Denver, South Park & Pacific 2-6-6 Locomotives in the USA

Class D H 1 (Locobase 16514)

Data from 17 November 2018 email from Chris Hohl; Ross Crain, "Denver, South Park and Pacific Railroad DSP&P Mason Bogie 2-8-6T Locomotives" at Crain's Denver, South Park & Pacific Railroad Pages ( []), last accessed 7 December 2018, as well as his "DSP&P LOCOMOTIVE SPECIFICATIONS -- 1885 Extracts from James Ehernberger's "Union Pacific Equipment List - 1885" at [], last accessed 21 November 2020. See also "Explanation of the Bogie System of Locomotives", Scientific American Supplement, Volume IX [9], No 215 (14 February 1880), p. 3418. (Thanks to Chris Hohl for correcting the confusion between road numbers and builders' numbers and for supplying additional data, including the link to the Ehernberger extract.) Works numbers were 591 in May 1878, 597 in November, 599-600 in April 1879, 601-602 in May, 607-608 in August, 609--610 in September, 611-612 in October.

These Mason "double bogies" comprised the bulk of the DSP&P's early motive power roster. Scientific American's 1880 explanation of this "indispensable" system eerily prefigures Herbert Garratt's very similar rationale for his famous articulated locomotives, although there were fundamental differences in how they were laid out. (Certain internal clues suggest the report was originally drafted by the Mason Works.)

Mason's design placed the boiler and tank (water and fuel) on a rigid frame. The three-axle powered bogie unit pivoted around a central post under the boiler; the after bogie similarly traversed under the tank at the rear of the cab. The bogies' "springs, jointed steam pipes, etc., the whole working becomes perfectly articulated" and insulated the rigid section from undulations and "divides its inequalities through the whole system that the disturbing forces are reduced to a minimum, or nearly lost."

The 1880 report consided the layout "particularly advantageous" to narrow-gauge oiperation for two reasons. One was the ease of traversing "quick curves" and climbing steep grades. Given its location between the pivots, the firebox and boiler could be made to "any width or length." SA praised the engines' "steaming qualities, their economy in fuel, and also wonderful performance on long steep grades, where they never 'get out of breath.'". The account referred to "immense loads".

All originally carried names: Oro City, San Juan, Ten Mile, Gunnison, Lake City, Kenosha, Granite, Ouray, Como, Ruby, Twin Lakes, and Breckenridge. The 9, 14, and 15 were delivered with the same boiler and firebox, but had 14" x 16" cylinders.

Despite the claims, however, the entire class had short careers. The Union Pacific bought a majority interest in the railroad in 1885 and in 1889 reorganized the DSP&P as the Denver, Leadville & Gunnison. By then, Locobase suspects, the railroad found that the design proved susceptible to derailments and that springs and those center posts may have failed too often because of the uneven, lightly built tracks. The entire class had been scrapped by the mid-1890s.

For the slightly larger set arrived soon after these, see Locobase 16515.

Class D L 1 (Locobase 16515)

Data from 17 November 2018 email from Chris Hohl; Ross Crain, "Denver, South Park and Pacific Railroad DSP&P Mason Bogie 2-8-6T Locomotives" at Crain's Denver, South Park & Pacific Railroad Pages ( []), last accessed 7 December 2018, as well as his "DSP&P LOCOMOTIVE SPECIFICATIONS -- 1885 Extracts from James Ehernberger's "Union Pacific Equipment List - 1885" at [], last accessed 21 November 2020. See also "Explanation of the Bogie System of Locomotives", Scientific American Supplement, Volume IX [9], No 215 (14 February 1880), p. 3418. (Thanks to Chris Hohl for correcting the confusion between road numbers and builders' numbers and for supplying additional data, including the link to the Ehernberger extract.) Works numbers were 613-614 in November 1879, 615-616 in December, and 617-618 in February 1880.

A full description of the slightly smaller 1787 Mason "double bogies" appears in Locobase 16514. This version, which

All originally carried names: Eureka, Silverton, Pitkin City, Crested Butte, Grant, and Buena Vista. All but the Buena Vista (renumbered 57 in 1889) were scrapped before the DL&G was reorganized with other railroads as the Colorado & Southern in 1894. The 57 took road #1, but was scrapped within the year.