Mobile & Ohio 4-4-0 "American" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class 77 (Locobase 16010)

Data from Birmingham & Northwestern Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Raildata collection. See also DeGolyer, Volume 10, p. 261.Works number was 5510 in February 1881.

The use of the B&NW diagram for data is a tip-off that these were not the original dimensions outlined in the Baldwin specification page found in Volume 10. And indeed as delivered to its predecessor Mobile & Girard, the 77 had a smaller boiler (144 shorter tubes), larger firebox (wider by 8"), smaller cylinders (16" x 24"), and shorter wheelbases (8' even for the drivers, 21 ft 9 inches for the engine).

So why did the M&O shrink the firebox's width by eight inches when they rebuilt the locomotive? It's a puzzle, because the ratio of heating surface area to grate area soared well above 100.

The 77 stayed with the M&O until 1911, when it was sold to the B&NW as their 10. By May 1927, the 10 was gone from the B&NW's rolls.

NB: Locobase uses the 1885 date because the M&O converted to standard gauge and it seems likely that the rebuild occurred then. He won't fall on his sword if a reader suggests another date.

Specifications by Steve Llanso of Sweat House Media
Locobase ID16,010
RailroadMobile & Ohio (M&O))
Number in Class1
Road Numbers77
Number Built
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft) 8.54
Engine Wheelbase (ft)22.54
Ratio of driving wheelbase to overall engine wheebase 0.38
Overall Wheelbase (engine & tender) (ft)44.96
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)54,000
Engine Weight (lbs)86,000
Tender Loaded Weight (lbs)75,000
Total Engine and Tender Weight (lbs)161,000
Tender Water Capacity (gals)3000
Tender Fuel Capacity (oil/coal) (gals/tons)10
Minimum weight of rail (calculated) (lb/yd)45
Geometry Relating to Tractive Effort
Driver Diameter (in)56
Boiler Pressure (psi)140
High Pressure Cylinders (dia x stroke) (in)17" x 24"
Tractive Effort (lbs)14,739
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.66
Heating Ability
Firebox Area (sq ft)107.80
Grate Area (sq ft)11.10
Evaporative Heating Surface (sq ft)1349
Superheating Surface (sq ft)
Combined Heating Surface (sq ft)1349
Evaporative Heating Surface/Cylinder Volume213.96
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1554
Same as above plus superheater percentage1554
Same as above but substitute firebox area for grate area15,092
Power L13913
Power MT319.51

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