The Baltimore and Ohio class N-1 was a class of experimental steam locomotive of which a single unit was built, designated #5600 and named "George H. Emerson". It was constructed by the Baltimore and Ohio Railroad (B&O) at its own Mount Clare Shops in Baltimore, Maryland, with completion in May 1937. The locomotive was the first duplex-drive steam locomotive and the first 4-4-4-4 wheel arrangement locomotive ever built.
Design and Construction
The N-1 was designed under the direction of George H. Emerson, the B&O's Chief of Motive Power, after whom the locomotive was named. It featured a duplex layout, meaning it had two sets of cylinders driving two separate groups of driving wheels, all mounted within a single rigid frame. The front pair of cylinders drove the front set of 76-inch drivers, while the rear pair of cylinders were placed beside the firebox and drove the rear set of drivers. This design was intended to avoid the need for overly long coupling rods and to reduce the mass of reciprocating parts.
The locomotive was notable for its water tube firebox, which was significantly larger than a conventional firebox. It operated at a boiler pressure of 350 psi (2.41 MPa) and produced a tractive effort of 65,000 lbf (289.1 kN). Power output at the cylinders was rated at approximately 3,936 hp (2,935 kW). The locomotive weighed 386,500 lb (175.3 metric tons), with an additional 350,000 lb (160 metric tons) for the Vanderbilt tender.
Operational History and Retirement
The N-1 was exhibited at the 1939 New York World's Fair. In service, the locomotive suffered from mechanical issues. The placement of the rear cylinders beside the firebox exposed them to excessive heat and dirt, causing premature cylinder wear. This same design limitation also constrained the size of the firebox. Similar problems later affected the Pennsylvania Railroad's Q1 duplex locomotive.
Due to these persistent issues and the onset of World War II, locomotive #5600 was retired from service in 1943. It was stored for several years before being scrapped in October 1950. No other locomotives of the N-1 class were ever built, making it a unique experimental design in American steam locomotive history.
