United States Government 2-6-2 "Prairie" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 10-12-1/4 D / 5100 (Locobase 13197)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University Volume 57, pp.263+. Works numbers were

September 46256-46266, 46419-46432, 46503-46514

October 46535-46553, 46606-46635, 46755-46764, 46821-46845

November 46996-47020, 47131-47150, 47151

December 47159-47166, 47168-47186

Locobase 4985 describes Baldwin's production of 450 light-railway 4-6-0T locomotives ordered by the British War Department to serve the front lines in France. These engines didn't actually reach the trenches themselves, but the very light rail network behind the fortifications called for small engines.

When the United States entered World War I in April 1917, the Army began stocking up on its own light locomotive needs. It took the War Department design, lengthened the tubes by about 14", recast the wheel arrangement as a double-ender, and ordered nearly 200 of these little Prairie tanks from Baldwin. One note in the specs suggested raising the question of moving the back truck 12" [306 mm] forward "to improve curving."

Many of the engines supported American offensives in 1918.

A few dozen had post-war careers that can be traced. Penrhyn Quarries in Wales bought 3 and named them Llandegai (ex-5159), Felin Hen (ex-5096), and Tregarth (ex-5104). Felin Hen was sold in 1940 to the Fairymead sugar plantation in Australia and had its pony truck removed. It later returned to France as a privately owned locomotive. See the Queenslands Heritage article on this engine at [], last accessed 24 September 2011.

Principal Dimensions by Steve Llanso of Sweat House Media
Class10-12-1/4 D / 5100
Locobase ID13,197
RailroadUnited States Government
Number in Class196
Road Numbers5100-5195
Gauge60 cm
Number Built196
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m) 5.83 / 1.78
Engine Wheelbase (ft / m)15.58 / 4.75
Ratio of driving wheelbase to overall engine wheebase 0.37
Overall Wheelbase (engine & tender) (ft / m)15.58 / 4.75
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)23,500 / 10,659
Engine Weight (lbs / kg)34,500 / 15,649
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)34,500
Tender Water Capacity (gals / ML)476 / 1.80
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)13 / 6.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)23.50 / 600
Boiler Pressure (psi / kPa)178 / 12.30
High Pressure Cylinders (dia x stroke) (in / mm)9" x 12" / 229x305
Tractive Effort (lbs / kg)6258 / 2838.58
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.76
Heating Ability
Firebox Area (sq ft / m2)23.50 / 2.18
Grate Area (sq ft / m2) 5.60 / 0.52
Evaporative Heating Surface (sq ft / m2)287 / 26.67
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)287 / 26.67
Evaporative Heating Surface/Cylinder Volume324.82
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation997
Same as above plus superheater percentage997
Same as above but substitute firebox area for grate area4183
Power L13192
Power MT898.36

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