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 Middle Run Media | |
|---|---|
| Class | Tunkas |
| Locobase ID | 11744 |
| Railroad | Merida- Valladolid |
| Country | Mexico |
| Whyte | 4-4-0 |
| Number in Class | 1 |
| Road Numbers | 7 |
| Gauge | 3' |
| Number Built | 1 |
| Builder | Burnham, Williams & Co |
| Year | 1898 |
| Valve Gear | Stephenson |
| 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 / 1240 |
| 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 Volume | 553.23 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 1739 |
| Same as above plus superheater percentage | 1739 |
| Same as above but substitute firebox area for grate area | 10,890 |
| Power L1 | 3702 |
| Power MT | 562.86 |