British Rail Class 302


The British Rail Class 302 was a class of electric multiple unit introduced between 1958 and 1960 for outer suburban passenger services on the London, Tilbury and Southend line. This class of multiple unit was constructed using the Mark 1 bodyshell with slam-doors.

Overview

Like all the Eastern Region AC EMUs of the period, they were equipped to operate on both 25 kV AC and the reduced 6.25 kV voltage in the inner London areas where headroom for the overhead wires was reduced. On the LT&S the changeover point was just east of Barking station on both Upminster and Tilbury routes with the link to Forest Gate being at 6.25kV ac.
Each unit was formed of four coaches, in the following formation: DTSOL – MBS – TCsoL – DTS. The initial set numbers were 201–312, later prefixed by the class number 302 with the introduction of TOPS.
The Battery Driving Trailer and Driving Trailer were fitted with drop head buckeye couplers with screw coupler in the Guards Van, retractable buffers are also fitted only on outer ends of the Battery Driving Trailer/Driving Trailer.

Service history

Public service started on 16 March 1959 with Class 302s working the first electric passenger trains between Colchester and Clacton at 25kV ac. A revised half hourly timetable started on 13 April from Colchester with a 8 car train splitting at Thorpe-le-Soken with half going to Walton-on-Naze
Some Class 302s were used for crew training in Manchester before the Class 304 units were introduced in April 1960.
They were among the first electric units delivered to the Eastern Region and, although ordered for the LT&S electrification, a route they were long associated with, they were used initially on the Liverpool Street to Hertford East, Bishop's Stortford and Enfield Town lines when they were electrified in November 1960. The 302s also stepped in when electrification was extended from Chelmsford to Colchester in 1961 and when the Class 305 units were having problems on the then new north-east London electric services. Some formations were temporarily reduced to three cars for the Enfield Town services.
The first 25 units remained on the GE main line for the bulk of their lives, with the remainder operating on the LT&S from Fenchurch Street from 1962.
Between November 1961 and June 1962, the class suffered traction motor insulation trouble which meant the motors had to be re-wound.
302312 was used as a test bed for silicon rectifier technology and a Brentford transformer from 1962 to 1964, then used to test thyristor control equipment until 1972, becoming the first electric train so fitted in the UK.
Unit 302 244 was involved in an accident in 1972 with a lorry at a level crossing at Low Street railway station in Tilbury, after which it was decided to scrap the leading carriage, BDTC 75292. This was replaced with DTSO 77164, originally belonging to a Manchester-Bury Line Class 504. It remained like this until May 1983 when it acquired a spare BDTC, 75298, from withdrawn unit 302250.
In 1987–88, 6 units were short formed with the removal of the trailer composite and based at Ilford EMD for work on the GE lines.
Old NumberBDTCOMBSODTSO
302434302234752076109375081
302439302239752876109875212
302459302259753076111875232
302462302262753106112175235
302494302294753426121075267
302497302297753456121375282

Following the privatisation of British Rail, ownership of the last 30 units passed to Eversholt Rail Group with all units being leased by LTS Rail.
The run-down of class 302s started in 1984 with the majority being phased out when Class 310 were introduced on to the LT&S in 1988 with last 30 units being withdrawn by 1998 with the introduction of Class 317 in 1997 and with extra Class 312 in 1998.

Electrical equipment

Electrical equipment was supplied by English Electric with the majority of equipment being interchangeable with Class 308 units.
Electrically there were three main systems, Control which operated at 110 volts DC, provided by nickel iron alkaline secondary cells, auxiliary 250 volts AC from the tertiary winding of the main transformer which provided power to the battery charger which was also rectified to power the main compressor, and finally power circuits derived from secondary winding of the main transformer at 1,500 volts AC.
The primary winding of the transformer was designed to operate on either 6.25 kV or 25 kV with voltage sensing equipment fitted to ensure the correct arrangement of primary windings for a given voltage. An incorrect voltage selection device was fitted to both the Class 302 and Class 308 stock so that if the primary winding was connected for 6.25 kV when supplied with 25 kV the air blast circuit breaker manufactured by Brown Boveri would remain closed but the pantograph would be lowered. Should this happen the transformer would require changing and overhaul as well as possibly other equipment due to flashover damage.
The transformer was also protected by a Buchholz relay which monitored any gas build-up within the cooling/insulating oil, as the acetylene gas generated is highly explosive. All Class 302 and 308 stock were fitted with Stone Faiveley pantographs for current collection from the overhead line. A particular oddity of Eastern/Anglian region EMU stock was the fitting of fibre glass snow shields between the pantograph and the supporting insulators.
One member of the class, 302 302, was experimentally fitted with thyristor control in the early 1970s. After the experiment it was converted back to the original tap changer control, although the guard's van remained slightly different internally.

Refurbished units

On refurbishment the trailer coaches were fitted with B5 bogies for both driving ends, along with conversions of the Battery Driving Second Open to a Battery Driving Trailer Composite Open having moved the first-class accommodation to a position over the Westinghouse CM38 main compressor which was noisy and caused vibration, Driving Standard Compartment to a Driving Standard Open DTSO having removed the compartments for an open layout. The centre trailer had B4 bogies fitted with the Trailer Composite Semi Open design converted to Trailer Standard Open. The motor coach retained its Gresley derived bogies after refurbishment with compartments removed for an open layout with guards van. All 30 units would also receive gangway connections between cars within the unit.
Originally the vehicles were insulated with blue asbestos which was removed and sealed during refurbishment between 1982 and 1984 with some of the compartments being removed and reconfigured to open saloons.
Units that received the original facelift with just Motor Brake Second and the Driving Trailer Second having their compartments removed for an open layout with the not receiving any layout changes and keeping the Gresley bogies were:
202, 204, 205, 213, 215, 216, 217, 218, 220, 225, 226, 227, 228, 231, 232, 234, 236, 239, 245, 251, 252, 254, 259, 261, 262, 263, 274, 277, 279, 280, 283, 284, 285, 292, 293, 297, 298, 299, 300, 301, 303, 304, 307, 308, 311
The 30 units that received the full refurbishment and would last until withdrawal of 302s from service on LT&S were:
Old NumberBDTCOMBSOTSODTSOOld NumberBDTCOMBSOTSODTSO
3022017508561060700607503330221675100610757007575063
3022027508661061700617503430221775190610767007675064
3022033022637531161122701227523630221875191610777007775065
3022047508861063700637503630221975192610787007875066
3022057508961064700647503730222075193610797007975067
3022067509061065700657503830222175194610807008075068
3022073023107535861226702267528330222275195610817008175069
3022083023087535661224702247528130222330229375341612097020975266
3022097509361068700687504130222475197610837008375071
3022107509461069700697504230222575198610847008475072
3022117509561070700707504330222675199610857008575073
3022127509661071700717504430222730227775325611937019375250
3022137509761072700727506030222875201610876108775075
3022143023047535261220702207527730222975202610887008875076
3022157509961074700747506230223030223275205610917009175079