| GWR 5400 Class | 
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| Specifications | 
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 Configuration:
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 |  • Whyte | 0-6-0PT | 
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 | Gauge | 4 ft 8+1⁄2 in (1,435 mm) standard gauge | 
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 | Driver dia. | 5 ft 2 in (1.575 m) | 
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 | Minimum curve | 
- 4 chains (264 ft; 80 m) normal
 
- 3.5 chains (231 ft; 70 m) slow
  
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 | Wheelbase | 14 ft 8 in (4.47 m) | 
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 | Length | Over buffers: 31 ft 1 in (9.47 m) | 
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 | Width | 8 ft 7 in (2.616 m) | 
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 | Height | 12 ft 6+3⁄16 in (3.815 m) | 
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 | Frame type | 
- Type: Inside
 
- Length: 26 ft 5 in (8.05 m)
  
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 | Axle load | 15 long tons 12 cwt (34,900 lb or 15.9 t) (17.5 short tons) | 
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 | Loco weight | 46 long tons 12 cwt (104,400 lb or 47.3 t) (52.2 short tons) full | 
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 | Fuel type | Coal | 
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 | Fuel capacity | 3 long tons 4 cwt (7,200 lb or 3.3 t) (3.6 short tons) | 
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 | Water cap. | 1,100 imp gal (5,000 L; 1,300 US gal) | 
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 | Firebox: |  | 
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 |  • Grate area | 16.76 sq ft (1.557 m2) | 
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 Boiler:
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 |  • Model | GWR Standard No. 21 | 
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 |  • Pitch | 7 ft 0 in (2.13 m) | 
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 |  • Diameter | Outside diameter: 4 ft 3 in (1.30 m) & 4 ft 2+1⁄8 in (1.273 m) | 
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 |  • Tube plates | Barrel: 10 ft 6 in (3.20 m) | 
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 | Boiler pressure | 165 psi (1.14 MPa) | 
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 | Heating surface: |  | 
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 |  • Firebox | 81.8 sq ft (7.60 m2) | 
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 |  • Tubes | 1,004.2 sq ft (93.29 m2) | 
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 |  • Total surface | 1,086.0 sq ft (100.89 m2) | 
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 | Cylinders | two inside | 
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 | Cylinder size | 16+1⁄2 in × 24 in (419 mm × 610 mm) | 
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 | Train heating | Steam from locomotive boiler | 
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 | Loco brake | steam | 
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 | Train brakes | vacuum | 
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 | Safety systems | ATC | 
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The Great Western Railway (GWR) 5400 Class was a class of 0-6-0 pannier tank steam locomotive. They were similar in appearance to many other GWR tank engines but smaller than the ubiquitous GWR 5700 Class.
The nominally Collett-designed 5400 Class had 5 ft 2 in (1.575 m) driving wheels for greater top speed with autocoaches, and were all fitted with the required remote control gear for working the push-pull autotrains. They had a modern cab and a larger bunker. They were frequently seen on inner suburban routes from Paddington.