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British Rail Class 421

British Rail Class 421
Unit 1498 4CIG at North Weald 2012.JPG
Class 421/7 no. 1498 at North Weald in 2012. This unit was restored to 1960s-era British Railways green livery for use on the Lymington Branch Line,it was at the Epping Ongar Railway, but has since moved to Ireland.
British Rail CIG Class 421 Standard Class Interior.jpg
The interior of Standard Class aboard a Class 421
In service 1964 - 2005 (Mainline services)
- 2010 (Lymington branch)
Manufacturer BREL York
Number built 166 (138 class 421 (4 CIG) and 28 class 422 (4 BIG) Units)
Formation Driving trailer + Motor coach + Trailer/Buffet + Driving trailer
Operator(s) British Rail, South West Trains, Connex South Central, Connex South Eastern, Network South East, Southern, South Eastern Trains
Specifications
Train length 265 feet 8 12 inches (80.988 m)
Width 9 feet 3 inches (2.82 m)
Height 12 ft 9 14 in (3.893 m)
Maximum speed 90 mph (140 km/h)
Weight 150 long tons (152 t; 168 short tons)
Traction motors Four
Power output 4 x 250 hp (190 kW)
total 1,000 hp (750 kW)
Electric system(s) 750 V DC third rail
Track gauge 4 ft 8 12 in (1,435 mm) standard gauge

The British Rail Class 421 (or 4Cig) electrical multiple units were built at BR's BREL York Works between 1964 and 1972. Units were built in two batches, and were initially introduced on services on the Brighton Main Line. Later units were introduced on services to Portsmouth. These units replaced older Southern Railway-designed units, such as the 5Bel "Brighton Belle" units, and 4Cor units. Towards the end of their life, with the increasing use of newer trains which were equipped with sliding or plug doors, these trains were known commonly as "slam-door trains". The fleet's lifespan was 46 years.

The standard units contained only passenger accommodation, and formed the bulk of the fleet. They were unusual in that all four traction motors were mounted on one non-driving motor coach. Units consisted of two driving trailers, sandwiching the non-driving motor coach and an intermediate trailer.

Units were built in two batches. 'Phase 1' units were built from 1963 to 1966 for the Brighton Line, and were numbered 7301-7336. These were followed in 1970-72 by the 'Phase 2' units, built primarily for the Portsmouth line, numbered 7337-7438.

The 4Big units were similar to the standard units, but contained a buffet car in place of the intermediate trailer.

These units were also built in two batches. 'Phase 1' units were built in 1965/66, and were numbered 7031-48. 'Phase 2' units were built in 1970, and were numbered 7049-7058.

The 4Big fleet were initially classified as Class 420 by British Rail under the new computer numbering system introduced in 1968, and then Class 422.

The numbering of individual vehicles and details of when units were built are shown in the table below.


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