SR Class 4Sub

The Southern Railway (SR) gave the designation Sub to the wide variety of electric multiple units that were used on inner-suburban workings in the South London area. Originally these units were formed as three-car units, but in the 1940s, all surviving units were increased to four cars by the addition of an 'Augmentation' trailer. New four-car units were also built at this time, and these survived in passenger use until late 1983, by which time British Rail had allocated to them TOPS Class 405.

Southern Railway 4-SUB British Rail Class 405
4101 (prototype) in 1941
In service	1941-1983
Manufacturer	Eastleigh Works
Constructed	1941-1951
Number built	185 units
Number preserved	1 unit
Formation	DMBSO-TS-TSO-DMBSO
Capacity	368 - 386 Seats
Operators	Southern Railway British Railways
Depots	Wimbledon Traincare Depot (London)
Specifications
Car length	DMBSO: 62 ft 6 in (19.05 m) TS & TSO: 62 ft (18.90 m)
Width	9 ft (2.74 m)
Maximum speed	75 mph (121 km/h)
Weight	134 long tons (136 t; 150 short tons)
Traction motors	Four
Power output	Early units: 4 x 275 hp (205 kW) total 1,100 hp (820 kW) Later units: 4 x 250 hp (190 kW) total 1,000 hp (750 kW)
Current collector(s)	Contact shoe
Braking system(s)	Air (Westinghouse)