South African Class FD 2-6-2+2-6-2

The South African Railways Class FD 2-6-2+2-6-2 of 1926 was an articulated steam locomotive.

South African Class FD 2-6-2+2-6-2
Class FD no. 2323, later renumbered no. 674
Type and origin
Power typeSteam
DesignerNorth British Locomotive Company
BuilderNorth British Locomotive Company
Serial number23294-23297
ModelClass FD
Build date1925
Total produced4
Specifications
Configuration:
  Whyte2-6-2+2-6-2 (Double Prairie)
  UIC1'C1'+1'C1'h4t
Driver3rd & 4th coupled axles
Gauge3 ft 6 in (1,067 mm) Cape gauge
Leading dia.28 12 in (724 mm)
Coupled dia.46 in (1,168 mm)
Trailing dia.28 12 in (724 mm)
Wheelbase58 ft 7 in (17,856 mm)
  Engine18 ft 7 12 in (5,677 mm) each
  Coupled8 ft 6 in (2,591 mm) each
Pivot centres36 ft 6 in (11,125 mm)
Length:
  Over couplers65 ft 7 34 in (20,009 mm)
Height12 ft 9 14 in (3,893 mm)
Frame typePlate
Axle load12 LT 7 cwt (12,550 kg)
  Leading10 LT 11 cwt (10,720 kg) front
10 LT 4 cwt (10,360 kg) rear
  1st coupled12 LT 7 cwt (12,550 kg)
  2nd coupled12 LT 3 cwt (12,340 kg)
  3rd coupled12 LT 5 cwt (12,450 kg)
  4th coupled12 LT 1 cwt (12,240 kg)
  5th coupled12 LT (12,190 kg)
  6th coupled12 LT 1 cwt (12,240 kg)
  Trailing10 LT 16 cwt (10,970 kg) front
9 LT 14 cwt (9,856 kg) rear
Adhesive weight72 LT 17 cwt (74,020 kg)
Loco weight114 LT 2 cwt (115,900 kg)
Fuel typeCoal
Fuel capacity5 LT (5.1 t)
Water cap2,500 imp gal (11,400 l) front
1,300 imp gal (5,910 l) rear
Firebox typeBelpaire
  Firegrate area41 sq ft (3.8 m2)
Boiler:
  Pitch7 ft 6 14 in (2,292 mm)
  Diameter6 ft (1,829 mm)
  Tube plates10 ft 8 in (3,251 mm)
  Small tubes190: 2 in (51 mm)
  Large tubes32: 5 12 in (140 mm)
Boiler pressure180 psi (1,241 kPa)
Safety valveRamsbottom
Heating surface1,730 sq ft (161 m2)
  Tubes1,552 sq ft (144.2 m2)
  Firebox178 sq ft (16.5 m2)
Superheater:
  Heating area371 sq ft (34.5 m2)
CylindersFour
Cylinder size15 in (381 mm) bore
24 in (610 mm) stroke
Valve gearWalschaerts
Valve typePiston
CouplersJohnston link-and-pin
AAR knuckle (1930s)
Performance figures
Tractive effort31,690 lbf (141.0 kN) @ 75%
Career
OperatorsSouth African Railways
ClassClass FD
Number in class4
Numbers2320-2323, renumbered 671-674
Delivered1926
First run1926
Withdrawn1949

In 1926, the South African Railways placed four Class FD Modified Fairlie articulated steam locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in service.[1][2][3]

Manufacturer

The Class FD Modified Fairlie locomotive was designed and built for the South African Railways (SAR) by the North British Locomotive Company in 1925, to the specifications of Colonel F.R. Collins DSO, Chief Mechanical Engineer of the SAR. Four locomotives were delivered in 1926, numbered in the range from 2320 to 2323. They were later renumbered in the range from 671 to 674.[1][2][3][4]

Characteristics

The Class FD was a heavier and more powerful version of the experimental Class FC which had been placed in service in 1925. It was the Modified Fairlie equivalent of the Class GD 2-6-2+2-6-2 Garratt which was similar in both size and mechanical respects, hence the Class FD designation of these Modified Fairlies. The FA and FB classifications were never used by the SAR. The Class FD locomotives had Walschaerts valve gear, plate frames and were superheated. They proved to be powerful locomotives and good steamers, but they were less successful than their Garratt equivalent.[1][2][3]

Shortcomings

They suffered from the same shortcomings as their Class FC predecessor. The 65 feet (19,812 millimetres) long rigid frame resulted in severe overhang on sharp curves and was also prone to metal fatigue and cracking, brought about by the long frame overhangs at the front and back beyond the engine unit pivot centres. The overhangs, laden with the water and coal bunkers of which about two-thirds of each extended beyond the respective pivot centres, tended to oscillate in an up-and-down motion while the locomotive was in motion.[1][5]

In addition to this rather serious defect, the pivot bearings were also subject to quite rapid wear since they carried a considerable additional load compared to those on the Garratt as a result of the water and coal bunkers which were mounted on the main frame instead of on the engine units. This resulted in increased frequency of maintenance and as a consequence, increased operating cost.[1][3][5]

Service

The locomotives joined the sole Class FC in service on the Cape Midland System, working on the Grahamstown branch. They were scrapped by 1949.[1][3]

The long rigid underframe of one of the Class FD locomotives was used to construct a footbridge across the single track at Poet’s Corner Halt on the old Natal mainline between Pinetown and Rossburgh junction in Durban. The underframe forms the main girder of the footbridge.[6]

Illustration

References

  1. Holland, D. F. (1972). Steam Locomotives of the South African Railways. 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 50–51. ISBN 978-0-7153-5427-8.
  2. Espitalier, T.J.; Day, W.A.J. (1945). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways (Continued). South African Railways and Harbours Magazine, December 1945. p. 968.
  3. Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 97. ISBN 0869772112.
  4. North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  5. Durrant, A. E. (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 31. ISBN 0715386387.
  6. Soul of A Railway, System 6, Part 4: The Old Main Line from Rossburgh to Cato Ridge. Caption 22. (Accessed on 15 March 2017)
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