Missouri Pacific 4-8-4 "Northern" Locomotives in the USA

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In the early 1940s, the Missouri Pacific Railroad converted all 25 of its 2-8-4 Berkshires into 4-8-4 Northerns. These rebuilt locomotives (road numbers 2101 through 2125) were given 75" drivers, greater boiler capacity, a cast steel engine bed and roller bearings on all axles. They had 28 x 30 cylinders, a boiler pressure of 250 psi, a total weight of 449,950 lbs and a tractive effort of 66,640 pounds.

In 1943, 15 more Northerns (road numbers 2201 through 2215) were delivered from the Baldwin Locomotive Works. These "war babies" were duplicates of the 1938 D&RGW 4-8-4s and had 73" drivers, 26 x 30 cylinders, a boiler pressure of 285 psi, a weight of 496,000 lbs and a tractive effort of 67,200 pounds.

There are no survivors.


Roster by Richard Duley

Qty.Road NumbersYear BuiltBuilder
252101-21251940-1942MP
152201-22151943Baldwin

Class Details by Steve Llanso of Sweat House Media

Class 2101/N-75 Victory Locomotives (Locobase 1372)

Data from 1956 Missouri Pacific Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for correcting the valve gear ID.)

Rebuilt 2-8-4s (Locobase 1371) that became very successful freight engines whose tall drivers turned on roller bearings. Feed water heater was the Worthington 4 1/4 BL-2. The firebox heating surface area includes the combustion chamber, 113 sq ft (10.5 sq m) in two thermic syphons (one in the combustion chamber, one in the firebox proper), and 15 sq ft (1.4 sq m) of arch tubes.

See http://www.steamlocomotive.com/northern/mp.html (visited 7 Jan 2003), where Wes Barris says they had cast-steel beds and roller bearings.


Class N-73 (Locobase 266)

Data from 1947 Locomotive Cyclopedia tables and MP 7 - 1956 - Locomotive Diagrams supplied in May 2005 from his extensive collection. Works numbers were 69714-69728 in 1943.

Firebox heating surface included 136 sq ft (12.6 sq m) of thermic syphons installed in the firebox itself and the combustion chamber. These freight engines were based on the Denver and Rio Grande Western's 1800-class 4-8-4s, with a little Northern Pacific A-5 blended in. Compared to the 2100-class rebuilds (Locobase 1371) of 1940-1942, these Northerns had smaller drivers and less cylinder volume, but a higher boiler pressure setting. Their axles turned on Timken roller bearings and, like the 2100s, 14" (356 mm) piston valves supplied the cylinders. Feed water was heated by a Worthington 6 - 5A.

The last of the class was scrapped in 1956.

Another 4-8-4 class on the MP's roster were the 2101-2125, which were rebuilds from 63-in DD 2-8-4 Berkshires to 75-in driver 4-8-4s. (See Locobase 1372).

Specifications by Steve Llanso of Sweat House Media
Class2101/N-75 Victory LocomotivesN-73
Locobase ID1372 266
RailroadMissouri Pacific (MP)Missouri Pacific (MP)
CountryUSAUSA
Whyte4-8-44-8-4
Number in Class2515
Road Numbers2101-21252201-2215
GaugeStdStd
Number Built15
BuilderMPBaldwin
Year19401943
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)19.50 / 5.9419.25 / 5.87
Engine Wheelbase (ft / m)45.17 / 13.7747.08 / 14.35
Ratio of driving wheelbase to overall engine wheebase 0.43 0.41
Overall Wheelbase (engine & tender) (ft / m)89.81 / 27.3793.48 / 28.49
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)279,300 / 126,688279,400 / 126,734
Engine Weight (lbs / kg)445,950 / 202,280489,000 / 221,807
Tender Loaded Weight (lbs / kg)287,700 / 130,499
Total Engine and Tender Weight (lbs / kg)776,700 / 352,306
Tender Water Capacity (gals / ML)17,250 / 65.3419,350 / 73.30
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)20 / 18.2020 / 18.20
Minimum weight of rail (calculated) (lb/yd / kg/m)116 / 58116 / 58
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)75 / 190573 / 1854
Boiler Pressure (psi / kPa)250 / 17.20285 / 19.70
High Pressure Cylinders (dia x stroke) (in / mm)28" x 30" / 711x76226" x 30" / 660x762
Tractive Effort (lbs / kg)66,640 / 30227.4367,299 / 30526.35
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.19 4.15
Heating Ability
Firebox Area (sq ft / m2)484 / 44.98559 / 51.93
Grate Area (sq ft / m2)88.30 / 8.21106 / 9.85
Evaporative Heating Surface (sq ft / m2)4839 / 449.725306 / 492.94
Superheating Surface (sq ft / m2)1938 / 180.112200 / 204.38
Combined Heating Surface (sq ft / m2)6777 / 629.837506 / 697.32
Evaporative Heating Surface/Cylinder Volume226.33287.82
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation22,07530,210
Same as above plus superheater percentage28,47738,971
Same as above but substitute firebox area for grate area156,090205,516
Power L136,10452,480
Power MT1139.931656.38

Reference