The 2-6-6-6 (in Whyte notation) is an articulated locomotive type with 2 leading wheels, two sets of six driving wheels and six trailing wheels. Only two classes of the 2-6-6-6 type were built. One was the "Allegheny" class, built by the Lima Locomotive Works. The name comes from the locomotive's first service with the Chesapeake and Ohio Railway beginning in 1941. The other was the "Blue Ridge" class for the Virginian Railway. These were the heaviest reciprocating steam locomotives ever built.
Other equivalent classifications are:
UIC classification: 1CC3 (also known as German classification and Italian classification)
French classification: 130+033
Turkish classification: 34+36
Swiss classification: 3/4+3/6
The UIC classification is refined to (1'C)C3' for Mallet locomotives.
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Two classes of 2-6-6-6 locomotives were built; the sixty H-8 "Allegheny" class locomotives for the Chesapeake and Ohio Railway (C&O) between 1941 and 1948,[1] and the eight AG "Blue Ridge" class locomotives for the Virginian Railway in 1945.[2] There is often confusion because the locomotives were Series AG on the Virginian, which was thought to be an abbreviation for Allegheny, but that referred to their being Articulated, Series G. All were built by the Lima Locomotive Works. The "Allegheny" name refers to the C&O locomotives' job of hauling heavy coal trains up and down the Allegheny Mountains.
To many, the writing was on the wall for reciprocating piston driven steam locomotives, even though they would live on almost another 20 years. Lima and C&O set out to build the ultimate in high power engines, and they succeeded as no other piston engine ever surpassed the output of these monsters. They were, as a result, also the heaviest steam locomotives ever constructed. The 3 axle trailing truck supporting the firebox was very unusual. That 3 axle truck carried over 190,000 lbs. This allowed the H-8 to have a huge firebox and was one of the reasons for the high horsepower achieved.
Gene Huddleston's "C&O Power" book reports test results of the C&O with a dynamometer car indicating peak power output of 7,498 hp (5.6 MW) with readings between 6,700 to 6,900 hp (5.0 to 5.1 MW) at about 45 mph (72 km/h). The state of calibration of the dynamometer car is not known. While the tractive effort was only 110,200 lbf (490.2 kN) at zero speed, this drawbar power at usable road speeds leads many to believe that the H-8 was the highest power steam locomotive.
The locomotive was designed for the 0.57% grade eastbound between White Sulphur Springs, WV, and Alleghany, VA, with loaded coal trains. One was set on the front, and another at the back, of typically 100 car coal trains, from Hinton, WV, up full throttle from out of White Sulphur Springs (a resort) to the top. Coal cars in the early 50's were 100,000 lb (45.4 t) nominal capacity, 169,000 lb (76.7 t) maximum gross loaded weight.[3] These locomotives also handled trains less spectacularly in Ohio. Gene H. says 23 locomotives were equipped with steam heat for passenger service, although only troop trains would be long enough to require this much power.
Electrical multiple unit operation in the diesel era removed the incentive to pack the highest horsepower in a single unit. The H-8 was so heavy that only some stretches of track were of sufficient capacity to operate it.
One H-8, the 1642, suffered a crown sheet explosion at Hinton, WV in June, 1953. The force of the explosion rocketed the boiler endwise off the running gear, killing all three crew. While these locomotives had three sources of water for the boiler, rotary pump and two injectors, it is not known whether any were defective at the time of dispatch. According to the family of the locomotive's engineer, Wilbur H. Anderson, of Hinton, previous crews had complained of a faulty water level gauge. Anderson's widow, Georgia Anderson, was given $10,000 in compensation by the C&O.
There are only two surviving Alleghenies. One resides in The Henry Ford museum in Dearborn, Michigan, and the other at the B&O Railroad Museum in Baltimore, Maryland. Neither is in operational condition and they are likely to remain static displays given their incredible size and weight.
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