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Technical Paper

Automotive Two-Cycle Diesel Engines

1938-01-01
380176
THE properly designed two-cycle Diesel is the answer to the problem of building an automotive-type Diesel engine that compares favorably with conventional gasoline engines as to size, weight, and power, Mr. Shoemaker asserts. His paper is chiefly concerned, he announces, with the problem of producing such an engine that will use the same materials, design practices, manufacturing methods, and mechanical parts as are common practice in production-type gasoline engines. Scavenging is effected in these engines, Mr. Shoemaker explains, by using piston-controlled inlet ports and poppet exhaust valves in the head. The author shows how a change in design of the blower to a three-lobe helical-rotor type reduced noise and improved discharge characteristics.
Technical Paper

Automotive Bearing Materials and Their Application

1938-01-01
380165
DEVELOPMENT of higher octane fuels, which will allow more power output through higher compression ratios with a given size engine, and the increasing use of Diesel engines for trucks and buses, will bring about a need for radically superior bearing materials, Mr. Underwood predicts in the early part of this paper. Stating that a bearing material does not always require excellence in all characteristics, he lists the properties which make a good bearing alloy as: fatigue strength; ability to resist seizure to the steel shaft during periods when there is metal-to-metal contact; good bonding characteristics; mechanical compressive strength; conformability; embeddability; and corrosion resistance. After describing tests for each characteristic, he treats the functional differences of the present available bearing materials, some of which are still in the final period of development. Mr.
Technical Paper

Motor-Car Engines in England

1938-01-01
380144
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.
Technical Paper

The Diesel as a High-Output Engine for Aircraft

1938-01-01
380137
FROM single-cylinder engine tests, power and fuel-consumption curves have been calculated for a highly boosted multicylinder Diesel engine. The influence of inlet-air temperature and maximum cylinder pressure on attainable mean effective pressure for a given specific fuel consumption is demonstrated. Theoretical Diesel-cycle performance curves are included to show gains possible by further improvement and control of combustion rates. Performance to be expected from the two-stroke-cycle Diesel is estimated. It is concluded that the boosted four-stroke-cycle Diesel engine can exceed the maximum sea-level output of the 100-octane gasoline engine and give lower specific fuel consumptions at any power output. A similar comparison holds for the altitude performances of the two types, although the Diesel will impose greater demands on the air blower. Adoption of the turboblower by the Diesel engine offers further advantages.
Technical Paper

The Reduction of Piston-Ring and Cylinder Wear

1938-01-01
380134
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.
Technical Paper

Wear Reduction of Valves and Valve Gear

1938-01-01
380162
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.
Technical Paper

Surface Finish Related to Wear in Internal-Combustion Engines

1938-01-01
380155
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.
Technical Paper

Diesel Deposits as Influenced by Fuels and Operating Conditions

1938-01-01
380149
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.
Technical Paper

BASIC PROBLEMS IN THE DESIGN OF HIGH-OUTPUT AIRCRAFT ENGINES

1938-01-01
380111
Here is presented an analysis of important technical problems in the design of high output aircraft engines. Different methods of boosting the output are fundamentally considered. The method of supercharging is revealed to be the most promising one. Design limitations to high outputs are stress, heat dissipation, piston speed and detonation; the removal of each limit would require, beside chemical and metallurgical improvements, the use of spark control valve overlap and injection of anti-detonating or artificially-cooling liquid. The utilization of energy from exhaust gas is highly advised. Numerical example is shown for a design of 3000 H.P. engine and possible arrangements of cylinders are compared. Necessary alterations in design are recommended to acquire high specific output.
Technical Paper

Maintenance of a Concentrated Fleet of Large Trucks

1938-01-01
380132
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.
Technical Paper

Quality Control of Aluminum-Alloy Aircraft Castings

1938-01-01
380119
ARTICLES of a wide variety of sizes and shapes can be produced easily by the sand-casting process. The advantage of simplicity and low cost offered by the sand-casting process for small numbers of identical parts is offset by certain inherent limitations which must be recognized clearly if it is to yield optimum results. The various methods of inspecting and controlling structural variations that affect the strength and serviceability of aircraft castings are described. It is recognized that the user of castings must rely to a considerable extent on the foundryman for careful inspection. Several direct tests worthy of consideration as final acceptance tests of quality, such as the proof test, radiography (X-ray examination), and the static breakdown test, are described. However, this discussion leads to the conclusion that there is not yet available a satisfactory direct method of predicting the normal life of an aircraft casting.
Technical Paper

ENGINE DEPOSITS

1938-01-01
380075
The engine deposits withwhich operators are concerned have their source in what is commonly called sludge. Sludge is composed of carbonaceous matter (either from blow-by or from high-temperature cracking); asphaltenes (oxidized oil products); ash (mostly lead oxide and iron bromide where gasoline is used, metals from wear and corrosion and dust from the air); and moisture from condensation. All these component parts of sludge vary greatly depending on engine design, operating conditions, fuel and lubricant used. The whole engine ina sense is a centrifuge and throws this variable called sludge to various parts of the engine. The dead spots collect most with the hottest portions covered with a brittle flint-like carbon or lacquer. In high output engines run for extended periods of time, ring sticking limits the time of complete overhaul. It causes increased cylinder and ring wear. Contrasted to this are sludges formed under cold weather conditions.
Technical Paper

Hypoid Lubricants-Test Results and Their Interpretation

1937-01-01
370190
A DETAILED report of the results obtained testing hypoid lubricants at the Chevrolet Motor Co. is presented in this paper. As a result of these tests it is announced that 182 hypoid lubricants have been put on the Chevrolet approved list. Seeking to correct an impression that only lead soap-active sulphur and lead soap-sulphur saponifiable-chlorine lubricants would be considered, the author states that other types that meet specifications also will be put on the approved list. Nine different characteristics are checked in the laboratory tests: load-carrying properties; viscosity; chemical analysis to determine the total lead, sulphur, and chlorine; oxidation; evaporation loss; non-combustible sediment; channeling; foaming; and copper-strip test. Scoring tests were conducted over a 3.8-mile speed loop in the proving ground at speeds varying from 10 to 70 m.p.h., and a new third member was used for each test of each lubricant.
Technical Paper

High Oiliness - Low Wear?

1937-01-01
370189
THE purpose of this paper is to call attention to the need for fundamental wear investigations and to show that wear does not correlate with oiliness. A testing machine suitable for measuring both friction and wear is described. The machine, which is a modification of one previously reported by the author, uses two sets of frictional surfaces - one in the form of a track having two concentric rails and the other consisting of three small buttons with recessed centers and flat tracks on the outer edges. An important feature of the machine is that the rubbing surfaces are maintained automatically at an almost uniform degree of surface smoothness by the lapping action produced by the combined rotating and sliding motion of the buttons.
Technical Paper

The American Picture - Diesel Fuel Research

1937-01-01
370170
PRIMARILY intended as a discussion and amplification of the paper of Messrs. Boerlage and Broeze presented at the April, 1936, meeting of the American Chemical Society1, this paper reviews fuel research conducted at the San Leandro laboratory of the Caterpillar Tractor Co. and, therefore, is limited to the precombustion-chamber type of Diesel engine burning California-base fuels. The paper describes investigations of ignition quality, fuel-spray characteristics, and injection phenomena by means of a single-cylinder test unit fitted with a quartz observation window, stroboscope, timing disc and phase-changing device. A discussion of the products of incomplete combustion as influenced by compounded lubricants and ring-belt temperatures concludes the paper.
Technical Paper

Oil Filters in Public Utility Fleet Operation

1937-01-01
370168
THIS paper has to do mainly with the care of the oil while in service, which care is considered as important, or more so, than its selection. The author points out that at present there is no reliable scientific method or test for determining whether or not an oil is suitable for further use, and that oils do not wear out but simply become contaminated with various impurities. Impurities that tend to produce changes in the characteristics of crankcase oils while in service are considered under headings of inherent impurities and extraneous or foreign impurities. A number of types of filters are discussed with the various types of elements in use. Desirable features of a good filter are enumerated. Although admittedly a controversial issue, the author believes that filters are decidedly advantageous and economically justifiable especially from the standpoints of fewer oil changes, decreased oil consumption, and reduced bearing and cylinder wear.
Technical Paper

Design Developments in European Automotive Diesel Engines

1937-01-01
370172
A GENERAL consideration of the particular factors which define the development of the compression-ignition engine for automotive as apart from other purposes is presented in this paper. The various combustion systems, their respective merits, and individual characteristics in the light of the particular conditions set forth previously are reviewed. The evolution of the general mechanical design is traced, as resulting from the requirements of the particular duty, and from experience gained under prolonged service conditions, including a survey of the most prevalent troubles and difficulties and of measures which have proved effective in overcoming them. The paper also discusses some economic aspects of compression-ignition engine operation, and the effects of such artificial factors as fuel taxation and the distribution of suitable fuels on design and on the choice of a combustion system.
Technical Paper

Compression-Ignition Engine Performance at Altitude

1937-01-01
370154
ENGINE-TEST results are presented for simulated altitude conditions using a displacer-piston combustion-chamber on a 5-in. by 7-in. single-cylinder compression-ignition engine operating at 2000 r.p.m. Comparison between maximum performance at altitude of the compression-ignition engine and a carburetor engine showed that the compression-ignition engine had a slight power advantage for the same conditions of inlet air. However, if the carburetor air is heated to prevent icing, the compression-ignition engine inducting the colder and more dense air of altitude will have a decided advantage over the carburetor engine. Analysis of the results for which the inlet-air temperature and pressure were varied independently indicates that maximum engine performance cannot be corrected reliably either on an inlet-air-density or weight-of-air-charge basis. Maximum engine power increases with inlet-air pressure and decreases with temperature very nearly as straight lines.
Technical Paper

The “Tocco” Process of Hardening

1937-01-01
370166
THE “Tocco” process of surface hardening, especially of the bearing surfaces of bus and truck crankshafts, is described in this paper. Desirable changes and modifications in production operations and their sequence made possible by the process are suggested. Examples are reported from service experience of the amount of resistance to wear and abrasion added to the bearing surfaces by this process.
Technical Paper

Behavior of High- and Low-Cetane Diesel Fuels

1937-01-01
370163
THIS paper is a sequel of the paper, “Photo-Electric Combustion Analysis,” presented at the 1936 Semi-Annual Meeting of the Society. The indicator described in that paper has been used to study combustion of 28 fuels and chemicals. A complete table of information of the materials used as fuels is included. The results obtained from over 1000 oscillograms show a different shape of ignition-lag curve versus injection advance angle than it is ordinarily thought to have. Even though the cetane values for these 28 fuels varied from 24 to 100, they all had nearly the same ignition lag when injected near the dead-center position. This minimum value is shown to be about 1/1000 sec. The fuels of higher-cetane value reach this minimum at an earlier injection angle than do those of low-cetane value. The paper shows how a high-cetane fuel can be just as rough as a low-cetane fuel if the injection timing is too early.
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