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

By 1912, the Denver Rio Grande & Western's premium passenger trains had grown so long that even double-headed 4-6-0s were having difficulty maintaining the schedules. Baldwin provided the answer to improve on-time performance in the form of six 4-6-2s. Using the same boiler as the 2-8-2s Baldwin built for the road in 1912, and the reletively low 67" drivers of the 4-6-0s, the P-44 class had fireboxes with twice the grate area and nearly fifty percent more tractive effort compared to the most modern 4-6-0s on the DRG&W. Double heading was eliminated, except for the four percent grades over Tennessee Pass and Soldier Summit.

The P-44 pulled the east bound "Atlantic Coast Limited" and the west bound "Pacific Coast Limited" until 1922, when they were replaced by 4-8-2s. The P-44s were then used on secondary mainline trains until 1945, when they replaced the 4-6-0s on the passenger trains of the Craig, Montrose, and Alamosa branches. The six pacifics were scrapped between 1949 and 1953.

Class Details by Steve Llanso of Sweat House Media

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 Raildata collection. (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.

Specifications by Steve Llanso of Sweat House Media
Locobase ID16211 1430
RailroadDenver & Rio Grande (D&RGW)Denver & Rio Grande (D&RGW)
Number in Class66
Road Numbers1001-1006800-805
Number Built6
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase12.50'12.50'
Engine Wheelbase33.67'33.67'
Ratio of driving wheelbase to overall engine wheebase 0.37 0.37
Overall Wheelbase (engine & tender)65.04'65.48'
Axle Loading (Maximum Weight per Axle)54800 lbs
Weight on Drivers162000 lbs160440 lbs
Engine Weight262000 lbs261080 lbs
Tender Light Weight175800 lbs183500 lbs
Total Engine and Tender Weight437800 lbs444580 lbs
Tender Water Capacity9000 gals9000 gals
Tender Fuel Capacity (oil/coal)14 tons17 tons
Minimum weight of rail (calculated)90 lb/yard89 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter67"67"
Boiler Pressure185 psi200 psi
Cylinders (dia x stroke)26" x 26"26" x 26"
Tractive Effort41251 lbs44596 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.93 3.60
Heating Ability
Firebox Area234 sq. ft317 sq. ft
Grate Area63 sq. ft63 sq. ft
Evaporative Heating Surface3497 sq. ft3654 sq. ft
Superheating Surface778 sq. ft778 sq. ft
Combined Heating Surface4275 sq. ft4432 sq. ft
Evaporative Heating Surface/Cylinder Volume218.88228.70
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1165512600
Same as above plus superheater percentage1375314868
Same as above but substitute firebox area for grate area5108274812
Power L11508817111
Power MT615.99705.37


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