SR class 3Sub
| Southern Railway 3-Sub Units | |
|---|---|
South Eastern division electric multiple units sandwich a trailer set. Orpington, 1928 | |
| In service | 1915-48 |
| Formation | power car + trailer car + power car |
| Operators | London and South Western Railway, Southern Railway and British Railways (Southern Region). |
| Specifications | |
| Maximum speed | 75 mph (121 km/h) |
| 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) |
| Track gauge | 4 ft 8+1⁄2 in (1,435 mm) |
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The class 3SUB were DC suburban electric multiple units, introduced by the London and South Western Railway in 1915. They were constructed by the Southern Railway in the period up to 1939, and though the class designation 3SUB was not used by the Southern Railway, some authors refer to these units as 3SUB. When rebuilt to four cars in the 1940s, they became class 4SUB.