Harriman Lines 4-4-2 "Atlantic" Locomotives in the USA

Class Atlantic A-105 (Locobase 5340)

Data from table in June 1906 AERJ and article earlier that year also in AERJ (p. 154). See also "Report of Committee on Power-Chicago, Rock Island & Pacific Railway-Descriptions of Standard Types of Locomotives," American Engineer and Railroad Journal, Volume 79 (March 1905), pp. 84-86, and Baldwin Locomotive Works, Record of Recent Construction, No. 57, "Associated Lines" (Philadelphia, Pa: 1906); DeGolyer, Volume 28, pp.110+; Volume 30, pp. 32+.

For a detailed discussion of locomotive boiler seam riveting patterns, see "Boiler Seam with Diamond-Shaped Welt," Railway and Locomotive Engineering, Volume 15, No 8 (August 1902), p. 336, and R J Finch, "Calculating the Efficiency of Boiler Seams", Boiler Maker, Volume 22, No 5 (May 1922), pp. 126-129.

Mister E H Harriman, having gained control of the Union Pacific, Southern Pacific, Oregon Railroad and Navigation Company, Oregon Short Line, Chicago & Alton, and Kansas City Southern lines in an 18,000-mile (28,980 km) network, now sought to standardize locomotive and rail car construction details. HF Loree formed a Committee on Power established by LF Loree that included FJ Cole of Alco, CA Seley, mechanical engineer of the Rock Island, and Robert Rennie of the Frisco.)

This policy resulted in the launch of the the Harriman Common Standard (HCS) locomotive series in July 1902. Further tweaking of the plans led to the adoption of standard Atlantic, Pacific, Consolidation, and six-wheel switcher designs. According to the Committee's report: "In all of the boilers the fire-box crown sheets are supported by slings to T-iron roof-bars which are continuous through the crown. All the crown-sheets are flat and all the boilers are straight top except as the fire-boxes slope to the rear. The boiler-sheets are telescopic in all the designs. The circumferential seams are double riveted. The horizontal seams are known as the Vauclain diamond boiler-seam, which has an efficiency of 96 per cent. The very long seams are welded over a length of 11 inches at each end. Except the switch-engines, which carry 180 lbs. per square inch steam-pressure, all the boilers are built for 200 lbs. with a seam-factor of five. "(NB: the "welding" mentioned here was accomplished through a mechanical process, not the heat-based process used later.)

The Atlantic design detailed here is in middle-of-the-road among 4-4-2s of the era. Its boiler is relatively modestly scaled for the volume of its cylinders, which raised its firebox/heating surface ratio to a relatively high value. See Locobase 1431 (Southern Pacific) and Locobase 4406 (Union Pacific) for examples and further commentary.