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.
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 Middle Run Media | |
|---|---|
| Class | J-1 |
| Locobase ID | 286 |
| Railroad | Western Maryland (WM) |
| Country | USA |
| Whyte | 4-8-4 |
| Number in Class | 12 |
| Road Numbers | 1401-1412 |
| Gauge | Std |
| Number Built | 12 |
| Builder | Baldwin |
| Year | 1947 |
| Valve Gear | Walschaert |
| 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 / 1760 |
| 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 Volume | 243.42 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 27,209 |
| Same as above plus superheater percentage | 35,371 |
| Same as above but substitute firebox area for grate area | 189,950 |
| Power L1 | 39,284 |
| Power MT | 1194.57 |
