Rock Island 2-2-4 Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class 2552 (Locobase 9249)

Data from Raymond S Zeitler, Self-Contained Railway Motor Cars and Locomotives (Chicago: American School, 1921), pp 7-9. See also "Steam Motor Car for the Rock Island", Railway Age Gazette, Volume XLV, No 16 (18 September 1908), pp 961-964.

This rail motor-car was similar to several such vehicles in service in Great Britain, but it was all American in appearance. Indeed, it resembled in size and general layout a typical passenger coach. The body was built by American Car & Foundry

The boiler was rigidly mounted on the truck frame and generated steam through an oil-fueled firebox mounted at the front and had the smoke box mounted above it. Exhaust gases traveled back to a combustion chamber, passed through a superheater, and then through return tubes to the smoke box.

Alco used the Mellin cross-compounding system, which included an intercepting valve in the high-pressure cylinder casting that diverted live steam to the larger cylinder when the car was starting.

But, according to Zeitler (who directed his own motor car company), there were many significant disadvantages. The weight of the engine, boiler, fuel, and water; scale and corrosion in the boiler and pipes; time taken to water and refuel, "the annoyance of exhaust steam", and the danger of boiler or pipes bursting. (All of which perils doubtlessly figured prominently in his sales material.)

He concluded: "The steam motor car, therefore, offered none of the advantages of increased travel, comfort, and efficiency demanded by the public and could hardly have been expected to compete with the trolley car. It has, in the United States at least, been entirely replaced by the internal-combustion engine."

Specifications by Steve Llanso of Sweat House Media
Locobase ID9249
RailroadRock Island (CRI & P)
Number in Class1
Road Numbers2552
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)
Engine Wheelbase (ft) 8.33
Ratio of driving wheelbase to overall engine wheebase
Overall Wheelbase (engine & tender) (ft)45.83
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)64,000
Engine Weight (lbs)104,000
Tender Loaded Weight (lbs)
Total Engine and Tender Weight (lbs)
Tender Water Capacity (gals)
Tender Fuel Capacity (oil/coal) (gals/tons)
Minimum weight of rail (calculated) (lb/yd)
Geometry Relating to Tractive Effort
Driver Diameter (in)38
Boiler Pressure (psi)250
High Pressure Cylinders (dia x stroke) (in)9.5" x 12" (1)
Low Pressure Cylinders (dia x stroke) (in)14" x 12" (1)
Tractive Effort (lbs)4147
Factor of Adhesion (Weight on Drivers/Tractive Effort)15.43
Heating Ability
Firebox Area (sq ft)37.60
Grate Area (sq ft)
Evaporative Heating Surface (sq ft)565
Superheating Surface (sq ft)59
Combined Heating Surface (sq ft)624
Evaporative Heating Surface/Cylinder Volume1147.82
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation
Same as above plus superheater percentage
Same as above but substitute firebox area for grate area10,246
Power L119,018
Power MT


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