Class Ls-1 (Locobase 327)

Some data from Southern Railway diagrams hosted on southern.railfan.net/images/archive/southern/steam_loco_diagrams (viewed September 2002)..

These 23 engines were built as Mallet compounds with 39-inch LP cylinders; the first 10 were completed in 1918, 2 more in 1919, 5 in 1924, and 6 in 1926. According to the April 1919 Railway and Locomotive Engineering, the Appalachia Division for which they were headed presented "... an undulating profile with frequent grades of one to two percent." The article especially highlighted 8 miles near the Bristol end of the Division: "The most difficult section of the line is between Philips and Mountain. From

mile-post 57 to mile-post 65 southbound, the average grade is 1.7 per cent with a

maximum, for short distances, of 3.4 per cent. This portion of the line is an almost

constant succession of curves, many of them of over 10 degrees."

Firebox heating surface included a 109-sq ft combustion chamber. Three -- 4018, 4021, 4025 -- were later rebuilt with four 23" diameter HP cylinders after the success of the new-construction Ls-2 became evident in the late 1920s. The others were not converted because of lack of funds. 6 were scrapped in 1937-1939, the remainder in 1949-1950.

Class Ls-2 (Locobase 5136)

Firebox heating surface included 109 sq ft of combustion chamber, boiler fitted with exhaust steam injectors. The 12" piston valves had a 7" travel with 1 5/8" lap and 3/16" lead.

The detailed roster in Prince (1965) shows that 4050 was the trial horse for simple-expansion Mallets. Its design was based on the compound locomotives delivered several years earlier. The boiler was a bit smaller, however, and did not provide the pattern for the 8 Ls-2 that followed in 1928. (See separate database entry.)

Some data from Southern Railway diagrams hosted on southern.railfan.net/images/archive/southern/steam_loco_diagrams (viewed September 2002)..

Class Ls-2 (Locobase 328)

Some data from Southern Railway diagrams hosted on southern.railfan.net/images/archive/southern/steam_loco_diagrams (viewed September 2002).

Firebox heating surface included 109 sq ft of combustion chamber and 97 sq ft of thermic syphons, boiler fitted with exhaust steam injectors. The 12" piston valves had a 7" travel with 1 5/8" lap and 3/16" lead.

The detailed roster in Prince (1965) shows that 4050 (see separate entry) was the prototype for simple-expansion Southern Mallets. Obviously successful, the single engine was joined by 8 others (works #60495, 60516-22) that were built to a slightly enlarged design and delivered in 1928. One major difference was the addition of thermic syphons, which significantly enhanced the firebox's contribution to overall heating efficiency.

These engines were the largest and most powerful locomotives the Southern ever purchased and operated on the 4.7% Saluda grade in North Carolina until retirement in 1951. They were simple-expansion variants of the earlier Ls-1 Mallet compounds; four of the latter were later converted to simple-expansion operation.