Denver & Rio Grande Western 2-6-6-2 "Mallet Mogul" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class 340/L-62 (Locobase 294)

Data from D&RGW 1956 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Eight Mallet compounds for helper service in Soldier Pass and Tennessee Pass. They were delivered as saturated-steam locomotives described in Locobase 16364. As shown in the specs, however, they were later superheated.

The usual exchange of small tubes for larger flues dropped the total evaporative heating surface area both because of the lower number but the smaller diameter (2" vs 2 1/4" in the original boiler) of each tube. They retained the short combustion chamber that contributed 40 sq ft (37.2 sq m) to the firebox heating surface area. The updated HP cylinders gained 1/2" (12.7 mm) in diameter.

Retired in 1947-1952.


Class L-76 (Locobase 1466)

These two Mallet compounds were bought from the Norfolk & Western by the Denver & Rio Grande Western in 1947 to beef up helper service Retired in 1952 and 1950, respectively.

Data from 1952 D & RGW locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Principal Dimensions by Steve Llanso of Sweat House Media
Class340/L-62L-76
Locobase ID294 1466
RailroadDenver & Rio Grande Western (D&RGW)Denver & Rio Grande Western (D&RGW)
CountryUSAUSA
Whyte2-6-6-22-6-6-2
Number in Class82
Road Numbers3300-33073350-3351
GaugeStdStd
Number Built
BuilderD&RGAlco-Schenectady
Year19101916
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10.33 / 9.2410 / 3.05
Engine Wheelbase (ft / m)46.33 / 14.1248.83 / 14.88
Ratio of driving wheelbase to overall engine wheebase 0.22 0.20
Overall Wheelbase (engine & tender) (ft / m)74.50 / 22.7190.77 / 27.67
Axle Loading (Maximum Weight per Axle) (lbs / kg)51,600 / 23,40562,600 / 28,395
Weight on Drivers (lbs / kg)295,500 / 134,037364,500 / 165,335
Engine Weight (lbs / kg)340,000 / 154,222427,000 / 193,684
Tender Loaded Weight (lbs / kg)159,000 / 72,121286,533 / 129,969
Total Engine and Tender Weight (lbs / kg)499,000 / 226,343713,533 / 323,653
Tender Water Capacity (gals / ML)8800 / 33.3316,000 / 60.61
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.7023 / 20.90
Minimum weight of rail (calculated) (lb/yd / kg/m)82 / 41101 / 50.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)57 / 144857 / 1448
Boiler Pressure (psi / kPa)210 / 14.50225 / 15.50
High Pressure Cylinders (dia x stroke) (in / mm)20.5" x 32" / 521x81322" x 32" / 559x813
Low Pressure Cylinders (dia x stroke) (in / mm)33" x 32" / 838x81335" x 32" / 889x813
Tractive Effort (lbs / kg)60,774 / 27566.6674,498 / 33791.76
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.86 4.89
Heating Ability
Firebox Area (sq ft / m2)250 / 23.23391 / 36.34
Grate Area (sq ft / m2)54.40 / 5.0572.20 / 6.71
Evaporative Heating Surface (sq ft / m2)3449 / 320.424629 / 430.20
Superheating Surface (sq ft / m2)657 / 61.04971 / 90.24
Combined Heating Surface (sq ft / m2)4106 / 381.465600 / 520.44
Evaporative Heating Surface/Cylinder Volume282.14328.79
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,42416,245
Same as above plus superheater percentage13,25219,007
Same as above but substitute firebox area for grate area60,900102,931
Power L166839192
Power MT299.16333.58

All material Copyright © SteamLocomotive.com
Wes Barris