Merida- Valladolid 4-4-0 Locomotives in Mexico

Class Details by Steve Llanso of Sweat House Media

Class Tunkas (Locobase 11744)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 21, p. 203. Baldwin works numbers 16203 in September 1898.

Four years after this engine arrived on the M-V, that railway merged with the Merida a Calkini and Merida a Peto to form the Ferrocarriles Unidos de Yucatán.

Among the 24 locomotives supplied by Baldwin over the years to the three railways, only the Tunkas originally arrived as a compound. In this pint-sized Vauclain compound Eight-wheeler, the two cylinders on each side were served by a 7" (177 mm) piston valve.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID11744
RailroadMerida- Valladolid
Number in Class1
Road Numbers7
Number Built1
BuilderBurnham, Williams & Co
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m) 7.50 / 2.29
Engine Wheelbase (ft / m)18.58 / 5.66
Ratio of driving wheelbase to overall engine wheelbase 0.40
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)29,000 / 13,154
Engine Weight (lbs / kg)45,000 / 20,412
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)
Tender Water Capacity (gals / ML)1400 / 5.30
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)24 / 12
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)45 / 1143
Boiler Pressure (psi / kPa)180 / 12.40
High Pressure Cylinders (dia x stroke) (in / mm)8" x 18" / 203x457
Low Pressure Cylinders (dia x stroke) (in / mm)14" x 18" / 356x457
Tractive Effort (lbs / kg)5905 / 2678.47
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.91
Heating Ability
Tubes (number - dia) (in / mm)113 - 2" / 51
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m) 8.81 / 2.69
Firebox Area (sq ft / m2)60.50 / 5.62
Grate Area (sq ft / m2) 9.66 / 0.90
Evaporative Heating Surface (sq ft / m2)577 / 53.62
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)577 / 53.62
Evaporative Heating Surface/Cylinder Volume553.23
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1739
Same as above plus superheater percentage1739
Same as above but substitute firebox area for grate area10,890
Power L13702
Power MT562.86

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