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Technical Paper

Economic Requirements of Automotive Vehicles Abroad

1929-01-01
290006
AFTER considering from all viewpoints the factors involved in the overseas motor-vehicle market, the authors come to the conclusion that, to satisfy more generally the economic requirements of automotive road-vehicles abroad, developments in three directions are desirable. First, we should continue to improve present American automobiles and intensify effort to make them more readily available to the buying public. Special consideration should be given to the open car. This phase is to provide products for income receivers above the level of the large class of small-income receivers. Second, an entirely new product should be provided for individual transportation, in the form of a car smaller and lighter than the present smallest American automobile and less expensive to own and operate. This would provide transportation for a larger number of income receivers and fulfill the needs of a much greater potential market than exists for the present product.
Technical Paper

Gyro-Accelerometer Analysis of Riding-Quality

1929-01-01
290001
This paper describes the construction, theory and some uses 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 the result of research into the riding-qualities of automobiles conducted by the Department of Mechanical Engineering at the State University of Iowa. These investigations demonstrated the necessity of measuring angular motions under road conditions which was impossible with available equipment. The instrument furnishes an analysis of angular movements whereby the characteristics of the springs and shock-absorbers can be so matched as to give the body the lowest values of angular acceleration and therefore the best riding-quality.
Technical Paper

The Relation of Riding-Quality to Angular Car-Acceleration

1929-01-01
290002
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.
Technical Paper

Preliminary Report on Fatigue Produced by Automobile Riding

1929-01-01
290003
THIS IS a preliminary report of the results obtained to date in the study of fatigue incident to motor travel, which is part of the Society's Riding-Qualities Research program. A series of physiological tests were conducted after muscular fatigue had been induced by a known amount of work, with the hope of finding some tests sufficiently sensitive to measure less pronounced types of fatigue. These fatigue tests conducted on subjects after riding showed that a decrease in the carbon-dioxide combining power of the blood and an increase in metabolism are fairly satisfactory indications of muscular fatigue, but the results led to the conclusion that the fatigue which accompanies riding in automobiles does not represent a very marked muscular fatigue, and suggested that it may represent a condition more closely similar to nerve fatigue. Consequently, a rather extensive study of various tests of nerve fatigue was undertaken.
Technical Paper

Poppet Exhaust-Valve Design

1929-01-01
290021
DESIGN and the material used in the construction of automotive poppet valves, particularly exhaus valves, are discussed in connection with the necessity of resistance of the valves to physical and chemical actions of wide variety. The problem of resisting these actions lends itself to mechanical and metallurgical solution. Each part of the valve-the head, the stem, and the end and tip of the stem-is discussed separately; and the design of the head is considered as it relates to the upper or combustion-chamber surface, the edge, the seat and the lower or manifold-radius portion. Provisions made for the grinding-in of the valves are shown and described.
Technical Paper

Dual Carburetion and Manifold Design

1929-01-01
290020
DUAL carbureters, as equipment for eight-cylinder passenger-car engines, have recently come into special prominence and, compared with a single carbureter, give a gain in power in the middle-speed range, between 1400 and 2800 r.p.m. This is an adaptation from airplane-engine practice, in which greater power-output and better distribution have been realized by multiplying carbureter units as the number of cylinders is increased. An absence of overlapping and interfering suction-strokes and the use of larger manifold-passages are apparently responsible for this gain. Tests made on a number of eight-cylinder engines of both the in-line and the V-types confirmed this gain, which was, however, unaccompanied by any particular gain in fuel economy.
Technical Paper

Idiosyncrasies of Valve Mechanisms and Their Causes

1929-01-01
290023
AFTER mentioning the detrimental effects of valve bouncing and valve-spring surge upon the power and durability of an engine and on noise, the authors list four factors that contribute to perfect action of the valve mechanism. These are: the spring forces, as related to the speed and weight of the moving parts; the rigidity of the parts; the cam contour; and the design of the spring. Four different methods of investigating valve behavior are then described in detail. The telescopic point-by-point indicator and the stroboscopic projector of the valve motion were the first of these to be developed. The former gives an accurate measure of the valve position at any point of the cycle, and the latter makes possible a visual inspection of the valve operation. These two instruments were used together, but they were found to be rather slow in operation.
Technical Paper

Electric Telemeter and Valve-Spring Surge

1929-01-01
290022
THE electric telemeter presents an excellent means for investigating the phenomenon of valve-spring surge. Basically, the telemeter is composed of two differentially connected stacks of thin carbon discs so arranged that, when the apparatus is subjected to strain, the pressure is increased on one stack and decreased on the other. Each stack forms one arm of a Wheatstone's bridge, and the resistances of the stacks vary with the pressure on them, thus slightly upsetting the balance of the bridge. If an oscillograph galvanometer-element be substituted for the usual bridging instrument, the arrangement will be found suitable for making photographic records. To study valve-spring surge, the telemeter is connected across the points of a stiff C-spring, one end of which is held against the valve-spring in such a way that vibrations of the spring are transferred to the C-spring and thence to the telemeter.
Technical Paper

Inlet-Manifold Design and Fuel Utilization

1929-01-01
290017
THE results of research concerning the problem of fuel utilization in auotmotive engines are presented. A large heavy-duty six-cylinder engine was used, and the experimental apparatus and methods employed are described in the Appendix. Charts summarizing the engine characteristics at seven-eighths full-open throttle, the important characteristics determined by exhaust-gas analysis and the actual distribution of the fuel charge to the individual cylinders are presented. The characteristics indicated by these charts are discussed in some detail and the conclusion is reached that the higher engine-speeds used not only resulted in somewhat higher air-fuel ratios for the engine but also produced a more even distribution of the fuel charge to all of the individual cylinders.
Technical Paper

Combustion Control by Cylinder-Head Design

1929-01-01
290016
DETONATION and shock, the two principal barriers to increased compression, are subject to a degree of control which can readily make possible the use of compression ratios in the neighborhood of 6-1 on commercial fuel without objectionable effects and without sacrifice of output. Since detonation depends primarily upon the temperature attained by the residual unburned gas, it can be controlled by combustion-chamber design which intensifies the heat transfer from the unburned gas to the walls. The shock tendency, which originates in the pressure-time characteristic of combustion, can be controlled only by deliberate incorporation of the desirable anti-shock characteristic in the chamber design by a method of calculation which is explained in detail.
Technical Paper

Report on Air-Fuel-Ratio Tests

1929-01-01
290019
TESTS conducted to determine how air-fuel ratios obtained by analyzing the exhaust gases checked with ratios obtained by measuring the air and fuel are analyzed by the author, the tests having been made on a six-cylinder 3½ x 5-in. engine and the air measured by using a Durley air-box having a 2-in. flat-plate orifice. As a check, a 1½-in. well-rounded orifice was also used with the same results. The exhaust gases were analyzed in conventional Orsat apparatus having four absorption bottles. The tests were made at a constant air-fuel ratio at an engine speed of about 1300 r.p.m. with a wide-open throttle and maximum-power carbureter-setting. Thus far, 31 samples have been taken by different men and the air and fuel were measured each time a sample was taken. Three methods of obtaining air-fuel ratios from the exhaust-gas analyses were used and compared, and the author comments upon the results obtained.
Technical Paper

Fuel-Mixture Distribution

1929-01-01
290018
AFTER outlining the effects of improper distribution of fuel mixture in an internal-combustion engine and stating how the distribution of a gas is governed, the author discusses motor-fuel condensation and states that, since preheating the air is objectionable and hot-spots do not supply sufficient heat to vaporize the fuel completely, the induction system must distribute wet mixtures; and the partial or complete solution of this problem ordinarily is the result of experimenting with different designs for any particular engine. Regarding the manifold action with wet fuel-mixtures, it is stated that the phenomena occurring in manifolds which distribute such mixtures are complicated and unstable but some insight into them can be obtained by studying the action in a two-cylinder engine. Analysis shows that the even distribution of wet mixtures is extremely difficult.
Technical Paper

Interpretation of the Indicator Card

1929-01-01
290013
TRUE thermodynamic interpretation of the indicator card must be based upon the properties of the actual medium working in the engine and must take into account the actual nature of the heat liberation. The temperature-energy diagram for the working combustible mixture and for the resultant combustion products provides for this interpretation a foundation that is universally applicable to engines using a given type of fuel. This diagram automatically includes the effect of variation in specific heat with temperature, because the entire energy content of a gas at any temperature is the energy required to raise it, at constant volume, from absolute zero to that temperature. The work done during the actual changes of state, as determined from the indicator card, can readily be represented on the same diagram, and the heat interchanges involved can be determined quantitatively by comparison with the adiabatic criterion.
Technical Paper

Engine-Torque Analysis

1929-01-01
290012
ANALYTICAL methods of investigating engine torque are given in this paper, which is an amplification of the method previously presented by the same author, accompanied by a number of sample analyses. This method is said to be easier to apply to a complete analysis than is the graphical method, and to be adaptable to several types of investigation that cannot be made by the graphical method. In the discussion is given an outline of the mathematics required to follow the analysis. Electrical engineering students are said to receive instruction in all the mathematics required beyond that used in the graphical method.
Technical Paper

Combustion-Chamber Design in Theory and Practice

1929-01-01
290015
POINTING out the difference between scientific and industrial progress as manifested by heat theory and engine design and the Carnot and Otto cycles, the author discusses the working principles of combustion. A simple synopsis of internal combustion is presented, followed by a discussion of influence of spark-plug location on detonation and pressure rise and some observations on overcooling and flame quenching. The reasons underlying the decision to use a particular type of engine in an automobile are commented on, and this is followed by a discussion of the limitations imposed upon induction and combustion by such a choice. The advance in combustion-chamber design is traced from the early T-head through the L-head, in various forms, the overhead-valve, the hemispherical and four-valve types. Drawings of the different heads supplement the text and some comparative power curves are included.
Technical Paper

Balancing Power-Output in Multi-Cylinder Engines

1929-01-01
290014
AN INVESTIGATION of the problems of fuel-mixture distribution in the cylinders of internal-combustion engines recently initiated at Purdue University is outlined by the author, who states his belief that the material submitted in his paper demonstrates that it is necessary to “get inside” an engine cylinder to obtain satisfactory data. He therefore presents and comments upon indicator diagrams from tests made on the road and in the laboratory. The effects of pulsations in the manifold of an engine having a rather complicated manifold system are studied by means of lower-loop light-spring diagrams, and diagrams obtained from six cylinders of an engine operating at about 0.7 load at 1400 r.p.m. are analyzed. The effects of changing the mixture delivered to one cylinder of an automobile engine are also illustrated and analyzed.
Technical Paper

Economics of the Chevrolet Engine

1929-01-01
290009
SIX CYLINDERS are used in the Chevrolet engine, because six cylinders give smoother action and a longer range of satisfactory performance than four. Maximum results per dollar has been the ideal in the design, and high output has been secured at a cost very little higher than for a four-cylinder engine. The piston displacement is large enough to give satisfactory performance without fine tuning. The bore is made as large as possible within the space required for water-cooling around the valves. The stroke is short, resulting in low inertia forces and a stiff crankshaft with the minimum amount of metal. Three main bearings are found sufficient, because of the stiffness of the shaft and the inherent balance of the groups of three cylinders. Positive lubrication is provided, without pressure. The overhead-valve mechanism is so proportioned and the cooling of the parts is so arranged that variations in expansion cancel each other and result in nearly constant valve clearance.
Technical Paper

Methods of Obtaining Greater Power from a Given Engine

1929-01-01
290011
DEMAND for increased car-performance forces manufacturers to provide more powerful engines. It is desirable to obtain the increased power without designing a new engine, particularly in the case of large-scale manufacturers. The author lists possible means of doing this as making increases in the speed, the volumetric efficiency, the compression ratio, the thermal efficiency and the mechanical efficiency; and explores each of these methods in the light of latest developments in engine design. Among the concrete suggestions are greatly increased valve-lift, hydraulic valve-gears, multiple car-bureters, injection of vaporized fuel into cold air, cutting out the fan at high speed, and the use of superchargers. Higher compression generally involves changes in cylinder-head design, which are covered in some detail. Subjects covered in the discussion include lubrication, roller-chain camshaft drives, form of combustion-chamber, availability of engine power, and two-cycle engines.
Technical Paper

Desirability of a Large-Bore Engine

1929-01-01
290008
COMPARISONS are made of the respective characteristics of the large-bore short-stroke engine and the small-bore long-stroke engine in connection with the argument of the author that the former engine best fulfills the requirement that an engine must be a good product that is easily produced. He chooses the L-head type of engine for purposes of illustration, since this type is within the scope of the experience of all automotive engineers. When consideration is being given the specifications of a new engine, the first problem to be met is the determination of length. Usually a certain length is set arbitrarily, but this circumscribes the designer at the outset and, for some unaccountable reason, a new project is thus compromised rather than to change the preconceived idea of what the length of wheel-base must be.
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