Central Mexicano 2-6-6 Locomotives in Mexico

Class Mason-Fairlie/E (Locobase 3163)

Data from DeGolyer, Volume 15, p. 198. See also the Iron Horse site [], last accessed 22 August 2009; and see also "Heavy Mason-Farlie [sic] Locomotive for the Central Mexicano", The Railway Trainman, Volume 7, No 6 [new series] (June 189), pp. 327-329. (Thanks to Chris Hohl for his 3 April 2020 email noting duplicate entries and correcting the driving wheelbase.) Works numbers were 10542 in December 1889; 10556, 10599, 10605 in January 1890; 10641 in February 1890; 10993, 11002, 11020 in June 1890; 11036, 11066-11067 in July 1890; and 11097, 11114, 11132-11133 in August 1890.

William Mason, the Taunton, Mass, locomotive builder famous for the elegance of his engine designs, came up with a variaion on the Fairlie articulated locomotive design that was dubbed the "Mason-Fairlie." (No surprises there ...) Rather than having two swiveling engine bogies under a single boiler as in the basic Fairlie design, Mason's front bogie had the cylinders, the rear one a six-wheel truck for the "tender." This arrangement offered a good deal more flexibility than a standard tender-engine layout, allowing negotiation of 14-deg curves on standard-gauge track. Moreover, the deep firebox located behind the drivers, which often resulted in unsteady riding qualities, was actually suspended between the two bogies. Note the very small drivers.

Although the Baldwin specs page shows a rigid and driving wheel base of 9 ft 4 in (2.84 m), they also describe a "steam truck" with the wheelbase shown in Locobase's specs.

The Railway Trainman's report pours scorn on the reversing gear developed for this design, describingt it as "the clumsiest and meanest reversing gear we have ever seen-the rack and pinion style. There is a quadrant, cut full of small teeth, the reversing lever comes up just under this quadrant, and forks around it."

The fork was fixed and carried a small pinion that meshed into the teeth in the quadrant. A "hand-wheel--like brake wheel--measuring just an inch (25.4 mm) across--turned this pinon which moved the rack from one side to the other. A smaller spoked wheel mounted on the fork held the lever through a setscrew where the engineer wanted it. "The device is very unhandy," pronounced Railway Trainman, "requiring both hands to set it, and is slow."

But, the report adds, the locomotives were "exceptionally neat, well designed, and well finished ...On top of the cab, and raised above the roof some six inches, there is a corrugated iron roof, or canopy; we suppose this is to make the cabs more endurable in the heat of a Mexican summer."

In summary, the article added a few more pluses and minuses:" This class of engines are noted for their easy riding qualities, and the cabs are particularly comfortable in winter; there is no pounding between engine and tender, no draw gear to break, no water or air hose, and no gangway, but there are objections to them in their great length, the flexible steam pipe, etc.

Although built by Baldwin, these tanks employed Mason bogies under both the boiler and tender, which was fixed to the firebox. They were described as heavy Mason-Fairlies, but applied the Mason patent because the Fairlie design was not technically available to US builders.

"These engines have the frame of the tender fastened solidly to the fire-box and boiler, the slab frame extending ahead just under the running board to the heavy center casting under the boiler, as shown. To those not familiar with the Farlie engine it may be necessary to state that the engine is separate from the boiler, and can move under it, just as a truck of a car can move under the car body. There is a heavy saddle casting bolted to the center of the barrel of boiler, that rests on an immense casting across the frame of the engine.

"The steam pipe comes down through the bottom of the front end, and has a ball joint between it and a pipe that extends back almost to the center casting; here is another ball joint held together with coil springs that joins a return pipe to the cylinder saddle, where it joins by another ball joint.

"The exhaust nozzle extends up into the arch through a slotted casting, the slot being covered by a slide that fits up against it, held by springs; this slide is tight around the nozzle, and will admit of considerable movement without opening the front end to the atmosphere.

Locobase likes the image conveyed by the following description:

"In rounding a curve, the steam pipe opens out, like a pair of lazy tongs, and keeps up the supply of steam, and the engine is enabled to dodge around under the boiler as much as the truck does under the tank.

Taking a broader view, the reporter liked what he saw:

These engines are exceptionally neat, well designed, and well finished; they are very large, and set up high; the boiler head in the cab is lagged, and every improvement at hand. On top of the cab, and raised above the roof some six inches, there is a corrugated iron roof, or canopy; we suppose this is to make the cabs more endurable in the heat of a Mexican summer.

"This class of engines are noted for their easy riding qualities, and the cabs are particularly comfortable in winter; there is no pounding between engine and tender, no draw gear to break, no water or air hose, and no gangway, but there are objections to them in their great length, the flexible steam pipe, etc. Like all other railroad devices, they have their advantages and disadvantages."

"Like all other railroad devices," the author concludes,"they have their advantages and disadvantages."

The engines cannot have been a great success as 126 and 131 were gone by 1899. 125, 128, 132 were not on the next year's roster in 1900. 136, 138-139 were eliminated by 1902, folowed by 134-135 in 1903. The rest--127, 129-130 (renumbered 125-126 in 1902), 134 (127), and 137 (129) --all were disposed of by 1908.