Berlin Mills 2-6-2 "Prairie" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 9 (Locobase 15493)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Vol 80, pp. 158. See also the Steamtown National Historical Site's Special History Study on the Berlin Mills Railway 2-4-2T Locomotive No. 7, as archived at [], last accessed 18 October 2013. Works numbers were 60863 in June 1929 and 61423 in July 1930.

By the time the 9 came into service, Brown Company's Berlin Mills railroad had reached its maximum extent: 3.75 miles (6 km) of "main line" track (the spur to the Grand Trunk) and 13.75 miles (22.1 km) of plant trackage, for a total track mileage of 17.50 (28.1 km). The NPS study says that the rail weighed 60 or 70 lb/yard (30-35 kg/metre), but the Baldwin specs say that the 9 would roll on 80 lb/yard (40 kg/metre) rail. Curves reached an extremely tight 46 degrees (radii of 125 feet).

These saddle tanks bulked quite large for the arrangement. A few had bigger boilers, but the 9 and 10 put more weight on the rail than any of them. They also used 10" (254 mm) to serve the cylinders. To accommodate the curves, both trucks had significant swing with the front truck moving up to 6 1/2" (165 mm) each side and th rear truck 6" (152 mm). Even with that provision, the specs still call on the builder to pay special attention "to swing of engine at front and rear on 46 degree curves."

Gene Connelly's Baldwin list doesn't record what became of the 9, but shows the 10 as scrapped in August 1960.

Principal Dimensions by Steve Llanso of Middle Run Media

Locobase ID15493
RailroadBerlin Mills
Number in Class2
Road Numbers9-10
Number Built2
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m) 8.50 / 2.59
Engine Wheelbase (ft / m)24.50 / 7.47
Ratio of driving wheelbase to overall engine wheelbase 0.35
Overall Wheelbase (engine & tender) (ft / m)24.50 / 7.47
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)131,000 / 59,421
Engine Weight (lbs / kg)167,000 / 75,750
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)167,000
Tender Water Capacity (gals / ML)3000 / 11.36
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)2 / 2
Minimum weight of rail (calculated) (lb/yd / kg/m)73 / 36.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)44 / 1118
Boiler Pressure (psi / kPa)185 / 12.80
High Pressure Cylinders (dia x stroke) (in / mm)19" x 24" / 483x610
Tractive Effort (lbs / kg)30,964 / 14045.05
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.23
Heating Ability
Tubes (number - dia) (in / mm)244 - 2" / 51
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)10.67 / 3.25
Firebox Area (sq ft / m2)115 / 10.68
Grate Area (sq ft / m2)22 / 2.04
Evaporative Heating Surface (sq ft / m2)1467 / 136.29
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)1467 / 136.29
Evaporative Heating Surface/Cylinder Volume186.17
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation4070
Same as above plus superheater percentage4070
Same as above but substitute firebox area for grate area21,275
Power L13516
Power MT177.51

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