Tennessee Central 4-8-2 "Mountain" Locomotives of the USA

The Tennessee Central Mountains were the third lightest of the type (behind Alaska Railroad and New Orleans Great Northern).

Roster by Richard Duley

CNRoad NumbersYear BuiltBuilder

Class Details by Steve Llanso of Sweat House Media

Class 551 (Locobase 7347)

Data from TC 1941ca Locomotive Diagrams and Miscellaneous Data supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

Locobase is intrigued by the unusual boiler pressure rating in these small Mountains. 213 psi converts to 15 bar (or atm), a unit of measure that was almost never used in North American railroading. In any event, these were small for their arrangement and had very low drivers, which suited the hilly terrain over which the class operated. They may have been the lightest 4-8-2s operating on the standard gauge anywhere in North America.

Specifications by Steve Llanso of Sweat House Media
Locobase ID7347
RailroadTennessee Central
Number in Class4
Road Numbers551-554
Number Built4
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)16.75
Engine Wheelbase (ft)37
Ratio of driving wheelbase to overall engine wheebase 0.45
Overall Wheelbase (engine & tender) (ft)69.94
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)180,500
Engine Weight (lbs)273,000
Tender Loaded Weight (lbs)158,800
Total Engine and Tender Weight (lbs)431,800
Tender Water Capacity (gals)9000
Tender Fuel Capacity (oil/coal) (gals/tons)14
Minimum weight of rail (calculated) (lb/yd)75
Geometry Relating to Tractive Effort
Driver Diameter (in)63
Boiler Pressure (psi)217.60
High Pressure Cylinders (dia x stroke) (in)24" x 28"
Tractive Effort (lbs)47,350
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.81
Heating Ability
Firebox Area (sq ft)234
Grate Area (sq ft)59.95
Evaporative Heating Surface (sq ft)2795
Superheating Surface (sq ft)752
Combined Heating Surface (sq ft)3547
Evaporative Heating Surface/Cylinder Volume190.64
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation13,045
Same as above plus superheater percentage15,785
Same as above but substitute firebox area for grate area61,611
Power L116,727
Power MT817.21

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