Rapid City, Black Hills & Western 2-6-2 "Prairie" Locomotives of the USA


Class Details by Steve Llanso of Sweat House Media

Class 48 (Locobase 13711)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 36, p. 126. Works number was 35630 in December 1910.

This Prairie logger was originally ordered by South Carolina's Sumter Logging as their #2, but was relettered and renumbered for the RCBH & W before its delivery. The RCBH & W originally was chartered in 1891 as the Dakota, Wyoming & Missouri River Railroad Company. Reorganized twice in 1904, ultimately as the Missouri River & North Western Railway Company, the road was sold at foreclosure in 1909 and reorganized as Rapid City, Black Hills & Western Railroad Company.

At the time of the 1909 sale, the Crouch Line (after founder Charles D Crouch) measured 32.8 miles as it wended its way through the Rapid Canyon from Rapid City to Mystic. John Hafner's Black Hills Believables: Strange-but-true Tales of the Old West (Fort Collins, CO: Lone Pine Productions, 2002) p. 26, claims that the route made 14 complete circles within the distance and was the crookedest railroad ever built.

(Gene Connelly's Baldwin file puts the transfer in 1919. Connelly also reports that the 48 was destroyed in a 1928 roundhouse fire.)


Class 49 (Locobase 13824)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 51, p. 310. Works number was 42092 in May 1915.

Four years after the RCBH & W bought its first logging Prairie from Baldwin, it returned for a similar engine. The only significant difference was the 12% increase in boiler pressure and a commensurate increase in adhesion weight and engine weight. Even with the weight increase, these were theoretically pretty slippery engines.

The 49 remained on the railroad for its entire career. It was scrapped in 1939.


Class 51 (Locobase 13825)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 53, p. 286. Works number was 43386 in May 1916.

With the 51, the RCBH & W addressed the factor-of-adhesion problem apparent in the 49 (Locobase 13824) by increasing the size of the boiler, raising the cylinder volume, slightly decreasing the boiler, and adding 9 1/2 tons to the weight pressing on the drivers. The result was a balanced, powerful logging Prairie. The Baldwin oil burner was placed in the front of the firebox.

51's career was cut short by the same 1928 roundhouse fire that totalled the 48 (Locobase 13711).

Specifications by Steve Llanso of Sweat House Media
Class484951
Locobase ID13711 13824 13825
RailroadRapid City, Black Hills & WesternRapid City, Black Hills & WesternRapid City, Black Hills & Western
CountryUSAUSAUSA
Whyte2-6-22-6-22-6-2
Number in Class111
Road Numbers484951
GaugeStdStdStd
Number Built111
BuilderBaldwinBaldwinBaldwin
Year191019151916
Valve GearWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase 9.17' 9.17' 9.17'
Engine Wheelbase23.75'23.75'24.67'
Ratio of driving wheelbase to overall engine wheebase 0.39 0.39 0.37
Overall Wheelbase (engine & tender)45.73'47.15'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers65000 lbs69000 lbs84000 lbs
Engine Weight90000 lbs93000 lbs111000 lbs
Tender Light Weight60000 lbs60000 lbs80000 lbs
Total Engine and Tender Weight150000 lbs153000 lbs191000 lbs
Tender Water Capacity3000 gals3000 gals4000 gals
Tender Fuel Capacity (oil/coal)1500 gals1800 gals
Minimum weight of rail (calculated)36 lb/yard38 lb/yard47 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter44"44"44"
Boiler Pressure160 psi180 psi175 psi
Cylinders (dia x stroke)15" x 24"15" x 24"16" x 24"
Tractive Effort16691 lbs18777 lbs20771 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.89 3.67 4.04
Heating Ability
Firebox Area86 sq. ft86 sq. ft109 sq. ft
Grate Area14.10 sq. ft14.10 sq. ft15.60 sq. ft
Evaporative Heating Surface1074 sq. ft1074 sq. ft1319 sq. ft
Superheating Surface
Combined Heating Surface1074 sq. ft1074 sq. ft1319 sq. ft
Evaporative Heating Surface/Cylinder Volume218.79218.79236.17
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation225625382730
Same as above plus superheater percentage225625382730
Same as above but substitute firebox area for grate area137601548019075
Power L1359540444283
Power MT365.80387.63337.23


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