4-4-2 Steam Locomotives in Mexico

Class Nc/A-3/A-5 (Locobase 6549)

Data from SP Menke All-Time Steam Loco Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 37, pp. 34+; "Engines for the Associated Lines," Railway and Locomotive Engineering, Volume 21, No 12 (December 1908), p. 524-525. Baldwin works numbers for a follow-on batch were 36214-36218 in March 1911.

The big 1908 Alco production run for the Associated Lines included 30 Moguls, 10 Atlantics, 24 Ten-wheelers, 43 Consolidations, and 18 switchers. The R&LE report describes the Harriman Common Standard Atlantics and Moguls in detail, particularly noting all of the components they shared. In the case of these two arrangements, the designers were able to use the same cylinder volume and the same boiler and grate, the principal differences lying in 3 ft 4 in (1,016 mm) longer tubes and a slightly deeper firebox in the Atlantic.

The list of common components runs to a surprising length. The author first notes the rocker-shaft setup in the valve motion is slightly different in the Atlantics from the Moguls. "As a result of this arrangement, the same cylinder heads, valves, valve bushings, pistons, piston rods, crossheads, connecting rod bearings, rocker shafts, eccentric straps and eccentrics are common to both classes of engines."

Impressive commonality, but there was more. For one thing, "The cylinders of both engines ... have the same spread, viz., 88 ins., and the same distance, 43 ins. between frame centers, and take a common frame section, so that the deck plates, reverse shafts and driving boxes are common to the two classes."

Using the same boiler allowed use of the "..same smokestack, smokebox, front and door, dome ring base and cap, throttle pipe, dry pipe elbow and end and minor details." And the engines shared the same "...steel cabs, sand boxes, injectors, injector checks, throttle levers, engine truck axles, engine truck boxes and grate bars."

Less unusual, but noteworthy for an age in which master mechanics could and would insist on minor differences from a standard in ordering locomotives, were the Vanderbilt tender commonalities: "axles, bolsters, journal boxes, truck center plates, springs, side bearings, wheels, air brakes, tender frame body bolsters, and draw gear."

Of the 1908 order, at least two were built for the FC de Sonora of the Mexican lines portion of the SP and three went to the Cananea, Rio Yaqui & Pacific. Baldwin's 1911 order supplied three more to the CRY &P and two more to the FC de Sonora.

They were virtually identical to the A-3s built for the Espee in 1904-1908 (Locobase 1431).

Of the 1911 Baldwins, the first 2 stayed in Mexico, where they operated until being retired in 1934 and scrapped in 1938. The other three moved across the border to the Arizona Eastern, and wound up on the Espee's Pacific Lines in 1924, where they ran until 1935.