Cundinamarca 4-8-0 Locomotives in Colombia

Class 9 (Locobase 15367)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 78, pp. 170 See also Jorge Arias de Greiff, "Un Momento Estelar de la Ingeniera Mecanica en Colombia: Los Disenos de Locomotoras de PC Dewhurst" (in Spanish), Boletin Cultural y Bibliographico, Volumne XXVI, No. 21, 1989, pp.19-29. Works number were 58944-58945 in January 1926.

Three Colombian railways combined to order six Twelve-wheelers on October 12, 1925. Each took a pair and the Cundinamarca's brace of superheated mixed-traffic locomotives came first. Greiff attributes the design to PC Dewhurst, who adopted the "Docerruedas" layout to put all of the non-adhesion weight of the locomotive on the leading truck without sacrificing the locomotive's ability to negotiate curves.

Indeed, Colombia's railways abounded in mountainous profiles and tight curves. Moreover, the dry-rail capacity of rail lines would be reduced by rainfall at least one out of every three days. So it made sense to put as much of the locomotive's weight to work under a large boiler and grate that would develop plenty of tractive power.

Greiff notes Dewhurst's conclusion that power for the grade would need to come from a relatively low factor of adhesion (given the narrow gauge and light rail), a wide-open throttle, high-capacity injectors to maintain water flow into the boiler under the most demanding service. These conditions inevitably pointed to a big boiler with plenty of openings to allow easy removal of the scale that bad water brought to the tubes and a wide grate to burn mediocre coal. (Dewhurst contended that while more firebox volume was usually preferred, a big grate should determine size while keeping the narrowness of the gauge in mind.)

Compared to the slightly later Consolidations (Locobase 15366), these had boilers and grates that were more than twice as big and they put 18 1/2 short tons more weight on their drivers than the 2-8-0s would weigh altogether. Dewhurst also designed the tubes to resist the strains put on them by heavy demands during long pulls up steep grades while twisting around tight curves.

Bar frames improved the ability of local machinists to get to the locomotive's innards for repairs. The leading drivers were blind (flangeless) while the last pair were set in Dewhurst-Cartazzi axle boxes that allowed some play. Thus, the engine's rigid wheel base measured only 8 feet 7 inches (2.62 metres). Indeed, curve resistances was so low that when snaking round properly superelevated curves, the "Culebras" (snakes) were known to accelerate.

Fitted with performance enhancers such as 10 sq ft (0.93 sq m) of arch tubes contributing to direct heating surface area and 9" (229 mm) piston valves for the hotter steam.

The two Cundinamarcas would later operate for the Ferrocarriles Nacionales (Centrales) as their 77-78. See Locobase 15368-15369 for the Tolima and Girardot locomotives. A total of 72 locomotives would be based on this "Tolima" design.