Class Y2/Y2a (Locobase 3560)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

The first of a long line of compound Mallet Consolidations, Y2s appeared in several batches. Roanoke built 5, Baldwin 20 in 1918-1919. Roanoke followed with 6 more in 1924; these had 24 1/2" cylinders. The earlier engines were all upgraded to the Y2a configuration and all eventually used 25" diameter HP cylinders.. Firebox heating surface included 45 sq ft of arch tubes.

Both classes served until 1957-1959.

Class Y3/Y3a (Locobase 1421)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

This design first came to the N & W as an example of the USRA heavy articulated design, which itself was based on Norfolk & Western's Y2. Firebox heating surface then included 134 sq ft of arch pipes and syphons, boiler pressure was set at 240 psi, and the piston valves measured 14" in diameter.

Alco built 45, Baldwin added 5. In 1923, Alco-Richmond delivered 30 more Y3a, which were similar except for a larger tender. Over time the Y3s received a different boiler with 30 fewer tubes, but more superheat and a firebox with 65 sq ft of arch tubes. That version is the one shown in the specifications.

Both classes served until 1957-1959.

Class Y3b/Y4 (Locobase 323)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Firebox had combustion chamber. Mallet compounds built in a total of 8 batches. The first in the series were five N&W-built Y-2s, built in 1918 and adopted by the USRA as the basis for their heavy articulated design. 50 Y-3 (USRA heavies) followed in 1919 and 30 more Y-3a were built in 1923.

The 10 Y-4s were originally classed as Y-3bs. The large LP cylinders posed some problems in steam exhausting due to the internal design of steam lines, ports, and valves.

Six Alco-built Y-3s -- 2000/2008/2027/2034/2036/2046 -- all completed in 1919) were operated by the Pennsylvania from 1943 to 1947-1949 as the HH1 class. Later N&W engines were built to a larger design; see the Y-6 record.

Several Y-3as were sold to the Santa Fe

Class Y4a/Y5 (Locobase 4396)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Continuation of the N&W series of large Mallet compounds, the Y-5s were first introduced in 1930 as the first "modern" 2-8-8-2s, according to EL King in Drury (1993). In addition to the 300-psi boiler, these engines had the "waffle-iron" nozzles for the low-pressure cylinder exhaust that reduced back pressure. Their outdated fabricated frames couldn't handle the immense power generated by the boiler and cylinder combination and at first they ate up maintenance time. In 1940-1941, however, the 19 remaining Y-4as were rebuilt with cast-steel frames and cylinders. This fixed the wracking problem and the Y-5s, now virtually identical to the later Y-6s, served out steam on the Norfolk & Western.

Class Y6 (Locobase 324)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Continuation of the N&W series of large Mallet compounds, the Y-5s were first introduced in 1930. Y-6 series engines had integrally cast cylinders in cast-steel frames, roller bearings on all axles, and piston valves as large as 18 inches in diameter.

Class Y6b (Locobase 1422)

Data from N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

HP piston valves measured 14" in diameter while the LP valves had an 18" bore. Heating surface data from N & W diagram book in Allen Stanley's large collection. Stanley also includes data on the extended combustion chamber variant. The tube and flue areas remained the same, but the superheater was reduced by 60 sq ft and the arch tubes by 41 sq ft while adding 100 sq ft of circulators.

Last in a series of compound articulated locomotives that ranked as the best. See earlier entries on the Y-3, Y-4, Y-5, and Y-6. All axles had Timken roller bearings and the valve gear used McGill multirol bearings.

The Y-6bs could divert live, high-pressure steam to the LP cylinders while working compound expansion. Pulling a load of 13,500 tons on the level at 25 mph, the Y-6b developed 5,500 indicated horsepower (cut-off of the HP cylinders of 60% and in the LP cylinders 55%). As E W King, Jr. (in Drury, 1993) summarizes the story: "In tinkering with the design over a period of 33 years, the road wound up with a locomotive capable of producing 5,600 drawbar horsepower at 25 mph with a top speed of 50 mph -- perfect matches for N&W's tonnage, grades, and curves ... while retaining the economies of compound operation and in a locomotive that weighed 100,000 lb less than either the [C&O's] 2-6-6-6 or [UP's] 4-8-8-4 [Big Boy]."

These engines were carefully maintained and well-designed, yielding to diesels only because the N&W could no longer afford to be the "odd man out" in the diesel parade. The last Y-6 was completed in 1952, and the last one ran in April 1960..