The TM was chartered in 1875 as the 3-foot-gauge (914 mm) Corpus Christi, San Diego & Rio Grande and completed 52 miles (84 km) to San Diego, Texas by 1879 and another 110 miles (177 km) to Laredo by September 1881. At that point, the owners sold the line to the Mexican National Railway then being built between Nuevo Laredo and Mexico City.
After seven years under the MNR's mantle, the TM regained its independence. It converted to standard gauge in 1902 and absorbed the Texas Mexican Northern in 1906.
These modestly scaled oil-burning Ten-wheelers were the passenger power on the TM (at least they were described as passenger engines by Baldwin. Superheated as they were, they used 9 1/2" (241 mm) piston valves to supply steam to the cylinders. A note entered on the 1922 spec instructed the painters that "Flat colors will not stand in this hot climate, nor will white lead primers." So they used instead "one coat of Celox liquid primer, rough stuffed, then two coats of Valspar black, lettered, then two coats of Valentine"s Valspar varnish."
The 1 was delivered to the TM, sometime later operated as a logging engine for the R Gonzalez and Brother operation, and returned to the TM. The 2 arrived almost three years later and weighed slightly more (1,500 lb/680 kg more on the drivers, 2,000 lb/907 kg).
Once the TM dieselized in 1939 (the earliest railroad to go all diesel in the US, or possibly anywhere), the 1 found a home on the Frost Lumber Company's Arkansas & Louisiana Missouri timber railway headquartered at Crossett, Ark. It was scrapped decades later in December 1961.
Locobase 14964 shows the two "passenger" engines delivered to the TM in 1920 and 1922. (We know they hauled people because Baldwin's spec said specifically that the service was "passenger".) A year after the 1 arrived, the 11 and 12 followed with longer, deeper fireboxes and more tubes and flues. Most ratios remained the same, however, and these were also oil-burning Ten-wheelers.
Although they rolled on 58" drivers (i.e. 2" taller than the 1's), the 'teen engines were classed as freighters. Their adhesive wheelbases stretched 33" (838 mm) further and the engine wheelbase measured 35" (889 mm) greater.
The 12 was sold to the Reader Railroad, but kept its road number. The 11 was off the roster by 1947.
The Midland Route was chartered on 1 December 1892 to run between Garrett and Greenville, but already included 51 miles of line between Garrett and Roberts built originally by the Houston & Texas Central. The railroad eventually reached the H & TC's original goal at Paris.
Locobase 14964 shows the two oil-burning Ten-wheelers that introduced a slightly bigger boiler and firebox to the TexMex compared to the 1 of 1920. In 1924, Baldwin produced more in this line in which weight distribution changed and power increased.
Tweaks to the power dimensions involved a 10 psi (0.7 bar) increase in boiler pressure and a 2" (50.8 mm) drop in driver diameter. The engines also registered a significant weight shift off the front bogie truck to the drivers. Piston valve diameter grew 1/2" to 10" (254 mm) Engine weight grew by only 1,500 lb (680 kg), but adhesion weight rose by more than six short tons to 123,500 lb (56,018 kg). Also, the front pair of drivers had only 53" (1,346 mm) between the insides of the tires to allow 1" (25.4 mm) of track play in either direction.
Gene Connelly's magisterial work on Baldwin production couldn't provide much data on this class's later career after the TM went all-diesel in 1939. Later information from Al Weber's creation of data cards for each works number showed that the 14 was scrapped in 1947, 15 went to Crossett, Ark in 1947 to run on the Arkansas & Louisiana Missouri. 16 was off the Tex-Mex roster by 1947.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Texas Mexican||Texas Mexican||Texas Midland||Texas Mexican|
|Number in Class||2||2||2||3|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.52||0.57||0.58||0.57|
|Overall Wheelbase (engine & tender)||51.27'||53.29'||46'||53.29'|
|Axle Loading (Maximum Weight per Axle)|
|Weight on Drivers||105500 lbs||111000 lbs||76500 lbs||123500 lbs|
|Engine Weight||137500 lbs||156500 lbs||104000 lbs||158000 lbs|
|Tender Light Weight||109000 lbs||132500 lbs||132500 lbs|
|Total Engine and Tender Weight||246500 lbs||289000 lbs||290500 lbs|
|Tender Water Capacity||5000 gals||6000 gals||3500 gals||6000 gals|
|Tender Fuel Capacity (oil/coal)||2000 gals||3000 gals||gals||3000 gals|
|Minimum weight of rail (calculated)||59 lb/yard||62 lb/yard||43 lb/yard||69 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||180 psi||180 psi||160 psi||190 psi|
|Cylinders (dia x stroke)||19" x 26"||20" x 26"||18" x 24"||20" x 26"|
|Tractive Effort||25644 lbs||27434 lbs||18885 lbs||29993 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.11||4.05||4.05||4.12|
|Firebox Area||138 sq. ft||162 sq. ft||133.28 sq. ft||162 sq. ft|
|Grate Area||28.30 sq. ft||28.50 sq. ft||17.23 sq. ft||28.50 sq. ft|
|Evaporative Heating Surface||1574 sq. ft||1714 sq. ft||1556 sq. ft||1714 sq. ft|
|Superheating Surface||332 sq. ft||363 sq. ft||363 sq. ft|
|Combined Heating Surface||1906 sq. ft||2077 sq. ft||1556 sq. ft||2077 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||184.48||181.30||220.13||181.30|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||5094||5130||2757||5415|
|Same as above plus superheater percentage||5960||6002||2757||6336|
|Same as above but substitute firebox area for grate area||29063||34117||21325||36013|