Baltimore & Ohio class N-1

This locomotive was the first modern one the USA that used a duplex layout with all drivers in the same frame, but driven by separate sets of cylinders. Numbered 5600 and named “George H Emerson”, production was completed in May 1937 at the B&O's own Mount Clare Shops. It was designed in an effort to avoid the use of overly long coupling rods and to reduce the mass of reciprocating components. So only the first two sets of drivers were connected to the front cylinders, while the rear two sets of drivers had their own cylinders of the same dimension located next to the firebox. 

In the result, the special chassis layout ensured that the minimum curve that can be run at normal speed by this locomotive was 13 degrees, what corresponds to a radius of 135 meters. This was the same value as for the Pacifics operated by the B&O. The boiler had a large Emerson water-tube firebox and operated at a high pressure of 350 psi or 24.1 bars. A large problem of the rear cylinder placement was that they became hot and dirty due to the proximity to the firebox. At the same time, the railroad decided to order the EA diesel locomotives from EMC that was better suited for express service. 5600 was used until 1943 and scrapped in 1950.