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

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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 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.

Specifications by Steve Llanso of Sweat House Media
ClassF-3P-44
Locobase ID16,211 1430
RailroadDenver & Rio Grande (D&RGW)Denver & Rio Grande (D&RGW)
CountryUSAUSA
Whyte4-6-24-6-2
Number in Class66
Road Numbers1001-1006800-805
GaugeStdStd
Number Built6
BuilderBaldwinD&RGW
Year19131924
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.50 / 3.8112.50 / 3.81
Engine Wheelbase (ft / m)33.67 / 10.2633.67 / 10.26
Ratio of driving wheelbase to overall engine wheebase 0.37 0.37
Overall Wheelbase (engine & tender) (ft / m)65.04 / 19.8265.48 / 19.96
Axle Loading (Maximum Weight per Axle) (lbs / kg)54,800 / 24,857
Weight on Drivers (lbs / kg)162,000 / 73,482160,440 / 72,774
Engine Weight (lbs / kg)262,000 / 118,841261,080 / 118,424
Tender Loaded Weight (lbs / kg)175,800 / 79,742183,500 / 83,234
Total Engine and Tender Weight (lbs / kg)437,800 / 198,583444,580 / 201,658
Tender Water Capacity (gals / ML)9000 / 34.099000 / 34.09
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.7017 / 15.50
Minimum weight of rail (calculated) (lb/yd / kg/m)90 / 4589 / 44.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)67 / 170267 / 1702
Boiler Pressure (psi / kPa)185 / 12.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)26" x 26" / 660x66026" x 26" / 660x660
Tractive Effort (lbs / kg)41,251 / 18711.1644,596 / 20228.43
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.93 3.60
Heating Ability
Firebox Area (sq ft / m2)234 / 21.74317 / 29.45
Grate Area (sq ft / m2)63 / 5.8563 / 5.85
Evaporative Heating Surface (sq ft / m2)3497 / 324.883654 / 339.46
Superheating Surface (sq ft / m2)778 / 72.28778 / 72.28
Combined Heating Surface (sq ft / m2)4275 / 397.164432 / 411.74
Evaporative Heating Surface/Cylinder Volume218.88228.70
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,65512,600
Same as above plus superheater percentage13,75314,868
Same as above but substitute firebox area for grate area51,08274,812
Power L115,08817,111
Power MT615.99705.37

Reference