31 series

31 series
KuMoHa 12053 (ex-MoHa 31088) in July 1993
Technical specifications
Manufacturer(s)	Kawasaki Sharyō, Kisha Seizō, Nippon Sharyo, Tanaka Sharyō
Type of locomotive	Electric multiple unit
Constructed	1929 – 1931
Number built	164 cars
Dimensions	17,000 mm × Unknown × Unknown
Gauge	3 ft 6 in (1,067 mm)
Power supply	Pantograph
Electric system(s)	1,500 V DC
Traction system	Resistor control
Traction system model	CS5
Service information
In service	1929 – 13 March 1996
Formation	Single car, 3 cars per set
Number in service	None
Fleet numbers	Various
Scrapped	1962 – 1986
Preservation information
Preserved	None
Number scrapped	163 cars

The 31 series is a Japanese commuter electric multiple unit operated by the Japanese National Railways from 1929 to March 1996.

Description

The 31 series was an early electric multiple unit used in Japan. The class was essentially an improved version of the 30 series cars, the Japanese Government Railways' first steel-bodied cars, and adopted a more rounded roof profile compared to the 30 series. A total of 164 cars were manufactured by four companies from 1929 to 1931; they were classified the MoHa 31, SaRo 37, KuHa 38 and SaHa 39 series respectively.

Intended for use in metropolitan regions, the 31 series cars were first introduced on the Chūō and Yamanote Lines from 1929, while the 30 series cars were concentrated around the Keihin Line (now the Keihin-Tōhoku Line). Due to their roof shape many passengers opted to board the 31 series cars opposed to older MoHa 1 series cars, leading the passengers to be described as "cranes in a cesspit". Many cars were destroyed during World War II, while numerous other modifications were conducted on the cars.

Many cars were renumbered again following naming regulations introduced on 1 June 1953, being renumbered in the MoHa 11, MoHa 12, KuHa 16, SaHa 17 and SaRo 15 series among others, while others were further modified into maintenance of way vehicles, such as the KuMoRu 23 series. The last remaining 31 series cars were withdrawn in March 1996, they being replaced by 103 series cars.

Specifications

The 31 series cars were nearly identical to the 30 series but featured a curved roof. It used a CS5 traction system controller, an improved version of Shibaura Seisakushō RPC101 controller, which was itself a copy of a General Electric PC controller.

There were a number of significant design changes made to the rolling stock over its production run.