Northern Pacific 2-6-2 "Prairie" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class T (Locobase 817)

Data from table in June 1907 American Engineer and Railroad Journal and from "'Prairie' Type Locomotive, Northern Pacific Ry," The Locomotive Magazine, Vol XII (15 December 1906), pp. 212-213. See also "Locomotive Boilers with Combustion Chambers", Engineering News, Volume LVI, No 21 (22 November 1906), pp. 531-534.

Procured for light freight service in a wheel arrangement that was a first for the NP. They were among 70 engines procured by the NP that year with combustion chambers. David Van Alstyne, the NP's mechanical superintendent, installed a combustion chamber in T-class engine 2378. He said that the principal reason for doing so was to reduce leakage in tubes (especially in regions of bad water) caused by direct contact with the firebox's fire. Van Alstyne reported that the test had borne out his hopes. The brick arch was in place and the tubes showed little sign of stress or leakage. In his report to the Northwest Railway Club, he added: "What seems to me an especially good feature is ...that it very materially increases the heating surface of the firebox."

10 were later converted to light Mikados as the W-4s. 18 more were modified as T-1s; see Locobase 918.

Class T-1 (Locobase 818)

Modified from Ts in the 1920s.

NB: The direct heating surface (including the firebox heating surface) is an estimate calculated by subtracting the calculated tube heating surface from the reported total evaporative heating surface.

Specifications by Steve Llanso of Sweat House Media
Locobase ID817 818
RailroadNorthern Pacific (NP)Northern Pacific (NP)
Number in Class15018
Road Numbers2300-24492450-2467
Number Built150
Valve GearWalschaertStephenson
Locomotive Length and Weight
Driver Wheelbase11'13'
Engine Wheelbase28.92'28.92'
Ratio of driving wheelbase to overall engine wheebase 0.38 0.45
Overall Wheelbase (engine & tender)57.29'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers152000 lbs156000 lbs
Engine Weight209500 lbs208500 lbs
Tender Light Weight148500 lbs148500 lbs
Total Engine and Tender Weight358000 lbs357000 lbs
Tender Water Capacity8000 gals8000 gals
Tender Fuel Capacity (oil/coal)12 tons12 tons
Minimum weight of rail (calculated)84 lb/yard87 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) 4.56 4.47
Heating Ability
Firebox Area235 sq. ft213 sq. ft
Grate Area43.50 sq. ft43.50 sq. ft
Evaporative Heating Surface2340 sq. ft1920 sq. ft
Superheating Surface400 sq. ft
Combined Heating Surface2340 sq. ft2320 sq. ft
Evaporative Heating Surface/Cylinder Volume208.47163.19
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation87008700
Same as above plus superheater percentage870010179
Same as above but substitute firebox area for grate area4700049842
Power L1657611753
Power MT286.14498.29


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