:Seibu Class E31

{{short description|Japanese electric locomotive}}

{{Use dmy dates|date=September 2020}}

{{Infobox locomotive

| name=Class E31

| electricsystem=1,500 V DC

| tractionmotors=DC

| powertype=Electric

| image=Seibu E34 Minami-Iriso 20070901.JPG

| caption= Seibu Class E31 electric locomotive No. E34 on display at Minami-Iriso Depot Open Day, September 2007

| builddate=1986-1987

| builder= Seibu (Tokorozawa)

| totalproduction = 4

| locoweight=

| uicclass=Bo-Bo

| gauge= {{RailGauge|1067mm}}

| firstrundate=

| disposition= 3 transferred to Ōigawa Railway

| numinclass=

| wheeldiameter=

| poweroutput= 520 kW

| wheelbase=

| tractiveeffort=

| maxspeed=

| length=

| width=

| height=

| transmission=

| operator= Seibu Railway
Ōigawa Railway

}}

The Class E31 (E31形) is a class of DC Bo-Bo wheel arrangement electric locomotives formerly operated by the private railway operator Seibu Railway in Japan until March 2010 and subsequently by the Ōigawa Railway.

Four locomotives (numbered E31 to E34) were built at Seibu's Tokorozawa factory between 1986 and 1987 to replace ageing first-generation electric locomotives on freight services and track maintenance train duties. The DT-20A bogies were reused from former JNR 80 series EMUs, and the traction motors were modified from former EMU motors.

File:Seibu-Railway-E31.jpg|Seibu Railway E31

File:Seibu-Railway-E31-DT20A.jpg|Closeup of the DT-20A bogie

File:Seibu E33+hoki+E34-2.JPG|Seibu Railway E33･34 Electric locomotive and Hoki 81 freight car

They were normally used in pairs by Seibu for top-and-tailing permanent way maintenance trains and to haul newly delivered rolling stock.

Locomotive number E33 was withdrawn on 31 January 2009, becoming the first of the class to be withdrawn.{{cite journal | script-title=ja:私鉄車両のうごき |trans-title=Private Railway Fleet Movements| journal = Tetsudō Daiya Jōhō | volume = 38 | issue = 303 | page =124 | language = Japanese | date = July 2009 }} The remaining three locomotives were withdrawn on 28 March 2010.{{Cite web | title = 西武鉄道　「E31形電気機関車 さよならイベント」を開催|trans-title=Seibu to stage "Class E31 Sayonara Event"| work = Hobidas | publisher = Neko Publishing | date = 15 March 2010 | url = http://rail.hobidas.com/news/info/article/114871.html | language = Japanese | accessdate = 15 March 2010}}

File:Seibu railway E34 20140824 001.jpg

In September 2010, three of the withdrawn Class E31 locomotives (E32 to E34) were transferred to the Ōigawa Railway to replace the ageing E10 and ED500 locomotives used there.{{cite magazine| title = 大井川鉄道が西武E31形電機を導入！|trans-title=Ōigawa Railway introduces Seibu Class E31 Electric Locomotives|magazine=Japan Railfan Magazine | volume = 50| issue = 596| page =143| publisher = Koyusha| location = Japan | language = Japanese | date = December 2010}} Initially they were used only for depot shunting duties, but from 2017 they underwent overhaul in preparation for use as helper locomotives on steam-hauled trains,{{cite web |url= http://tetsudo-shimbun.com/headline/entry-1029.html |script-title=ja: 大井川鐵道、元西武E31形電気機関車営業デビューへ 2018年度中めざす |trans-title=Oigawa Railway former Seibu Class E31 electric locomotives to enter revenue service in fiscal 2018 |date= 2 May 2017 |publisher= Tetsudo Shimbun |location= Japan|language= Japanese|archiveurl= https://web.archive.org/web/20170503010100/http://tetsudo-shimbun.com/headline/entry-1029.html |archivedate= 3 May 2017 |url-status=live |accessdate= 3 May 2017 }} with the first locomotive treated, E34, scheduled to enter revenue service on 15 October 2017.{{cite web |url= http://railf.jp/news/2017/09/05/003000.html |script-title=ja: もと西武E31形電気機関車が大井川鐵道で営業運転へ |trans-title=Former Seibu Class E31 electric locomotives to enter revenue service on the Oigawa Railway |date= 5 September 2017|work= Japan Railfan Magazine Online|publisher= Koyusha Co., Ltd.|location= Japan|language= Japanese|archiveurl= https://web.archive.org/web/20170905024703/http://railf.jp/news/2017/09/05/003000.html |archivedate= 5 September 2017 |url-status=live |accessdate= 5 September 2017}} Occasionally, they are used to haul the EL Kawane michi-gō express.

Locomotive E31 remains preserved at Seibu's Yokoze Depot.