Fitchburg 4-8-0 "Mastodon" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class L1a/L1b (Locobase 7342)

Data from the B&M 8 -1919 Locomotive classes book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Originally purchased as compounds by the Fitchburg, these Twelve-wheelers came from Schenectady (L-1a 1076-1085) in 1899 and the Rhode Island works in 1900 (L1b 1086-1093). They were soon simpled (1904) as shown and renumbered as 2900s. Although the 4-8-0 was not a very popular arrangement, it still wound up on a number of roads and the B & M kept its group until 1926.

An odd note in the class listing: The 1919 listing shows "Mastodons" with numbers 2900-2924, but no evidence otherwise of 2018-2024.

NB: The direct heating surface (including the firebox heating surface) is an estimate calculated by subtracting the calculated tube heating surface from the reported total evaporative heating surface.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID7342
RailroadFitchburg (B&M)
Number in Class18
Road Numbers2900-2917
Number Built18
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)15.75 / 4.80
Engine Wheelbase (ft / m)26.50 / 8.08
Ratio of driving wheelbase to overall engine wheelbase 0.59
Overall Wheelbase (engine & tender) (ft / m)53.42 / 16.28
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)128,000 / 58,060
Engine Weight (lbs / kg)168,000 / 76,204
Tender Loaded Weight (lbs / kg)98,000 / 44,452
Total Engine and Tender Weight (lbs / kg)266,000 / 120,656
Tender Water Capacity (gals / ML)4500 / 17.05
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)8 / 7
Minimum weight of rail (calculated) (lb/yd / kg/m)53 / 26.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55 / 1397
Boiler Pressure (psi / kPa)180 / 12.40
High Pressure Cylinders (dia x stroke) (in / mm)20" x 28" / 508x711
Tractive Effort (lbs / kg)31,156 / 14132.14
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.11
Heating Ability
Tubes (number - dia) (in / mm)320 - 2" / 51
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)15 / 4.57
Firebox Area (sq ft / m2)170 / 15.80
Grate Area (sq ft / m2)29.90 / 2.78
Evaporative Heating Surface (sq ft / m2)2673 / 248.42
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)2673 / 248.42
Evaporative Heating Surface/Cylinder Volume262.57
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation5382
Same as above plus superheater percentage5382
Same as above but substitute firebox area for grate area30,600
Power L15710
Power MT393.39

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