Seaboard Air Line 2-6-6-4 Locomotives in the USA

Class R-1 (Locobase 302)

Data from tables and diagrams in 1947 Locomotive Cyclopedia and from from the 1948 SAL locomotive diagram supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "Seaboard Air Line Buys Five Locomotives", Baldwin Locomotive Magazine, Volume 14, No 1 (April 1935), p. 25; and William Withuhn, American Steam Locomotives: Design and Development: 1880-1960 (Bloomington, IN: Indiana University Press and Pflugerville, TX: Railway & Locomotive Historical Society, 2019), p. 301-302. (Thanks to Chris Hohl-1 for his 28 February 2020 email correcting the error in engine wheelbase and for noting KB designations assigned to both classes by the B&O.) Works numbers ran 61829-61833 in 1934.

In addition to the long combustion chamber, the firebox heating surface area included two Nicholson thermic syphons as well as 19 sq ft (1.77 sq m) of arch tubes. See Trains Magazine (August 1979) for an account of how these engines ran. They were well-liked with many engineers feeling that they were capable of higher speeds than the road would let them reach. William Withuhn offered a terse summary judgement in favor as well. They "ran beautifully, with excellent traction."

See Locobase 10077 for the later batch of R-2s, which had slightly different specs.

In August 1947, the SAL sold all ten of its 2-6-6-4s to the Baltimore & Ohio. The R-1s were classed KB-1 by the B&O and given road numbers 7700-7704. Like the later KB-1a (ex-R-2s), these engines had leaky slip joints in the front engines; these were replaced by ball joints.

Four of the five were sent to the ferro-knacker in 1953. For some reason, 7701 remained on the roster until April 1955.

Class R-2 (Locobase 10077)

Data from tables and diagrams in 1947 Locomotive Cyclopedia and from from the 1948 SAL locomotive diagram supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also William Withuhn, American Steam Locomotives: Design and Development: 1880-1960 (Bloomington, IN: Indiana University Press and Pflugerville, TX: Railway & Locomotive Historical Society, 2019), p. 302. (Thanks to Chris Hohl-1 for his 28 February 2020 email correcting the error in engine wheelbase and for noting KB designations assigned to both classes by the B&O.) Works numbers were 62054-62058 in 1937.

These R-2s had slightly fewer tubes than the earlier R-1 (Locobase 302), a cleaner-looking Walschaerts valve motion, single crosshead guides, and Elesco feedwater heaters replaced by Worthingtons, but otherwise varied little from the earlier R-1s.

These engines later (August 1947) went on to the B&O as KB-1a and given road numbers 7705-7709. The B&O were displeased enough by leaking slip joints in the piping to the front engine unit (which leaked frequently) to replace them with ball joints. They were slippery on grades and not as well liked as the Big Sixes (2-10-2), although a later relocation of the air pumps to the pilot on one engine reduced the slipping.

Not quite six years later, the B&O sent all five to the scrapyard in May-June 1953.