SR Class 4Sub

The Southern Railway (SR) and the British Railways (Southern Region) (BR(S)) used the designation Sub to cover a wide variety of electric multiple units that were used on inner-suburban workings in the South London area. The designation ‘Sub’ was first officially used in 1941 to refer to newly built 4-car units. However, during the 1940s large numbers of earlier ‘3-Car Suburban Sets’ were increased to four cars by the addition of an 'Augmentation' trailer, and became part of the 4-Sub category. The SR and BR (S) continued to build or else rebuild 4-car units to slightly different designs which became part of the 4-Sub Class. Many of these later examples survived in passenger use until late 1983, by which time British Rail had allocated to them TOPS Class 405.

Southern Railway 4-Sub Units
Prototype 4-sub Unit 4101 with domed front cab
In service1941–1983
ManufacturerSR Eastleigh
Number built185 new built sets
Formationpower car + 2 trailer cars + power car
Operator(s)Southern Railway and British Railways (Southern Region).
Specifications
Maximum speed75 mph 121 km/h
WeightDMBS - 39–43 long tons (40–44 t)
Prime mover(s)Early units: 4 x 275 hp (205 kW) traction motors
total 1,100 hp (820 kW)
Later units: 4 x 250 hp (190 kW) traction motors
total 1,000 hp (750 kW)
Braking system(s)Air (Westinghouse)

History

3-Car Suburban Sets
Main article: SR class 3Sub

In 1923 the Southern Railway inherited 84 3-car suburban electric multiple units from the London and South Western Railway (LSWR), dating from 1914.[1] These could be enhanced by 24 2-car trailer sets coupled between two units, creating 8-car formations. Over the next 18 years the SR acquired a further 516 3-car sets.[2] These were either new; rebuilt from steam stock inherited from the LSWR, the London Brighton and South Coast Railway (LBSCR) and the South Eastern and Chatham Railway; or rebuilt from LBSCR AC multiple units. Some rebuilt units has ‘torpedo style’ front ends, others had the newer, flatter, front ends used on the main-line stock introduced during the early 1930s. They were designated ‘3-Car Suburban Sets’ to differentiate them from main-line units, and were numbered between 1201 and 1800. They are sometimes referred to as ‘3-Sub units’, but this designation does not appear to have been used whilst they were in use.

The 3-car units ultimately proved to be inadequate for most trains and inconvenient as the trailer sets had no driving cabs and so had to be marshaled between two 3-car units. Therefore, many were augmented by the addition of a new trailer car and rebuilt as 4-Sub units between 1942 and 1948. The remainder of the 3-car units were withdrawn. The last 2-car trailer set was withdrawn in September 1948, and the last 3-car formation ran in 1949.[3]

4-Sub Units
Preserved 4-Sub unit 4732 with vertical ‘slab’ front end

In 1939, following the appointment of Oliver Bulleid as Chief Mechanical Engineer, the SR announced a new welded steel 4-car suburban unit with curved sides, seating six passengers across rather than the normal five.[1] The prototype unit, 4101, was not completed until 1941 due to the advent of the Second World War. This had composite (both First Class and Third Class) seating accommodation in one trailer car and domed cab roofs. A further nine units were built in 1944-5 with Third Class accommodation only. Twenty units were introduced from 1946 with a vertical, ‘slab’ front end, and Third Class accommodation only. The underframes were built at Lancing Carriage Works and the bodies at Eastleigh Works.

Rebuilt 4Sub Motor Car with ‘torpedo’ style front.

As mentioned above, between 1942 and 1948 many 3-Car Suburban Sets were rebuilt and enhanced by the addition of a new 'Augmentation' trailer car to create 4-Sub units. This was done by inserting new steel trailers rather than one of the existing trailer cars. The rebuilt units were renumbered between 4131 and 4249.

BR(S) continued to introduce 4-Sub units, both new and converted from existing units, until 1951.

Formations

The usual formation for the newly built units was to have a Driving Motor Brake Third (DMBT) car at each ends, with accommodation for 108 passengers in nine compartments, together with two Trailer Third (TT) cars between with ten or eleven compartments giving a total passenger accommodation for 456 in all four coaches.[4] (After the renaming of 'Third Class' to 'Second Class' in 1956 these became DMBS and TS respectively.) However some of the rebuilds had Trailer Composite (TC) cars. The earlier coaches provided compartments, whereas the post war newly built carriages tended to provide saloon or semi-saloon style accommodation to allow for more standing room. These new 'open' carriages were designated DMBTO or TTO.

Usage

Throughout their careers the 4-Sub units were used on the London suburban services of all three divisions of BR (S).

Withdrawal

The rebuilt units began to be withdrawn in the late 1950s and all had been withdrawn by the end of the 1960s. Apart from a few accident damaged units, the newly built units began to be withdrawn in 1972, and had all been withdrawn by 1983.[5] Those units surviving in the early 1970s were designated as British Rail Class 405 under the TOPS computer system.

Preservation

A handful of Sub stock carriages have survived in preservation, thus:

  • Driving Motor car number 8143 (formerly of Sub unit 1293, later 4Sub 4308) is in the care of the National Railway Museum, York.
  • 4Sub unit number 4732, formed of DMBTO 12795, TT 10239, TTO 12354 and DMBTO 12796, was retained by British Rail after withdrawal from normal passenger service for use on special occasions. It was stored at the Electric Railway Museum, Warwickshire, after spending many years stored in the open at various locations, but has subsequently been moved to the Locomotive Storage Ltd site in Margate, Kent.[6]
  • Former Departmental Converted 4 Sub Carriage TT 10400 is stored at a private site.
Unit number
(current in bold)		 DMBTO TT TTO DMBTO Built Livery Location
1293 4308 8143 - - - 1925 Eastleigh SR Maunsell Green National Railway Museum
- 4732 12795 12354 10239 12796 1951 Eastleigh Southern Green Locomotive Storage Ltd, Margate
- - - 10400 - - 1951 Eastleigh Network South East Finmere

History of individual units
Unit Numbers Type Introduced Formation Notes
989-1200 - 1920–1937 Various Two-car Sub Trailer sets. Converted from LSWR, SECR and LBSCR steam stock and LBSCR AC electric stock. Disbanded between 1941 and 1948, some cars used to augment 3-car Suburban to 4Sub.
1201–1284 3-car Suburban 1914–1917 DMBT+TC+DMBC Built by London and South Western Railway, their numbers E1-E84, ex-steam stock. Most augmented to 4131-4171 and 4195-4234 series in 1942–1948.
1285–1310 3-car Suburban 1925 DMBT+TC+DMBT Western Section (London to Guildford & Dorking) units, new-build, short frames. Augmented to 4300-4325 series in 1945–1946.
1401–1495 3-car Suburban 1925–1926 DMBT+TC+DMBT Eastern Section units, ex-SECR steam stock. Most augmented to 4431-4594 series in 1946–1949.
1496–1524 3-car Suburban 1925 DMBT+TC+DMBT Eastern Section units, new-build, standard frames. Augmented to 4326-4354 series in 1945–1946.
1525–1534 3-car Suburban 1926 DMBT+TC+DMBT Eastern Section units, ex-SECR steam stock. Most augmented to 4431-4594 series in 1946–1949.
1579–1599 3-car Suburban 1932–1937 DMBT+TC+DMBT Ex-LSWR steam stock. Most augmented to 4401-4594 series.
1601–1630 3-car Suburban 1927–1928 DMBT+TC+DMBT Central Section units, ex-SECR steam stock. Most augmented to 4431-4516 series.
1631–1657 3-car Suburban 1928–1929 DMBT+TC+DMBT Central Section units, ex-LBSCR steam stock. Most augmented to 4517-4614 series.
1658–1701 3-car Suburban 1927–1928 DMBT+TC+DMBC Central Section units, ex-LSWR steam stock. Most augmented to 4172-4194 and 4235-4250 series.
1702–1716 3-car Suburban 1928 DMBT+TC+DMBC Central Section units, ex-LBSCR steam stock. Most augmented to 4517-4614 series.
1717–1772 3-car Suburban 1929–1930 DMBT+TC+DMBC Central Section units, ex-LBSCR AC electric stock. Most augmented to 4517-4579 series.
1773–1785 3-car Suburban 1930–1931 DMBT+TC+DMBC Ex-LSWR steam stock. Most augmented to 4517-4614 series.
1786–1796 3-car Suburban 1931–1932 DMBT+TC+DMBT Ex-LSWR steam stock. Most augmented to 4517-4614 series.
1797–1801 3-car Suburban 1932 DMBT+TC+DMBT Ex-LBSCR steam stock. 1801 later renumbered 1600. Some augmented to 4580-4614 series.
4101 4-Sub 1941 DMBT+TT+TC+DMBT Prototype new-build, steel bodied 4-Sub unit with domed cab roof.
4102-4110 4-Sub 1944–1945 DMBT+TT+TT+DMBT New-build, steel bodied 4-Sub units with domed cab roof.
4111-4120 4-Sub 1946 DMBT+TT+TT+DMBT New-build, steel bodied 4-Sub units with vertical cab roof.
4121-4130 4-Sub 1946 DMBTo+TTo+TT+DMBTo New-build, steel bodied 4-Sub units with vertical cab roof.
4131-4171 4-Sub 1942–1948 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with additional ex-3-car Suburban trailer car.
4131-4132 4-Sub 1969 DMBT+TT+TT+DMBT Second use of unit numbers. Formed from spare steel-bodied Sub cars, including those used in the 7TC unit.
4172-4194 4-Sub 1947–1948 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with steel-bodied Augmentation trailer.
4195-4234 4-Sub 1942–1948 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with additional ex-3-car Suburban trailer car.
4235-4249 4-Sub 1947–1949 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with steel-bodied Augmentation trailer.
4250-4257 4-Sub 1942–1948 DMBT+TT+TT+DMBT Formed from a variety of spare Sub cars.
4277-4299 4-Sub 1948–1949 DMBTO+TTO+TT+DMBTO New build, steel-bodied 4-Sub units.
4300-4354 4-Sub 1945–1946 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with steel-bodied Augmentation trailer.
4355-4376 4-Sub 1947–1948 DMBT-TT-TT-DMBT New build, steel-bodied 4-Sub units.
4377 4-Sub 1947 DMBT-TTO-TT-DMBT New build, steel-bodied 4-Sub unit, including prototype full saloon trailer car.
4378-4387 4-Sub 1948 DMBTO+TTO+TT+DMBTO New build, steel-bodied 4-Sub units.
4401-4594 4-Sub 1946–1947 DMBT+TT+TT+DMBT Ex-3-car Suburban units, with steel-bodied Augmentation trailer.
4601-4608, 4610/13/14 4-Sub 1947 DMBT+TT+TT+DMBT First use of unit numbers. Ex-3-car Suburban units, with steel-bodied Augmentation trailer.
4601-4607 4-Sub 1950 DMBTO+TT+TT+DMBTO Second use of unit numbers. New Driving Motor cars formed with trailers built between 1946 and 1948.
4617-4620 4-Sub 1972–1976 Formed from spare Sub cars built between 1946 and 1950.
4621-4754 4-Sub 1949–1951 DMBTO+TT+TT+DMBTO Most cars had new bodies on old frames, though some were entirely new build. 4667-4754 included an Augmentation trailer from withdrawn units.
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References

Notes
  1. Moody 1968, p. 88
  2. The ABC of Southern Electrics. 1943. p. 12.
  3. Moody 1968, p. 137
  4. "The 4-SUB Units". Suburban Electric Railway Association.
  5. "4-Sub (Class 405)". Southern E-Group.
  6. Bailes, Kathy (7 June 2018). "Locomotive Storage Ltd in Margate welcomes the only surviving 4732 4-SUB unit". Isle of Thanet News. Retrieved 8 June 2018.

Sources
  • The ABC of Southern Electrics. Ian Allan. 1968.
  • Marsden, Colin J. (1983). Southern Electric Multiple Units; 1898 - 1948. Ian Allan. ISBN 0-7110-1253-9.
  • Moody, G.T (1968). Southern Electric 1909–1968. Ian Allan.
  • Rayner, Bryan; Brown, David (1983). The "4-Sub" Story. Southern Electric Group. ISBN 0-906988-09-8.
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