Baltimore & Ohio 2-8-8-4 Yellowstone Type Locomotives

Class Details by Steve Llanso

Class EM-1 (Locobase 333)

Data from tables and diagrams in 1947 Locomotive Cyclopedia and B&O to 1954 Asstd Loco Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Works numbers were 70062-70081 (1943) and 71502-71511 (1945).

Firebox heating surface included 211 sq ft of thermic syphons (5) and arch tubes. Lateral cushioning devices on each lead driver axle eased the locomotive into curves; the lead axle in the trailing truck also had one. Every axle on the engine and tender turned with roller bearings, which significantly reduced friction.

Drury (1993) says that "they were truly modern locomotives -- and they weren't what B&O wanted. The EM-1s probably wouldn't have been built but for the restrictions on diesels imposed by the War Production Board." On the other hand, they were very highly regarded engines that were the heaviest to be bought by the B&O, but among the lightest super-sized articulateds to be produced. They were, in fact almost 20 tons lighter on the drivers than the next heaviest engine (the Espee's AC-9 backup).

Despite the cool reception, the EM-1s soon established themselves as one of the premier articulateds in the East. In their initial assignments on the Cumberland and Pittsburgh Divisions and later on the ore-boat shuttles in northern Ohio, they proved powerful, quite reliable, and fast enough even to work an occasional passenger train. One less-obvious reason for this success was the relatively low boiler pressure setting, which raised the factor of adhesion. Some of the heavier coal and ore trains needed two EM-1s on the point and a third as pusher on the rear.

As dieselization progressed, the EM-1s were sidelined, being reawakened in several years to pick up the slack during times of heavy freight volume. The last retired in 1960.


Specifications by Steve Llanso
Class EM-1
Locobase ID 333
Railroad Baltimore & Ohio (B&O)
Whyte 2-8-8-4
Road Numbers 7600-7629
Gauge Std
Builder Baldwin
Year 1944
Valve Gear Walschaert
Locomotive Length and Weight
Driver Wheelbase 16.50'
Engine Wheelbase 65.17'
Ratio of driving wheelbase to overall engine wheebase 0.25
Overall Wheelbase (engine & tender) 112.50'
Axle Loading (Maximum Weight per Axle) 62100 lbs
Weight on Drivers 485000 lbs
Engine Weight 628700 lbs
Tender Light Weight 382000 lbs
Total Engine and Tender Weight 1010700 lbs
Tender Water Capacity 22000 gals
Tender Fuel Capacity (oil/coal) 25 tons
Minimum weight of rail (calculated) on which locomotive could run 101 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter 64"
Boiler Pressure 235 psi
Cylinders (dia x stroke) 24" x 32" (4)
Tractive Effort 115056 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.22
Heating Ability
Firebox Area 756 sq. ft
Grate Area 117.50 sq. ft
Evaporative Heating Surface 5298 sq. ft
Superheating Surface 2118 sq. ft
Combined Heating Surface 7416 sq. ft
Evaporative Heating Surface/Cylinder Volume 158.10
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation 27613
Same as above plus superheater percentage 35620
Same as above but substitute firebox area for grate area 229181
Power L1 21050
Power MT 765.48

Photos

Reference

Credits

Introduction and roster provided by Richard Duley . Class details and specifications provided by Steve Llanso of Sweat House Media.

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