Abstract
Cole’s Ratios, by the use of which the tractive-force curves of locomotives can be calculated and plotted, knowing certain of the locomotive dimensions, have been successfully used for the past 15 to 18 years. The Type E superheater, the feedwater heater, long-travel valve motions, and certain changes and refinements in proportion and design have tended to increase the power of steam locomotives built since 1920. The power calculated by Cole’s method does not therefore accurately represent the actual power of modern steam locomotives. In his paper the author reviews the work of Cole and others, checking it against available test-plant and road-test data, and finds that some of Cole’s constants still hold good in a great many cases. Others he finds it necessary to modify not only as to the figures, but also as to the method itself.
He develops constants for a new, easily applied method, based on boiler evaporation and a factor depending on the number of revolutions of the driving wheels, for use in connection with modern locomotives, and suggests the continued use of Cole’s Ratios for locomotives in the design of which the modern factors are not included.
