JNR Class ED74
The Class ED74 was developed as a four-axle version of the six-axle (Bo-Bo-Bo) Class EF70 electric locomotives introduced a year earlier on the Hokuriku Main Line, and was intended for use on services north of Fukui where the gradients were easier.
A total of six locomotives were built by Mitsubishi in 1962, coinciding with the electrification of the Hokuriku Main Line between Fukui and Kanazawa. The six locomotives were delivered to Tsuruga Depot.
Displaced by the arrival of Class EF81 multi-voltage AC/DC electric locomotives, the Class EF74 locomotives were transferred to Kyushu in October 1968 for use on the recently electrified Nippo Main Line. To enable use alongside the six axle (Bo-2-Bo) Class ED76 AC locomotives, a dead weight of 1.4 t was added to increase the axle load from 16.25 t to 16.8 t. As the Class EF74 locomotives did not have steam generators and were unable to provide train heating for passenger services, they were mostly used on freight services between Moji and Oita, as well as on overnight sleeping car services that did not require a separate heating supply from the locomotive. Despite electrification south to Miyazaki in 1974, the Class EF74 locomotives were not allowed south of Oita due to their axle load, and were subsequently replaced by an additional build of Class ED76 locomotives. The entire class was withdrawn by 1982.
The ED74 classification for this locomotive type is explained below.
- E: Electric locomotive
- D: Four driving axles
- 7x: AC locomotive with maximum speed exceeding 85 km/h (55 mph)
- Inoue, Koichi (1999). 国鉄機関車事典: 蒸気・電気・ディーゼル機関車66形式 国鉄機関車辞典 [JNR Locomotive Encyclopedia]. Japan: Sankaido. pp. 142–143. ISBN 978-4-381-10338-3.
- 国鉄電気機関車の系譜 [JNR Electric Locomotive Lineage]. Railway Journal (in Japanese). Vol. 51 no. 610. Japan: Tetsudo Journal. August 2017. p. 149.
- 交流電気機関車ED74 [AC electric locomotive ED74]. Japan Railfan Magazine (in Japanese). Vol. 3 no. 19. Japan: Koyusha Co., Ltd. January 1963. p. 15.