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Viewing 7741 to 7770 of 7786
1943-01-01
Technical Paper
430019
Ralph L. Leadbetter
1943-01-01
Technical Paper
430021
Ralph M. Guerke, George P. Knapp
1939-01-01
Technical Paper
390023
S. M. Cadwell, R. A. Merrill, C. M. Sloman, F. L. Yost
1939-01-01
Technical Paper
390126
E. S. Ewart
1939-01-01
Technical Paper
390185
Charles M. Kearns
COMPLETE isolation of the airplane propeller from the engine, except for a very flexible torque drive, appears to be the only satisfactory solution of the vibration problem in the future, Mr. Kearns believes. Under such conditions, he explains, much lighter propeller blades can be used to maintain even greater horsepowers than are available at present so that, in spite of the trend toward more power, the increase in overall weight of the powerplant may be delayed considerably. This problem of the vibration characteristics of the engine and propeller when operating jointly, he points out, recently has become practically the determining factor in the selection of the proper propeller for use with a given airplane-engine combination. An intensive investigation of this problem, studying both experimental and analytical approaches to the causes and solution of the high-stress conditions found in some engine-propeller combinations, is reported. In his paper, Mr.
1939-01-01
Technical Paper
390156
Ernest E. Wilson, Paul Huber
THE authors introduce their paper by outlining the various sources of noise existing in the motor car, together with some of the suppression means. Noise measurement, test methods, and the mechanism of the transmission of forces generated by the contact between the tire and the road to the body and frame are discussed. The authors state that, since these forces produce motion and deflection of the body, they are responsible for the road noise, and conclude that the proper approach to a method for suppressing road noise is through the structural design of the vehicle. They suggest, in the main, the localizing of stress to stress members, the raising of the resonant frequencies of the structure, the detuning of the suspension system, the body, and the frame, together with some isolation at selected points.
1938-01-01
Technical Paper
380117
H. W. Prentis
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
380042
Thomas H. Peirce
1937-01-01
Technical Paper
370118
E.S.L. Beale, R. Stansfield
1937-01-01
Technical Paper
370025
Sidney Oldberg, Maynard Yeasting, Max M. Roensch
1936-01-01
Technical Paper
360101
P. M. Heldt
ROUGHNESS in the operation of engines has increased in seriousness with increase in the compression ratio and in the provisions for inducing turbulence in the combustion chamber, both of which factors tend to increase the rate of pressure rise in the engine. In this paper the thesis is maintained that this roughness consists of synchronous transverse vibration of the crankcase, due to variations in gas pressure and inertia forces. By synchronous vibration is meant a vibration which passes through a cycle in exactly the same time as the periodic force which produces it, so that the amplitude of the vibration builds up from cycle to cycle until the damping forces become equal to the exciting force. Owing to the angularity of the connecting rod in all except the dead-center positions, the gas pressure produces an alternating horizontal force on the crankcase at the main bearings.
1936-01-01
Technical Paper
360136
John S. Parkinson
OF all problems involving noise measurement, the human ear is the final judge and the court of last resort. In most situations, as in the case of the motor-car buyer, it is the untrained ear of the average customer that ultimately passes judgment. Likewise in all instrument calibration, it is necessary in the final analysis to depend upon the ear as a basis. For this reason the measurement of noise must be so conducted that results and predictions will agree with ear judgments. A discussion is given of the various characteristics of noise that the ear recognizes, that is, loudness, pitch, quality, and discomfort or annoyance. The physical quantities corresponding to these psychological characteristics are discussed, and also methods of converting from one set of quantities to the other. The experimentally established relationships between pitch, loudness, and annoyance are given.
1936-01-01
Technical Paper
360139
H. M. Jacklin
PRESENTING the analysis of several thousand observations of the reactions of humans to vibration when sitting on a controlled vibrating seat or platform and in moving vehicles. Physical reactions are defined carefully as a result of many experiments under controlled conditions. The perfection of a three-directional wave-recording accelerometer is described. Its use in determining vibration conditions when the defined physical reactions occur is displayed. The relative effects of vibration in three directions on hard and upholstered seats are disclosed together with suggested instrumentation with the accelerometer. The rating of vehicles of transportation by a comfort scale is easily accomplished by the use of the accelerometer.
1936-01-01
Technical Paper
360147
Karl Lürenbaum
MUCH remains to be desired in the vibration characteristics of present crankshaft-propeller systems, in the opinion of the author. Discrepancies between torque-stand and flight measurements of torsional vibration on the same engine may explain propeller fractures due to the vibration of flexure. Recent fatigue fractures of crankshafts, differing from those due to torsional vibration, must be attributed to longitudinal vibration. Degrees of freedom are discussed with a graphical summary of vibration frequencies. Vibration forms, sources, stresses, and resonances are subjected to mathematical analysis. Three roads open to effective measures against vibration are given as: direct elimination of sources; subsequent destruction or damping of existing vibrations; and changing the pitch of the vibrating system, or displacing the resonance points to fields outside of the operating range. Of these methods the last is believed to be the most promising.
1936-01-01
Technical Paper
360137
George R. Cunnington
THE noise problem in the automobile body is complex and encompassing due to the fact that no single angle of attack is either complete or by itself sufficient to produce the desired results. Such results must be in the final analysis appreciable to the passenger's ear. For practical purposes and to meet the requirements of the industry, the problem has been divided into two parts: (a) To secure better results or greater improvements, for the same cost or less, by finding the best materials suitable in the general body-insulation practices of today. (b) To secure a complete and well-balanced job, involving a broader application of materials found to be most practical and economical, or to develop unusual products possessing unusual properties and larger capacities to function properly under given conditions. The instruments and very thorough method used are just means to an end, as in other fields of research or experimentations in which so many here have played a part.
1936-01-01
Technical Paper
360105
E. S. Taylor
CRANKSHAFT torsional vibration has become a serious problem in aircraft engines. Thanks to much experimental work, we now have a good working knowledge of the two phases of the problem, the elastic and inertia characteristics of the crankshaft-propeller combination and the forces to which this system is subjected. Methods used in the past to reduce vibration have been to change the elastic characteristics of the crankshaft, or to incorporate direct damping or some form of vibration damper of which the Lanchester and the resonant damper are examples. All of these methods have serious limitations. An interesting device which is capable of eliminating vibration in constant speed machinery is the undamped absorber. For variable speed machinery this absorber is of no value. By arranging an undamped absorber so that the restoring force varies with speed, it is possible, theoretically, to eliminate vibration in certain variable speed machinery.
1935-01-01
Technical Paper
350020
J. S. Parkinson
1934-01-01
Technical Paper
340005
Arthur W. Bull
1934-01-01
Technical Paper
340026
Schuyler Hazard
1934-01-01
Technical Paper
340076
Stephen J. Zand
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
340101
Theodore M. Prudden
1934-01-01
Technical Paper
340102
E. J. Abbott
THE desirability of measuring sound by soundmeter, rather than by listening with human ears, is expressed by the author, who states that soundmeter measurements indicate definitely just what components of noises must be reduced and also just what has been accomplished by any given change. Usually, they may be taken so as to indicate the part responsible for the noise, and even the nature of the defect. He then considers some fundamental characteristics of human ears and of various sounds. The apparent inconsistencies of the mass of data obtained from soundmeter measurements made in connection with practical noise-problems are explained, and the physical problem of what soundmeters measure is presented, together with a discussion of the subject of sound pressure and the use of the decibel scale of sound measurement which includes definitions of the various terms and units employed.
1934-01-01
Technical Paper
340027
R. F. Norris
1934-01-01
Technical Paper
340006
W. Briggs, M. L. Fox
1933-01-01
Technical Paper
330042
O. E. Kurt
THIS paper presents the solution of the factors in tires and wheels that cause a particular type of front-end vibration termed “tramp,” which is a vertical vibration of the front axle accompanied by a small degree of simultaneous oscillation of the wheel assembly about the king pin. This vibration in turn sets up the disturbance of the body and chassis. The front-axle vibration is caused by the unbalance and variation in rolling radius of the rotating front-wheel assemblies. The theoretical action of these two factors is developed in detail and supported by experimental results. The foregoing two factors act independently. The resultant of the two periodic forces which they set up depends on their phase relationship.
1932-01-01
Technical Paper
320050
C. L. Humphrey
INSULATING of automobile bodies against noise and heat has been made more complicated by the trend toward lower and more compact bodies and larger and more powerful engines, as more noise and heat are created and must be excluded from the body. Development of the all-steel body also has presented a new problem that calls for different treatment than the composite steel and wood body. Elimination of noise and heat from the body is the mutual problem of the chassis and the body engineers and must be attacked jointly, correction of the trouble being made at the most logical and practical places. Much successful work has been done in the last few years to eliminate noise and heat, but much more can be accomplished by further concentrated effort. After listing the more objectionable chassis noises which have received most attention, the author considers the remaining noise and the heat against which the body must be insulated.
1931-01-01
Technical Paper
310026
Harry F. Huf, J. R. Sabina, J. Bennett Hill
MEASURING knock-sound intensity by a microphone and vacuum-tube amplifying set is described in this paper. Widely varying fuels are compared with mixtures of normal heptane and iso-octane at knock intensities ranging from incipient knock to a knock severe enough to cause preignition. The conclusion is drawn that, for tests on the L-head Cooperative Fuel-Research knock-testing engine, the intensity of knock at which tests are made does not affect the knock ratings if a fuel-matching method is used.
1931-01-01
Technical Paper
310014
A. D. Gardner
STATING the automotive cooling-fan problem as being constituted of the delivery of more air, decrease of fan horsepower, reduction of fan noise so that it is comparable with or less than other powerplant noises and the installation of the fan in a restricted space, the author describes the testing apparatus and method used in analyzing the subject. Fan speeds and the most effective number of blades are then considered, followed by analyses of fan diameter and pitch and curvature of fan blades. The manner in which air is discharged from the fan and the adaptation of a fan to an automobile are also discussed. Following statements concerning the desirable number of fan blades and blade spacing, noise characteristics of fans are analyzed in detail as a preface to the author's consideration of means of reducing fan noise, and a summary listing the conclusions reached as a result of the study is appended.
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