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FAQ: BR(S) Mk1 corridor EMUs

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Q:
I am at heart a steam fan, but I have just purchased a book called "Southern Survey " by Brian Denton whose content is EMU's, Diesels and DMU's. Looking through the book there are pictures of 4 Reps, Beps, Bigs, Cigs and Ceps. How, by looking at, them do you tell the difference?

A:
We'll handle this answer from the spotting point of view rather than give a detailed technical explanation. Reps have already been withdrawn, and the other classes are due to be over the next few years, so it is useful to record such gricer details, much practiced on station platforms and by the line side since 1951, for posterity.

All of the above units are BR Mark 1 design corridor EMUs. They were built in phases for particular electrification projects or to replace older types of EMU. As such it is easy to identify the differences in stages which correspond to the phases. We have presented the key differences in a tabular form illustrated by photographs. We have also included the TC units for completeness as they are of the same generation.

 
EMU class 411 4Cep 412 4Bep 421 4Cig 422 4Big 423 4Vep 432 4Rep 438 4TC
"Stock" series 1951/1957 1951/1957 1963/1970 1963/1970 1967 1967/1974 1966-7/1974
Spotting factors:              
cab front to roof roof slightly overhangs cab front roof slightly overhangs cab front rounded rounded rounded rounded rounded
Headcode box in corridor door surface mounted slightly off centre surface mounted slightly off centre flush and central flush and central flush and central flush and central flush and central
MU Jumper cables surface mounted on cab front surface mounted on cab front mounted in recesses on cab front mounted in recesses on cab front mounted in recesses on cab front mounted in recesses on cab front mounted in recesses on cab front
Motor bogies 1 under each driving cab (MBSO/MSO) 1 under each driving cab (MBSO/MSO) 2 under non driving motor brake second saloon car (MBSO) 2 under non driving motor brake second saloon car (MBSO) 2 under non driving motor brake second saloon car (MBSO) 2 under each motor second saloon car(MSO) unpowered trailer unit
Driving cars Originally motor brake second saloon (MBSO), 1979 (onwards) rebuilds motor second saloon (MSO) Originally motor brake second saloon (MBSO), 1979 (onwards) rebuilds motor second saloon (MSO) Driving trailer composite (DTC) 1st class compartments at front of car behind each driving cab Driving trailer composite (DTC) 1st class compartments at front of car behind each driving cab Driving trailer composite (DTC) - compartments (mostly 1st class) at the inner end of the car Motor second saloon (MSO) Driving trailer second saloon (DTSO)
Guard/Luggage compartment Originally had a small guard and luggage compartment behind each driving cab, 1979 (onwards) rebuilds had a single guard and luggage compartment in a trailer brake composite car (TBCK) Originally had a small guard and luggage compartment behind each driving cab, 1979 (onwards) rebuilds had a single guard and luggage compartment in a trailer brake composite car (TBCK) In non driving motor brake second saloon car (MBSO) In non driving motor brake second saloon car(MBSO) In non driving motor brake second saloon car(MBSO) In trailer brake first corridor car (TBFK) In trailer brake second corridor car (TBSK)
Passenger entry doors Mainline unit - 3 per side per car Mainline unit - 3 per side per car (1 or 2 per side on the buffet car) Mainline unit - 3 per side per car (2 per side on the brake car) Mainline unit - 3 per side per car (2 per side on the buffet and brake cars) Outer suburban unit - entry doors to (almost) every passenger seating bay Mainline unit - 3 per side per car (2 per side on the brake car, none to buffet car) Mainline unit - 3 per side each DTSO car, 2 per side TBSK, 2/3 per side TFK
Seating layout in saloons 2+2 2+2 2+2 2+2 3+2 2+2 2+2
Cars in formation Has a trailer second corridor (TSK) in original formation, a trailer second saloon (TSO) in rebuilt formation Has a trailer buffet (TBuf) in formation Has a trailer second saloon (TSO) in formation Has a trailer buffet second saloon (TBuf) in formation   Has a trailer buffet (TBuf) in formation  Has a trailer first corridor (TFK) in formation)
Other factors Original build had sliding ventilator windows, 1979 rebuild had hopper ventilator windows Original build had sliding ventilator windows, 1979 rebuild had hopper ventilator windows     Large original guards/luggage accommodation rebuilt smaller to include an additional two bay seating saloon   An unpowered trailer car unit used in conjuction with 4Rep EMUs and class 33/1, 73 and 74 locos
Variants 3 Cep removal of TSO   8Mig - temporary 4Cig formations including a RMB to cover for 4Big refurbishment;
8Dig - semi-permanently coupled 4Cig+4Big formations for the "Capital Coast Express" prior to introduction of 319/2 units on the service;
rebuilding of 1DTC to DTSOL
3Cop - removal of TBuf and rebuilding DTC to DTSOL;
to 4Cig by substituting an ex 4Cep TSO for the TBuf clearly denoted by hopper windows on one car in an otherwise sliding ventilator equipped unit
4Veg (class 427) for Victoria to Gatwick services - some seats replaced by luggage racks;
8Vab temporary formation including a trailer buffet to make up for a shortage of 4Rep units;
4Vop rebuilding of DTCs to DTSOLs;
3Vep - Some units have had their TSO removed and the DTC converted to a DTSOL
In later days many temporary formations whilst traction equipment was removed for installation into class 442 units When first introduced there were three 3TC units (minus a TFK), which were augmented in 1974 to 4TC.
In later days many temporary formations, including with trailer buffets, whilst traction equipment on 4Rep units was removed for installation into class 442 units
Link to pictures and further information class 411/412 picture page class 421/422 picture page class 423 picture page class 432 picture page class 438 picture page
 

How do you know a bogie is a power bogie you ask? Well that is a subject for another FAQ and one this author does not feel completely qualified to answer. However as a quick guide - compare with other bogies on the unit. Because a power bogie has to carry the traction motors and gears it needs to be of stronger construction and therefore the bogie frame is bulkier and has more suspension compared with a non powered bogie (note this generalisation does not apply to modern ac drive bogies, but we are not describing units of that particular generation here). Note that neither the presence nor the absence of a third rail pickup on a bogie (consisting of a horizontal beam (the "shoebeam") running between and below the axle boxes which carries electrical pickup shoes underneath) denotes whether a bogie is a power bogie.

 
4 Cep 4 TC

Compare the slab front end, slightly overhanging roof, surface mounted MU jumper cables and a slightly offset surface mounted headcode box on a 4Cep (note also the hopper ventilator windows of the 1979 rebuild).....

.....with the rounded cab roof top, MU jumper cables mounted in recesses and a flush central headcode box on the 4Cig/4Big/4Vep/4Rep/4TC series - in this case a 4TC. Note also the mainline accommodation with three passenger entry doors.....

 
4 Vep 4 Bep

.....compared with an entry door to each seating bay as seen on an outer suburban 4Vep unit. On this unit the compartment next to the saloon is standard class, on many; Veps the compartment next to the lavatory was standard class.

A catering vehicle - a dying breed - in this case a rebuilt 4Bep buffet car within one of the remaining 4 Bep units. Note the fewer number of passenger entry doors, only one on this side of the car.

Colin Duff

All photographs on this page are by Colin Duff and are copyright

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This page was last updated 11 June 2005

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