Nacional Mexicano 4-6-0 Locomotives in Mexico

Class Details by Steve Llanso of Sweat House Media

Class 103/PF-1 (Locobase 6958)

Data from FCM 1920 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 14, p. 51. Works number was 8911.

Similar to the F-1s procured by the Mexican Railway in 1882, this engine had smaller cylinders and pressed the boilers to a lesser extent. Also, the locomotives were considerably lighter and had smaller drivers. The FCM diagram credits the grate ("parrillas") with 21 sq ft (1.95 sq m) in area, the firebox ("fogon") with 611 sq ft. (56.75) and gives the total area as 1,334 sq ft.(123.95 sq m). But the numbers are all laughably high.

If, on the other hand, the original diagram meant to record 61.1 sq ft (5.67 sq m) a more likely number), then the ratios are much more likely. This supposition is further strengthened by the actual measurements of the firebox: 83 15/16" long x 24 3/8" wide x 48" deep at the front and 40 1/2" high in the back.

Later, the only survivor was placed in its own PF-1 class and assigned to the Pachuca a Tampico.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID6958
RailroadNacional Mexicano
Number in Class10
Road Numbers103-112
Number Built10
BuilderBurnham, Parry, Williams & Co
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.50 / 3.81
Engine Wheelbase (ft / m)21.83 / 6.65
Ratio of driving wheelbase to overall engine wheelbase 0.57
Overall Wheelbase (engine & tender) (ft / m)47.79 / 14.57
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)51,989 / 23,582
Engine Weight (lbs / kg)69,985 / 31,745
Tender Loaded Weight (lbs / kg)61,981 / 28,114
Total Engine and Tender Weight (lbs / kg)131,966 / 59,859
Tender Water Capacity (gals / ML)3200 / 12.12
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)1564 / 5920
Minimum weight of rail (calculated) (lb/yd / kg/m)29 / 14.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)42 / 1067
Boiler Pressure (psi / kPa)140 / 9.70
High Pressure Cylinders (dia x stroke) (in / mm)16" x 20" / 406x508
Tractive Effort (lbs / kg)14,507 / 6580.27
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.58
Heating Ability
Tubes (number - dia) (in / mm)132 - 2" / 51
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)11.83 / 3.61
Firebox Area (sq ft / m2)61.10 / 5.68
Grate Area (sq ft / m2)14.20 / 1.32
Evaporative Heating Surface (sq ft / m2)784 / 72.86
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)784 / 72.86
Evaporative Heating Surface/Cylinder Volume168.60
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1988
Same as above plus superheater percentage1988
Same as above but substitute firebox area for grate area8554
Power L12296
Power MT292.09

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