JNR Class D51

The Class D51 (D51形) is a type of 2-8-2 steam locomotive operated by the Japanese Government Railways (JGR) and later by the Japanese National Railways (JNR). Designed by JGR's chief mechanical engineer Hideo Shima, they were built by Kawasaki Heavy Industries Rolling Stock Company, Kisha Seizo, Hitachi, Nippon Sharyo, Mitsubishi Heavy Industries and JGR's factories from 1936 to 1945.
Although surpassed in speed, power, and size by other locomotives, it is recognised as the most mass-manufactured locomotive in Japanese rail history. A total of 174 units are preserved in Japan, including five operational examples. An additional 13 are preserved in Russia and Taiwan, bringing the total number of preserved units to 187.
The classification consists of a "D" for the four sets of driving wheels and the class number 51 for tender locomotives that the numbers 50 through 99 were assigned to under the 1928 locomotive classification rule.
Following the Great Depression of 1929, Japan's rail freight demand declined. This delayed plans for the development and production of new freight locomotives, which were set to become successors to the Class D50. By the mid-1930s, economic recovery led to increased transport demand. Although electrification was in progress, steam locomotives remained the backbone of railway operations. The result was the D51, a mechanically simple, versatile and fuel-efficient freight locomotive. The D51's chief designer, Hideo Shima, later described it as one of his most satisfying designs.
The D51 was based on the earlier Class D50, with which it shares many design fundamentals, such as a straight boiler and a 1D1 (2-8-2) wheel arrangement. Notable changes from the Class D50 included:
Otherissues identified in the D50, such as derailments during reverse operations, were also addressed in the D51's design.
The D51 is divided into three types based on the production period and design changes: early type, standard type, and wartime type.
Units produced: D51 1–85, 91–100
Period produced: 1936–1937
Early models are noted for their semi-streamlined appearance, with the feedwater heater positioned between the sand dome and chimney and enclosed in a long casing. This design earned the nickname "Slug" (ナメクジ, Namekuji). Two locomotives, D51 22 and 23, had an extended casing reaching the cab, referred to as "Super Slug" or "Big Slug." These were later modified to match other units because the extended casings required extra maintenance. To balance the shortened overall length compared to the D50, the cab was made smaller. While this reduced weight, it also made the cab more confined, which some crews found uncomfortable. The weight of the first driving axle was lighter than the others, which caused wheel slip under heavy loads. The air-powered reverser was also found to be difficult to use due to its sensitivity. Later modifications, such as adding weight to the front deck, improved traction.
Units Produced: D51 86–90, 101–954
Period produced: 1937–1944
The feedwater heater was relocated to a crosswise position in front of the chimney, and the suspension system was adjusted to improve axle weight distribution. The air-powered reverser was replaced with a manual version for better control. From D51 101 onwards, this updated design became standard, and most of the class was built to this specification. Wartime versions of these later units used simplified materials and construction methods, including wooden components and the omission of some design details to conserve resources.
Units Produced: D51 1001–1161
Period produced: 1944–1945
Wartime models were built with substitute materials and reduced decorative elements. The dome was reshaped to a flat design, and wooden parts were used for components such as the smoke deflectors. Some tenders adopted a simpler 'ship-bottom' design. To increase hauling capacity, boiler pressure and axle load were raised, but the use of substandard materials and simpler welding caused reliability issues. This resulted in several boiler explosions, notably with D51 1140. After the war, many of these units were retrofitted with standard parts to improve safety and reliability.
The D51 was widely used across Japan and was a common sight throughout the country. Primarily a freight locomotive, the D51 was occasionally assigned to passenger services, particularly on steeply graded lines such as the Chūō Main Line and the mountainous section of the Hakodate Main Line (Oshamambe–Otaru). On some flatter lines, such as the Uetsu Main Line, it also hauled passenger trains. Notable examples of its service include locomotives assigned to royal trains (on Emperor Shōwa's visit to Shimane in 1971) and units used at yards on main lines, such as Shintsurumi and Suita, for hump shunting.
From the 1960s, D51 locomotives began to be retired as electrification and dieselisation progressed. However, many remained in service until the final years of steam operation in Japan. During the 1960s and 1970s, they were particularly prominent on steeply graded lines such as the Sekihoku Main Line, Tōhoku Main Line, Ōu Main Line, and Hakubi Line, often operating in double- or triple-headed configurations. These operations attracted railway enthusiasts, photographers, and media attention during the 'SL boom' period. While its ubiquity made the D51 an iconic machine, some enthusiasts seeking rarer locomotive classes expressed disappointment when encountering D51s.
The first D51s in Hokkaidō were assigned to the Otaru-Chikkō and Iwamizawa depots, with units such as D51 6 at Otaru-Chikkō and Nos. 48 and 126 at Iwamizawa. On the Nemuro Main Line, D51 locomotives assigned to the Shintoku depot were used on the old Karikachi Pass section without smoke deflectors and with limited installations of oil-fired systems. D51 241 at the Oiwake depot hauled JNR' final steam-hauled train on 24 December 1975, on the Yūbari Line.
D51s were extensively used on major lines such as the Tōhoku Main Line, Ōu Main Line, Jōban Line, and Uetsu Main Line. On the Tōhoku Main Line, triple-heading operations were notable at Jūsanbongi Pass in Ichinohe, Iwate, with locomotives from Morioka, Ichinohe, and Shiriuchi depots. Similarly, triple-heading was common at Yatate Pass on the Ōu Main Line until 1971, by locomotives from depots such as Aomori, Hirosaki, and Akita.
In the Kantō region, D51s were assigned to depots including Takasaki, Utsunomiya, Mito, Ōmiya, Hachiōji, Tabata, Shintsurumi, and Shinkoiwa. At Mito, some units were fitted with automatic coal-feeding equipment in 1957 to accommodate the low-calorific coal from the Jōban coalfield. The electrification of lines such as the Sōbu Main Line and Takashima Line in 1970 led to the withdrawal of D51s from depots such as Shintsurumi. D51 791 was used for farewell passenger services in October 1970, which operated between Tokyo and Yokohama.
D51s were assigned to the Hokuriku Main Line, including depots at Tsuruga, Fukui, and Kanazawa, where they handled freight operations over steep passes such as the Yanagase and Yamano Tunnels. The electrification of the Hokuriku Main Line was completed by 1964, but some D51s remained in use for local and yard duties until 1971. On the Takayama Main Line, they replaced C58s and 9600s from 1959 until dieselisation in 1969.
In Kansai, D51s were used on lines like the Kansai Main Line, San'in Main Line, and the Fukuchiyama Line. On the Kansai Main Line, they operated in double-headed configurations to manage the steep gradients of the Kabuto Pass.
D51s operated on lines such as the Sanyō Main Line, Hakubi Line, and Mine Line. On the Hakubi Line, D51s based at Niimi depot were used for triple-headed limestone freight trains, which attracted significant attention from railway enthusiasts.
Thirteen D51s were assigned to the Dosan Line, based at the Kōchi depot. These locomotives were eventually replaced by DF50 diesel locomotives by 1960.
In Kyūshū, D51s were assigned to depots including Mojikō, Tosu, and Kumamoto. On the steeply graded Hisatsu Line, D51s replaced older locomotives such as the Class 4110 for services over the Yatake Pass. These locomotives were equipped with smoke collectors and oil-firing systems.
The 30 specially built D51s that were left on Sakhalin (formerly Karafuto) by the retreating Japanese at the end of the Second Sino-Japanese War (1937-1945) and after the Soviet-Japanese War (1945), were used from 1945 until 1979 by Soviet Railways. One was left outside Yuzhno-Sakhalinsk railway station, and one is in running condition and is kept at the Yuzhno-Sakhalinsk railway station. Additionally two wrecks were left to the north of the city.
Two locomotives were built for the Korean National Railroad in 1950 by Mitsubishi for South Korea during the Korean War. Designated Mika7 (미카7) class, they were nearly identical to JNR class D51 except for the gauge.
According to the a journal published in 1956, ten locomotives were built by Nippon Sharyo for the Manila Railroad Company. These entered service in 1951. Numbered the 300 class, they were named after the cog locomotive class built in the 1910s for the Manila Railway. These locomotives differed from the rest of the D51 builds through the lack of smoke deflectors.
The locomotives had a short service life in the Philippines as Manila Railroad ordered the dieselization of its entire network, having all steam locomotives retired by 1956.
From 1936 to 1944, Kawasaki, Kisha Seizō and Hitachi had built 32 D51s for Imperial Taiwan Railway. After World War II, they were taken over by Taiwan Railways Administration, and were classified DT650. In 1951, Kisha Seizō built three DT650s and Mitsubishi Heavy Industries built two DT650s for Taiwan Railways Administration.
Over 173 Class D51 locomotives are preserved in Japan.
The following is a list of preserved locomotives as of July 2023.
Built in 1938 at the JNR Hamamatsu Works, locomotive number D51 200 has been overhauled and restored to operational condition for use as SL Yamaguchi and SL Kitabiwako starting in 2017.
Hiro, a character based on the Class D51 and voiced by Togo Igawa, appears in the 2009 animated film Thomas & Friends: Hero of The Rails and thereafter became one of the show's mainstays and the first character introduced after the change to CGI.
In the anime Hikarian the character Dozilas is based on the D51 498.
The Transformers Decepticon Astrotrain transforms into a Class D51 and a space shuttle.
The Gobots aka Machine Robo character Loco (Steam Robo) has a vehicle mode based on the D-51 steam train and has the number D-5147 on him.