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|
|Railroad||Mobile & Ohio (M&O))|
|Number in Class||1|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.38|
|Overall Wheelbase (engine & tender)||44.96'|
|Axle Loading (Maximum Weight per Axle)|
|Weight on Drivers||54000 lbs|
|Engine Weight||86000 lbs|
|Tender Light Weight||75000 lbs|
|Total Engine and Tender Weight||161000 lbs|
|Tender Water Capacity||3000 gals|
|Tender Fuel Capacity (oil/coal)||10 tons|
|Minimum weight of rail (calculated)||45 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||140 psi|
|Cylinders (dia x stroke)||17" x 24"|
|Tractive Effort||14739 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||3.66|
|Firebox Area||107.80 sq. ft|
|Grate Area||11.10 sq. ft|
|Evaporative Heating Surface||1349 sq. ft|
|Combined Heating Surface||1349 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||213.96|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||1554|
|Same as above plus superheater percentage||1554|
|Same as above but substitute firebox area for grate area||15092|