Abstract
Tendencies toward increase in speed have focussed attention on modifications in present axle proportions. High-speed locomotives require corresponding considerations, particularly in the proportioning of locomotive crank pins.
Great credit should be given to those responsible for the introduction of the standard A.A.R. axle, which has suitable proportions for normal operating conditions. With increased speeds, modifications of these established proportions are necessary. While the necessity for modification in the proportions has been recognized, the question of proper ratings for high-speed axles is still a matter for considerable discussion. The object of this paper has been to set forth various aspects of loading conditions and stress limitations. A comparison of various methods of axle proportioning has been made with the suggestion of a new interpretation of loadings. While axle design is necessarily empirical, based on statistical data of axle failures, it is desirable to guide the interpretation of such data by closer approximation to the true loading conditions. For this reason, the subject of axle design has been divided into two parts. Part 1 covers the subject of present methods of axle proportioning and an analysis of the division of the loading into various components; some consideration is given to stress concentrations and endurance limits of the material. In Part 2 some characteristics of the nature of dynamic loadings is given, based on simplification of various conditions met in actual operation. Part 3 of the paper discusses a correlated subject, locomotive crank pins.