Chesapeake & Ohio 4-4-2 "Atlantic" Locomotives in the USA

Class A-16 (Locobase 5047)

Data from "Atlantic Type for the C & O," Railway & Locomotive Engineering, Volume 15, No 11 (November 1902), p. 464; and "Atlantic Type Locomotive, Chesapeake & Ohio Railway", Railway Master Mechanic, Volume 26 , No 10 (October 1902), pp. 358-359. (Thanks to Chris Hohl for his 24 July 2023 email reporting his calculation of the tender's loaded weight and the original road-number sequence.) Schenectady works numbers were 26265-26267 in August 1902 and 28447-28449 in August 1903; Richmond works numbers were 30708-30710 in June 1905; 41088, 41127-41128 in October 1906, and 42391-42397 in 1907.

Firebox heating surface included 27.09 sq ft (2.52 sq m)of water tubes. The design featured a "traction increaser" that could be applied to put an additional 12,000 lb (5,443 kg) on the drivers. The cab had the typical C & O clerestory on top.

The only Atlantics on the Chesapeake and Ohiom but a class whose numbers stood well above the typical. Their relatively small drivers lent a more workaday appearance than the racehorse style of many other 4-4-2s with taller wheels. The wheel arrangement may not seem the best choice for the line's profile (hence the traction increasers for hill climbing and, perhaps, autumn leaves on the rails); indeed these were the only 4-4-2s. But they held on for decades in their superheated form. (See 5048).

Class A-16s (Locobase 5048)

. Data from C & O's 1936 Locomotive Diagram book supplied by Allen Stanley in May 2005 from his extensive Rail Data Exchange. (Thanks to Chris Hohl for his 24 July 2023 email clarifying the relationship between the single Pittsburgh locomotive and the rest of the class as well as pointing out the two different tube counts and diamters.) Alco's Pittsburgh plant's works number was 55656 in September 1916.

Alco's Pittsburgh Works delivered the 278 (works number as the trial horse for a superheated update; its data is as shown above in the specs -- the other 19 were modified to match. Beginning with the last of the class, the Chessie's Atlantics (Locobase 5047) were made over in the early 1920s.

Notice the choices made in the renovation. Tractive effort remained nearly identical because at the same time the cylinders gained a inch in diameter, the boiler pressure was knocked down 15 psi. Piston valves measured a healthy 12" (305 mm) in diameter. Weights increased considerably. Overall heating surface declined, but having 16.3% in superheater area could only improve efficiency. Firebox heating surface includes 23 sq ft (2.14 sq m) in four arch tubes.

Most of the modified A-16 engines used the tube and flue numbers and diameters. The change represented a nearly 200 small tube reduction in favor of the 30 superheater flues. Chris Hohl noted that 282 and 285 presented 153 2 1/4" small tubes instead of the 190 tubes of the others. Heating surface area measured 2,121 sq ft (197.05 sq m) from the tubes for a total of and 2,322 sq ft (215.72 sq m) for total evaporative heating surface area.

The makeover must have been satisfactory as 13 of the engines remained in use until 1949