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

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

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 Raildata collection. (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)
Number in Class2515
Road Numbers2101-21252201-2215
Number Built15
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)19.5019.25
Engine Wheelbase (ft)45.1747.08
Ratio of driving wheelbase to overall engine wheebase 0.43 0.41
Overall Wheelbase (engine & tender) (ft)89.8193.48
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)279,300279,400
Engine Weight (lbs)445,950489,000
Tender Loaded Weight (lbs)287,700
Total Engine and Tender Weight (lbs)776,700
Tender Water Capacity (gals)17,25019,350
Tender Fuel Capacity (oil/coal) (gals/tons)2020
Minimum weight of rail (calculated) (lb/yd)116116
Geometry Relating to Tractive Effort
Driver Diameter (in)7573
Boiler Pressure (psi)250285
High Pressure Cylinders (dia x stroke) (in)28" x 30"26" x 30"
Tractive Effort (lbs)66,64067,299
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.19 4.15
Heating Ability
Firebox Area (sq ft)484559
Grate Area (sq ft)88.30106
Evaporative Heating Surface (sq ft)48395306
Superheating Surface (sq ft)19382200
Combined Heating Surface (sq ft)67777506
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


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