Norfolk & Western Class Y6b

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.

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.

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 EW 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..