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Viewing 7741 to 7770 of 7797
1947-01-01
Technical Paper
470153
D. S. KING
1947-01-01
Technical Paper
470136
JOHN M. PICTON
1947-01-01
Technical Paper
470135
HAROLD L. ERICSON
1947-01-01
Technical Paper
470119
L. F. HOPE
1947-01-01
Technical Paper
470098
W. E. BURNHAM
1946-01-01
Technical Paper
460106
L. M. Ball
ABSTRACT
1946-01-01
Technical Paper
460038
Stanley Lippert
Investigators in this country and abroad have experimentally determined human response to the kinds of vibration encountered in street traffic, elevators, ships, trains, automobiles and airplanes. Each has covered a limited range of frequencies and amplitudes and employed different descriptive terms for grading their effects on the human body. In this article the findings of a number of studies on the effects of vertical vibration are reconciled graphically, making possible an easy classification of the human responses to a vertical sinusoidal motion. The range of vibrations covered by the graph - namely, for frequencies between 0.1 and 256 cps and amplitudes between 100 and 0.00003 inches, includes the regions of interest in all modes of transportation.
1945-01-01
Technical Paper
450067
Frederic P. Porter
1944-01-01
Technical Paper
440155
LLOYD WITHROW, ARTHUR S. FRY
EXPERIMENTS have been run to find relationships between the primary causes and the outward effects of roughness as produced by a single-cylinder engine and by an 8-in-line engine. This was done by recording simultaneously on a multi-element oscillograph, oscillograms of the following phenomena: 1. Sound pressure near the engine. 2. Vibrations of the crankcase structure. 3. Lateral vibrations of the flywheel. 4. Lateral vibrations of the crankshaft. 5. Pressure development in the combustion chamber. A study of the oscillograms reveals that the sensation of roughness in both of these engines is closely related to a shock type of excitation that is developed in the crankshaft-flywheel system. In the single-cylinder engine this phenomenon was affected by any change in engine conditions which altered the development of the combustion pressures. Moreover, the sensation of roughness was greatly diminished by using a so-called “flexi-disc flywheel.”
1944-01-01
Technical Paper
440074
R. H. Widmer
1943-01-01
Technical Paper
430021
Ralph M. Guerke, George P. Knapp
1943-01-01
Technical Paper
430019
Ralph L. Leadbetter
1939-01-01
Technical Paper
390023
S. M. Cadwell, R. A. Merrill, C. M. Sloman, F. L. Yost
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.
1939-01-01
Technical Paper
390126
E. S. Ewart
1938-01-01
Technical Paper
380042
Thomas H. Peirce
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
380117
H. W. Prentis
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
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
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.
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
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.
1935-01-01
Technical Paper
350020
J. S. Parkinson
1934-01-01
Technical Paper
340005
Arthur W. Bull
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