Missouri, Oklahoma & Gulf 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 300 (Locobase 9472)

Data from KO&G 8 - 1923 Locomotive Diagrams book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange and from Data from Record of Recent Construction #91 (Baldwin Locomotive Works, 1918), p.20-21.A summary of the Muskogee Company empire appears in the Muskogee Company records, DeGolyer Library, Southern Methodist University, [], last accessed 26 April 2015; and "Missouri Kansas & Gulf 300-Class 2-6-6-2s", Muskogee Roads Historical &Technical Society's Web Site, last accessed at [] on 10 June 2018, (Thanks to Chris Hohl for his 2 May 2018 email correcting the boiler pressure and for his 27 April 2020 email correcting the engine wheelbase.) Works numbers were 38574-38578 in December 1912.

See Locobase 17 for a Handbook of Texas description of the KO&G, which succeeded the MO&G after its bankruptcy in 1919. In its palmier days (e.g., 1912), the Gulf Route treated itself to these light-footed Mallets. As the Baldwin record stated, Mallet locomotives, "...under favorable conditions, are specially suitable for heavy service onlines where wheel loads are limited on account of comparatively light tracks and bridges." And on the MO&G, rail weights could be as low as 70 lb/yard (35 kg/metre).

The locomotives had big boilers for their size and 13" (330 mm) piston valves on all four cylinders to aid steam distribution. They were rated to pull 3,000 short tons (2,727 metric tons) up a 0.6% grade when the train's frictional resistance did not exceed 6 lb/ton (3 kg/metric tonne).

The caption under a Rick Morgan photograph states "The entire class was replaced by the 500-class 2-10-2s in 1927." Condren's compilation of the KO&G roster reports that the class was retired in 1927.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID9472
RailroadMissouri, Oklahoma & Gulf (KO&G)
Number in Class5
Road Numbers300-304
Number Built5
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)19.67 / 6
Engine Wheelbase (ft / m)43.75 / 13.33
Ratio of driving wheelbase to overall engine wheelbase 0.45
Overall Wheelbase (engine & tender) (ft / m)72.64 / 22.14
Axle Loading (Maximum Weight per Axle) (lbs / kg)44,500 / 20,185
Weight on Drivers (lbs / kg)265,000 / 120,202
Engine Weight (lbs / kg)310,000 / 140,614
Tender Loaded Weight (lbs / kg)144,000 / 65,317
Total Engine and Tender Weight (lbs / kg)454,000 / 205,931
Tender Water Capacity (gals / ML)8000 / 30.30
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)13 / 12
Minimum weight of rail (calculated) (lb/yd / kg/m)74 / 37
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55 / 1397
Boiler Pressure (psi / kPa)210 / 14.50
High Pressure Cylinders (dia x stroke) (in / mm)21" x 30" / 533x762
Low Pressure Cylinders (dia x stroke) (in / mm)32" x 30" / 813x762
Tractive Effort (lbs / kg)60,024 / 27226.46
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.41
Heating Ability
Tubes (number - dia) (in / mm)191 - 2.25" / 57
Flues (number - dia) (in / mm)26 - 5.5" / 140
Flue/Tube length (ft / m)21 / 6.40
Firebox Area (sq ft / m2)198 / 18.39
Grate Area (sq ft / m2)53.40 / 4.96
Evaporative Heating Surface (sq ft / m2)3407 / 316.52
Superheating Surface (sq ft / m2)685 / 63.64
Combined Heating Surface (sq ft / m2)4092 / 380.16
Evaporative Heating Surface/Cylinder Volume283.33
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,214
Same as above plus superheater percentage13,120
Same as above but substitute firebox area for grate area48,649
Power L17281
Power MT363.44

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