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Viewing 188461 to 188490 of 190968
1938-01-01
Technical Paper
380162
A. T. Colwell
THE factors affecting the rate of wear of valves and valve gear are summarized. Reasons for recent marked improvements in the life of aircraft valves are discussed. Surface finish developments are described that are designed to decrease the initial rate of wear. Ten means of getting close initial clearance are outlined. Progress of work in three laboratories on surface treatments is reported. The relative amount of wear with various material combinations is compared.
1938-01-01
Technical Paper
380149
J. R. MacGregor, W. V. Hanley
FUEL deposition and ring-sticking tests are described which were performed in several single-cylinder and multicylinder service Diesel engines in the laboratory. The development of an accelerated test method is outlined with special reference to the effects of engine variables on deposition. Decrease in load, speed, or jacket temperature or increase in altitude were found to increase fuel deposition. Increase in running time increased the exhaust deposits linearly but, within the combustion-chamber, equilibrium deposition was reached in a few hours of operation. Marked differences were found among fuels in the single-cylinder test engine after 24 hr. of operation under the accelerated conditions. Fuels doped with different types of cetane-number improvers indicated that ignition quality is a factor in fuel deposition under certain operating conditions in some engines.
1938-01-01
Technical Paper
380150
H. O. Mathews
1938-01-01
Technical Paper
380155
Kirke W. Connor
UNTIL recently factual investigation of wear, lubrication, and maintenance of operating tolerances in internal-combustion engines have been handicapped by the lack of factory-type equipment which would permit standardized measurement in all conditions of manufacture and service. The combined characteristics of surface character and finish in bearing and operating parts may now be determined practically and efficiently by means of the new portable Profilometer, combined with photographic or microscopic study. Newly developed honing tools and new tool actuations now accomplish a large amount of stock removal rapidly by the hone abrading process. These new tools remove all stock which has been deformed or disturbed in previous processing under conditions of actuation which produce increased accuracy, controlled surface character, and final surface finish in which roughness is held within one or two micro-inches in some parts.
1938-01-01
Technical Paper
380156
C. R. Paton
DISCUSSION is limited in this paper to ride problems pertinent to cars equipped with independent-type front and non-independent rear suspensions. Emphasis is placed on problems arising in connection with the newer so-called “flat-type” rides. Approach is made to the problem of the control or damping of springs and some of the factors, important from a balance standpoint, in securing these flat pitch-free ride characteristics. It is pointed out that shock absorbers should more properly be called “ride controls,” so great is the importance of proper damping characteristics in obtaining the newer flat-type drives. The tremendous number of interrelating factors involved in the attainment of ride excellence is given as the reason why effective instrumentation has never been developed. The author concludes that the maze of compromises involved will always require the experienced observer.
1938-01-01
Technical Paper
380154
G. A. Round
1938-01-01
Technical Paper
380144
Alex Taub
VARIATION in engineering practice between European and American motor cars is to be expected. Many of these differences are brought about by local conditions and must be accepted. However, there are practices that vary from the American that do not justify themselves by result or local conditions. The two outstanding are bore wear and carburetion. This paper deals only with the high spots of these two differences.
1938-01-01
Technical Paper
380141
J. Trueman Thompson
PRESENT interest in ways and means of improving the speed at which many slow-moving vehicles climb grades, springs from a real necessity and an honest desire on the part of all agencies concerned to produce a practical solution. The United States Bureau of Public Roads recently has undertaken to develop apparatus and a procedure which may be used to secure a large amount of data on current hill-climbing practice. It is planned that this method will be applied shortly through the agencies of several of the State Highway Planning Surveys. The apparatus and procedure referred to were used during the past summer to secure a limited amount of “trial” data. Both the tests and data are discussed as well as certain plans which are now being formulated to make a special study of both new and used trucks in the dynamometer laboratory of the Motor Transport Division of the Army, and to correlate these data with actual hill-climbing tests.
1938-01-01
Technical Paper
380142
Russell Pyles
METHODS of increasing engine output are discussed, and supercharging is said to involve few difficulties. The location of the blower drive as it affects frequency and gear loading is considered. Bearing-load diagrams are analyzed for a high-speed and a low-speed engine. Tests indicate a negligible increase in piston temperatures. Fuel-consumption curves show fuel economy comparable with that of the normal engine.
1938-01-01
Technical Paper
380148
A. S. Van Halteren
MODERN developments in the automobile industry have created a paradox. On the one hand, increased speeds have placed greater demands on the brakes whereas, on the other hand, the trend toward streamlining has greatly handicapped brake performance. As a result brake drum and wheel diameters have been reduced and the flow of air to the brakes has been restricted by shrouding them with wheels and skirted fenders. In the solution of brake heat-transmission problems, the subject is considered under the following headings: the amount of heat generated; the manner and rate of heat flow into the brake; and the manner and rate of heat flow out of the brake. Heat-transmission calculations of specific examples are made that indicate the amount of heat dissipated by conduction, radiation, and convection.
1938-01-01
Technical Paper
380147
L. W. Child
ALL factors necessary for year-around air conditioning of cars and buses are covered generally in this paper. How the desired results were obtained in both winter and summer air conditioning is explained with the aid of a chart of air requirements. Types of equipment are discussed, especially the refrigerating system, giving powers, capacities, and safety factors.
1938-01-01
Technical Paper
380145
T. A. Boyd
THIS paper deals with the road-test portion of the extensive efforts made during 1937 by the Cooperative Fuel Research Committee to get as precise a correlation as possible between the laboratory knock ratings of automobile fuels and their corresponding ratings in cars on the road. It is anticipated that the comprehensive results of car tests reported here, taken together with the results of the laboratory rating program reported in the companion paper, will serve as the basis of the continuing studies aimed at developing the best possible correlation between road and laboratory knock ratings. Work similar to that reported here has been conducted concurrently in England by the Institution of Petroleum Technologists, using British cars and fuels. An exchange of information between the British and American groups working on this problem is being made.
1938-01-01
Technical Paper
380134
Macy O. Teetor
THE elimination of wear of piston-rings and cylinders can be the ultimate goal toward which to strive but, in reaching this Utopia if it can be reached, the most practical road seems to be by way of wear reduction. Many factors indicate the necessity for a “wear-in” period. At some point in service wear-in ceases and “wear-out” starts. As wear-in takes place, performance only improves to a certain point and, from there on, piston-rings and cylinders can be considered as wearing out. The rubbing action of a piston-ring on a cylinder wall breaks particles loose from the surfaces that act as an abrasive. This breakdown of the rubbing surfaces, regenerative because of the abrasive action of the resulting loose material, causes wear. The ease with which the surface of a material will break down and the physical characteristics of the loose particles so produced are indicated to a great extent by structure. The structure of a material is therefore an indication of expected wear.
1938-01-01
Technical Paper
380133
J. L. McCloud
1938-01-01
Technical Paper
380135
Earl Bartholomew, Harold Chalk, Benjamin Brewster
INCREASED performance at high speed, which is an important characteristic of cars built during the last few years, has required the use of intake manifolds of considerably greater cross-sectional area which, together with certain other changes in engine design, cause unequal distribution of the less volatile portions of the fuel not vaporized in the manifold. Consequently, the fuel which enters the cylinders varies in composition. If other conditions are equal, the relative knocking tendency of the cylinders is determined by the distribution of antiknock value through the fractions of the fuel and by the air-fuel ratios of the mixtures in the cylinders. Ordinarily the leanest cylinder knocks the most. Fuels rated in the laboratory by conventional methods as having equal antiknock value may differ considerably in road performance because of differences in volatility and distribution of antiknock value through their fractions.
1938-01-01
Technical Paper
380136
J. L. S. Snead
1938-01-01
Technical Paper
380138
Ernest J. Abbott
GREAT simplification of understanding and unusual results in production often follow new approaches to old problems. When noise problems are stated in terms of the familiar physical units of pressure, velocity, weight, and stiffness, basic ideas are obtained which can be applied directly to practice. In this way, most of the mysteries and the contradictions of noise problems are eliminated. In their elements, noise problems involve only simple physical factors which are understood easily, and which can be measured with available equipment. Similarly, the solutions involve the straightforward application of known and definite engineering principles. Although simple in their elements, most practical noise problems are very complex because of their combinations. Often much ingenuity is required to measure the physical characteristics of the noise which determine the human impressions obtained from it.
1938-01-01
Technical Paper
380126
D. A. Wallace
1938-01-01
Technical Paper
380125
A. E. Becker
THIS paper is a progress report of the Cooperative Fuel Research Committee, dealing with the laboratory section of the study of the knock-rating correlation problem. It is proposed that these results and those obtained on the road be the basis for further study aimed at the development of better correlation between road and laboratory ratings.
1938-01-01
Technical Paper
380128
W. J. Cumming
1938-01-01
Technical Paper
380130
J. E. Hale
THIS paper is a non-technical review of an up-to-date survey of the lines of tires needed in all types and classes of fleet operation. To understand better how to get the best results from their operations, operators must know the proper type of tire to use. The author first describes and catalogs the principle forms of tire failures, then reviews the characteristics of the fundamental lines of tires available at the present time. Next, an attempt is made to classify the different types of fleet operation so that definite recommendations can be made as to the most appropriate tire equipment for these vehicles. The types of tire trouble most commonly encountered in each group are brought out with suggestions on how to avoid them. This part is followed by a section giving advice on the care of tires. The paper concludes with a brief survey of worthwhile facts about repairs and retreading. An appendix contains the load-inflation tables which are most widely used.
1938-01-01
Technical Paper
380127
J. G. Moxey
ALTHOUGH dealing with a subject of unlimited breadth, this paper touches on the primary guides for an operating engineer in the purchase of automotive equipment from a practical standpoint, treating only lightly the operating phase of the subject. Torques, engine displacements, ability factors, gross vehicle weights, and recommended practices, together with their relative relationship one to another, are discussed in detail, and also are shown in chart form as a ready guide for a prospective purchaser. The economical fields of operation of four-wheel trucks, six-wheel trucks, and tractor semi-trailers, together with basic operating costs, acting as a further purchasing as well as operating guide, are brought out, the general conclusion being that each type of transportation under discussion has a definite economic field of operation and should be held definitely in its respective field as indicated advisable by operating surveys.
1938-01-01
Technical Paper
380132
Gavin W. Laurie
MAINTENANCE economy is seldom a realization unless sufficient consideration has been given to the major factors entering into the cause for maintenance. The expenditures necessary to correct normal wear conditions often represent a very small portion of the total maintenance cost. The operator is presented too frequently with the problem necessitating design corrections before the truck has operated many thousand miles. The responsibility for failures of this nature may rest with either the purchaser or the manufacturer. The purchaser may, due to insufficient thought having been given to the contemplated assignment of the truck, misinform the manufacturer as to the load to be carried or the terrain to be traversed; or his appropriation for purchase may be insufficient for a suitable piece of equipment. The manufacturer, on the other hand, may accept the order, knowing that he cannot furnish suitable equipment.
1938-01-01
Technical Paper
380129
Roland V. Hutchinson
A PARTLY descriptive, partly analytical discussion of facts and opinions concerning the fundamentals of occurrences in the zone of metal removal in conventional surface- and cylindrical-grinding operations is set forth in this paper. The paper considers in sequence the basic geometrical interrelationships involved; it discusses broadly the contributing causes of heat production in both work and wheel; it comments on effects of dressing practice and kinds and uses of coolants; and finally it illustrates what is attempted in the selection of a wheel for a particular job. Cam-profile grinding in some of its phases is touched upon as one familiar example of a peculiarly repetitive process cycle occurring while the grinding wheel progressively is changing remarkably in cutting characteristics. And it was all started by the innocent query: “Do We Understand the Grinding Process?”
1938-01-01
Technical Paper
380117
H. W. Prentis
1938-01-01
Technical Paper
380131
B. B. Bachman
AFTER tying in truck development with that of passenger cars, this paper differentiates between “engine-under-the-seat” and “cab-over-engine” types, lists the advantages and disadvantages of each, and discusses their design features. A comparison of these types with trucks of conventional design is made by contrasting specific data, such as capacities and dimensions.
1938-01-01
Technical Paper
380118
R. B. Haynes
DEVELOPMENTS in spline and gear cutting discussed in this paper include actual production results in climb-hobbing of splines and experimental results in climb-hobbing of gears. “Climb-hobbing” is defined as that method of hobbing wherein the cutting action starts at the surface of the part being hobbed and ends at the root of the spline or tooth - the direct opposite of the conventional method. Important advantages claimed for the method are a superior finish, increase in hob life, and lower power consumption. Finishing-process developments considered are finish-cutting, burnishing, shaving, and grinding.
1938-01-01
Technical Paper
380120
null, R. P. Gaylord
THE cooperative tractor tire tests described in this paper were discussed originally at a meeting of the Society several years ago. The tractor engineers present at the discussion suggested to the tire engineers that there was need for a cooperative test program to determine the efficiency of the various tire sizes over a range of soil conditions. Among the ten conclusions drawn from the comprehensive tests reported in this paper are that the most important factor affecting the coefficient of traction or tire thrust of rubber-tired tractors is the nature or surface of the operating soil; that, for a given soil, the most important factor is the weight that the tire carries; and that inflation pressure has a relatively small effect.
1938-01-01
Technical Paper
380121
C. H. Baxley, T. B. Rendel
FOLLOWING the adoption of a suitable design of engine and a tentative procedure for operating this engine, the work of the Volunteer Group has covered the investigation of other methods of measuring cetane number of Diesel fuels looking towards a simplification and improvement of reproducibility of the procedure. Results of a second series of cooperative tests are given, using the procedure adopted in the Group's last report together with a series of tests on the same fuel using the critical-compression-ratio method with an interval timing-control device. Results of the first series do not show such good agreement, the grand average deviation on twelve samples being of the order of ±1.9. Results of the critical-compression-ratio tests show improved agreement due to better standardization. Tests on three alternative methods based on the delay method, but using different instruments for recording the delay, are given. Results on two different full-scale engines also are presented.
1938-01-01
Technical Paper
380122
Frederick K. Glynn
THE truck manufacturers have made available to fleet operators a wealth of truck chassis with sufficient models and interchangeability of units to create special models to meet any transportation job requirements no matter how particular or peculiar. Within reasonable limits, the first costs of these chassis are indicative of relative chassis strength, durability, and ability. The selection of a chassis cannot be made from first cost or from operating cost expectancy alone, for these two go hand-in-hand to form the total cost and either may be increased with impunity if the overall cost of transporting the product is thereby decreased. One of the most important requirements in the selection of a chassis is a thorough operation and transportation job-analysis. Other considerations include availability of service, inherent safety, legal limitations, and appearance.

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