Bangor & Aroostook 4-8-2 "Mountain" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class M (Locobase 192)

Data from tables in 1930 Locomotive Cyclopedia and BAR 7 - 1951 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for supplying the valve gear ID and for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .) Works numbers were 68218-68221 in 1928 and 68525-68527, 68705-68706 in 1930.

Firebox had thermic syphons. Relatively small Mountain types with small drivers for low-speed freight hauling. Originally listed weight on the drivers came to 204,000 lb (92,533 kg). All ten had the same boiler and firebox.

Somehow the BAR managed to apply seven different classifications to them. 106 received its M-H subclass designation when the shops removed 40 small tubes from its boiler. Tube heating surface area dropped by 159 sq ft (14.75 sq m), which reduced total evaporative heating surface area to 3,424 sq ft (318.1 sq m).

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID192
RailroadBangor & Aroostook
Number in Class10
Road Numbers100-109
Number Built10
Valve GearBaker
Locomotive Length and Weight
Driver Wheelbase (ft / m)16.50 / 5.03
Engine Wheelbase (ft / m)38.08 / 11.61
Ratio of driving wheelbase to overall engine wheebase 0.43
Overall Wheelbase (engine & tender) (ft / m)73.67 / 22.45
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)213,360 / 96,779
Engine Weight (lbs / kg)317,490 / 144,011
Tender Loaded Weight (lbs / kg)232,000 / 105,234
Total Engine and Tender Weight (lbs / kg)549,490 / 249,245
Tender Water Capacity (gals / ML)10,000 / 37.88
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)15 / 13.60
Minimum weight of rail (calculated) (lb/yd / kg/m)89 / 44.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)62 / 1575
Boiler Pressure (psi / kPa)240 / 16.50
High Pressure Cylinders (dia x stroke) (in / mm)22.5" x 30" / 572x762
Tractive Effort (lbs / kg)49,972 / 22666.94
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.27
Heating Ability
Firebox Area (sq ft / m2)351 / 32.62
Grate Area (sq ft / m2)65.60 / 6.10
Evaporative Heating Surface (sq ft / m2)3583 / 332.99
Superheating Surface (sq ft / m2)932 / 86.62
Combined Heating Surface (sq ft / m2)4515 / 419.61
Evaporative Heating Surface/Cylinder Volume259.53
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,744
Same as above plus superheater percentage19,050
Same as above but substitute firebox area for grate area101,930
Power L124,657
Power MT1019.11

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Wes Barris