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

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

Class FD no. 2323, later renumbered no. 674
Type and origin
Power type Steam
Designer North British Locomotive Company
Builder North British Locomotive Company
Serial number 23294-23297
Model Class FD
Build date 1925
Total produced 4
Specifications
Configuration 2-6-2+2-6-2 "Double Prairie" Modified Fairlie
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia 28.5 in (724 mm)
Driver diameter 46 in (1,168 mm)
Trailing dia 28.5 in (724 mm)
Wheelbase Total: 58 ft 7 in (17,856 mm)
Engines:
8 ft 6 in (2,591 mm) coupled
18 ft 7.5 in (5,677 mm) total
Length 65 ft 7.75 in (20,009 mm)
Height 12 ft 9.25 in (3,893 mm)
Frame Plate frame, 36 ft 6 in (11,125 mm) between pivot centres
Axle load 12.35 long tons (12.5 t) on 1st driver
Adhesive weight 72.85 long tons (74.0 t)
Loco weight 114.1 long tons (115.9 t) w/o
Fuel type Coal
Fuel capacity 5 long tons (5.1 t)
Water cap 2,500 imp gal (11,000 l) front
1,300 imp gal (5,900 l) rear
Firebox:
  Firegrate area
41 sq ft (3.809 m2)
Boiler 6 ft (1,829 mm) inside diameter
10 ft 8 in (3,251 mm) inside length
7 ft 6.25 in (2,292 mm) pitch
Boiler pressure 180 psi (1,240 kPa)
Heating surface 1,730 sq ft (160.722 m2)
  Tubes 190 tubes 2 in (51 mm) diameter
32 tubes 5.5 in (140 mm) diameter
1,552 sq ft (144.186 m2)
  Firebox 178 sq ft (16.537 m2)
Superheater:
  Heating area
371 sq ft (34.467 m2)
Cylinders Four
Cylinder size 15 in (381 mm) bore
24 in (610 mm) stroke
Valve gear Walschaerts
Performance figures
Tractive effort 31,690 lbf (141 kN) at 75% pressure
Career
Operators South African Railways
Class Class FD
Number in class 4
Numbers 2320-2323, renumbered 671-674
Delivered 1926
First run 1926
Withdrawn 1949

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

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]

Manufacturer

The Class FD Modified Fairlie locomotive was designed and built for the South African Railways (SAR) by the North British Locomotive Company (NBL) in 1925. 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]

Characteristics

The Class FD was a larger and more powerful version of the experimental Class FC that was placed in service in 1924. 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 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]

Shortcomings

They suffered from the same shortcomings as their Class FC predecessor. The 65 feet (19.8 metres) 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 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 vibrate in an up-and-down motion while the locomotive was in motion.[1][4]

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 that were mounted on the frame instead of on the engine units. This resulted in increased maintenance and, as a consequence, increased operating cost.[1][2][4]

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][2]

References

  1. 1 2 3 4 5 6 Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 50–51. ISBN 978-0-7153-5427-8.
  2. 1 2 3 4 5 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 97. ISBN 0869772112.
  3. North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  4. 1 2 Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 31. ISBN 0715386387.
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