Northern Minnesota didn't have much call for passenger service, but the Iron Range found a need for more power than the Ten-wheelers could provide. They bought these small Pacifics that possessed a free-steaming boiler and 14" (356 mm) piston valves.
Original superheater area was given as 561 sq ft (52.12 sq m), possibly because of a difference in computing that figure in 1913. Arch tubes contributed 25.8 sq ft (2.40 sq m) to the firebox heating surface area. Adhesion weight when delivered came to 134,500 lb (61,008 kg), 1,500 lb more than specified. Original tender capacity amounted to 12 tons (10.9 tonnes) of coal and 7,000 US gallons (24,695 litres) of water.
Boiler pressure increased from 190 psi in 1913 to 200 psi, which yielded the tractive effort shown in Locobase's specifications. Retirements came in 1953-1955.
See the larger DM & N Pacifics delivered by Baldwin in the same year in Locobase 7284.
In the same time the Duluth & Iron Range took delivery of four light Pacifics (Locobase 7283), the same builder supplied these substantially larger engines to the DM&N.
Whereas the Iron Range's engines were branch-liners, the Northern's trio were headed to the main line. As delivered, their boilers were pressed to 190 psi, which according to Baldwin's spec, led to a starting tractive effort of 39,000 lb and a factor of adhesion of 4. Chris Hohl's calculation of the data, which Locobase later confirmed, yielded 40,960 lb and an FofA of 3.81. Also, the original superheater area calculation was considerably lower at 721 sq ft (66.98 sq m) even though the layout was the same. Small tube count decreased by 9 from the original 177.
Free-steaming and fitted with 15" piston valves, these 4-6-2s would later increase boiler pressure to 200 psi and would gain 17,310 lb (7,852 kg) in adhesion weight over the original estimate of 156,000 lb (70,760 kg). The resulting data are those shown in Locobase's specifications.
The class served the DM&N and successor DM&IR into the 1950s before retiring in 1955 (401), 1958 (402), and 400 in 1959.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Duluth & Iron Range (DM&IR)||Duluth, Missabe & Northern (DM&IR)|
|Number in Class||4||3|
|Locomotive Length and Weight|
|Driver Wheelbase (ft)||12.50||12.50|
|Engine Wheelbase (ft)||31.83||35|
|Ratio of driving wheelbase to overall engine wheebase||0.39||0.36|
|Overall Wheelbase (engine & tender) (ft)||63.04||65.83|
|Axle Loading (Maximum Weight per Axle) (lbs)|
|Weight on Drivers (lbs)||140,000||173,310|
|Engine Weight (lbs)||223,900||254,600|
|Tender Loaded Weight (lbs)||137,400||171,800|
|Total Engine and Tender Weight (lbs)||361,300||426,400|
|Tender Water Capacity (gals)||6300||8600|
|Tender Fuel Capacity (oil/coal) (gals/tons)||14||14|
|Minimum weight of rail (calculated) (lb/yd)||78||96|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in)||69||69|
|Boiler Pressure (psi)||200||190|
|High Pressure Cylinders (dia x stroke) (in)||22" x 28"||25" x 28"|
|Tractive Effort (lbs)||33,389||40,960|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.19||4.23|
|Firebox Area (sq ft)||205||243.10|
|Grate Area (sq ft)||47.70||58.60|
|Evaporative Heating Surface (sq ft)||2716||3087|
|Superheating Surface (sq ft)||610||906|
|Combined Heating Surface (sq ft)||3326||3993|
|Evaporative Heating Surface/Cylinder Volume||220.47||194.05|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||9540||11,134|
|Same as above plus superheater percentage||11,257||13,695|
|Same as above but substitute firebox area for grate area||48,380||56,812|