Indian locomotive class XB

The Indian locomotive class XB was a 4-6-2 (or Pacific) passenger locomotive with a 17-long-ton (17 t; 19-short-ton) axle load. It had a lot of problems. It was built with the help of British Engineering Standards Association (BESA). It was up to date as any locomotive in England. It had American 3-point suspension with compensating levers for indifferent tracks in India. The trailing wheels were mounted on a Cartazzi truck as it was for the rest of British Pacifics at the time. Goodall-type drawgear was fitted between engine and tender to facilitate free movement. They still proved to be successful as they survived till the 1980s. The modifications in India to this class was implemented in LMS Railway in UK. Copper firebox had combustion chamber extension.[1]

Class XB
Vulcan Foundry works photograph of an XB
Type and origin
Power typeSteam
DesignerM/s Rendel Palmer and Tritton
BuilderVulcan Foundry
Armstrong Whitworth (12)
North British Locomotive Company (4)
Build date1927–1936
Total produced99
Specifications
Configuration:
​
 • Whyte4-6-2
 • UIC2′C1′ h2
Gauge5 ft 6 in (1,676 mm)
Leading dia.3 ft 0 in (0.914 m)
Driver dia.6 ft 2 in (1.880 m)
Trailing dia.3 ft 7 in (1.092 m)
Wheelbase13 ft 2 in (4.013 m)
Axle load17 long tons (17 t; 19 short tons)
Loco weight90.2 long tons (91.6 t; 101.0 short tons)
Tender weight49.4 long tons (50.2 t; 55.3 short tons)
Fuel typeCoal
Fuel capacity6-wheel: 10 long tons (10 t; 11 short tons)
8-wheel: 7.5 long tons (7.6 t; 8.4 short tons)
Water cap6-wheel: 4,000 imp gal (18,000 l; 4,800 US gal),
8-wheel: 4,500 imp gal (20,000 l; 5,400 US gal)
Firebox:
 • Firegrate area		45 sq ft (4.2 m2)
Boiler pressure180 psi (1.24 MPa)
Heating surface:
 • Tubes and flues		1,642 sq ft (152.5 m2)
 • Firebox198 sq ft (18.4 m2)
Superheater:
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 • Heating area463 sq ft (43.0 m2)
CylindersTwo, outside
Cylinder size21.5 in × 28 in (546 mm × 711 mm)
Valve gearWalschaerts
Performance figures
Maximum speed72 mph (116 km/h)
Tractive effort26,760 lbf (119.03 kN)
Factor of adh.4.33
Career
OperatorsIndian Railways
LocaleEIR, M&SM and BB&CI
Scrapped1983
Dispositionall scrapped but one preserved in Pakistan

Problems

Like other X series Pacifics, it was prone to frame fractures. One unit had 9 fractures in 9 years. 18 XBs of the East Indian Railway Company (EIR) spent 3 years in repair shop, out of 8 years. Again due to it being an X series Pacific, it had chronic coupling rod failure. Tubeplates had to be frequently changed due to cracking in the radius of flanges. Cross-sectional area of the boiler was too small for the flue gas generated by the firebox. Tube cross-section area to the grate was only 9%. The boiler was poor, having pressure below 150 pounds per square inch (1,000 kPa). Testing showed that the engine was unable to haul a 350-long-ton (360 t) train at 60 mph (97 km/h) at 33% cylinder cut-off. It oscillated laterally at a right-angle to the tracks causing damage to the tracks. In 9 years, there were 68 such cases due to XB and XC class locomotives.

Development

The trailing bogie was moved 30 inches (760 mm) back and engine was fitted with American drawgear. But this did not work. In 1937, Bihta accident occurred with the engine jumping the tracks and derailing at 60 mph (97 km/h). The tracks were twisted like noodles. 100 people lost their lives. The Pacific Locomotive Committee was formed on public demand. Robert Leguille came up with a solution. He decided to fit leading and trailing bogie with stiffer side springs and better damping. He was proven right with experiments. The Bombay, Baroda and Central India Railway and Madras and Southern Mahratta Railway followed his advice and EIR restricted the engines to slow-speed trains.

Technical specifications
Length between tube plates18 ft 6 in (5.64 m)
95 small tubes diameter2.25 in (57.15 mm)
22 smoke tubes diameter5.5 in (139.7 mm)
4 arch tubes3 in (76.2 mm)
22 smoke tubes diameter5.5 in (139.7 mm)
Superheater22 elements

Preservation

No XB's from Indian Railways have survived Preservation today but in Pakistan, an ex-EBR XB class loco, 450 survives and is preserved at Lahore workshops.

Trains hauled by XB

See also

References
  • Hughes, Hugh (1990). Indian Locomotives: Part 1 – Broad Gauge 1851–1940. Harrow, Middlesex: The Continental Railway Circle. ISBN 0-9503469-8-5.
  1. "XB 4-6-2". Archived from the original on 2 October 2013. Retrieved 30 September 2013.
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