Norfolk & Western Y6a Class No. 2156 2-8-8-2 Articulated Steam Locomotive
Norfolk & Western 2156 is the strongest-pulling extant steam locomotive in the world, although it is not operational. It is a four-cylinder compound articulated (Mallet) locomotive with a 2-8-8-2 (Whyte notation) wheel arrangement. The Norfolk & Western Railway built it in 1942 at its Roanoke Shops in Roanoke, Virginia, and it was part of the Norfolk & Western's Y6a class. It was retired from regular rail service in July 1959, and today it is owned by the Museum of Transportation in St. Louis, Missouri, U.S.A. In 2014, the St. Louis Museum of Transportation announced that a 5-year lease had been agreed upon between them and the Virginia Museum of Transportation in Roanoke, Virginia. It was towed from St. Louis to Roanoke, Virginia on May 10, 2015.

Historic significance
Norfolk & Western 2156 is the sole survivor of the railroad's Y5, Y6, Y6a, and Y6b classes (in final form referred to as the "Improved Y5/Y6 class"). These locomotives were among the hardest-pulling steam locomotives ever built. They were originally rated for a tractive effort of 152,206 pounds-force (677.0 kN), and improvements in the 1950s resulted in most of these locomotives (including N&W 2156) having their tractive effort increased to a measured 166,000 pounds-force (738.4 kN), which necessitated adding about 28,000 pounds (12.7 t) of lead to the front engine frame, to improve traction. (By comparison, the famous Union Pacific Big Boy locomotives developed 135,375 pounds-force (602.2 kN) of tractive effort.) This pulling power is all the more remarkable insofar as the only successful steam locomotives that developed somewhat more tractive effort, the Virginian AE class 2-10-10-2s, pulled trains at about 8 mph (13 km/h), while the N&W Y6’s regularly pulled trains 50 mph (80 km/h), and some anecdotal evidence exists that they pulled trains successfully up to 63 mph (101 km/h).

N&W 2156 is also one of the Y6a's that received a new firebox with an extended combustion chamber of the type used on the Y6b class, which increased drawbar horsepower from 4400 hp (3.3 MW) at 20 mph (32 km/h) to 5600 hp (4.2 MW) at 25 mph (40 km/h).

Steam versus diesel tests, upgrades, and controversies
No discussion of N&W 2156 and its siblings would be complete without referring to their epic contest against new diesel locomotives in 1952, and the related modifications to the locomotives, which have been a source of some debate among rail historians. N&W had coal traffic as its most important source of revenue, and it had arguably the most modern and efficient steam locomotives of any major U.S. railroad. Accordingly, N&W resisted conversion from coal-burning steam locomotives to oil-burning diesels longer than most major railroads. In 1952 N&W tested its A-class and Y6b-class locomotives against a four-unit Electro-Motive Division (at that time, of General Motors) F7 diesel set. The tests indicated that fuel costs and similar items were roughly the same, and the test was considered a tie. However, eventually diesels won out for lower maintenance and other operational costs.

Retrospective analyses of these tests have caused a few, even in published articles by knowledgeable historians, to assert that diesel locomotive builder EMD and/or N&W used secretly modified locomotives for these tests. If N&W's modified Y6b locomotive number 2197, in addition to its publicized improvements, had received secret upgrades that would not be appropriate for daily-use locomotives, then the claims of substantially upgraded performance were something of a fraud. However, the greater weight of evidence and analysis indicates that N&W did not cheat on these tests, and that the only improvements were the ones N&W publicized and later incorporated into many locomotives. Also, the major participants in this debate all appear to agree that N&W did ultimately modify most of its Y5, Y6, Y6a, and Y6b locomotives (including N&W 2156) with a new "intercepting/reducing valve" and ballast on the front engine, which significantly increased their tractive effort.

Operational history
Norfolk & Western used 2156 and the other Y6-class locomotives primarily for slower, heavy freight trains in the more mountainous districts. Although they were used throughout the N&W, their primary work occurred on the Pocahontas, Radford, and Shenandoah Divisions. They mostly hauled manifest freight and coal trains.

When diesel locomotives took over the main-line steam operations, the Y6-type locomotives spent their last two years mostly on mine and other coal-field runs. During this period, specifically in July 1959, N&W donated 2156 to the Museum of Transportation.

Current status

Until May 2015, N&W 2156 was one of the attractions at the Museum of Transportation in St. Louis. It had been cosmetically restored in 1985, but had not operated since its retirement in 1959. In 2014, Norfolk Southern announced it and the Virginia Museum of Transportation in Roanoke, Virginia, had negotiated a deal to swap the 2156 for an EMD FT B unit. On May 9–12, 2015, the locomotive was towed to its temporary home. On May 31 that year, 2156 reunited with 1218 and the recently restored 611 together as N&W's The Big Three.

Norfolk & Western 2156 Overview
Type and origin
Power type: Steam
Builder: N&W's Roanoke Shops
Serial number: 317
Build date: March 19, 1942
Configuration: 2-8-8-2
UIC class: (1′D)D1′ hv4
Gauge: 4 ft 8 1⁄2 in (1,435 mm)
Leading diameter: 30 in (762 mm)
Driver diameter: 58 in (1,473 mm) (as built 57 in (1,448 mm))
Trailing diameter: 30 in (762 mm)
Adhesive weight: 548,500 lb (248.8 tonnes)
Loco weight: 611,500 lb (277.4 tonnes)
Total weight: 990,100 lb (449.1 tonnes) (as built 961,500 lb (436.1 tonnes))
Fuel type: Coal
Fuel capacity: 60,000 lb (27.2 tonnes)
Water capacity: 22,000 gal (83,000 l; 18,000 imp gal)
 • Firegrate area: 106.2 sq ft (9.87 m2)
Boiler pressure: 300 psi (2.07 MPa)
​ • Heating area: 1,478 sq ft (137.3 m2)
Cylinders Four: two low-pressure (front), two high-pressure (rear)
High-pressure cylinder: 25 in × 32 in (635 mm × 813 mm)
Low-pressure cylinder: 39 in × 32 in (991 mm × 813 mm)
Performance figures
Power output: 5,600 hp (4,200 kW) (as built 4,400 hp (3,300 kW))
Tractive effort: 166,000 lbf (738.4 kN) (as built 152,206 lbf (677.0 kN))
Factor of adhesion: 3.30
Operator: Norfolk & Western Railway
Class: Y6a
Number in class: 2 of 16
Locale: United States, South and Midwest
Retired: July 1959
Current owner: Museum of Transportation, St. Louis, Missouri
Disposition: On display at the Virginia Museum of Transportation during 5 years loan until 2020

See also:

Steam Locomotives

Norfolk & Western

St. Louis Museum of Transportation Official Website:

Virginia Museum of Transportaion Official Website:

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Norfolk and Western class Y6a No. 2156, class J No. 611, and class A No. 1218 on display at the Big Three celebration at the Virginia Museum of Transportation in Roanoke, VA, on May 31, 2015.
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Norfolk & Western 2156 on display at the Museum of Transportation.

Norfolk and Western class Y6a No. 2156, class J No. 611, and class A No. 1218 on display at the "Big Three" celebration at the Virginia Museum of Transportation in Roanoke, VA, on May 31, 2015.    By D. Michael McIntyre - Own work, CC BY-SA 4.0, - NFL Jerseys and Gear
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Norfolk & Western 2156 on display at the Museum of Transportation.

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