Denver & Rio Grande 4-6-2 "Pacific" Locomotives in the USA

Class F-3 (Locobase 16211)

Data from DeGolyer, Volume 45, p. 315. (Thanks to Chris Hohl for his 1 May 2016 reporting the original road numbers, boiler pressure setting, and tender capacity and weights as delivered. A review of the entry prompted Locobase to add a entry here on the original design.) Works numbers were 39144-39149 in January 1913.

Originally delivered to the Denver-Grand Junction, these were the Rio Grande's only Pacifics. The class's operating environment included high altitudes, 4% ruling grades, rail elevation of 6 deg, and curve radii as tight as 16 deg. In the Baldwin specs is a stricture limiting adhesion weight to 162,000 lb (73,482 kg), which which the builder successfully complied.

They were also among the few classes of 4-6-2s that had square cylinder dimensions. It seems clear that the D&RG was very interested in steam supply; it specified 16" (406 mm) piston valves, an unusually large diameter for a Pacific. Exhaust steam injectors of two types preheated the water. On the right side was a No. 11 size Simplex 12-tube lifting type and a no 11 Nathan non-lifting type was fitted on the left. These are probably the "Cylinders and operating mechanism" mentioned in the specs "for heating the steam to not less than 200 degrees superheat."

The sextet went through an update later on; see Locobase 1430.

Class P-44 (Locobase 1430)

Data from 1937 D&RGW locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for his 1 May 2016 reporting the original road numbers, boiler pressure setting, and tender capacity and weights as delivered. A review of the entry prompted Locobase to add a entry on the original design.)

Originally delivered to the Denver-Grand Junction as class F-3 and numbered 1001-1006, these were the Rio Grande's only Pacifics; see Locobase 16211 for the original specifications.

A later upgrade included the addition of 84 sq ft of Nicholson thermic syphons and a rise in boiler pressure to 200 psi (13.8 bar). Sellers E2 exhaust steam injectors replaced the original Nathan installation and tender capacity increased to 17 tons.

The class served the D&RGW until 1949.