South African Class 25NC 4-8-4

South African Class 25NC 4-8-4

No. 3410 at Sannaspos, Free State, 4 July 1999
Type and origin
♠ Type EW1 tender - ♥ Type EW2 tender
Power type Steam
Designer South African Railways
(L.C. Grubb)
Builder Henschel and Son
North British Locomotive Company
Serial number NBL 27287-27296, 27311
Henschel 28731-28769
Model Class 25NC
Build date 1953
Total produced 137
Specifications
Configuration 4-8-4 (Northern)
Driver 2nd coupled axle
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia. 30 in (762 mm)
Coupled dia. 60 in (1,524 mm)
Trailing dia. 30 in (762 mm)
Tender wheels 34 in (864 mm)
Minimum curve 275 ft (84 m)
Wheelbase ♠ 81 ft 4 11⁄16 in (24,808 mm)
♥ 95 ft 1 11⁄16 in (28,999 mm)
 • Engine 38 ft (11,582 mm)
 • Leading 6 ft 10 in (2,083 mm)
 • Coupled 15 ft 9 in (4,801 mm)
 • Trailing 5 ft 6 in (1,676 mm)
 • Tender ♠ 32 ft (9,754 mm)
♥ 45 ft 10 in (13,970 mm)
 • Tender bogie 10 ft (3,048 mm)
Length:
 ​
 • Over couplers ♠ 91 ft 6 9⁄16 in (27,903 mm)
♥ 107 ft 6 1⁄16 in (32,768 mm)
Height 13 ft (3,962 mm)
Frame type Cast
Axle load 18 LT 14 cwt (19,000 kg)
 • Leading 21 LT 2 cwt (21,440 kg)
 • 1st coupled 18 LT 10 cwt (18,800 kg)
 • 2nd coupled 18 LT 14 cwt (19,000 kg)
 • 3rd coupled 18 LT 12 cwt (18,900 kg)
 • 4th coupled 18 LT 9 cwt (18,750 kg)
 • Trailing 22 LT 12 cwt (22,960 kg)
 • Tender bogie Bogie 1:
♠ 51 LT 6 cwt (52,120 kg)
Bogie 2:
♠ 54 LT 5 cwt (55,120 kg)
 • Tender axle ♠ 18 LT 1 cwt 2 qtr (18,370 kg)
Adhesive weight 74 LT 5 cwt (75,440 kg)
Loco weight 117 LT 9 cwt (119,300 kg)
Tender weight ♠ 105 LT 11 cwt (107,200 kg)
Total weight ♠ 223 LT (226,600 kg)
Tender type EW1 (3-axle bogies)
EW2 (3-axle bogies)
Fuel type Coal
Fuel capacity ♠ 18 LT (18.3 t)
♥ 19 LT (19.3 t)
Water cap ♠ 10,500 imp gal (47,700 l)
♥ 11,200 imp gal (50,900 l)
Firebox type Round-top
 • Firegrate area 70 sq ft (6.5 m2)
Boiler:
 ​
 • Type Domeless
 • Pitch 9 ft 1 5⁄8 in (2,784 mm)
 • Diameter 6 ft 4 1⁄8 in (1,934 mm)
 • Tube plates 19 ft (5,791 mm)
 • Small tubes 158: 2 1⁄2 in (64 mm)
 • Large tubes 40: 5 1⁄2 in (140 mm)
Boiler pressure 225 psi (1,551 kPa)
Safety valve Ross Pop
Heating surface 3,390 sq ft (315 m2)
 • Tubes 3,059 sq ft (284.2 m2)
 • Arch tubes 37 sq ft (3.4 m2)
 • Firebox 294 sq ft (27.3 m2)
Superheater:
 ​
 • Type Melesco
 • Heating area 630 sq ft (59 m2)
Cylinders Two
Cylinder size 24 in (610 mm) bore
28 in (711 mm) stroke
Valve gear Walschaerts
Valve type Piston
Valve travel 7 3⁄8 in (187 mm)
Loco brake Vacuum
Couplers AAR knuckle
Performance figures
Tractive effort 45,360 lbf (201.8 kN) @ 75%
Career
Operators South African Railways
Class Class 25NC
Number in class 50 original, 87 rebuilt Class 25
Numbers 3401-3450, 3452-3510, 3512-3539
Delivered 1953-1954
First run 1953

The South African Railways Class 25NC 4-8-4 of 1953 was a steam locomotive.

Between 1953 and 1955, the South African Railways placed fifty Class 25NC steam locomotives with a 4-8-4 Northern type wheel arrangement in service. The Class 25NC was the non-condensing version of the Class 25 condensing locomotive, of which ninety were placed in service at the same time. Between 1973 and 1980, all but three of the condensing locomotives were converted to non-condensing and also designated Class 25NC.[1][2]

Manufacturers

L.C. Grubb

The Class 25NC non-condensing and Class 25 condensing 4-8-4 Northern type steam locomotives were designed by the South African Railways (SAR) under the direction of L.C. Grubb, Chief Mechanical Engineer of the SAR from 1949 to 1954, in conjunction with Henschel and Son of Kassel in Germany, who designed the condensing apparatus and the condensing tender of the Class 25 sister locomotive. Between 1953 and 1955, eleven Class 25NC locomotives, numbered in the range from 3401 to 3411, were built by the North British Locomotive Company (NBL), while 39 locomotives, numbered in the range from 3412 to 3450, were built by Henschel.[3][4][5]

Characteristics

The Class 25NC was superheated and used piston valves, actuated by Walschaerts valve gear. Roller bearings were used throughout, including on the three-axle tender bogies, the coupling and connecting rods as well as the crosshead gudgeon pins, while the locomotive's leading bogies and coupled wheels had Cannon-type axle boxes. The cylinders and frames were cast in one piece by Commonwealth Steel Castings Corporation in the United States of America. The tender frame was also a one-piece steel casting and was a water-bottom frame, with the frame itself forming the bottom of the tank, instead of being a separate tank and frame as in previous designs. The steel cylinders and steam chests were fitted with cast iron liners. Being entirely mounted on roller bearings, very little effort was required to move these locomotives.[1][6][7]

The crossheads, of the Alligator type, were split on the vertical centre line and clamped on to the end of the piston rods, which had three coned rings engaging in grooves in the crossheads. The original coupling rods differed from the usual in being three separate rods, thereby doing away with four knuckle joints and pins.[1]

The multiple-valve superheater header was of the Melesco type. The boiler was fitted with four Ross Pop safety valves, each 2 1⁄2 inches (64 millimetres) in diameter, and two Hopkinson boiler blowdown cocks on the firebox wrapper, one on each side. Feedwater was delivered to the boiler by two Friedmann vertical type non-lifting injectors, each with a capacity of 5,200 imperial gallons (23,600 litres) per hour.[6]

Teething troubles

Soon after being placed in service, problems were experienced with failing connecting rods, big end bearings breaking up as well as cracks developing in the motion girder of the Alligator crossheads. After investigations by SAR engineers, with assistance from the South African Council for Scientific and Industrial Research (CSIR), the crossheads, slide bars and coupling rods were modified. The crossheads were converted to the multiple-bearing type with single guide bars, while the three independent coupling rods were replaced with the more conventional single coupling rod with knuckle joints.[1][8]

Service

The Class 25NC initially served on the unelectrified mainlines from De Aar via Kimberley to Klerksdorp. They initially worked through to Welverdiend as well, until electrification was extended from Welverdiend to Klerksdorp. In later years, they also worked from Kimberley via Bloemfontein to Harrismith in the Free State, and some joined the Class 25 condensers on the line from De Aar via Beaufort West to Touws River.[3]

When the line south from De Aar was dieselised between 1973 and 1974, the Class 25 condensers working there were moved north to work the section from De Aar to Kimberley, where they replaced twenty-two Class 25NCs, which were then relocated to Bethlehem in the Free State. From 1982, Class 25NCs also replaced Class 19Ds and Class GMAM Garratts on the line from Warrenton via Vryburg to Mafikeng.[9]

Class 25 rebuilding

Along with the Class 25NC, ninety Class 25 condensing locomotives were built as part of the same order, one by Henschel and the rest by NBL. The condensing apparatus for these engines and their condensing tenders was designed and patented by Henschel.[1]

Between 1973 and 1980, all but three of the ninety Class 25 condensers were converted to non-condensing locomotives and reclassified to Class 25NC, the exceptions being numbers 3451, 3511 and 3540. The number plates of some were copied and recast with the additional "NC" for "non-condensing" squeezed in next to the existing "25", which resulted in a lopsided class indication on their cabside plates. Locomotives with all four characters neatly in line and centred were therefore usually identifiable as original Class 25NCs.[2][10]

In the process, their Type CZ condensing tenders were also rebuilt to ordinary coal-and-water Type EW2 tenders by removing the condensing radiators and roof fans and replacing it with a massive water tank. Since the Type CZ tenders were built on single cast steel main frames, it was impractical to attempt to shorten them, which resulted in the rebuilt Type EW2 tenders with their long round topped water tanks. Locomotives with these rebuilt tenders were soon nicknamed Worshond (Sausage dog or Dachshund).[9]

The Class 26 Red Devil

Between 1979 and 1981, no. 3450, the last Class 25NC to be built, was rebuilt to the sole Class 26, the Red Devil, at the SAR workshops at Salt River in Cape Town. The primary objectives of the project were to improve the combustion and steaming rate, to reduce the emission of wasteful black smoke and to overcome the problem of clinkering.[11][12]

This was achieved by the use of a Gas Producer Combustion System (GPCS), which relies on the gasification of coal on a low temperature firebed so that the gases are then fully burnt above the firebed. These extensive modifications justified reclassification and the locomotive became the first and only Class 26, although the locomotive's original Class 25NC number was retained.[11][12]

Works numbers

The locomotive numbers, builders and works numbers are listed in the table. On the builders' works lists, all the locomotives are shown as having been built in 1953. All tenders bore the same works number as the engines they were built with, except the sixty tenders which were built by Henschel for condensing engines which were built by NBL. These 60 tenders were allocated Henschel works numbers as shown.[1][13][14][15]

Illustration

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. p. 110. ISBN 978-0-7153-5427-8.
  2. 1 2 South African Railways and Harbours Locomotive Diagram Book, 2'0" & 3'6" Gauge Steam Locomotives, 15 August 1941, as amended
  3. 1 2 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10–11, 77–78. ISBN 0869772112.
  4. ↑ North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  5. ↑ Henschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow
  6. 1 2 South African Railways "25NC" Class Locomotives. The Railway Gazette, 15 May 1953. pp. 568-569.
  7. ↑ Pivnic, Les (1970). S.A.R. Class 25NC 4-8-4. South African Transport, October 1970. pp. 548-550.
  8. ↑ Information supplied by R.S. Loubser, son of M.M. Loubser
  9. 1 2 Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. pp. 107–109. ISBN 0715386387.
  10. ↑ Diamond Fields Advertiser, 27 March 1986
  11. 1 2 Gas Producer Combustion System (GPCS)
  12. 1 2 The Ultimate Steam Page
  13. ↑ South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 2'0" & 3'6" Gauge/Spoorwydte, Steam Locomotives/Stoomlokomotiewe. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. VIII, 6a-7a, 29a.
  14. ↑ Condenser fitter Albie Bester's reminiscences
  15. ↑ Sabatini, Richard (2006). South African Locomotive Tender Classification, Compatibility & Allocation (1st ed.) Richard Sabatini, Kimberley, January 2006. pp. 21, 38
External video
South African Steam: Trans Karoo Steam Finale: 2nd Last Run - March 1997 A short video featuring the second last run of steam on the Trans Karoo Express on 15 March 1997. The locomotives are Class 25NC no. 3422, a regular on the Trans Karoo, and Class 25NC no. 3407, a relatively rare engine on this train. The other two regular locomotives, nos. 3404 and 3476, were not available as they were being spruced up for the final run the following week. (Time 4:36)
External video
Class 25NC 3533, 5 October 2009 Rovos Rail's Class 25NC 3533, converted from a Class 25 condenser, enters Capital Park yard on 5 October 2009, in the process of turning The Pride of Africa around on the Capital Park triangle. (Time 1:00)
Wikimedia Commons has media related to South African Class 25NC (4-8-4).
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