, under the Whyte notation for the classification of locomotives, represents the wheel arrangement of four leading wheels, six powered and coupled driving wheels and four trailing wheels. In France where the type was first used, it is known as the Baltic while it became known as the Hudson in most of North America.
Overview Tender locomotives The 4-6-4 tender locomotive was first introduced in 1911 and throughout the 1920s to 1940s, the wheel arrangement was widely used in North America and to a lesser extent in the rest of the world. The type combined the basic design principles of the 4-6-2 type with an improved boiler and larger firebox that necessitated additional support at the rear of the locomotive. In general, the available tractive effort differed little from that of the 4-6-2, but the steam-raising ability was increased, giving more power at speed. The 4-6-4 was best suited to high-speed running across flat terrain. Since the type had fewer driving wheels than carrying wheels, a smaller percentage of the locomotive's weight contributed to traction, compared to other types. Like the 4-6-2, it was well suited for high speed passenger trains, but not for starting heavy freight trains and slogging on long sustained grades, where more pairs of driving wheels are better.
The first 4-6-4 tender locomotive in the world was a four-cylinder compound locomotive, designed by Gaston du Bousquet for the Chemins de fer du Nord in France in 1911. Since it was designed for the Paris-Saint Petersburg express, it was named the Baltic after the Baltic Sea, which was a logical extension of the naming convention that started with the 4-4-2 and 4-6-2.Reed, Brian. (1972). Loco Profile, Nord Pacifics. Windsor: Profile Publications.
The first 4-6-4 in the United States of America, J-1a #5200 of the New York Central Railroad, was built in 1927 to the railroad's design by the American Locomotive Company (ALCO). There, the type was named the Hudson after the Hudson River. They are also designed to pull 16-18 passenger cars in passenger service.
The world speed record for steam locomotives was held by a 4-6-4 at least twice. In 1934, the Milwaukee Road's class F6 no. 6402 reached and, in 1936, the German class 05.002 reached . That record was broken by the British 4-6-2 number 4468 Mallard on 3 July 1938, when it reached , still the world speed record for steam traction.
Tank locomotives The 4-6-4T was also a fairly common wheel arrangement for passenger tank locomotives. As such, it was essentially the tank locomotive equivalent of a tender locomotive, with water tanks and a coal bunker supported by four trailing wheels instead of in a tender. In New Zealand, some 4-6-4T locomotives (the Wab class) were tank versions of 4-6-2 locomotives (of the Ab class).
The first known 4-6-4 tank locomotive was rebuilt from a Natal Government Railways (NGR) K&S Class 4-6-0T which was modified in 1896 to enable it to run equally well in either direction on the Natal South Coast line, where no turning facilities were available at the time. This sole locomotive later became the Class C2 on the South African Railways (SAR). The first known locomotive class to be designed with a 4-6-4T wheel arrangement, the NGR's Class F tank locomotive, was based on this modified locomotive and built by Neilson, Reid & Company in 1902. These became the Class E on the SAR in 1912.
One streamlined 4-6-4T was built for the Deutsche Reichsbahn in 1935.
Use Australia Tender locomotives
Seventy R class 4-6-4 tender locomotives, the only class of this configuration in Australia and built by North British Locomotive Company, were introduced by the Victorian Railways in 1951 for mainline express passenger operations. However, the introduction in 1952 of the B class diesel-electric locomotives saw the R class almost immediately being relegated to secondary passenger and freight use, with many being staged at depots around the state. A number were preserved and some of these continued to operate on special excursion trains.
With the privatisation of regional passenger operations in Victoria in the mid-1990s, two R class locomotives were brought back into normal revenue service by the West Coast Railway, for regularly scheduled mainline passenger trains between Melbourne and Warrnambool. The locomotives underwent a number of modifications to allow for reliable high speed operation, including dual Lempor exhausts, oil firing and the addition of a diesel control stand for multiple unit operation. The use of these R class locomotives ceased after the demise of the private operator in 2004.West Coast Railway Modernised R Class Locomotives R711 & R766Anatomy of West Coast Railway's "Super" R Class, Introduced and compiled by Barry Merton
Tank locomotives The tank locomotive configuration was a popular type with the Western Australian Government Railways. The D class was introduced for suburban passenger service in 1912. Its successors, both also of the 4-6-4T wheel arrangement, were the Dm class of 1945 that was rebuilt from older E class 4-6-2 tender locomotives, and the Dd class of 1946.
The New South Wales Government Railways 30 Class 4-6-4T locomotives were used on Sydney and Newcastle suburban passenger train workings from 1903 until the end of steam operations in the 1970s. No. 3046 is preserved at the Dorrigo Steam Railway & Museum. No. 3013 is stored, dismantled at the Canberra Railway Museum. 3085 is awaiting restoration at Goulburn Roundhouse. 3112 operated tour trains for a number of years but is currently out of service in Canberra. 3137 saw regular use in the 1970s and 1980s as part of the NSW Rail Museum operating fleet, but is out of service and now on static display at Thirlmere.
Canada Tender locomotives
The second-largest user of the type in North America was the Canadian Pacific with 65 H1a to H1e class locomotives, numbered 2800 to 2864 and built by Montreal Locomotive Works (MLW) between 1929 and 1940. They were highly successful and improved service and journey times on the CPR's transcontinental routes. The third and later batches of CPR Hudsons, H1c to H1e numbers 2820 to 2864, were dubbed Royal Hudsons and were semi-streamlined. Royal permission was given for these locomotives to bear the royal crown and arms after locomotive No. 2850 hauled King George VI across Canada in 1939.
Five CPR Hudsons survived. H1b class no. 2816 Empress is the sole remaining unstreamlined CPR Hudson. It was repatriated from static display at Steamtown in Scranton, Pennsylvania, to the CPR in 1998 and was restored and converted to oil-burning to haul excursions for CPR. The other four remaining H1 class locomotives are all Royal Hudsons. As of 2010, the four Royal Hudsonswere on display in museums, No. 2839 in California, No. 2850 in Quebec, No. 2858 in Ontario, and No. 2860 – the first oil-burning Royal Hudson of the class – in British Columbia. By 2008, the CPR Hudsons were the only operational Hudsons in North America.CP2816 - Rebirth of a mechanical Wonder. (CPR News, Number 2, 2001) (Also see North American production list)
Tank locomotives The Grand Trunk Railway (GTR) had six K2 class locomotives, built in September 1914 by MLW and acquired for suburban service. Numbered 1540 to 1545 on the GTR, they were reclassified as X-10-a and renumbered 45 to 50 after being absorbed by the Canadian National (CN) in 1923. Three of them are preserved, numbers GT 1541 (CN 46) in Vallee-Jonction, QC, (CN 47) at the Steamtown National Historic Site in Scranton, Pennsylvania, and GT 1544 (CN 49) at the Canadian Railway Museum in Delson, Quebec. (Also see North American production list)
Finland
The Finnish State Railways Class Pr2, nicknamed Henschel, was a gauge passenger tank locomotive class, ordered from Henschel & Son by the Estonian State Railways in the spring of 1939 and completed in 1941. The outbreak of the Second World War prevented their delivery to Estonia, but a few of these engines did operate in Latvia in 1942. They became superfluous when the Germans began converting the Baltic tracks to , and the four locomotives were sold to Finland. They were classified Pr2 and numbered 1800 to 1803 upon their arrival in Finland in December 1942.Pölhö, Eljas; Pykälä-Aho, Mia (1996). Suomen juna- ja raitiovaunukuvasto (Finnish Motive Power).
The Class Pr2 tanks were quite advanced locomotives and were based on the Henschel-built DRG Class 62 tank engine design of 1928 for the Deutsche Reichsbahn. After their initial teething problems were solved, they proved to be fast runners and an ideal addition to the motive power stable. They were originally built as oil-burners and reverted to this type of fuel between 1947 and 1954, when oil prices were low. With its coupled wheels, it was very fast and one of them achieved during a test run. No. 1803, the last Class Pr2 in service, was withdrawn in May 1960. Only no. 1800 has been preserved.Sakari K. Salo (2009): Höyryveturikirja, s. 14. Helsinki: Kustantaja Laaksonen.
France The four-cylinder compound locomotive designed by Gaston du Bousquet for the French Chemins de fer du Nord, of which two (3.1101 and 3.1102) were built at the company's workshops in 1911, was the first tender locomotive in the world with this wheel arrangement. Named the Baltic since it was intended for service on the Paris-Saint Petersburg express, its most remarkable feature was the en echelon arrangement of the two low-pressure inside cylinders in order to accommodate the very large bore. One of them was built with a water-tube firebox. Although they were not multiplied, they were the forerunners of the highly successful 4-6-2 Nord Pacifics and Super-Pacifics. One survives in the Cité du Train at Mulhouse in eastern France, cut up in sectioned form to display its interior during the World Exhibition in Paris in 1937. Its tender was not preserved.
France also produced some of the last Baltic locomotives. In 1938, Marc de Caso, the last Chief Mechanical Engineer of the Nord, originated the construction of eight Baltic locomotives, all delivered to the newly established SNCF. Of these eight, three were 232.R class three-cylinder simple expansion (simplex) locomotives with rotary cam poppet valve gear, while four were 232.S class four-cylinder compound locomotives, initially also with poppet valve gear that was later replaced by Walschaerts valve gear driving oscillating cams. Built for comparative purposes, it was found that the compounds outperformed the simples.
The eighth of the class, the final French Baltic type, was completed in 1949 as the 232.U.1 class. This was another four-cylinder compound with Walschaerts valve gear, but with very large and light piston valves, that proved capable of more than . This locomotive is also preserved at Mulhouse.Ransome Wallis (ed). Concise Encyclopedia of World Railway LocomotivesChapelon, Andre. La Locomotive a Vapeur (Also see Netherlands)
Germany Tender locomotives
Three tender locomotives were built for the Deutsche Reichsbahn (DRG) by August Borsig in 1935. Designated Class 05, they were designed for high speed running. They were three-cylinder locomotives with giant driving wheels and powerful clasp brakes on all wheels.
The first two locomotives were conventional locomotives, but the third was built as a cab forward and burned pulverised coal. All three were built streamlined, in shrouds that covered the locomotives almost to the railhead. On 11 May 1936, the 05.002 set a world speed record of that was bettered by the British 4-6-2 Mallard two years later, on 3 July 1938. The 05.003 was converted to conventional boiler-forward running in 1944.