Analyses have been conducted on the influence of axle load, track gage, and wheel contour on the hunting behavior of simplified models of wheelsets for typical freight- and passenger-car suspensions. The capability of the wheel flange to limit hunting oscillations is found to increase with wheel axle load. The use of worn wheel contours or excessively tight gage is found to increase the susceptibility of the wheelset to excessive and unstable hunting oscillations. For freight-car applications, coulomb friction in the suspension (e.g., constant-contact side bearings) may act to increase the range of speeds over which hunting will not occur and may permit operation at higher speeds for extremely straight track. However, if track irregularities are sufficient to cause a breakout of the friction, drastic hunting oscillations leading to derailment can occur. Regions of stable limit-cycle hunting and unstable operating conditions are defined. Computational algorithms and computer programs for predicting the boundaries of stable, unstable, and limit-cycle behavior for the wheelset and more complex rail-car analytic models, using the describing-function type of analysis, are presented and reviewed.
Carlos Chávez is a composer before he is anything else. Although he has become known, in his native Mexico and elsewhere, as a conductor, administrator, and writer as well, he himself has regarded those other activities as adjuncts to, necessary extensions of (rather than substitutes for), his composing. For the academic year 1958–59 he is Charles Eliot Norton Professor at Harvard University. He will deliver the six required lectures. He is arranging concerts as part of his tenure of the honored professorship. But he undoubtedly regards the concerts, the lectures, and the book that will come out of them as integrally relevant to his continuing education and development as a composer.
A passenger railcar was modeled using quasi-linear, frequency domain computer simulation models to compute lateral and vertical rms wheelset forces and relative displacements over a range of speeds, in response to power spectra representations of track geometry deviations in surface, alinement, and crosslevel. A simplified wheel-climb criterion (Lateral to Vertical Force Ratio, L/V) was used to estimate the margin of safety for wheel-climb and to impose limits on combined track geometry deviations which result in development of lateral and vertical forces which would cause a commonly used threshold value to be exceeded on a statistical basis. “Constant performance” contours of speed versus combined track geometry deviations are developed for selected L/V threshold values and exceedance probabilities.
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