Class D51

Class D51
JR East's D51 498 on the Jōetsu Line in December 2008
Type and origin Power type Steam Designer Hideo Shima Builder etc Build date 1936-1951
Specifications Configuration: ​  • Whyte 2-8-2 Mikado Gauge 1,067 mm (3 ft 6 in) Length 19,730 mm (64 ft 8 3⁄4 in) Loco weight 76.8 t (75.6 long tons; 84.7 short tons) Total weight 123.0 t (121.1 long tons; 135.6 short tons)
Performance figures Maximum speed 85 km/h (55 mph) Tractive effort 184.3 kN (41,400 lbf)
Career Retired 24 December 1975

The Class D51 (D51形) is a type of 2-8-2 steam locomotive built by the Japanese Government Railways (JGR), the Japanese National Railways (JNR), and various manufacturers from 1936 to 1945. The Class D51 is popularly called "Degoichi" in Japanese.

The design of Class D51 was based on the earlier Class D50, introduced in 1923. Wartime production featured some substitution of wood for steel parts like running boards, smoke deflectors and tender coal bunkers. A total of 1,115 D51s were built, the largest number in any single class in Japan. Early D51s were known as "Namekuji type" (or "slug"). The locomotive was designed by Hideo Shima. It was used mainly in freight service through the 1960s.

The specially built D51s that were left on Sakhalin (formerly Karafuto) by the retreating Japanese at the end of World War II were used 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. Designated Mika7 (미카7) class, they were nearly identical to JNR class D51 except for the gauge.

From 1936 to 1944, Nippon-Sharyo was built 32 D51s for Governor-General of 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.

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.