Although relatively small and possessing a modest amount of calculated tractive effort, this design seems to have struck a good balance between cylinder volume and boiler size. It was a light Pacific with passenger-train drivers that gave decades of good service.
As the RG acknowledged, this locomotive had a big boiler for its cylinder volume, observing that the ratio of 287:1 was "...a figure which would indicate a large boiler capacity for sustained high speed." Accompanying the larger boiler was a large enough grate that "there should be no difficulty, with an average grade of bituminous coal, in generating plenty of steam without forcing the fire to an uneconomical rate of combustion."
The author helpfully "calls attention" to the flexible staybolts used along the front and top of the side sheets of the firebox, the forward slope of the tubesheet, as well as 38 sq ft of arch tubes, "... all indicative of current practice."
In 1922, the 250 was rebuilt with superheaters, piston valves, and Walschaert valve gear. Renumbered 251, the engine was sold to the Georgia Railroad in 1934, which reconditioned the engine in 1937, taking the opportunity to fit it with Southern valve gear, and renumbered it 254.
See Locobase 11418 for details on this 2-locomotive class, one of which went to the West Point, the other to the WRA as shown in the specs. Alco-Richmond added the 151 in 1910 that was fitted with Walschaert gear from the beginning.
Like the 250 on the WPR, the 150 was updated with superheaters, piston valves, and Walschaert valve gear in 1922-1923. Renumbered 152, the engine was sold to the Georgia Railroad in 1934. 151 was sold to the GaR in 1936 - the locomotives were renumbered 252-253 and rebuilt one more time with 73" drivers. The two served out their time on the Georgia, retiring in 1953-1954.
This trio of light Pacifics originally were delivered to the Atlanta & West Point in 1907 by Rogers (works #43024) as 251 and as Western Railway of Alabama 150 (works #43025); 151 was delivered to the WRA in 1910 by Richmond (works #48868). The A & WP rebuilt 251 with piston valves and Walschaerts gear and later sold it to the GRR in 1934. WRA sold its 151 to the GRR in 1934 and added the 150 (by then renumbered 252) in 1936.
In 1938, the GRR reworked them yet again, fitting them with outside-journal trailing trucks and 254 was fitted with Southern valve gear.
This variegated threesome then served the Georgia RR until the demise of steam in 1954.
Dennington explains that this two-locomotive order was split between the WPR constituents Atlanta & West Point (290) and the Western Railway of Alabama (190)
His summary comment on this pair suffices: "The USRA design on locomotives was classic and beautiful. Lima built a very good version of the design when they built 290 and 190." Compared to the Southern's more famous Ps-4s, these engines had a higher superheater area and ratio and 14" piston valves. The diagram does not show if the P-74s had arch tubes, but it seems likely given the total area of the firebox.
Like the Ps-4s, the valves had outside lap of 1 1/4", full-gear lead of 1/4", but a total travel of 7", 1/2" less than the Ps-4. Dennington's comment, recorded below, that they handled heavy trains effortlessly stems in large part from having a large boiler with generous steam admission.
Dennington's experience on the 290 in 1992 as she pulled the Southern Crescent was ".... a real thrill ...290 could easily handle 16 to 18 heavy-weight coaches. She was a powerful engine. Running at fifty and sixty mph seemed to be effortless and she rode well at those speeds." He noticed that her stack talk revealed "... a fairly loud exhaust, although deeper and more resonant than the bigger Freedom Train engines."
|Specifications by Steve Llanso of Sweat House Media|
|Class||P||P||P||P - updated||P-74|
|Railroad||Atlanta & West Point (WPR)||Atlanta & West Point (WPR)||Western Railway of Alabama (WPR)||Georgia Railroad (WPR)||West Point Route (WPR)|
|Number in Class||2||1||1||2||2|
|Road Numbers||280-281||250||150||253-255||290, 190|
|Locomotive Length and Weight|
|Driver Wheelbase (ft)||13||12.67||12.67||12.67||14|
|Engine Wheelbase (ft)||33.25||32.46||32.46||33.79||37|
|Ratio of driving wheelbase to overall engine wheebase||0.39||0.39||0.39||0.37||0.38|
|Overall Wheelbase (engine & tender) (ft)||68.46||60||60||69.17||72.44|
|Axle Loading (Maximum Weight per Axle) (lbs)||54,400||52,200||64,500|
|Weight on Drivers (lbs)||163,000||130,000||130,000||151,300||192,500|
|Engine Weight (lbs)||258,000||212,000||212,000||248,600||303,500|
|Tender Loaded Weight (lbs)||196,300||133,000||133,000||181,100||200,500|
|Total Engine and Tender Weight (lbs)||454,300||345,000||345,000||429,700||504,000|
|Tender Water Capacity (gals)||10,000||7000||7000||10,000||11,000|
|Tender Fuel Capacity (oil/coal) (gals/tons)||17||12||12||15||15|
|Minimum weight of rail (calculated) (lb/yd)||91||72||72||84||107|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in)||74||72||72||73||74|
|Boiler Pressure (psi)||200||200||200||200||200|
|High Pressure Cylinders (dia x stroke) (in)||24" x 28"||22" x 28"||22" x 28"||23" x 28"||27" x 28"|
|Tractive Effort (lbs)||37,051||31,998||31,998||34,494||46,892|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.40||4.06||4.06||4.39||4.11|
|Firebox Area (sq ft)||273||276||276||271||327|
|Grate Area (sq ft)||56.55||55||55||54||70.80|
|Evaporative Heating Surface (sq ft)||3458||3532||3532||2737||3669|
|Superheating Surface (sq ft)||894||894||990|
|Combined Heating Surface (sq ft)||4352||3532||3532||3631||4659|
|Evaporative Heating Surface/Cylinder Volume||235.87||286.71||286.71||203.28||197.74|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||11,310||11,000||11,000||10,800||14,160|
|Same as above plus superheater percentage||13,685||11,000||11,000||13,500||17,134|
|Same as above but substitute firebox area for grate area||66,066||55,200||55,200||67,750||79,134|