Built by Alco-Schenectady (16) and Baldwin (16) 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 (http://www.nhrrvolunteers.org/NHRR3028.htm, 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.
| Specifications | |
|---|---|
| Class | QR-1 |
| Locobase ID | 974 |
| Railroad | Nacional de Mexico |
| Whyte | 4-8-4 |
| Road Numbers | 3025-3056 |
| Gauge | Std |
| Builder | several |
| Year | 1946 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase | 18.25' |
| Engine Wheelbase | 45.09' |
| Ratio of driving wheelbase to overall engine wheebase | 0.40 |
| Overall Wheelbase (engine & tender) | 86.31' |
| Axle Loading (Maximum Weight per Axle) | |
| Weight on Drivers | 240000 lbs |
| Engine Weight | 387000 lbs |
| Tender Light Weight | 242400 lbs |
| Total Engine and Tender Weight | 629400 lbs |
| Tender Water Capacity | 15000 gals |
| Tender Fuel Capacity (oil/coal) | 6000 gals |
| Minimum weight per yard of rail on which locomotive could run | 100 lb rail |
| Geometry Relating to Tractive Effort | |
| Driver Diameter | 70" |
| Boiler Pressure | 255.30 psi |
| Cylinders (dia x stroke) | 25" x 30" |
| Tractive Effort | 58126 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.13 |
| Heating Ability | |
| Firebox Area | 437 sq. ft |
| Grate Area | 77.30 sq. ft |
| Evaporative Heating Surface | 4185 |
| Superheating Surface | 1721 |
| Combined Heating Surface | 5906 |
| Evaporative Heating Surface/Cylinder Volume | 245.54 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 19734.69 |
| Same as above plus superheater percentage | 25485.35 |
| Same as above but substitute firebox area for grate area | 144076.30 |
| Power L1 | 38198.87 |
| Power MT | 1403.57 |
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