Nacional de Mexico 4-8-4 Locomotives in Mexico

The Ferrocarriles Nacionales de Mexico (National Railways of Mexico) bought a total of 32 Northern type, Class QR-1, locomotives in 1946. NdeM purchased 16 from the American Locomotive Company and 16 from the Baldwin Locomotive Works.

On the NdeM these locomotives were called "Niágaras" and were among the few that it bought new. Most of its motive power was obtained second-hand from U. S. railroads.

All 32 of the "Niágaras" (road numbers 3025 through 3056) had 70" drivers, 25 x 30 cylinders, a boiler pressure of 250 psi, a tractive effort of 57,000 lbs and weighed 387,000 pounds.

There are 12 surviving "Niágaras". Here are their locations.

Class Details by Steve Llanso of Sweat House Media

Class QR-1 (Locobase 974)

Data from NdeM 1946 locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Built by Alco-Schenectady (16 - works numbers 74380-74387, 74825-74832 in 1946; road numbers 3025-3032, 3049-3056) and Baldwin (16 - works numbers 73018-73033, road numbers 3033-3048) for freight service. Drury (1993) notes that they were among the lightest of Northerns. NdeM called them "Niagaras." The last of these was retired in 1965. (A 1947 Alco advertisement in the Locomotive Cyclopedia shows a superheat area of 1,667 sq ft.) Firebox heating surface included 97 sq ft in three thermic syphons. Valve travel measured 8" with a lead of 1/4".

See the Pennsylvania-based New Hope and Ivyland's website ([], last accessed 3 July 2006) for an encomium, which says in part:

"Built in ...1946 by the American Locomotive Company in Schenectady, New York, these nimble and graceful engines were the finest match between a locomotive design and the environment of its railroad that was ever achieved during the steam era.

"Thoroughly modern in appearance and in specifications, these 32 engines brought a welcomed increase to the roster of the hard working N. de M. Their design included a wisely balanced compromise of features that was absolutely essential for the widely diversified areas where they ran ....For over 20 years these "Niagaras" served throughout Mexico, handling heavy international freight and passenger movements between Mexico City and Nuevo Lare[d]o as well as regular runs to Guadalajara and Aguascalientes through the difficult high altitude mountain country"

The NH & I site claims that the multiplication of axles coincident with adopting the 4-8-4 "...gave the N. de M. the broadest possible usage over the limitations of

the light rail and mountain curves making up much of its right of way." Yet, the minimum average axle loading was 60,000 lb (27.22 metric tons) which required a rail weight of at least 100 lb/yard (49.4 kg/m), which does not imply lightly built track.

Principal Dimensions by Steve Llanso of Middle Run Media

Locobase ID974
RailroadNacional de Mexico (NdeM)
Number in Class32
Road Numbers3025-3056
Number Built32
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)18.25 / 5.56
Engine Wheelbase (ft / m)45.09 / 13.74
Ratio of driving wheelbase to overall engine wheelbase 0.40
Overall Wheelbase (engine & tender) (ft / m)86.31 / 26.31
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)240,000 / 108,862
Engine Weight (lbs / kg)387,000 / 175,540
Tender Loaded Weight (lbs / kg)242,400 / 109,951
Total Engine and Tender Weight (lbs / kg)629,400 / 285,491
Tender Water Capacity (gals / ML)15,000 / 56.82
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)6000 / 22,710
Minimum weight of rail (calculated) (lb/yd / kg/m)100 / 50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)70 / 1778
Boiler Pressure (psi / kPa)255.30 / 17.60
High Pressure Cylinders (dia x stroke) (in / mm)25" x 30" / 635x762
Tractive Effort (lbs / kg)58,126 / 26365.54
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.13
Heating Ability
Tubes (number - dia) (in / mm)49 - 2.25" / 57
Flues (number - dia) (in / mm)169 - 3.5" / 89
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)437 / 40.60
Grate Area (sq ft / m2)77.30 / 7.18
Evaporative Heating Surface (sq ft / m2)4185 / 388.94
Superheating Surface (sq ft / m2)1721 / 159.94
Combined Heating Surface (sq ft / m2)5906 / 548.88
Evaporative Heating Surface/Cylinder Volume245.60
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation19,735
Same as above plus superheater percentage25,458
Same as above but substitute firebox area for grate area143,920
Power L138,208
Power MT1403.90

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Wes Barris