Tennessee Central 4-8-2 "Mountain" Locomotives in 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
665725511925ALCO
665735521925ALCO
665745531925ALCO
665755541925ALCO

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 Rail Data Exchange.

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
Class551
Locobase ID7347
RailroadTennessee Central
CountryUSA
Whyte4-8-2
Number in Class4
Road Numbers551-554
GaugeStd
Number Built4
BuilderAlco-Brooks
Year1926
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)16.75 / 5.11
Engine Wheelbase (ft / m)37 / 11.28
Ratio of driving wheelbase to overall engine wheebase 0.45
Overall Wheelbase (engine & tender) (ft / m)69.94 / 21.32
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)180,500 / 81,874
Engine Weight (lbs / kg)273,000 / 123,831
Tender Loaded Weight (lbs / kg)158,800 / 72,031
Total Engine and Tender Weight (lbs / kg)431,800 / 195,862
Tender Water Capacity (gals / ML)9000 / 34.09
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.70
Minimum weight of rail (calculated) (lb/yd / kg/m)75 / 37.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)63 / 1600
Boiler Pressure (psi / kPa)217.60 / 15
High Pressure Cylinders (dia x stroke) (in / mm)24" x 28" / 610x711
Tractive Effort (lbs / kg)47,350 / 21477.62
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.81
Heating Ability
Firebox Area (sq ft / m2)234 / 21.75
Grate Area (sq ft / m2)59.95 / 5.57
Evaporative Heating Surface (sq ft / m2)2795 / 259.76
Superheating Surface (sq ft / m2)752 / 69.89
Combined Heating Surface (sq ft / m2)3547 / 329.65
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