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

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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 Wheelbase (ft / m)11 / 3.3513 / 3.96
Engine Wheelbase (ft / m)28.92 / 8.8128.92 / 8.81
Ratio of driving wheelbase to overall engine wheebase 0.38 0.45
Overall Wheelbase (engine & tender) (ft / m)57.29 / 17.46
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)152,000 / 68,946156,000 / 70,760
Engine Weight (lbs / kg)209,500 / 95,028208,500 / 94,574
Tender Loaded Weight (lbs / kg)148,500 / 67,359148,500 / 67,359
Total Engine and Tender Weight (lbs / kg)358,000 / 162,387357,000 / 161,933
Tender Water Capacity (gals / ML)8000 / 30.308000 / 30.30
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)12 / 10.9012 / 10.90
Minimum weight of rail (calculated) (lb/yd / kg/m)84 / 4287 / 43.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)63 / 160063 / 1600
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)21" x 28" / 533x71121.5" x 28" / 546x711
Tractive Effort (lbs / kg)33,320 / 15113.7234,926 / 15842.19
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.56 4.47
Heating Ability
Firebox Area (sq ft / m2)235 / 21.84213 / 19.80
Grate Area (sq ft / m2)43.50 / 4.0443.50 / 4.04
Evaporative Heating Surface (sq ft / m2)2340 / 217.471920 / 178.44
Superheating Surface (sq ft / m2)400 / 37.17
Combined Heating Surface (sq ft / m2)2340 / 217.472320 / 215.61
Evaporative Heating Surface/Cylinder Volume208.47163.19
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation87008700
Same as above plus superheater percentage870010,179
Same as above but substitute firebox area for grate area47,00049,842
Power L1657611,753
Power MT286.14498.29