On the stability of running of locomotives

Abstract

In a paper entitled “The Electric Locomotive,” read before the Institution of Civil Engineers in 1916, the author gave the beginnings of a rational discussion of the riding qualities of electric locomotives, as affected by their fundamental type. It was shown that, aside from all questions of unevenness of track or of the nature of the springing and equalizing arrangements, there might exist in a locomotive an inherent tendency to deviate from a motion of pure progression, which, although perhaps within the control of the wheel flanges and therefore deemed unobjectionable on good track, might give reason for anxiety if poor track were encountered or other external circumstances conspired with inherent tendencies to bring about a condition involving danger of derailment. It is the intention, in the present paper, to discuss the matter further with the view of determining to what extent inherent riding qualities of a design can be brought within the realm of rational investigation. In applying mathematical analysis to such a subject as the present, it is necessary to assume that all parts fulfil their intentions; though, actually, few do so perfectly. The track is assumed smooth, uniform and level; the clearances required by mechanical considerations, except in so far as they enter into the problem, are assumed to be zero; lubricated slides are assumed frictionless; and so on. I t must be postulated that a tendency shown by a machine in which the parts fulfil their intentions will, in general, evince itself in some form in such machines as can actually be constructed. The observed phenomena are likely to reflect the conditions in being less definite, less regular, and more catastrophic than the analysis would indicate; and the results of the present analysis are not expected to possess metrical value of a high order. This, however, is in the nature of the subject and does not detract from the value of the study of tendencies, and the importance to the designer of a knowledge of conditions tending to produce stable running.