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Steam Locomotives of the Northern Pacific (NP)[Inhalt]
Northern Pacific class S-10
United States | 1905 | 20 produced
The preserved No. 328
The preserved No. 328

These 20 Ten-Wheelers were built by ALCO-Rogers for the Chicago Southern Railroad between 1905 and 1907. When this company went bankrupt, 14 locomotives had not yet been delivered. Ten of these were purchased by Northern Pacific and designated class S-10. The remaining four went to other customers.

Eight of the Southern Pacific were retired between 1928 and 1933. Only 321 and 328 remained in use on branch lines. While 321 was scrapped in 1946, 328 ran for the last time in 1948. After being restored by the Minnesota Transportation Museum, it was operational from 1981 to 2001. Today it can be found at the Jackson Street Roundhouse in St. Paul, Minnesota.

General
Built1905-1907
ManufacturerALCO
Axle config4-6-0 (Ten-wheeler) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length58 ft 6 in
Wheelbase29 ft 1 in
Fixed wheelbase12 ft
Total wheelbase49 ft 10 1/2 in
Service weight153,000 lbs
Adhesive weight115,000 lbs
Total weight257,000 lbs
Axle load38,333 lbs
Water capacity5,000 us gal
Fuel capacity16,000 lbs (coal)
Power
Power sourcesteam
Estimated power950 hp (708 kW)
Optimal speed23 mph
Starting effort26,594 lbf
Power Plant
Driver diameter57 in
Boiler pressure190 psi
Expansion typesimple
Cylinderstwo, 19 x 26 in
Boiler
Grate area38.5 sq ft
Firebox area145 sq ft
Tube heating area2,010 sq ft
Evaporative heating area2,155 sq ft
Total heating area2,155 sq ft
Calculated Values
steam locomotive
passenger
freight
last changed: 03/2024
Northern Pacific classes WA, WB and W-1
United States | 1904 | 200 produced
WA No. 1517
WA No. 1517
Railway and Locomotive Engineering, January 1905

The Northern Pacific was the first US railroad to purchase a significant number of Mikados. These machines grouped under the class W were 55 locomotives of the subclass WA without a combustion chamber and 105 WB with a combustion chamber. Some of these were built as compound locomotives and later rebuilt. 40 class W-1 locomotives followed in 1910, which differed mainly in that they had Walschaerts valve gear in contrast to the Stephenson valve gear of their predecessors. Most of the locomotives were superheated from 1912, and the boiler pressure was increased to 200 psi with thicker boiler plates.

VariantWAWBWA/WB superheatedW-1
General
Built1904190619121910
ManufacturerALCONorthern PacificALCO
Axle config2-8-2 (Mikado) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase34 ft 9 in
Fixed wheelbase16 ft 6 in
Service weight259,000 lbs258,000 lbs263,500 lbs269,600 lbs
Adhesive weight203,500 lbs201,500 lbs206,000 lbs208,900 lbs
Total weight407,500 lbs435,800 lbs455,300 lbs461,400 lbs
Axle load58,000 lbs57,700 lbs58,700 lbs59,600 lbs
Water capacity8,000 us gal10,000 us gal
Fuel capacity24,000 lbs (coal)38,000 lbs (coal)
Power
Power sourcesteam
Estimated power1,500 hp (1,119 kW)1,450 hp (1,081 kW)1,750 hp (1,305 kW)1,600 hp (1,193 kW)
Optimal speed24 mph23 mph24 mph
Starting effort39,634 lbf46,629 lbf43,006 lbf
Power Plant
Driver diameter63 in
Boiler pressure170 psi200 psi170 psi
Expansion typesimple
Cylinderstwo, 24 x 30 intwo, 25 x 30 in
Boiler
Grate area43.5 sq ft
Firebox area209 sq ft245 sq ft250 sq ft270 sq ft
Tube heating area3,798 sq ft3,247 sq ft2,611 sq ft2,563 sq ft
Evaporative heating area4,007 sq ft3,492 sq ft2,861 sq ft2,833 sq ft
Superheater area570 sq ft465 sq ft
Total heating area4,007 sq ft3,492 sq ft3,431 sq ft3,298 sq ft
Calculated Values
steam locomotive
freight
last changed: 04/2023
Northern Pacific classes W-3 and W-5
Spokane, Portland & Seattle class O-3
United States | 1913 | 160 produced
W-3 No. 1713 in January 1958 at Duluth, Montana
W-3 No. 1713 in January 1958 at Duluth, Montana
Twin Ports Rail History / Jeff Lemke

The W-3 class was created in 1913 as an enlarged successor to the W class. It was factory fitted with a superheater and, from the second batch, also with a combustion chamber. This made it possible to increase the train weight by almost 30 percent. 135 W-3s were built in 1913 and 1917 to 1920. Ten made it to the Spokane, Portland & Seattle where they became Class O-3. In 1922 another 25 W-5 followed, which were almost identical but had a higher boiler pressure.

VariantW-3W-5
General
Built1913, 1917-19201922
ManufacturerALCO
Axle config2-8-2 (Mikado) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase35 ft 3 in36 ft 3 in
Fixed wheelbase16 ft 6 in
Total wheelbase68 ft 2 in73 ft
Service weight320,000 lbs342,800 lbs
Adhesive weight240,500 lbs251,200 lbs
Total weight513,900 lbs545,100 lbs
Axle load64,400 lbs61,800 lbs
Water capacity10,000 us gal
Fuel capacity32,000 lbs (coal)
Power
Power sourcesteam
Estimated power2,700 hp (2,013 kW)3,000 hp (2,237 kW)
Optimal speed30 mph
Starting effort57,120 lbf63,467 lbf
Power Plant
Driver diameter63 in
Boiler pressure180 psi200 psi
Expansion typesimple
Cylinderstwo, 28 x 30 in
Boiler
Grate area70.4 sq ft70.3 sq ft
Firebox area325 sq ft307 sq ft
Tube heating area3,266 sq ft3,285 sq ft
Evaporative heating area3,591 sq ft3,592 sq ft
Superheater area846 sq ft845 sq ft
Total heating area4,437 sq ft
Calculated Values
steam locomotive
freight
last changed: 07/2023
Northern Pacific classes Z-6 to Z-8
United States | 1936 | 47 produced
Still gleaming fresh from factory is Z-6 No. 5120 in th year 1937 in Duluth, Minnesota
Still gleaming fresh from factory is Z-6 No. 5120 in th year 1937 in Duluth, Minnesota
collection Taylor Rush

The first Challenger locomotives, i.e. the wheel arrangement 4-6-6-4, were built in 1936. In addition to the well-known Challenger of the Union Pacific, this was the Z-6 class of the Great Northern. Since these had to burn lignite, the firebox had to be of enormous size to achieve the required output. The grate alone was 16 feet long, the entire firebox including the combustion chamber was 20 feet 6 inches long, 9 feet 6 inches wide and up to 7 feet 6 inches high. This made a grate area of 152.3 square feet and made the trailing bogie necessary to be able to carry the load.

Z-6 No. 5106 in September 1952 in Spokane, Washington
Z-6 No. 5106 in September 1952 in Spokane, Washington
D. W. Eldridge / collection Taylor Rush

21 examples of the Z-6 were delivered by ALCO in Schenectady in 1936 and 1937. The first four examples still had friction bearings on the axles and were approximately 4,500 pounds or two tons heavier than the rest with Timken roller bearings, the weights of which are given in the table below. With a coupling wheel diameter of 69 inches, they could also pull heavy passenger trains if necessary.

Z-7 No. 5121 waiting for it's clear signal with a long freight train in November 1941 somewhere in Montana
Z-7 No. 5121 waiting for it's clear signal with a long freight train in November 1941 somewhere in Montana
W. R. McGee / collection Taylor Rush

In 1941, six heavier examples followed with slightly different boiler dimensions, one inch larger drivers and a boiler pressure increased by 10 psi, which formed the Z-7 class. Instead of the six-axle tender with a water capacity of 22,000 gallons, seven-axle 25,000-gallon tenders were used. In the years 1943 and 1944, 20 almost identical Z-8 were manufactured, but because of the wartime conditions, many of the high-strength steels had to be replaced with conventional, heavier steels. This added about 1,000 pounds to the mass.

The Z-8s were the last steam locomotives procured by the Northern Pacific. Because they were fired with lignite, they consumed gigantic amounts of fuel. On the 65 mile route from Townsend to Bozeman, Montana with a constant incline, there were reports of coal consumption of 831 pounds per mile. The relatively young locomotives were retired between 1954 and 1959. The Spokane, Portland & Seattle Railway procured almost identical locomotives, namely six Z-6 and two Z-8 with oil firing.

VariantZ-6Z-7Z-8
General
Built1936-193719411943-1944
ManufacturerALCO
Axle config4-6-6-4 (Challenger (Mallet)) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase61 ft 10 in62 ft 2 in
Fixed wheelbase24 ft 4 in24 ft 8 in
Total wheelbase110 ft 0 1/2 in
Service weight626,540 lbs643,000 lbs644,000 lbs
Adhesive weight435,000 lbs444,000 lbs
Total weight1,024,940 lbs1,081,000 lbs1,082,000 lbs
Axle load72,850 lbs74,000 lbs
Water capacity22,000 us gal25,000 us gal
Fuel capacity54,000 lbs (coal)
Power
Power sourcesteam
Estimated power6,500 hp (4,847 kW)
Optimal speed40 mph39 mph
Starting effort104,267 lbf106,888 lbf
Power Plant
Driver diameter69 in70 in
Boiler pressure250 psi260 psi
Expansion typesimple
Cylindersfour, 23 x 32 in
Boiler
Grate area152.3 sq ft
Firebox area839 sq ft756 sq ft
Tube heating area5,019 sq ft4,993 sq ft
Evaporative heating area5,858 sq ft5,749 sq ft
Superheater area2,114 sq ft2,105 sq ft
Total heating area7,972 sq ft7,854 sq ft
Calculated Values
steam locomotive
freight
Articulated
last changed: 10/2022
Northern Pacific class Z-3
United States | 1913 | 21 produced
ALCO / collection Taylor Rush

In 1913, the Northern Pacific had its first superheated Mallets made for the operation of heavy, slow freight trains over the Cascades and in the Rocky Mountains. The ten locomotives came from ALCO in Schenectady and had the wheel arrangement 2-8-8-2. Four were coal-fired and destined for the Rocky Mountains, while the other six were oil-fired for the Seattle Division. A total of eleven more from ALCO Brooks followed in 1917 and 1920.

With cylinders measuring 26 and 40 inches in diameter, respectively, they developed more than 85,000 pounds of pulling power. However, these had such a high steam consumption that the highest power was already available at 10.6 mph. In operation, it had been shown that they could pull almost 30 percent more load as pilot compared to a class Z-1 locomotive while consuming the same amount of coal. In the cascades they pulled up to 2,400 short tons alone over most of the run, but were helped by another Mallet on the steeper sections with up to 2.2 percent.

Variant1913 variant1917 variant
General
Built19131917, 1920
ManufacturerALCO
Axle config2-8-8-2 (Mikado Mallet) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase55 ft 2 in
Fixed wheelbase15 ft
Total wheelbase83 ft 6 1/4 in
Service weight456,000 lbs483,000 lbs
Adhesive weight399,500 lbs419,500 lbs
Total weight649,200 lbs688,600 lbs
Axle load53,700 lbs56,900 lbs
Water capacity10,000 us gal
Fuel capacity3,500 us gal (oil)32,000 lbs (coal)
Power
Power sourcesteam
Estimated power3,200 hp (2,386 kW)
Optimal speed24 mph
Starting effort85,039 lbf
with start valve102,047 lbf
Power Plant
Driver diameter57 in
Boiler pressure200 psi
Expansion typecompound
Cylindersfour, HP: 26 x 30 in
and LP: 40 x 30 in
Boiler
Grate area84.2 sq ft84.3 sq ft
Firebox area368 sq ft373.6 sq ft
Tube heating area5,129 sq ft5,123.4 sq ft
Evaporative heating area5,497 sq ft
Superheater area1,225 sq ft1,305 sq ft
Total heating area6,722 sq ft6,802 sq ft
Calculated Values
steam locomotive
freight
Mallet
last changed: 03/2023
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