The JGR Class 4100 was a 0-10-0T high-pressure side tank steam locomotive operated by the Japanese Government Railways from 1913 to September 1931.
History[]
The Class 4100s were procured out of a need for a dedicated freight train which was capable of pulling heavy freight trains over the 33‰ Itaya Pass. At the time the main locomotives used to pull trains up the pass were the Class 9200 heavy 2-8-0 Consolidation-type as the main source of motive power and the Class 2120 light tank locomotives as auxiliary locomotives, with multiple locomotives typically coupled back to back; even with multiple Class 9200 locomotives there was still skidding on this gradient and a fatal accident even occurred when some trains were running in the wrong direction. To solve this issue, the JGR placed an order with J.A. Maffei for a heavy tank locomotive capable of scaling steep gradients without issue.
A total of four locomotives were built by Maffei in 1912 at their Hirschau factory and imported into Japan by ship the same year; the locomotives were also mainly imported with a view of taking the design and modifying it for mass domestic production so only the bare minimum of four locomotives were built. These were assembled locally in 1913, with noted locomotive designer and engineer Kiichi Asakura looking over these locomotives, as well as the Class 10000 racked electric locomotives ordered from Esslingen and AEG around the same time for use on the Usui Pass. Following assembly the 4100s were used for test runs on both the Ōu and Tōhoku Main Lines starting in March; these tests only serve to affirm the locomotives's power, them being able to easily pull a 440-ton train at a balanced speed of 10 mph (16 km/h) and a 318-ton train at a balanced speed of 15 mph (24 km/h) up the Itaya Pass with some assistance from pusher locomotives. From these test results, the concept of a heavy freight tank locomotive was refined, resulting in the Class 4110s being developed and manufactured by the Kawasaki Dockyard; a total of 39 locomotives were manufactured of that type from 1914 to 1918.
Mainly stationed at Niwasaka Depot on the Ōu Main Line, the locomotives worked alongside the domestically-produced Class 4110s; 4101 to 4103 were later moved to Hokkaido with a further influx of Class 4110s where they would be trialed on the Nemuro Line up the Karikachi Pass as well as the Yūbari Line (now part of the Sekishō Line), but returned to Niwasaka in October 1919 likely due to the design of the locomotive making it difficult for it to work with other locomotive types and their low top speed. By the late 1920s the Class 4100s saw less and less use due to the opening of the Uetsu Main Line and Jōetsu Line, causing less freight to pass through the Itaya Pass combined with the effects of the Great Depression; additional 4110s originally stationed at Hitoyoshi were deployed to Niwasaka in 1927. All 4100s were effectively withdrawn from service on 1 September 1931 and were struck from JGR's roster on 20 May 1935. Following them being struck from the roster, the boiler of 4102 was used for a pressure test at Kōriyama Works, recording a maximum pressure of 40 kg/cm².
No Class 4100s have been preserved, with all said to have been scrapped at Kōriyama around 1937, although it is believed that E43-301, sighted at Hsinchu Station in 1938, used parts from 4100 and 4103 and was later remanufactured in Taiwan to replace a similar locomotive of the same number based on the 4110s that was scrapped the same year; this was likely done for counterintelligence purposes considering the locomotives were used by a military railway tied to Hsinchu Airfield. E43-301 was last sighted in April 1950, also at Hsinchu Station.