Interstate 2-8-8-2 "Chesapeake" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 20 (Locobase 6441)

Data based on [] (visited 26 December 2004). Works numbers were 64996-64997 in November 1923.

The diagram indicates that these were based on the USRA heavy articulated (Locobase 330), but were intended to negotiate 22-deg curves. As a result, each set of drivers had a 3" (76.2 mm) longer wheelbase and the engine wheelbase measured a total of 3" longer. One source states that they were originally meant for the Clinchfield, which took ten with slightly shorter wheelbases (Locobase 1321).

The diagram is less informative about heating surfaces, giving only the total of evaporative and superheater combined as 8,332 sq ft (774.07 sq m). This is 737 sq ft (68.44 sq m) more than the USRA standard.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID6441
RailroadInterstate (IRR)
Number in Class2
Road Numbers20-21
Number Built2
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)31.50 / 9.60
Engine Wheelbase (ft / m)58 / 17.68
Ratio of driving wheelbase to overall engine wheelbase 0.54
Overall Wheelbase (engine & tender) (ft / m)94.25 / 28.73
Axle Loading (Maximum Weight per Axle) (lbs / kg)62,000 / 28,123
Weight on Drivers (lbs / kg)486,500 / 220,673
Engine Weight (lbs / kg)541,000 / 245,394
Tender Loaded Weight (lbs / kg)209,200 / 94,892
Total Engine and Tender Weight (lbs / kg)750,200 / 340,286
Tender Water Capacity (gals / ML)12,000 / 45.45
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)16 / 15
Minimum weight of rail (calculated) (lb/yd / kg/m)101 / 50.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)57 / 1448
Boiler Pressure (psi / kPa)240 / 16.50
High Pressure Cylinders (dia x stroke) (in / mm)25" x 32" / 635x813
Low Pressure Cylinders (dia x stroke) (in / mm)39" x 32" / 991x813
Tractive Effort (lbs / kg)101,465 / 46023.80
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.79
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)
Grate Area (sq ft / m2)96.50 / 8.97
Evaporative Heating Surface (sq ft / m2)
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)
Evaporative Heating Surface/Cylinder Volume
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation23,160
Same as above plus superheater percentage23,160
Same as above but substitute firebox area for grate area
Power L1
Power MT

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Wes Barris