Southern 4-8-2 "Mountain" Locomotives of the USA

As steel cars became more numerous on Southern Railroad passenger trains between Washington, DC and Atlanta, GA, the 4-6-2 "Pacifics" were unable to maintain running times. In need of more power the Southern bought 23 "Mountains" (road numbers 1450 through 1472) from the Baldwin Locomotive Works in 1917.

These locomotives were designated Class Ts and weighed 314,800 lbs and had 27 x 28 cylinders, 69" drivers, a boiler pressure of 200 psi and exerted 50,300 lbs of tractive effort.

In 1919, Baldwin delivered 25 USRA "Mountains" (road numbers 1475 through 1499). They were designated Class Ts-1 and weighed 327,000 pounds. They had 27 x 30 cylinders, 69" drivers, a 200 psi boiler pressure and exerted 53,900 lbs of tractive effort.

The Southern "Mountains" ran on the Washington to Atlanta main line working in both directions out of Spencer, NC.

There were ten other "Mountains" built by Baldwin for two of the Southern Railroad subsidiaries. Five of the Class Ts locomotives (road numbers 6490 through 6494) were built for the Cincinnati, New Orleans & Texas Pacific in 1917. Five were built for the Alabama Great Southern. These were two Class Ts (road numbers 6695 and 6696) built in 1917 and three Class Ts-1 (road numbers 6692 through 6694) built in 1919.

Neither the Southern Railroad nor its subsidiaries saved any of the "Mountains" for posterity.

Roster by Richard Duley

ClassQty.Road NumbersYear BuiltBuilderLine
Ts26695-66961917BaldwinAlabama Great Southern
Ts-136692-66941919BaldwinAlabama Great Southern

Class Details by Steve Llanso of Sweat House Media

Class Ts (Locobase 227)

Prince (1965) and some data from Southern Railway diagrams hosted on (viewed September 2002). See also DeGolyer, Vol 56, pp.369+, 424-443. Works numbers were 44666-44667 in December 1916; 44811-44813, 44871-44875, 44903, 44925 in January 1917; 45085-45087 (SRS), 45116, 45240-5243 (CNO & TP); 45117, 45269 (AGS) in February; 45844-45847 in June; 45982-45983, 46001 in July and 46062 in August.

Nearly square (i.e. bore/stroke ratio) cylinders were supplied by 14" (356 mm) piston valves. Firebox heating surface included 30 sq ft (2.8 sq m) in four arch tubes, although that installation may have been removed before long as the heating surface area in a 1926 diagram is too low to include arch tubes.

Thirty Ts were built by Baldwin in 1917: 23 for the Southern (1450 series), five for the Cincinnati, New Orleans & Texas Pacific (850-854, later renumbered 6490-6494), and two for the Alabama Great Southern (280-281, later 6690-6691, still later 6695-6696).

These Mountains pulled passenger trains on the hilly Atlanta-Birmingham, Bristol-Memphis, and Macon-Chattanooga routes. Like the Ps-4s, these engines received a striking apple green and gold paint job in the late 1920s that they retained for the rest of their operating life.

Class Ts-1 (Locobase 1429)

Data from tables and diagram in 1930 Locomotive Cyclopedia and in SRY 6 - 1947 List and Description of Locomotives supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Baldwin works numbers were 51647, 51653-51654, 51704-51705, 51730-51733 in April 1919; 51798-51800. 51814, 51865 in May. (Thanks to Chris Hohl for correcting the valve gear ID.) Alco-Richmond's works numbers were 59800-59800.

Boiler had feedwater heater. Firebox heating surface includes 27 sq ft of arch tubes.

Standard light "Mountain" design as conceived for mass production during World War I by the USRA. The Southern's 25 came from Baldwin and Alco-Richmond. The six sent to the Cincinnati, New Orleans & Texas Pacific were produced by Richmond (works 59805-59809) and Baldwin (works 51601 in March 1919). Alabama Great Southern received 3 of the Southern's Baldwins (road 1484, 1488-1489).

Like the Ts and Ps-4 class passenger engines, Ts-1 locomotives were decked in an attractive apple green and gold paint scheme in the late 1920s that the Southern maintained right up to retirement in 1952-1953.

Specifications by Steve Llanso of Sweat House Media
Locobase ID227 1429
RailroadSouthern (SRS)Southern (SRS)
Number in Class2325
Road Numbers1450-1472, 6490-6494, 6695-66961475-1499, 6495-6499, 6692-6694
Number Built2325
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)1818.25
Engine Wheelbase (ft)38.9240
Ratio of driving wheelbase to overall engine wheebase 0.46 0.46
Overall Wheelbase (engine & tender) (ft)73.2975.70
Axle Loading (Maximum Weight per Axle) (lbs)54,90056,500
Weight on Drivers (lbs)209,800224,500
Engine Weight (lbs)314,800327,000
Tender Loaded Weight (lbs)171,000192,000
Total Engine and Tender Weight (lbs)485,800519,000
Tender Water Capacity (gals)900010,000
Tender Fuel Capacity (oil/coal) (gals/tons)1216
Minimum weight of rail (calculated) (lb/yd)8794
Geometry Relating to Tractive Effort
Driver Diameter (in)6969
Boiler Pressure (psi)200200
High Pressure Cylinders (dia x stroke) (in)27" x 28"27" x 30"
Tractive Effort (lbs)50,29053,883
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.17 4.17
Heating Ability
Firebox Area (sq ft)329356
Grate Area (sq ft)7770.30
Evaporative Heating Surface (sq ft)36684121
Superheating Surface (sq ft)942966
Combined Heating Surface (sq ft)46105087
Evaporative Heating Surface/Cylinder Volume197.68207.29
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,40014,060
Same as above plus superheater percentage18,48016,731
Same as above but substitute firebox area for grate area78,96084,728
Power L117,09516,885
Power MT718.55663.25


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