Northern Pacific 4-8-4 "Northern" Type Locomotives

Introduction

By the 1920s the Northern Pacific Railroad needed bigger passenger locomotives. The NP had its motive power department work with the American Locomotive Company's design engineers to develop a new locomotive. They designed a new locomotive with a massive firebox that had a 115 square foot grate area supported by a four wheel trailing truck. It was the first locomotive with a 4-8-4 wheel arrangement.

ALCO delivered the first of 12 of these new locomotives in December of 1926, with the balance arriving early in 1927. Designated Class A, and assigned road numbers 2600 through 2611, they had 73" drivers, 28 x 30 cylinders, a boiler pressure of 210 psi, a tractive effort of 57,500 lbs and weighed 426,000 pounds. Later, the boiler pressure was raised to 240 psi which increased the tractive effort to 65,700 pounds. These were the first of this new wheel arrangement and thus were to be the namesake, with the name "Northern Pacific" selected which was very quickly shortened to just "Northern".

In 1930, the Timken demonstrator came to the NP. While being tested, it suffered crown sheet damage. The NP bought it, repaired it and put it on the roster as number 2626.

Ten Class A-2s (road numbers 2650 through 2659) came from the Baldwin Locomotive Works in 1934. These heavy "Northerns" had 77" drivers, 28 x 31 cylinders, a boiler pressure of 260 psi, a tractive effort of 69,800 lbs and a weight of 489,400 pounds.

In 1938, eight Class A-3s (road numbers 2660 through 2667) were delivered from Baldwin. The specifications for these locomotives were identical to the Class A-2s except that each weighed 2,400 pounds more.

The eight Class A-4s (road numbers 2670 through 2677) were delivered by Baldwin in 1941, and had the same basic specifications as the A-3s, but were different in appearance, with 14 wheel centipede tenders and vestibule cabs, and they were 1000 pounds heavier.

The last of the 4-8-4s purchased by the NP were the Class A-5s, which were built by Baldwin in 1943. This group of 10 (road numbers 2680 through 2689) were built to the same specifications as the Class A-4s, but turned out to be 16,200 lbs heavier. They were among the heaviest of all the Northern type locomotives ever built, at 508,500 pounds only the Santa Fe Class 2900s weighed more.

There are no surviving Northern Pacific Northerns.

Roster by Richard Duley

ClassRoad NumbersYr. BuiltBuilderLocomotive Wt.
A2600-26111926ALCO426,000 lbs
A-12626 (ex Timken 1111)1930ALCO477,500 lbs
A-2s2650-26591934Baldwin489,400 lbs
A-3s2660-26671938Baldwin491,800 lbs
A-4s2670-26771941Baldwin492,800 lbs
A-5s2680-26891943Baldwin508,500 lbs

Class Details by Steve Llanso

Class A (Locobase 272)

Data from http://www.nprr.org/Steam%20Diagrams/Forms/AllItems.aspx (7 Feb 2004) . (Thanks to Chris Hohl for correcting the valve gear ID.)

Valve motion had limited cutoff. These were the very first 4-8-4s to be bought and go into service, that event occurring in 1926. One significant factor in the development of the big-firebox version of the 4-8-2 Mountain was the predominance of low-calorie "Rosebud" coal in the NP's region.

According to Richard Drury (1993), tests on trains while trailing a dynamometer car revealed two main truths: "The engines produced more horsepower when they were worked hard, and they were slightly under-boilered." Drury also notes notes one unusual design feature - the outside cradle frame carrying the trailing truck, a feature shared with the Canadian National and the Chicago & North Western Hs (Locobase 252).

The power was evident in several service areas, according to Drury, who cites the substitution of 1 A for 2 Pacifics on passenger trains between Glendive, North Dakota and Jamestown, Mont and less-frequent call for helpers on the Livingston-Missoula stretch. They also could run longer without an engine change.

There were break-in glitches, Drury notes, including "...initial difficulties with driver bearings that resulted in broken axles." So big and powerful a locomotive would find its full voice when fitted with roller bearings, as Timken would demonstrate in 1930; see Locobase 930.

Most eventually converted to oil-firing and gave up their booster engines in the late 1940s.

Class A-2 (Locobase 273)

Data from 1930 Locomotive Cyclopedia, "4-8-4 Locomotives on the Northern Pacific," Baldwin Locomotives (1937), pp. 27-28 and NP to 1944 Locomotive Diagrams supplied in May 2004 by Allen Stanley from his extensive collection. Works numbers were 61771-61780 in 1934.

Similar to the earlier Alco-built 4-8-4s (Locobases 272 and 930) with the important addition of Timken roller bearings on the axles. The prototype was given the number 1111 and known as the "Four Aces." She was later taken into NP service as the 2626 (Locobase 930). The A-2 was ordered from Baldwin and introduced disc driving wheels. The A-2s had a cast-steel locomotive bed with integral cylinders. 12" (305 mm) piston valves with 8 1/4" (210 mm) travel supplied the cylinders with steam.

Baldwin's report sheds a great deal of detailed light on this class. Like all NP Northerns, the A-2s burned Rosebud coal, a fuel with 22-28% moisture content and 7-9% percent ash. Compared to more typical locomotive coal, which were rated at 11,000-15,000 BTU/pound, Rosebud generated 8,750 BTU. Such low-grade brown stuff was laid by a Standard modified type B stoker on a large grate. The firebox was joined to a very long combustion chamber to extract every last BTU.

Five of the locomotives had a Worthington preheater and the latter five had the Wilson feedwater conditioner. According to his patent filing of 10 October 1929, Lyndon Wilson's conditioner was mounted in the tender instead of on the boiler because it was designed to preheat, treat, and clean the water at the same time. (Patent 1,901,216 was awarded on 14 March 1933.) It used a separate hot-water tank in which the impurities dropped to the bottom and the clean, treated, and preheated water was drawn off the top to supply the boiler. 2655 to 2659 still had the Wilson conditioner in 1944.

Baldwin's report naturally proclaimed that the A-2s were "doing fine work in heavy passenger service." Six of them then operated on the 664 miles (1,069 km) between Jamestown, NDak and Livingston, Mont over the Fargo and Yellowstone Divisions. In summer months, train loads averaged between 12 and 19 cars over ruling grades of 1.1%. Mileage averaged 9,000 (14,490 km) during the summer months and a little less in the winter.

The other four A-2s wrangled trains between Livingston and Missoula, Mont, some 240 miles (386 km). This profile provided a sterner test of 2.2% out of Butte and Helena and 1.8% between Livingston and West End. On the steeper grades, such trains needed a helper.

See Locobases 932 (A-3), 933 (A-4), and 274 (A-5) for later Northern Pacific 4-8-4s.

NB: The direct heating surface (including the firebox heating surface) is an estimate calculated by subtracting the calculated tube heating surface from the reported total evaporative heating surface.

Class A-3 (Locobase 932)

Data from "4-8-4 Locomotives on the Northern Pacific," Baldwin Locomotives (1937), pp. 27-28 and NP to 1944 Locomotive Diagrams supplied in May 2004 by Allen Stanley from his extensive collection. Works numbers were 62163-62166 in March 1938, 62167-62168. in April and 62169-62170 in May.

As suggested by the 1937 account of the A-2s success on the road (Locobase 272), this class was virtually identical except for slightly larger flues and a few more tubes. 14" (356 mm) piston valve travel was 8 inches (203 mm). The Wilson feedwater conditioner was not installed in the tenders of these engines.

The class was divided between the NP (8) and the Spokane, Portland & Seattle (3).

Class A-4 (Locobase 933)

Data from diagrams and tables in 1974 Locomotive Cyclopedia. Works numbers 64155-64158 in September 1941, 64159-64161 in October, 64162 in November.

This octet continued the basic Northern Pacific Northern line with a slight adjustment in heating surface area due to an increase in the number of tubes and and a reduction of the flue count because of the 1/4" (6.3 mm) greater diameter. Firebox heating surface, which is not shown on the 1949 diagram from which the data are taken, included 99.5 sq ft (9.25 sq m) in six circulators. 14" (356 mm) piston valve travel was 8 inches (203 mm).

Like the others, this set had Timken roller bearings. Unlike the earlier engines, though, the A-4s (and A-5s) had vestibule cabs that offered more protection against Northern Tier winters.

Class A-5 (Locobase 274)

Data from tables and diagrams in 1947 Locomotive Cyclopedia. Works numbers were 64667-64676.

Firebox heating surface included 99.7 sq ft (9.25 sq m) in circulators (6) and arch tubes. Heavier engines with larger cylinders and higher drivers. The low-calorie "Rosebud" coal must have streamed through the stoker at a prodigious rate, considering that the grate demand factor is nearly as high as other engines burning higher-grade coal. These engines had a very high adhesive weight.

This class was booked to run 999 miles without an engine change, a record for a coal-burning locomotive.

Class Four Aces/A-1 (Locobase 930)

Data from the Timken Roller Bearing Company's builder's card, supplied in June 2012 by Chris Hohl, an email correspondent who contacted Wes Barris's http://www.steamlocomotive.com and later conducted a correspondence with Locobase. See also the detailed account in Allen Merta, Wig-Wag (published by Eastern Iowa Division Mid-Continent Region / NMRA), Vol 3, No 9 (September 2007), pp. 3-11 at http://eid.mcor-nmra.org/PDFs/WigWag200709.pdf . This engine demonstrated Timken's roller bearings while bearing the number 1111. (Its nickname was "The Four Aces.") Timken's builder's card shows a different distribution of weights among the axles for the 235-psi boiler and for the 250-psi vessel. Locobase uses the latter in its specifications.

Allen Merta summarizes some of the specifics of the roller-bearing installation: "The roller bearings on all driving axles surrounded the axle a full 360 degrees. This took up the piston thrust in all directions. Driver pounding was reduced to a minimum. Bearing overheating was eliminated. The roller bearings were completely immersed in oil on all wheels. The oil needed to be changed only 2 to 4 times per year." Other than the roller bearings on all axles (a big exception), the locomotive was a typical big Alco. In addition to the Walschaert valve gear and Type E superheater, the 1111 was fitted with a Worthington feed water heater, a tender-mounted stoker, a Franklin booster, and a ALCO Type G power reverse gear.

Alexander (American Locomotives, 1950, p. 178) describes its tour of 88,992 miles on fourteen railroads including turns on elite passenger varnish such as the New Haven's Merchants Limited and the C&O's Sportsman. "On the Pennsylvania it handled twelve passenger cars up the Allegheny mountain grade without a helper and even saved three minutes on the standard schedule." Merta comments on the assiduity of most of the trial railroads: "Twelve of the 14 railroads seriously tested the Four Aces. In freight service, the locomotive made 328 freight runs pulling an average of 83+ cars per trip, an average speed 29.8 mph. On the Chesapeake & Ohio, Four Aces started and pulled a 132 car coal train weighing 9,864 tons. In passenger service, Four Aces made 227 runs with an average of almost 11 cars per trip at an average speed of 41.2 mph."

Most often remembered from this tour were the publicity shots in which a few men (or fetchingly clad young women) pulled the 1111 along a track to demonstrate the silky smooth, low-friction qualities of the roller-bearing installation.

Former employee Daniel Simon forwarded a photo of the 4 Aces and wrote at http://www.railpictures.net/viewphoto.php?id=307329&nseq=0#remarks (last accessed 9 June 2012) and quotes the Wikipedia entry for the 1111 as saying, "A total of 52 different parts manufacturers agreed to supply their parts for the locomotive 'on account' until the locomotive operated over 100,000 miles (161,000 km).

The NP's number for this engine was 2626. Ironically, Drury (1993) reports, the Northern Pacific wasn't particularly persuaded by the tests because the 1111's firebox wasn't designed to burn the railroad's low-grade coal. It stayed on the NP largely because it had suffered crown sheet damage while on the railroad (the last of the 14 to trial it) and Timken didn't want it back.

Merta reports: "The [crown sheet] damage occurred when locomotive crews allowed it to run low on water near Auburn, Washington." He also contends that the NP set up a adversely biased comparison between its A-class 2607, which run only 3,465 miles since fitted with new driving boxes, and the 1111, which had seen little maintenance in the previous 91,780 miles.

The NP purchased the engine on 8 February 1933.

After repairs, the NP found 1111/2626 "durable and inexpensive to operate." A later Northern Pacific diagram shows slightly different distribution for the boiler's evaporative and superheater heating surface areas. EHS is given as 5,061 sq ft while the superheater is credited with 2,157 sq ft (most likely due a difference in how one handled Type E superheater areas from the Timken calculations.)

Adhesion weight came out closer to the 235-psi figure, even though NP operated the A-1 at 250 psi. Adhesion is given as 244,900 lb (111,985 kg) while the total engine weight comes in 12 tons lighter at 399,000 lb (180,984 kg). The A-1 pulled Trains 1 and 2 between Seattle and Yakima, Wash at first. Despite a less than enthusiastic reception, the NP could only agree that Timken's claims had been borne out, says Merta: "When the first complete "general shopping" of 2626 was done in 1934, the driving boxes were disassembled. The roller bearings were in excellent condition and could have returned to service, but

the decision was made to replace them because the locomotive had 280,000 miles on it."

By 1935, the 2626 ran the 656-mile (1,056-km) stretch between Seattle and Missoula, Mont. Throughout its career, the 2626 trailed the same tender, which Timken's T.V.Buckwalter conceded was too small.

2626's last run came on 4 August 1957 when it hauled a train from Seattle to Cle Elum, Wash (about 80 miles away) and returned.


Specifications by Steve Llanso
ClassAA-2A-3A-4A-5Four Aces/A-1
Locobase ID272 273 932 933 274 930
RailroadNorthern Pacific (NP)Northern Pacific (NP)Northern Pacific (NP)Northern Pacific (NP)Northern Pacific (NP)Northern Pacific (NP)
Whyte4-8-44-8-44-8-44-8-44-8-44-8-4
Road Numbers2601-26122650-26592660-26672670-26772680-26891111 / 2626
GaugeStdStdStdStdStdStd
BuilderAlco-SchenectadyBaldwinBaldwinBaldwinBaldwinAlco
Year192619341938194119431930
Valve GearBakerWalschaertWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase20.25'20.66'20.66'20.67'20.66'19.25'
Engine Wheelbase47.17'48.42'48.58'45.58'48.58'45.83'
Ratio of driving wheelbase to overall engine wheebase 0.43 0.43 0.43 0.45 0.43 0.42
Overall Wheelbase (engine & tender)90'96.25'96.25'96.75'97.50'88'
Axle Loading (Maximum Weight per Axle)63000 lbs73800 lbs74000 lbs74000 lbs
Weight on Drivers251000 lbs294000 lbs294000 lbs294000 lbs295000 lbs256000 lbs
Engine Weight418000 lbs489400 lbs491800 lbs502500 lbs508500 lbs423500 lbs
Tender Light Weight313000 lbs387600 lbs386050 lbs443300 lbs443500 lbs299000 lbs
Total Engine and Tender Weight731000 lbs877000 lbs877850 lbs945800 lbs952000 lbs722500 lbs
Tender Water Capacity15000 gals20000 gals20000 gals25000 gals25000 gals14550 gals
Tender Fuel Capacity (oil/coal)24 tons27 tons27 tons27 tons27 tons21 tons
Minimum weight of rail (calculated) on which locomotive could run105 lb/yard123 lb/yard123 lb/yard123 lb/yard123 lb/yard107 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"77"77"77"77"73"
Boiler Pressure210 psi250 psi260 psi260 psi260 psi250 psi
Cylinders (dia x stroke)28" x 30"28" x 31"28" x 31"28" x 31"28" x 31"27" x 30"
Tractive Effort57511 lbs67073 lbs69756 lbs69756 lbs69756 lbs63663 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.36 4.38 4.21 4.21 4.23 4.02
Heating Ability
Firebox Area485 sq. ft512 sq. ft490 sq. ft589.70 sq. ft589.70 sq. ft483 sq. ft
Grate Area115 sq. ft115 sq. ft115 sq. ft115 sq. ft115 sq. ft88.30 sq. ft
Evaporative Heating Surface4884 sq. ft4964 sq. ft4703 sq. ft4673 sq. ft4672 sq. ft5120 sq. ft
Superheating Surface1992 sq. ft2174 sq. ft2095 sq. ft1930 sq. ft1930 sq. ft2100 sq. ft
Combined Heating Surface6876 sq. ft7138 sq. ft6798 sq. ft6603 sq. ft6602 sq. ft7220 sq. ft
Evaporative Heating Surface/Cylinder Volume228.43224.69212.87211.52211.47257.54
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation241502875029900299002990022075
Same as above plus superheater percentage311543737539169385713857128477
Same as above but substitute firebox area for grate area131387166400166894197785197785155768
Power L1301593934039279377443774340445
Power MT1059.591180.001178.171132.121128.261393.22

Photos

Reference

Credits

Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.