Western Maryland 4-8-4 "Northern" Locomotives of 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 Raildata collection. Works numbers were 73082-73093 in January 1947.

Firebox heating surface included 153 sq ft in 4 thermic syphons in the firebox proper as well as in the combustion chamber. Known as "Potomacs," these engines had very nearly the same performance at 45 mph as the M-2 class 4-6-6-4s. They were the last 4-8-4s built new for a railroad in the US and retired with the rest of Western Maryland's steam in 1954.

Specifications 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 Wheelbase19.25'
Engine Wheelbase46.83'
Ratio of driving wheelbase to overall engine wheebase 0.41
Overall Wheelbase (engine & tender)95'
Axle Loading (Maximum Weight per Axle)72500 lbs
Weight on Drivers290000 lbs
Engine Weight506500 lbs
Tender Light Weight421500 lbs
Total Engine and Tender Weight928000 lbs
Tender Water Capacity22000 gals
Tender Fuel Capacity (oil/coal)30 tons
Minimum weight of rail (calculated)121 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter69"
Boiler Pressure255 psi
Cylinders (dia x stroke)26.5" x 32"
Tractive Effort70591 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.11
Heating Ability
Firebox Area573 sq. ft
Grate Area106.70 sq. ft
Evaporative Heating Surface4973 sq. ft
Superheating Surface2170 sq. ft
Combined Heating Surface7143 sq. ft
Evaporative Heating Surface/Cylinder Volume243.44
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation27209
Same as above plus superheater percentage35371
Same as above but substitute firebox area for grate area189950
Power L139288
Power MT1194.69



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