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 Power type Steam Designer South African Railways Builder Henschel and Son North British Locomotive Company Serial number 3401-3410: NBL 27287-27296 3411: NBL 27311 3412-3450: Henschel 28731-28769 Model Class 25NC Build date 1953 Total produced 50 Rebuilder South African Railways

Specifications Configuration 4-8-4 "Northern" Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia 30 in (762 mm) Driver diameter 60 in (1,524 mm) Trailing dia 30 in (762 mm) Wheelbase Total: 81 ft 4.6875 in (24,808 mm) Engine: 6 ft 10 in (2,083 mm) bogie 15 ft 9 in (4,801 mm) coupled 5 ft 6 in (1,676 mm) trailing 38 ft (11,582 mm) total Tender: 10 ft (3,048 mm) bogie 32 ft (9,754 mm) total Length 91 ft 6.5625 in (27,903 mm) total Height 13 ft (3,962 mm) Frame Cast steel Axle load 18.7 long tons (19.0 t) on 2nd driver Adhesive weight 74.25 long tons (75.4 t) Loco weight 231,400 lb (105.0 t) empty 117.45 long tons (119.3 t) w/o Tender weight 97,300 lb (44.1 t) empty 105.55 long tons (107.2 t) w/o Loco & tender weight 328,700 lb (149.1 t) empty 223 long tons (226.6 t) w/o Tender type EW1 - EW2, rebuilt CZ permitted * 3 axle bogies * 34 in (864 mm) wheels * Length 42 ft 10.5 in (13,068 mm) Fuel type Coal Fuel capacity 18 long tons (18.3 t) Water cap 10,500 imp gal (48,000 L) Boiler 6 ft 4.125 in (1,934 mm) inside diameter 19 ft (5,791 mm) inside length 9 ft 1.625 in (2,784 mm) pitch Boiler pressure Firegrate area 70 sq ft (6.503 m2) Heating surface 3,390 sq ft (314.941 m2)  • Tubes 158 tubes 2.5 in (64 mm) diameter 40 tubes 5.5 in (140 mm) diameter 3,059 sq ft (284.190 m2)  • Flues 37 sq ft (3.437 m2)  • Firebox 294 sq ft (27.313 m2) Superheater:  • Heating area 630 sq ft (58.529 m2) Cylinders Two Cylinder size 24 in (610 mm) bore 28 in (711 mm) stroke Valve gear Walschaerts Loco brake Vacuum

Performance figures Tractive effort 45,360 lbf (202 kN) at 75% pressure

Career Operators South African Railways Class Class 25NC Number in class 50 Numbers 3401-3450 Nicknames Worshond (with Type CZ tender) Delivered 1953-1954 First run 1953

The South African Railways Class 25NC 4-8-4 of 1953 is 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 is 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 ninety Class 25 condensing locomotives were converted to non-condensing locomotives and also classified as Class 25NC.

Manufacturers

The Class 25NC non-condensing and Class 25 condensing 4-8-4 Northern type steam locomotives were designed by the South African Railways (SAR) in conjunction with Henschel and Son of Kassel in Germany. 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) and thirty-nine, numbered in the range from 3412 to 3450, by Henschel.

Characteristics

The Class 25NC had Walschaerts valve gear and 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, while the steel cylinders and steam chests were fitted with cast iron liners. The tender frame was also a one piece steel casting. Being entirely mounted on roller bearings, very little effort was required to move these locomotives.

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 the engine and the condensing tender were designed and patented by Henschel.

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 coupling rods differed from the usual in the provision of three independent rods, thereby doing away with four knuckle joints and pins.

Teething troubles

Soon after being placed in service problems were experienced with connecting rods failing, 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, with the crossheads 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.

Service

File:SAR Class 25NC 3442 (4-8-4) ID.JPG

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The Class 25NC initially served on the unelectrified mainlines from De Aar via Kimberley to Klerksdorp. Until electrification was extended from Welverdiend to Klerksdorp, they worked through to Welverdiend as well. 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.

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 that 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.

Class 25 reclassification

File:SAR Class 25NC 3467 (4-8-4) ID.JPG

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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 plates. Locomotives with all four characters neatly in line and centred are therefore usually identifiable as original Class 25NCs.

In the process their Type CZ condensing tenders were also rebuilt to ordinary coal-and-water 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 CZ tenders with their long round topped water tanks. Locomotives with these rebuilt tenders were soon nicknamed "Worshond" (Sausage dog or Dachshund).

The Red Devil

Between 1979 and 1981 number 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.

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 3450 was retained.

Illustration

The main picture shows no. 3410 at Sannaspos in the Free State on 4 July 1999.

• SAR Class 25NC 3411 (4-8-4) 1.jpg

  NBL built no. 3411 relieving a Class 4E on a northbound train at Beaufort West, Cape Province, 26 June 1966

• SAR Class 25NC 3410 (4-8-4) a.jpg

  NBL built no. 3410 "Paula" making its way to the water tanks at Springfontein in the Free State, circa 1995

• SAR Class 25NC 3422 (4-8-4).jpg

  Henschel built no. 3422 "Bergrivier" with a Worshond tender working the Union Express, circa 2002

• SAR Class 25NC 3440 (4-8-4) 1.JPG

  Henschel built no. 3440 being prepared to be hauled to Pretoria for restoration, Beaconsfield, 25 August 2007

• 

  Henschel built "Red Devil" no. 3450, shortly after being rebuilt to the only Class 26, Pretoria, 25 April 1981

• SAR Class 25NC (4-8-4) Tender F.JPG

  Type EW1 tender with mechanical stoker, Beaconsfield, Kimberley, 18 September 2009

External links

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) or South African Class 25 (4-8-4)