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 recognized as the most mass-manufactured locomotive, among all power types, in Japanese rail history. A total of 174 units are preserved in Japan, including five operational examples. An additional 6 are preserved in Russia and Taiwan, bringing the total number of preserved units to 180. Classification 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. Design and production Background of Development 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. Design The D51 was based on the earlier Class D50, with which it shares many design fundamentals, such as a parallel boiler and a 1D1 (2-8-2) wheel arrangement. Notable changes from the Class D50 included: Boiler pressure and tractive effort: The boiler pressure was initially raised from the 13 to 14 kg/cm2 (1,300 to 1,400 kPa; 180 to 200 psi) and later to 15 kg/cm2 (1,500 kPa; 210 psi) in wartime models. Despite a smaller cylinder bore, these changes enhanced tractive effort. Weight reduction and adaptability: Electric welding replaced traditional riveting, which resulted in reduction of axle load and overall weight. The maximum axle load was reduced from 14.99 to 14.30 t (16.52 to 15.76 short tons; 14.75 to 14.07 long tons), which allowed operation on lighter secondary lines previously inaccessible to the D50. Length reduction: The D51 was 571 mm (1 ft 10.5 in) shorter than the D50 to fit on standard 60 ft (18 m) branch line turntables, thus broadening its operational range. Wheel design: The D51 adopted boxpok wheels, which distributed force more evenly across the wheel circumference. Other issues identified in the D50, such as derailments during reverse operations, were also addressed in the D51's design. Variants The D51 is divided into three types based on the production period and design changes: early type, standard type, and wartime type. Early type (Namekuji) 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. Standard type 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. Wartime type 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. Operations 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. Hokkaidō 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. Tōhoku 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. Kantō 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. Chūbu 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. Kansai 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. Chūgoku 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. Shikoku Thirteen D51s were assigned to the Dosan Line, based at the Kōchi depot. These locomotives were eventually replaced by DF50 diesel locomotives by 1960. Kyūshū 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. Outside Japan Soviet Railways D51 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. Korean National Railways Mika7 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. Manila Railroad 300 class (1951) 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. Taiwan Railways Administration DT650 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. Preserved examples Over 173 Class D51 locomotives are preserved in Japan. The following is a list of preserved locomotives as of July 2023. Taiwan DT652: Preserved at Tainan Sports Park. DT654: Preserved at East Stone Township, Chiayi County. (The current number is DT651) DT668: Preserved in operational condition at Changhua Locomotive Depot. DT670: Preserved at Art and Literature Center, Banqiao District, New Taipei City. (The current number is DT675) Russia D51-4: Sakhalin (Static display at the Museum of the Sakhalin Railway) D51-22: Sakhalin (Plinthed outside Yuzhno-Sakhalinsk railway station) Japan Operational D51 146: Operated on the Mooka Railway, runs on compressed air. (Semi-operational) D51 200: Preserved in operational condition by JR West at the Kyoto Railway Museum, and was operating the SL Yamaguchi train on the Yamaguchi Line from November 2017 to May 2022, when a crack in one of its bogies was discovered. Restoration work and trial runs were carried out at the Kyoto Railway Museum; the locomotive re-entered service in 2024. From 2017 to 2019, it operated the SL Kita-Biwako on the Hokuriku Main Line. D51 320: Operated at a railway museum in Abira, Hokkaido on compressed air. (Semi-operational) D51 498: Restored by JR East, based at Takasaki Rolling Stock Center, and pulls special-event trains on JR East lines. D51 827: Operated at Aridagawa Railway Park in Wakayama Prefecture, runs on compressed air. D51 1149: Operates on compressed air in Toyota, Aichi. Static preservation See also List of operational steam locomotives in Japan JNR Class D50 JNR Class D52 References