Western Maryland 4-8-4 "Northern" Locomotives in the USA

The Western Maryland Railroad pooled motive power with the Reading Railroad and when the Reading started using its new Class T-1s running times were improving on the Allentown, PA to Hagerstown, MD freight trains. This caught the attention of the Western Maryland and in 1947 it took delivery of twelve 4-8-4s from the Baldwin Locomotive Works. Being a "southern" railroad WM rejected the name "Northern" and called its 4-8-4s "Potomacs".

These twelve Class J-1 "Potomacs" (road numbers 1401 through 1412) were designed for freight service with 69" drivers, 26.5 x 32 cylinders, a boiler pressure of 255 psi, a weight of 506,500 pounds and a tractive effort of 70,600 pounds.

All were taken out of service by the end of May 1954 and placed in storage in Hagerstown and Cumberland. They were not sold for scrap until the equiment trusts ran out in 1957.

Class Details by Steve Llanso of Sweat House Media

Class J-1 (Locobase 286)

Data from 1947 Locomotive Cyclopedia, supplemented by WM Misc Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also R P Stoddart, "4-8-4 type locomotives on the Western Maryland", Baldwin Magazine, Volume 4, No 1-2, pp. 26-32. (Thanks to Reg Mitchell for his 18 March 2019 email correcting information about the WM's order.) Works numbers were 73082-73093 in January 1947.

Firebox heating surface included 153 sq ft (14.21 sq m) in four thermic syphons in the firebox proper as well as in the combustion chamber. Very nearly the last of the steam line, these "Potomacs"had very nearly the same performance at 45 mph (72 kph) as the M-2 class 4-6-6-4s. Timken roller bearings were fitted on all engine and tender axles and on the back end of the eccentric rod. All link motion pins used needle bearings. Baldwin's General Steel Castings Corporation supplied the integrally cast locomotive bed that included the cylinders and cradle and the Boxpok wheels. Driving axles, main and side rods, and main crank pins were "normalized" and tempered manganese vanadium streel.

Reg Mitchell's email said about the WM order: "I think it would be accurate to say the Western Maryland was the last North American road to embrace the 4-8-4 type with their dozen from Baldwin in 1947. The C&O and N&W engines were reorders [from Lima and Roanoke, respectively]. Unfortunately the WM machines had very short service lives of only seven years." They retired with the rest of Western Maryland's steam in 1954.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID286
RailroadWestern Maryland (WM)
Number in Class12
Road Numbers1401-1412
Number Built12
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)19.25 / 5.87
Engine Wheelbase (ft / m)46.83 / 14.27
Ratio of driving wheelbase to overall engine wheelbase 0.41
Overall Wheelbase (engine & tender) (ft / m)95 / 28.96
Axle Loading (Maximum Weight per Axle) (lbs / kg)72,500 / 32,885
Weight on Drivers (lbs / kg)290,000 / 131,542
Engine Weight (lbs / kg)506,500 / 229,745
Tender Loaded Weight (lbs / kg)421,500 / 191,189
Total Engine and Tender Weight (lbs / kg)928,000 / 420,934
Tender Water Capacity (gals / ML)22,000 / 83.33
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)30 / 27
Minimum weight of rail (calculated) (lb/yd / kg/m)121 / 60.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)69 / 1753
Boiler Pressure (psi / kPa)255 / 17.60
High Pressure Cylinders (dia x stroke) (in / mm)26.5" x 32" / 673x813
Tractive Effort (lbs / kg)70,591 / 32019.58
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.11
Heating Ability
Tubes (number - dia) (in / mm)42 - 2.25" / 57
Flues (number - dia) (in / mm)178 - 4" / 102
Flue/Tube length (ft / m)21 / 6.40
Firebox Area (sq ft / m2)573 / 53.25
Grate Area (sq ft / m2)106.70 / 9.92
Evaporative Heating Surface (sq ft / m2)4973 / 462.17
Superheating Surface (sq ft / m2)2170 / 201.67
Combined Heating Surface (sq ft / m2)7143 / 663.84
Evaporative Heating Surface/Cylinder Volume243.42
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation27,209
Same as above plus superheater percentage35,371
Same as above but substitute firebox area for grate area189,950
Power L139,284
Power MT1194.57

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