Works numbers were
June 49081; July 49237, 49350; August 49488, 49644; September 50000; October 50132, 50346, November 50674; December 50786, 50991
These 23 engines were built as Mallet compounds with 39-inch LP cylinders; all four cylinders were served by 14" (356 mm) piston valves. Articulation of the vanadium-steel frame allowed the engines to take 16-deg radius curves, despite the provision of flanges on all drivers. (The front pair in each group used flange lubricators.) Erecting a brick wall (similar to if not identical with a Gaines wall) across the firebox's throat separated the grate from the combustion chamber, which contributed 109-sq ft (10.1 sq m) to the firebox heating surface area.. . Even with the five-foot long combustion chamber, however, the tube length still stretched out to 24 feet (7.3 metres).
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."
Eleven locomotives that were produced in 1924 had fewer tubes and more flues; see Locobase 11083.
The others were not converted because of lack of funds. Six were scrapped in 1937-1939, the remainder in 1949-1950.
Five years after the Southern bought the first batch of Ls-1 Mallets, it went back to Baldwin for more. Baldwin took the opportunity to reallocate boiler space by reducing the number of tubes and increase the number of flues. The result was a high percentage of superheater area as part of the overall combined heating surface. More direct heating surface area was supplied by the 112 sq ft (10.4 sq m) of the 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. Six were scrapped in 1937-1939, the remainder in 1949-1950.
Firebox heating surface included 109 sq ft (10.1 sq m) of combustion chamber and 97 sq ft (9 sq m) of thermic syphons, boiler fitted with exhaust steam injectors. The 12" (305 mm) piston valves had a 7" (177 mm) travel with 1 5/8"(41.28 mm) lap and 3/16" (4.76 mm) 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 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.
Firebox heating surface included 109 sq ft (10.1 sq m) of combustion chamber, boiler fitted with exhaust steam injectors. The 12" (305 mm) piston valves had a 7" (229 mm) travel with 1 5/8" (41.275 mm) lap and 3/16" (4.77 mm) lead. As delivered, the boiler had 216 tubes; six were later deleted or blocked off.
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 at the same time (see Locobase 11083). The boiler was a bit smaller, however, and did not provide the pattern for the eight Ls-2 that followed in 1928. (See Locobase 328.)
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Southern (SRS)||Southern (SRS)||Southern (SRS)||Southern (SRS)|
|Number in Class||10||11||8||1|
|Locomotive Length and Weight|
|Driver Wheelbase (ft)||15.50||15.50||15.50||15.50|
|Engine Wheelbase (ft)||56.25||56.75||56.75||56.75|
|Ratio of driving wheelbase to overall engine wheebase||0.28||0.27||0.27||0.27|
|Overall Wheelbase (engine & tender) (ft)||86.98||87.87||87.85||95.64|
|Axle Loading (Maximum Weight per Axle) (lbs)|
|Weight on Drivers (lbs)||374,000||374,000||409,000||390,000|
|Engine Weight (lbs)||427,000||427,000||469,000||448,000|
|Tender Loaded Weight (lbs)||176,000||191,400||191,400||261,600|
|Total Engine and Tender Weight (lbs)||603,000||618,400||660,400||709,600|
|Tender Water Capacity (gals)||9000||10,000||10,000||14,000|
|Tender Fuel Capacity (oil/coal) (gals/tons)||12||16||16||16|
|Minimum weight of rail (calculated) (lb/yd)||78||78||85||81|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in)||56||56||57||57|
|Boiler Pressure (psi)||210||210||210||210|
|High Pressure Cylinders (dia x stroke) (in)||25" x 30"||25" x 30"||23" x 30" (4)||23" x 30" (4)|
|Low Pressure Cylinders (dia x stroke) (in)||39" x 30"||39" x 30"|
|Tractive Effort (lbs)||84,719||84,719||99,396||99,396|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.41||4.41||4.11||3.92|
|Firebox Area (sq ft)||335||335||436||335|
|Grate Area (sq ft)||82.80||82.80||82.80||83|
|Evaporative Heating Surface (sq ft)||4990||4925||4976||4825|
|Superheating Surface (sq ft)||1260||1350||1420||1350|
|Combined Heating Surface (sq ft)||6250||6275||6396||6175|
|Evaporative Heating Surface/Cylinder Volume||292.77||288.95||172.46||167.23|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||17,388||17,388||17,388||17,430|
|Same as above plus superheater percentage||20,866||21,213||21,213||21,265|
|Same as above but substitute firebox area for grate area||84,420||85,827||111,703||85,827|