Duluth & Iron Range / Duluth, Missabe & Northern 4-6-2 "Pacific" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class A (Locobase 7283)

See data from DM&IR 6 -1951 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 46, pp.281+ and "Mikado and Pacific Locomotives for the Duluth and Iron Range," Railway and Locomotive Engineering, Volume 26, No 8 (August 1913), pp. 280-281. (Thanks to Chris Hohl for his 16 September 2015 email and spreadsheet showing the differences between the original Baldwin delivery and the later DM&IR updates.) Works numbers were 39861-39864 in May 1913.

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.


Class P (Locobase 7284)

See data from DM&IR 6 -1951 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 46, pp. 179+. (Thanks to Chris Hohl for his 16 September 2015 email and spreadsheet showing the differences between the original Baldwin delivery and the later DM&IR updates.) Works numbers were 39877-39879 in May 1913.

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
ClassAP
Locobase ID7283 7284
RailroadDuluth & Iron Range (DM&IR)Duluth, Missabe & Northern (DM&IR)
CountryUSAUSA
Whyte4-6-24-6-2
Number in Class43
Road Numbers107-110/1107-1110400-402
GaugeStdStd
Number Built43
BuilderBaldwinBaldwin
Year19131913
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.50 / 3.8112.50 / 3.81
Engine Wheelbase (ft / m)31.83 / 9.7035 / 10.67
Ratio of driving wheelbase to overall engine wheebase 0.39 0.36
Overall Wheelbase (engine & tender) (ft / m)63.04 / 19.2165.83 / 20.06
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)140,000 / 63,503173,310 / 78,612
Engine Weight (lbs / kg)223,900 / 101,559254,600 / 115,485
Tender Loaded Weight (lbs / kg)137,400 / 62,324171,800 / 77,927
Total Engine and Tender Weight (lbs / kg)361,300 / 163,883426,400 / 193,412
Tender Water Capacity (gals / ML)6300 / 23.868600 / 32.58
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.7014 / 12.70
Minimum weight of rail (calculated) (lb/yd / kg/m)78 / 3996 / 48
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)69 / 175369 / 1753
Boiler Pressure (psi / kPa)200 / 13.80190 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)22" x 28" / 559x71125" x 28" / 635x711
Tractive Effort (lbs / kg)33,389 / 15145.0140,960 / 18579.17
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.19 4.23
Heating Ability
Firebox Area (sq ft / m2)205 / 19.05243.10 / 22.59
Grate Area (sq ft / m2)47.70 / 4.4358.60 / 5.45
Evaporative Heating Surface (sq ft / m2)2716 / 252.423087 / 286.90
Superheating Surface (sq ft / m2)610 / 56.69906 / 84.20
Combined Heating Surface (sq ft / m2)3326 / 309.113993 / 371.10
Evaporative Heating Surface/Cylinder Volume220.47194.05
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation954011,134
Same as above plus superheater percentage11,25713,695
Same as above but substitute firebox area for grate area48,38056,812
Power L117,23417,109
Power MT814.17652.91

Reference