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1925-01-01
Technical Paper
250067
W L GILMORE
A racing airplane seems to possess a special quality that sets it distinctly apart from the conventional type of airplane; but, unless a person has at least dabbled in its design, he cannot realize the enormous amount of time, effort and ingenuity that has been expended by the designers who have made these super-speed airplanes possible. Therefore, an outline is given of the procedure adopted in designing and producing a specific model of racing airplane, as well as an outline of the yearly progress made in development. The first procedure is to allocate the work to the various members of the engineering organization. Finally, a type of design is chosen after a series of engineering conferences, and the design section studies the detail design of the component parts. A wing section that is adapted to the design already chosen is developed, and an accurate weight estimate is made of each unit part of the complete airplane.
1925-01-01
Technical Paper
250068
THOMAS H FROST, WALTER E RICHARDS
Principal stresses in one type of eye-bolt have been determined in the laboratory of photoelasticity at the Massachusetts Institute of Technology by the photoelastic method. In the test, an eye-bolt, designed in accordance with a method suggested for circular eyes in a course in machine design by the Institute, was made of celluloid 0.25 in. thick, 1 in. wide on either side of the eye, with a 1.405-in. diameter of eye, and a 1.333-in. width of shank. Steel loading-plates were pinned to the broadened end of the shank and a load of 100 lb. was suspended from the bolt, which gave a mean stress of 300 lb. per sq. in. in the shank. Plain polarized light was passed through the celluloid model and the isoclinic lines, or lines of equal inclination of principal stress, were observed and recorded. Two families of lines of principal stress, designated as P and Q stresses, were determined graphically from these isoclinic lines.
1925-01-01
Technical Paper
250033
D P BARNARD
General laws governing the rate of flow of oil through complete journal bearings are developed in the paper. These laws are based on the assumption that axial flow obeys Poiseuille's Law and is, therefore, a function of the bearing load. Dimensional reasoning indicates that the volumetric efficiency of a bearing considered as a pump is given by an equation of a form in which efficiency equals a function of the viscosity times the rubbing speed divided by the bearing load, the length divided by the clearance and the length divided by the diameter. Experimental evidence is presented which substantiates this point of view. The general relation of rubbing speed to heat generation and oil-flow is discussed for the purpose of indicating a possible solution of certain high-speed-bearing problems. A plain bearing is, in effect, a pump in which the flow of a viscous lubricant through a passage of varying area develops a pressure sufficient to sustain the imposed load.
1925-01-01
Technical Paper
250027
L M WOOLSON
Advances in airplane performance during the last few years may be ascribed mainly to advances in aerodynamics and to improvements in powerplants. The latter have resulted in producing more power for the same weight of engine and smaller over-all dimensions for engines of the same power-rating. The accompanying paper describes two engines of 500 and 800 hp. respectively that have been recently developed by the Packard Motor Car Co. for aircraft service. When these engines are compared with previous types they are found to be more compact and to produce more power per pound of weight. When each is operated at its rated speed, the Model 1500 engine develops 100 hp. more than the Liberty while weighing 140 lb. less, and the Model 2500 engine develops 250 hp. more than its predecessor, the Model 2025, with a decrease in weight of 75 lb.
1925-01-01
Technical Paper
250024
J H HUNT, G F EMBSHOFF
Electrical instrumentation for research work has been developed to a high degree because of the great speed of action and the convenience of application of the electric current. The current serves to transmit instantly to a recording instrument the impulses imparted to it by a detecting device. There is available a great wealth of indicating, integrating and recording devices that can be used readily for automotive research by the aid of auxiliary devices, some of which can be purchased and some of which can be easily made in any ordinary model shop or toolroom. In the study of automotive mechanism the research engineers have drawn upon the investigation work of men in other lines of industry and have found it necessary to go back of these men to the scientific investigators who are attacking the elements of various problems in the physical and chemical laboratories.
1925-01-01
Technical Paper
250023
JOHN A C WARNER
Due to tremendous production schedules and rapid advancement, the automotive industry is characterized by its effort to learn the answers to engineering research-problems with utmost dispatch, but the procedure is not without attendant risks. Costly errors have resulted from experimental work improperly planned and executed, from conclusions too quickly drawn and from unjustified interpretation of observed indications. Cut-and-try procedure is resorted to in many instances after hastily applied research methods have failed and, often, the apparently longer course involving systematic research would, in fact, have been fruitful of more prompt and more satisfactory results at a lower net cost. As originally presented, the paper was accompanied by a demonstration of instruments and apparatus especially adapted to automotive-research problems.
1925-01-01
Technical Paper
250026
F A MOSS, H H ALLEN
Although many variables enter into the personal equation of the driver of an automobile, this paper concerns principally his reaction-time. The tests described had for their objects the determining of (a) the average time that elapses between the hearing of a signal, such, for example, as the shot of a pistol, and the applying of the brake; (b) the relation between the reaction-time and the variability of the individual; and (c) the effect on reaction-time of such factors as the speed of driving, training, age, sex, race, and general intelligence. The reaction-time was determined by two pistols mounted on the under-side of the running-board of an automobile and pointed toward the ground, the first being fired by the experimenter when the car had reached the desired speed, the second, by the person under test in making the initial motion of operating the brake-pedal.
1925-01-01
Technical Paper
250020
E A De Waters
In the summer of 1922 the Buick Company began experimenting with balloon tires. The first tires tested, being four-ply and 32 x 6.20 in. in size, produced a galloping action that was sufficient to prejudice the company's engineers against them, and the tests were discontinued. In addition to the galloping effect, other difficulties encountered included those usually present in steering, the development of wheel shimmying to a serious degree, the lack of proper clearance for external brakes because of the small 20-in. wheels, the excessively rapid wear of the tire tread, and the greater susceptibility to puncture. Leaks because of the pinching of the inner tubes also occurred. When, later, a set of 5.25-in. tires was tried on a smaller car, the galloping was noticeably less; but punctures were more numerous than was the case with high-pressure tires.
1925-01-01
Technical Paper
250047
R W BROWN
Inasmuch as the forces that act when a vehicle passes over a road obstruction are very complex, comparative analysis of the riding-qualities of the different parts of a vehicle is difficult; hence, to obtain even an approximation of them, measurement of the different displacements that occur must be confined to a given representative condition or series of conditions. The displacement that causes the most discomfort to a passenger is probably that which takes place in a vertical plane. Its three leading characteristics are the amplitude of the vertical movement, the velocity of the motion and the rate of change of the velocity. Of these the last mentioned is the most important. It is sufficiently exact to assume that tires and springs which reduce motion increase riding-comfort.
1925-01-01
Technical Paper
250043
H H ALLEN
Claims and counter-claims as to the deceleration possible under certain conditions, especially when applied to the legal questions arising at the time of an accident, induced the author to make an investigation of the subject. An attempt has been made to include all the variables that are of significance or of sufficient magnitude to affect appreciably the performance of a car under a given set of conditions of the vehicle or of the environment. Inasmuch as the calculations are simplified by doing so and because the difference between the amounts of deceleration and of power involved are small, the assumption is made that the maximum deceleration occurs when the wheels are locked, rather than when they are still rotating. The stopping-distances, theoretically obtained, apply to level-road conditions only.
1925-01-01
Technical Paper
250041
E E WEMP
Reviewing briefly the history of the automotive clutch and summarizing the most interesting achievements in clutch design during recent years, the author discusses friction facings and says that the development of the asbestos-base friction-bearing has made possible the multiple-disc dry-plate and the single-plate types. For severe service, the qualifications of a satisfactory friction-facing are density of structure, together with a reasonably high tensile-strength; the coefficient of friction should be high and fairly constant over a wide range of temperature; the facing must be able to withstand high temperature without deterioration; the impregnating compound must not bleed out at high temperature; and the permeation of the impregnating solution must be complete so that the wear resistance is constant throughout the thickness of the facing. The molded and the woven types of facing are treated at length.
1925-01-01
Technical Paper
250014
F F Chandler
Relative ease or difficulty of steering has in the past been largely a matter of psychology, of comparison rather than of measurement. One driver may find a car difficult to steer that another finds easy. Safety is the first essential, then comfort. Because the parts used in steering seldom break, present practice is considered safe, but the steering-ratio is very important. A low ratio that produces fast steering-effects may be entirely safe in the hands of a strong, safe, experienced driver, but absolutely unsafe in those of a weaker driver, even though he may be expert. Fatigue, however, will eventually affect the strong as well as the weak driver, so that comfort enters as well as safety.
1925-01-01
Technical Paper
250013
H D HUKILL
In an endeavor to find an engineering justification for the use of the airbrake on automotive vehicles, an investigation was first made as to what actually causes a car to stop when the brakes are applied; and it was ascertained that nothing that can take place within the car itself can directly influence the motion of the automobile as a unit, that its motion can be changed only by some force external to the car itself. Four such forces are normally present, namely, wind resistance, road resistence, gravity, and the adhesion of the road to the wheels. The first two are negligible. Grades have a measurable effect on the stopping distance, but the force that actually stops the car is the last named: the force that is applied from a point external to and in a direction opposite to that of the motion of the automobile.
1925-01-01
Technical Paper
250011
ETHELBERT FAVARY
Benefits gained by distributing truck weights and loads among six wheels rather than four, include less liability to cause road destruction, greater carrying capacity and more economical operation. The author classifies the causes of road destruction under headings of excessive loads on tires, impacts between road and tires, traction effects of wheels, and braking effects and says that the remedy is to reduce load or to correct improper weight-distribution. Impacts probably contribute most destructive effects.
1925-01-01
Technical Paper
250018
J W White
Inasmuch as the use of low-pressure tires has become established, the conditions of car design affected by them are reviewed, particular reference being had to the members of the chassis included under the term unsprung weight, namely, the axles, the wheels and the tires. Referring to the principles that underlie basic design, the author first investigates the effect on the steering of such changes and compromises from the perfect structure as failure of the king-pin to coincide with the vertical load-plane, the inclination of the king-pin toward the wheel, or the wheel toward the king-pin, or both, and the giving of a toe-in to the front wheels. Further modifications have served to reduce the car shock, to add to the strength of all the parts by increasing the dimensions, to improve the spring-suspension, and to reduce the car weight per passenger.
1925-01-01
Technical Paper
250016
R B DAY
Shimmying, although known for many years, did not become a serious problem until the arrival of the balloon tire and the four-wheel brake. Apparently, shimmying is of two kinds: the low-speed variety, which is merely a persistent front-wheel wabble without an abnormal bouncing of the axle, and the high-speed species, which is chiefly a persistent bouncing of the axle accompanied by wabbling of the wheels. The two most obvious effects are wheel wabble and axle bounce. As low air-pressure seemed to be the cause, the attention of the tire makers was first devoted to stiffening the body of the tire in various ways, but the results obtained were not satisfactory; and the conclusion was reached that the solution lay in making the car control the tire rather than attempting to control the car through the design of the tire. These considerations led to a search for mechanical means of control.
1925-01-01
Technical Paper
250015
O M BURKHARDT
Shimmying is an oscillating motion produced by repeated impacts or forces in the linkage of a mechanism that lacks stability or has become loose because of wear. Although previously existent in chassis in which the steering-gear was imperfect, it has become particularly noticeable since the introduction of low-pressure or balloon tires. But increasing the rigidity means increasing the unsprung weight, which, in turn, means greater impacts, hence, more shimmying. This is apparent in the effect produced by front-wheel brakes. Consequently, as the amount of looseness that can be removed is limited, the periodic forces that cause shimmying must be overcome.
1925-01-01
Technical Paper
250006
DALE S COLE
Progress made in the development of electrical equipment to serve adequately the needs of motorcoach service is reviewed. Electrical loads on motorcoaches are comparatively high, including the usual head, tail and dash lamps, body-marking and destination lamps and buzzer systems. As more and more electrical energy is used, the source of supply and its control become relatively more important. Not only does the electric generating system have to meet the demands of battery charging, but it should be able to carry the connected load with no battery in the circuit. This means that not only is sufficient energy necessary, but the voltage must be regulated in such a manner that the battery can be charged without endangering the life of the lamps because of excessive voltage, and no flicker in the light from the lamps must be perceptible. All these results must be attained under conditions of variable load, variable speed and the changeable temperatures encountered in service.
1925-01-01
Technical Paper
250008
A H HOFFMAN
Utilizing an opportunity presented by a mountain-road construction-project in California, eight Class-B 3½-ton trucks were assigned to the work and a test of air-cleaners was conducted during its progress. Six trucks were each equipped with an air-cleaner; two were not. The trucks had dump-bodies and were specially prepared for the test, details of this preparation being specified. Due to varied air-cleaner design, it was not feasible to locate the cleaners identically on all the trucks, and differences in mounting may have influenced the resulting air-cleaner efficiency, but mountings were made as nearly identical as possible. Tables of average wear of piston-rings, engine cylinders and crankpins, for 1000 hr. of use, are presented, and details of how the measurements were made are stated, together with a discussion of the “growth” of pistons and of the peculiarities of wear.
1924-01-01
Technical Paper
240056
F D HOWELL
Transportation by motorbus, although of recent origin, has advanced rapidly in its development but is still undergoing a process of evolution. Less than 10 years ago, motor carriers were mostly “jitneys” and were heartily disliked by electric-railway officials. Now, motorbuses are developing a field of their own and are rendering a service not supplied by any other transportation agency, two of their most valuable functions being the building up of new territory and acting as feeders to established lines in the more thickly settled areas. The first steps in their development took place while engaged in local service, but the trend toward interurban business soon became manifest. In California, within the last 10 years, the interurban business has increased from that of a few isolated individuals to the operating of approximately 1000 vehicles, which cover the entire State and, in 1923, carried about 25,000,000 passengers.
1924-01-01
Technical Paper
240055
S D WALDON
Public thoroughfares have invariably been laid out to meet the requirements of age-old horse-and-buggy equipment and little thought has been given to the needs of the future. Until the middle of the last century, man was dependent for transportation upon his own strength or upon that of the animals that he could domesticate. Caesar could have traveled from Rome to Paris as quickly as could Napoleon 17 centuries later. Now, the humblest American farmer could make the round-trip with his whole family in less time than either emperor could travel one way. Within the last century have been developed in rapid succession the railroad train, the steamship, the electric trolley-car, the automobile, the motor truck, the tractor and the airplane. The most permanent thing we have is land; the very slowness and regularity with which buildings are replaced tend to make a route and the width in which it is established almost as permanent as the land of which it is a part.
1924-01-01
Technical Paper
240054
HARRY D TIEMANN
Peculiarly complex in its cellular structure, wood is subject to a deformation that accompanies changes in its moisture content that is neither uniform nor isometric. Deformation is generally about 50 times as great in the radial direction of the log as longitudinally and about twice as great circumferentially as radially; so, when moisture changes occur due to changes in the degree of humidity of the surrounding air, the behavior of wood is very uncertain. Conditions are complicated further by the manner in which drying takes place. A description is given of how water is contained in wood, including details of wood structure, and the action of moisture in causing swelling and subsequent shrinking is discussed. The fiber-saturation point marks the limit of the amount of moisture that can enter between the fibrils, at which limit swelling ceases. It is determined by making endwise compression tests on a series of small blocks of the wood, as its drying proceeds.
1924-01-01
Technical Paper
240057
H C RICHARDSON
Principal developments along the lines of the HS, H-16 and F-5-L types of seaplane, which were used during the war for convoy work, submarine patrol and scouting, are represented by present types PN-7, equipped with Wright T-2 engines, and PN-8, having Wright T-3 engines, a metal hull and metal tail-surfaces. Brief statements about their construction and performance are made and the subject of metal floats for seaplanes is discussed. “Training,” scouting and other types of seaplane are mentioned, and outlines given of their characteristics and performance. Launching airplanes from a catapult is described, some details of the development of the apparatus being given, and reference is made to a late development in which the catapult is actuated by the explosion of a powder charge instead of being operated by compressed air.
1924-01-01
Technical Paper
240011
L L ROBERTS
Remarking upon the progress made by the builders of machine-tools in providing equipment for locating and correcting the unbalance of rotating parts, the author divides into three major groups the units of a motor car that require particular attention and treatment to assure a smooth-running mechanism and gives details of the actual methods employed by the company he represents to balance the parts that constitute each group in the vehicles it produces. Representatives of the engineering and the manufacturing departments of this company studied the subject intensively and determined the types of balancing-machine and the methods to be employed, and special balancing equipment was devised also. Details of the balancing practice for crankshafts, flywheels, connecting-rods, clutches and propeller-shafts are presented and the subjects of impulse balance and the maintenance of balance for assemblies of parts are discussed.
1924-01-01
Technical Paper
240049
W L BEAN
Gasoline rail-cars for branches of trunk-line railroads and for short-line roads have been the subject of much discussion since 1920. Mechanical officers of interested railroads, the engineers of companies building highway motor-trucks and others specializing on this subject have now developed designs to meet the different service requirements. Several hundred cars of various types have been built and are in service. The railroad with which the author is connected has in operation or on order 24 cars. Consideration of several principal factors of design is necessary if a selection is to result in obtaining equipment suitable for the particular service requirements of the carrier and if the knowledge accruing from the engineering development and operating experience of the past several years is to be of value.
1924-01-01
Technical Paper
240050
A L DELEEUW
This paper is confined to a discussion of machine-shop operations, and is intended to indicate by a few examples certain important economies that might be introduced in the shops of the automotive industry. It deals chiefly with the economies that can be effected without much capital outlay, though others are also mentioned. Calling attention particularly to the fact that, in the past, improvements of methods and of equipment have been confined largely to the more important operations on the more important parts and that relatively little study has been made of the smaller pieces and the less important operations, emphasis is placed on the necessity for carefully determining which tools and which makes of tool will best serve the purposes for which they are intended and for carefully sharpening the tools and providing means of setting them accurately.
1924-01-01
Technical Paper
240022
ARTHUR T UPSON, LEYDEN N ERICKSEN
Shortage of the most desirable kinds of wood for automobile-body purposes has necessitated the substitution of second-choice woods having the essential required properties and the buying of stock for body parts in cut-up dimensions that conform in size with those now produced in the cutting-room. An investigation by the United States Forest Products Laboratory as to the species, kinds, grades, sizes and amounts used by the automotive industry shows that maple and elm comprise over one-half the total amount used and that ash and gum constitute one-half of the remainder. Although the quantity of ash used has not decreased, the increase in the production of medium and low-priced cars in the last few years bas caused a proportional increase in the demand for maple and elm.
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