Spokane, Portland & Seattle 4-4-2 "Atlantic" Locomotives in the USA

Class C-1 (Locobase 16531)

Data from SP&S All-Time Steam 2011 from Paul Hobbs supplied in 2019 by Allen Stanley from his extensive Rail Data Exchange collection.

Locobase 13332 describes the decade of saturated-boiler balanced-compound Atlantics that arrived on the SP&S in 1909. Fourteen years later, the Great Northern Railway converted all of the engines to the two-cylinder, superheated simple-expansion variant shown here. Modifying the boiler meant trading about half of the small tubes for the 30 flues that hosted superheater elements. Exchanging an increased cylinder diameter for a lower boiler pressure kept the tractive effort about the same as the GN's similar K-1-S (Locobase 6944).

Boosters seemed like a good idea for these ezpress passenger engines, so the railway installed Franklin C-1 (603, 609) or C-2 (the other eight) boosters. Perhaps results didn't match expectations because all boosters were removed in 1931.

Six of the locomotives were "dismantled" before the US entered World War II beginning with 600 and 606 in Aprl 1937. 608-609 were sent to the ferro-knacker in September 1947 and 603 and 605 finished the class in April 1949.

Class K/C-1 (Locobase 13332)

Data from DeGolyer, Volume 32, p. 39. (Thanks to Chris Hohl for his 22 February 2021 email correcting the valve gear, engine weight, and grate area.) Works numbers were 33228-33233 in February 1909; 33273-33276 in March.

Each big 15" (381 mm) piston valve fed both cylinders on one side of the four-cylinder battery under this balanced compound Atlantic. Based on the Great Northern compounds of 1906 (Locobase 6945), the SP&S engines arrived three years later. They had the GN-signature Belpaire fireboxes.

Chris Hohl pointed out the "soft coal" entry in the fuel field and a coal capacity of 13 tons (11.8 metric tons) in the Baldwin specs, but the tender description presents the oil capacity as the main specification.

Drury (1993) says they were the "mainstay" of the SP&S express passenger service for years. In 1923, they were converted to simple-expansion locomotives; see Locobase 16531.