4-8-4


Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of four leading wheels on two axles, eight powered and coupled driving wheels on four axles and four trailing wheels on two axles. The type was first used by the Northern Pacific Railway, and initially named the Northern Pacific, but railfans and railroad employees have shortened the name since its introduction. It is most-commonly known as a Northern.

Overview

Development

The wheel arrangement was a progression from the Mountain type and, like the Berkshire and Hudson types, an example of the "Super Power" concept in steam locomotive design that made use of the larger firebox that could be supported by a four-wheel trailing truck, which allowed greater production of steam. The four-wheel leading truck gave stability at speed and the eight driving wheels gave greater adhesion. The type evolved in the United States soon after the Lima Locomotive Works introduced the concept of "Lima Super Power" in 1925, making heavy 2-8-2 and 2-8-4 locomotives. The prototype was built by American Locomotive Company for the Northern Pacific Railway in 1926, with a very large firebox with a grate, designed to burn low quality lignite coal. The four-wheel trailing truck weighed about more than two-wheel trucks of the time and could carry an additional of engine weight; the difference of was available for increased boiler capacity.
The type arrived when nearly all the important steam locomotive design improvements had already been proven, including Superheaters, mechanical stokers, outside valve gear and the Delta trailing truck. One-piece, cast steel bed-frames with integrally cast cylinders gave the strength and rigidity to use Roller bearings. In 1930, the Timken Company used the Timken 1111, a built by ALCO with roller bearings on all axles, to demonstrate the value of their sealed roller bearings. The Timken 1111 was subsequently sold to the NP, where it became NP No. 2626, their sole Class A-1 locomotive.
The stability of the wheel arrangement meant that driving wheels up to diameter could be used for high speed passenger and fast freight operation. Lateral control devices allowed these locomotives to traverse relatively sharp curves despite their drivers. The increased boiler size possible with this type, together with the high axle loads permitted on mainlines in North America, resulted in the design of some massive locomotives, some of which weighed as much as 450 tons, including the tender. The was suitable for both express passenger and fast freight service, though it was not suited to heavy drag freight trains.
Although locomotives of the wheel arrangement were used in a number of countries, those that were developed outside North America included various design features which set them apart from North American practice. Scaled down examples of the type were exported by two American builders, ALCO and Baldwin Locomotive Works, for lines in Brazil. Most were two-cylinder locomotives, but five classes of three-cylinder s were built:
Since the was first used by the Northern Pacific Railway, the type was named "Northern". Most North American railroads used this name, but some adopted different names.
The Richmond, Fredericksburg and Potomac Railroad gave each of its three classes a separate name, the "General" of 1937, the "Governor" of 1938 and the "Statesman" of 1944.

Demise

The big-wheeled was at home on heavy passenger trains and quite capable of speeds over, but freight was the primary revenue source of the railroads; in that service the Northern had limitations. The adhesive weight on a was limited to about 60% of the engine's weight, not including the dead weight of the tender. Henry Bowen, the Chief Mechanical Engineer of the Canadian Pacific Railway from 1928 to 1949, tested the first two CPR K-1a Northerns introduced by his predecessor, then he designed a Selkirk type using the same boiler. The resulting T-1a Selkirk locomotive had the same number of axles as the Northern, but the driving wheels were reduced from in diameter, while the additional pair of driving wheels increased the tractive effort by 27%. In a later variant, Bowen added a booster to the trailing truck, enabling the Selkirk to exert nearly 50% more tractive effort than the similar-sized K-1a Northern.
When it was demonstrated that a three-unit EMD F3 diesel-electric consist that weighed slightly less than the total engine and tender mass of a CPR K-1a Northern could produce nearly three times its tractive effort, high-powered steam locomotives were retired as quickly as finance allowed.

Usage

Australia

A total of twenty-three locomotives operated in Australia, built to three distinct designs.
In 1929, the ten gauge South Australian Railways 500 class Mountain types of 1926 were equipped with steam boosters in the form of small auxiliary steam engines to increase their power. This necessitated the replacement of their two-wheel trailing trucks with four-wheel bogies. The booster contributed an additional to the tractive effort and permitted an increase in the locomotive's load across the Mount Lofty Ranges to 540 tons. In their new configuration, they were reclassified to 500B class.
In 1943, the first of twelve streamlined South Australian Railways 520 class locomotives were delivered from the Islington Workshops in Adelaide. Although they were large locomotives, they were designed to run on lightly constructed track, with the engine's weight being spread over eight axles. Their coupled wheels were specially balanced for running.
File:H220-Newport.jpg|thumb|left|Victorian Railways H220 Heavy Harry
The H class three-cylinder of the Victorian Railways, built in 1941, was designed for heavy passenger work on the line between Melbourne and Adelaide. Nicknamed Heavy Harry, it was the largest steam locomotive built in Australia and, after the NSWGR D57 4-8-2 and the South Australian Railways 500/500B class, the third-most-powerful non-articulated locomotive. It was one of the five Australian classes of three-cylinder locomotives.
Construction of three locomotives commenced at the Newport Workshops in 1939 and three sets of frames were manufactured. Although work was halted due to the outbreak of the Second World War, a shortage of motive power caused by increased wartime traffic resulted in authorisation being given for the completion of class leader H220. The locomotive went into service on 7 February 1941, but remained the sole member of the class because the other two partly built locomotives were never completed. Since the necessary upgrades to the Adelaide line was deferred, H220 operated only on the line between Melbourne and Albury in New South Wales.

Brazil

To meet the acute locomotive shortages in Brazil after the Second World War, 27 scaled down American Niágara locomotives were ordered by the Brazilian i=unset from ALCO in 1946. These locomotives were supplied to the i=unset, which then purchased another fifteen directly from ALCO in 1947. They were designated the 1001 class. In 1956 and 1957, some of them were sold to Bolivia. The Baldwin Locomotive Works supplied similar locomotives to the i=unset, the i=unset and the i=unset.
After his retirement from the i=unset in France, French engineer André Chapelon was appointed as the chief designer of locomotives at the French state-owned sales consortium i=unset. In 1949, a contract was signed between DNEF and GELSA for the construction of 24 locomotives with a axle load. The order also included 66 Berkshires. All ninety locomotives were delivered by January 1953.
The 24 class 242F Niágara locomotives were built by Société de Construction des Batignolles. They were two-cylinder simple expansion locomotives, designed to burn poor quality local coal with a low calorific thermal value, with coupled wheels of diameter and a grate area of. They were coupled to big tenders which a coal capacity of. The Belpaire firebox included a combustion chamber and the boiler pressure was a high. One member of the class was tested on the Reseau Breton line in France before being shipped to Brazil.
The DNEF allocated the locomotives to four of Brazil's state railways. Under Brazilian railway conditions, these modern locomotives were not popular with local railwaymen and were not used as much as had been hoped. Their maximum axle load of restricted their usefulness, as did their long tenders. In some places the turntables were too short to turn the locomotives and they had to be turned on triangles. In addition, the building specifications had called for a locomotive capable of a maximum speed of and the ability to negotiate curves with a minimum radius of. This last point proved to be a source of contention when it was later discovered that the curves in some places were of less than radius. As a consequence, the locomotives were involved in a number of derailments.
In the late 1960s, they were relegated down from first class passenger trains. Some locomotives, allocated to Southern Brazil, were also tried in Bolivia.