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Viewing 6691 to 6720 of 6755
1940-01-01
Technical Paper
400055
R. A. McMurtrie
1939-01-01
Technical Paper
390091
R. J. Vedovell
1939-01-01
Technical Paper
390048
W. A. Witham
1939-01-01
Technical Paper
390158
A. T. Colwell
THE trend in poppet valves during the past year, like many other advances in science, Mr. Colwell points out, has been an improvement upon existing performance, rather than an entirely new development. To effect a steady improvement in existing designs, the study of fundamentals, such as grain flow, structure, forging temperatures, coolants, and interior construction, has been resorted to, and thorough research on valve steels has been carried out, he reports. In the study of valve steel, 300 analyses were examined; intensive work was done on 20; and 4 showed definite merit, he says. Grain flows in aircraft valves made by the extrusion and gather-upset processes are compared. Results of an investigation of sodium cooling and head designs of aircraft valves by means of glass valves are reported and illustrated. Four outstanding automotive valve steels are analyzed chemically and physically - Silcrome No. 1, Silcrome XB, Silcrome X-10, and Silcrome XCR. Mr.
1938-01-01
Technical Paper
380031
Ralph H. Upson
1938-01-01
Technical Paper
380042
Thomas H. Peirce
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
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
380052
R. A. WATSON
1937-01-01
Technical Paper
370181
Austin M. Wolf
1937-01-01
Technical Paper
370158
C. R. Maxon
ADAPTABILITY of die castings to economical manufacture, to close dimensions, to complex shapes, and to thin sections is stressed. Die-casting alloys are reviewed, emphasizing the suitability of the zinc alloys in cost, physical properties, and die cost, along with their limitations as to temperature and otherwise. A discussion of applications to automotive grilles includes comparison with other methods of producing these parts and a description of the built-up type of die-cast grille. Steering-wheel applications considered include hubs, horn rings, and light switches. Windshield-frame parts, louvres, radio grilles, lamp mountings, body-interior parts, horn bodies, and a number of chassis applications also are discussed. A review of finishing processes and notes and suggestions on design conclude the paper.
1937-01-01
Technical Paper
370025
Sidney Oldberg, Maynard Yeasting, Max M. Roensch
1936-01-01
Technical Paper
360066
A. B. Gordon
1935-01-01
Technical Paper
350059
H. W. McQuaid
1935-01-01
Technical Paper
350046
H. D. Allee
1934-01-01
Technical Paper
340088
Alex Taub
VIBRATION formerly was classed as such without much thought as to the determination of its sources, Mr. Taub states, and then came isolation of the various causes. The first two vibrations to be segregated and vigorously attacked were the secondary inertias of reciprocating units and torsional vibration. The development of the six-cylinder engine was among the earliest attempts to eliminate secondaries, and it was also the earliest producer of torsional vibration. Dynamics, combustion roughness, torsional roughness and structural weakness, are a few of the contributing causes of engine roughness. Consideration must be given to all these factors if an engine is to be considered inherently smooth, and each is analyzed. Engine mountings should have low resistance to rotation about the longitudinal principal axis and to rotation about the vertical axis through the center of gravity, together with minimum shift of affective principal axis and vertical axis.
1934-01-01
Technical Paper
340096
R. F. Gagg, E. V. Farrar
THE rapidly increasing use of aircraft engines fitted with superchargers for improving the power output at high altitudes has focused attention on means for predicting their performance in advance of actual flight tests in an airplane. A considerable amount of engine testing has been performed in several well-equipped laboratories in the past. These results have been carefully compared to determine the degree of similarity of the performance of these engines, and to form conclusions from which the performance of other engines may be predicted. Since the gear-driven centrifugal supercharger has demonstrated its superiority for use at moderate altitudes over other types on the grounds of simplicity, capacity, weight and space requirements, the data considered are almost entirely concerned with this type. It is shown, however, that naturally aspirated engines have quite similar characteristics.
1933-01-01
Technical Paper
330047
K. L. Herrmann
A ROLLER having the same diameter as a corresponding ball and a length equal to the ball diameter has approximately four times the carrying capacity of a ball, according to Mr. Hermann. The data presented on cageless roller bearings are based upon knowledge of the carrying capacity and life of the ball bearing. The reason for the increased carrying capacity of a roller over that of a ball is due to the distribution of the load over a line of contact rather than at a point of contact. The roller bearing increases the number of such line contacts and therefore further distributes the load to the raceways. By increasing the number of line contacts, the cageless rollers reduce the stress per roller and failure due to fatigue. The fatigue factor is reduced 40 per cent, comparing a cageless with a caged roller.
1933-01-01
Technical Paper
330057
Ford L. Prescott
1932-01-01
Technical Paper
320049
D. P. Barnard
THE PAPER suggests a criterion for the tendency toward overheating of plain journal bearings of the high-speed type. The application of a criterion consisting of the product of oil viscosity by the square of the running speed is considered on a heat-balance basis and is compared with a series of observations of crankcase temperatures in a number of typical cars. Quoting the fact that in a plain journal bearing the coefficient of friction is a function of the term “viscosity times rate of sheer divided by unit load,” the author states the symbols and units employed and analyzes heat generation in the fluid film. An analysis of the dissipation of frictional heat is presented also, together with a discussion of the subject of bearing-temperature estimation. Curves are presented which resulted from data based on observations taken during a series of tests on a number of representative passenger-cars on the Indianapolis Speedway.
1932-01-01
Technical Paper
320058
H. C. Dickinson, O. C. Bridgeman
SATISFACTORY performance of a lubricant depends upon characteristics of the lubricant, operating conditions and design of the device in which the lubricant is used. Applied lubrication requires a study of the relation among these factors in their effect upon performance. The authors treat journal bearings, ball and roller bearings and gears. Equations are given for journal bearings operating under various conditions of design, lubrication, friction and heat dissipation. The authors conclude that neither ZN/P nor PV alone is adequate as a measure of the power dissipated by a bearing, a composite relation involving both terms being required over a large part of the operating range. They show that each bearing has a minimum value of ZN/P below which it may get into the unstable region of thin-film lubrication and fail.
1932-01-01
Technical Paper
320009
S. A. McKee, T. R. McKee
AUTOMOTIVE engineers, who have to deal with high-speed high-load journal bearings and are confronted with fear of the consequences of “ragged-edge” thin-film lubrication, will find much of interest and value in this report. It covers the information obtained and conclusions reached as a result of the extension of research into the region of thin-film lubrication, in which little investigation has heretofore been made. Tests made in a four-bearing machine, using both high-tin babbitt and high-lead bronze bearings and operated on lubricants of various viscosities over a wide range of speed and load, showed conclusively that the coefficient of friction depends directly upon the viscosity even in the thin-film region. They indicated defnitely that the friction coefficient is more likely a function of ZN/√P than of ZN/P.
1931-01-01
Technical Paper
310040
Ford L. Prescott, Roy B. Poole
FOR the rapid calculation of bearing loads in aircraft engines the authors have developed an analytical method that is described for the first time in the paper. This was derived from the long tedious graphical method that was formerly used and its accuracy is asserted to be sufficient for all purposes of engine design. Results of an analysis of the bearing loads in the Curtiss V-1570 Conqueror engine which were obtained by the graphical method are first presented in considerable detail. The Wright R-1750 Cyclone is next analyzed, the method that was employed not being as precise as that used for the other engine. An application of the analytical method using empirical constants derived from a graphical analysis of various engines is also presented. Numerous illustrations and tables supplement the text.
1931-01-01
Technical Paper
310007
A. T. Colwell
AFTER stating that increased speed, mean effective pressure and piston displacement of engines have made valve conditions more difficult during the last few years, the author recalls the path which development has followed by a brief list of materials and methods of cooling. Where the stem joins the head is the hottest part of the valve. A shield for this point is shown, also a shroud to protect the end of the valve-stem guide. Cooling the valve increases its life. Salt and sodium cooling are compared, and methods of sealing the coolant in place are described. The construction and behavior of copper-cooled valves are illustrated and recounted, and a one-piece hollow-head valve is described. Reasons for valve-seat inserts are given.
1929-01-01
Technical Paper
290043
A. B. Cox
1929-01-01
Technical Paper
290021
RICHARD E. BISSELL, GORDON T. WILLIAMS
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.
1928-01-01
Technical Paper
280062
CHARLES H. LOGUE, R. B. FEHR
BY means of the gear-correcting process described, spur and helical gears are corrected to give a high degree of uniformity in spacing and profile so that the gears become practically interchangeable. They acquire a “crown face” which enables them to run with unusual quietness under practical conditions. This is essentially an inspection-correction process, as it automatically finds and eliminates the errors. The lap is the important item in the process. It is of chilled cast-iron, gray cast-iron, or type metal, and is made by casting in a mold around a steel chill cut to approximate the gear to be corrected but has a face-width several times that of the gear. The lap, when completed, looks like a wide-faced internal gear.
1927-01-01
Technical Paper
270014
E. F. BEHNING
ACCORDING to the author, gear clatter and clash caused by metal-to-metal contact develops into an annoying whir or howl at high gear-speeds, and a material was sought that is flexible and resilient enough to absorb the vibrations or change their frequency to a pitch inaudible to the average human ear. Since vibrations in the crank, the cam and the generator shafts are transmitted to the timing-gears, which run at high speeds, a material was needed that would silence the consequent noise and provide a noiseless timing-gear train. A great variety of materials was investigated and the development of laminated, phenolic, condensation products resulted; these have proved mainly suitable for timing-gear-blank stock and stock for other gears such as those suitable for crankshafts and generator shafts. A further development was that of the flexible-web cam-gear made of the composition material.
1927-01-01
Technical Paper
270015
R. S. DRUMMOND
AFTER outlining the present status of the forms of drive for timing-gear trains, the author describes modifications of gear design made by the company he represents to overcome noise that involve lengthening gear-teeth for a given pitch. Various modifications in this regard were made and one having 16-pitch teeth with 12-pitch length had 10,000 miles of use in fourth speed without developing excessive wear. A further development resulting from experiments was the use of case-hardened timing-gears for motorcoach engines, such usage being thought to provide the most extreme conditions. Characteristics of so-called anti-stub gears are stated and predictions are made as to the future of timing-gear practice.
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