Japanese Government Railways 2-8-2 Locomotives in Japan

Class 9900/D50 (Locobase 3838)

Data from Hiroshi Takagi, both from his website ([]) and personal communication August 2000. His indispensable assistance is gratefully acknowledged. See also A Profile of Japanese Steam Locomotives website put up in 2007 by "Toki S." at [], last accessed 26 September 2015.

These Mikados had relatively large 280 mm (11") piston valves. Toki S comments that the 9600-class Consolidations (Locobase 3816) could not handle the longer, heavier trains. The appreciably greater cylinder volume, larger grate and firebox, and bigger boiler "spectacularly increased" horsepower from the 870 hp of the 9600s to the 1,270 hp of the D50s. On the Tokaido line, where the 9600s could manage 600 tons, the D50s hauled 950 tons.

The first 260 were designated 9900 under the older class designation system when they were delivered in 1923-1928. They took the D50 class ID in the latter year and continued producton added another 120 engines by 1931, when the Depression forced an end to acquisition.

Many of the engines were retired relatively early due to wear and a high axle loading. But 78 were converted to a 2-8-4 arrangement to reduce axle loading; see Locobase 3839.

Class D51 (Locobase 2880)

It wasn't an accident that these engines were produced in large numbers; they were a good size and engineered to deal with the conditions at hand. A principal example of the latter, according to OS Nock (RWC VI, pl 137) was a large reservoir into which the valves exhausted. This softened the exhaust, which made the locomotive quieter and, perhaps more important, kept the soft coal from blowing off the grate before it was burned.

Data from Hiroshi Takagi, both from his website ([]) and personal communication August 2000. His indispensable assistance is gratefully acknowledged. His table shows that many were originally delivered with boilers pressing 199 psi.

Because the measurements above represent the fire side of tubes and flues, a direct comparison with tube & flue heating surface areas of North American and British locomotives requires adding approximately 6-10% to the figures shown.

Information from Ejii Nozawa's web site ([]) gives details of this the most numerous class of steam locomotives to have been built in Japan. From 1935-1944, Hitachi, Kawasaki, KSK, Mitsubishi, and Nippon supplied engines as well as 8 JNR Works: Hamamatsu, Kokura, Kouriyama, Naebo, Nagano, Oomiya, and Tsuchizaki.

33 were later converted to C61 4-6-4s.

Class D52 (Locobase 3841)

Data from Hiroshi Takagi, both from his website ([]) and personal communication August 2000. See also kira Saito, in an overview of Japan's modern steam locomotives published in December 2002 on [] . Takagi's tables show that this boiler had a large combustion chamber. He gives two values 1000 mm (39.4") and 920 mm (36.2"), but there's no additional explanation for the two values.

Akira Saito explained that Hideo Shima (who later pioneered the Shinkansen and other great civil engineering works) recognized the value of the combustion chamber and incorporated it in this, the last major steam locomotive design in Japan.

Information from Ejii Nozawa's web site ([]) gives detailson the building of this large wartime engine. From 1943 to 1945, Hitachi, Kawasaki, KSK, Mitsubishi, and Nippon supplied engines as well as the JNR Works at Hamamatsu and Takatori.i.

49 were later converted to C62 4-6-4s and another 20 became D62 2-8-4s (Locobases 3842-3443).