parts on the chassis in general and the engine in particular is emphasized as being of greater importance than the actual saving in the weight of the parts themselves, it being brought out that the bearing loading due to inertia is really the factor that limits the maximum engine speed. Reference is made to the mathematical investigation by Lanchester in 1907 of the advantages of using materials of high specific-strength and the conclusions arrived at are quoted in full. A tabulation of the specific strengths of various materials used in automotive engineering practice is presented as showing the advantages of aluminum as compared with steel.

Stating that the trend of tractor development must be toward the small tractor that is capable of handling all of the power work on a farm, the author quotes farm and crop-acreage statistics and outlines diversified farming requirements, inclusive of row-crop cultivation. Tractor requirements are stated to be for a sturdy compact design to meet the demands of the diversified farm, which include plowing, seeding, cultivating, hauling and belt-power usage, and these requirements are commented upon in general terms. Consideration is given to farm implements in connection with tractor operation, and the placing of cultivating implements ahead of the tractor is advocated.

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.

That all of the variable factors of automobile friction-losses such as the quantity and viscosity of lubricants, the efficiency of worm-gearing and part-load Modifications are not appreciated, is indicated by an examination of the literature on this subject which reveals a lack of necessary data. Experiments to determine the mechanical losses, including all friction losses between the working gases in the engine and the driving-wheels of the vehicle, are described and supplementary data are included from Professor Lockwood's experiments at Yale. Three distinct possibilities for increasing the fuel economy of a motor vehicle are specified and enlarged upon, gearset experiments to secure and develop data for a four-speed gearset being then described and commented upon at length; photographs and charts illustrative of the equipment used and the resultant data are included.

Statistics taken from a report made by the Department of Agriculture regarding the number and size of farms in the United States indicate that approximately 2,580,000 farms are available as a market for the isolated gas-electric lighting plant. The common types of lighting plant are classified in three groups, each of which is subdivided into three classes, and these are illustrated, described and discussed. The characteristics of the ideal farm lighting-plant are enumerated and discussed as a preface to a somewhat lengthy consideration of the factors that influence the design of the component parts, which are grouped as pertaining to the engine, the generator, the switchboard and the battery. Storage batteries are still considered the weakest part of the isolated plant and they are specially commented upon. The author emphasizes that much still remains to be accomplished as regards the stability of design, reliability and economy of the isolated plant.