Pennsylvania Railroad class N1s

The Pennsylvania Railroad's N1s was a class of steam locomotive built for Lines West. They were of 2-10-2 "Santa Fe" wheel arrangement, ten driving wheels with a two-wheel leading truck and a two-wheel cast KW-pattern trailing truck under a giant firebox. This arrangement was well suited to the N1s' intended purpose, which was as a heavy drag freight engine for coal and iron ore traffic to and from lakeside ports. The design was developed by the PRR's Fort Wayne Shops and orders were placed with Alco (Brooks) (35 locomotives) and Baldwin (25 locomotives) for a total of 60; the first Alco locomotive was delivered in December 1918, with the remainder arriving during 1919.

PRR N1s #8363 in its official builders' photo.

Pennsylvania Railroad N1s
PRR N1s #7246 at Youngstown, Ohio in 1919, when less than a year old. Note the Lines West central headlight (later relocated higher) and high slope-sided tender coal space
Type and origin Power type Steam Builder ALCO-Brooks (35), Baldwin Locomotive Works (25) Build date 1918–1919 Total produced 60
Specifications Configuration: ​  • Whyte 2-10-2  • UIC 1'E1'h Gauge 4 ft 8 ^1⁄2 in (1,435 mm) Leading dia. 33 in (0.838 m) Driver dia. 62 in (1.575 m) Trailing dia. 36 in (0.914 m) Wheelbase Locomotive: 41 ft 11 ^1⁄2 in (12.79 m) Length 91 ft 4 ^5⁄8 in (27.85 m) Axle load 75,600 lb (34,300 kg; 34.3 t) Adhesive weight 351,000 lb (159,000 kg; 159 t) Loco weight 435,000 lb (197,000 kg; 197 t) Tender weight Empty: 86,800 lb (39,400 kg; 39.4 t); Loaded: 206,100 lb (93,500 kg; 93.5 t) Tender type 100 F 85 Fuel type Coal Fuel capacity 39,300 lb (17,800 kg; 17.8 t) Water cap 9,600 US gal (36,000 l; 8,000 imp gal) Firebox:  • Firegrate area 79.9 sq ft (7.4 m^2) Boiler pressure 215 psi (1.48 MPa) Cylinders Two Cylinder size 30 in × 32 in (762 mm × 813 mm) Valve gear Walschaerts
Performance figures Maximum speed 35 mph (56 km/h)
Career Retired by 1950 Disposition All scrapped

The N1s was a large locomotive; the boiler was the largest then used on any non-experimental PRR locomotive, with a large Belpaire firebox with 79.9 square feet (7.4 m²) of grate area and a 5-foot (1.52 m) long combustion chamber. No feedwater heater was fitted, but a mechanical stoker and power reverse were, necessities on such a large locomotive. Boiler pressure was 215 pounds per square inch (1.48 MPa), although it was designed to take a pressure of 250 psi (1.72 MPa).

To allow the locomotive to negotiate tight 23-degree curves, the first and fifth driving axles were fitted with lateral motion devices and the center axle was blind.

In many respects, the N1s was similar in ability to the I1s 2-10-0 "Decapod". Driver diameter, weight on drivers and cylinder size were almost identical. The N1s' boiler was larger, but of a lower pressure. The I1s' tractive effort was a little higher, while the N1s had a superior factor of adhesion. The N1s, as a low-speed drag hauler, was limited to 35 mph (56 km/h), while the I1s was capable of 50 mph (80 km/h) or greater.

The N1s were the first class of large power withdrawn after diesel locomotives appeared; all were gone by 1950, and none were saved for display. Their task, low-speed drag haulage, was the diesel locomotive's forte.

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