Milwaukee Road 2-6-2 "Prairie" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class K1 (Locobase 815)

Brooks built 125 of these very useful Prairie freight locomotives from 1907-1909, and the Milwaukee Road's (then the Chicago, Milwaukee, & St. Paul) own West Milwaukee shops completed another 70. They burned lignite coal (low-calorie, therefore requiring a large firebox).

Those that weren't superheated were retired in the late 1930s, others lasted until diesels took over in 1the 1950s.

Class K1-as (Locobase 6795)

Data from Milwrd 1930a Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

As big a holding as the Milwaukee had in Prairies (Locobase 815), it only made sense to superheat them. This was the result. The firebox heating surface included 27 sq ft of arch tubes.

Specifications by Steve Llanso of Sweat House Media
Locobase ID815 6795
RailroadMilwaukee Road (CMStP&P)Milwaukee Road (CMStP&P)
Number in Class19570
Road Numbers5500-+5500-+
Number Built195
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase11'11'
Engine Wheelbase29.25'29.25'
Ratio of driving wheelbase to overall engine wheebase 0.38 0.38
Overall Wheelbase (engine & tender)60'59.81'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers154500 lbs153950 lbs
Engine Weight209000 lbs205550 lbs
Tender Light Weight155300 lbs155300 lbs
Total Engine and Tender Weight364300 lbs360850 lbs
Tender Water Capacity8000 gals8000 gals
Tender Fuel Capacity (oil/coal)14 tons
Minimum weight of rail (calculated)86 lb/yard86 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter63"63"
Boiler Pressure200 psi200 psi
Cylinders (dia x stroke)21" x 28"21.5" x 28"
Tractive Effort33320 lbs34926 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.64 4.41
Heating Ability
Firebox Area238 sq. ft238 sq. ft
Grate Area44 sq. ft44 sq. ft
Evaporative Heating Surface2348 sq. ft1980 sq. ft
Superheating Surface412 sq. ft
Combined Heating Surface2348 sq. ft2392 sq. ft
Evaporative Heating Surface/Cylinder Volume209.18168.29
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation88008800
Same as above plus superheater percentage880010296
Same as above but substitute firebox area for grate area4760055692
Power L1661912276
Power MT283.35527.39


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