Class 25NC 3401-3540 4-8-4 South African Railways Gauge 3ft 6in

Weight	Locomotive – 117t 9cwt Tender – EW1 – 105t 11cwt
Driving Wheels	5ft 0ins
Boiler Pressure	225psi Superheated
Cylinders	Two Outside – 24in x 28in
Tractive Effort	45,360lbf
Valve Gear	Walschaert

The class 25NC locomotives were designed by the South African Railways (SAR) under the direction of LC Grubb, who was the Chief Mechanical Engineer, in conjunction with Henschel & Son of Kassel in Germany. Between 1953 and 1955, eleven locomotives (3401 – 3411) were built by the North British Locomotive Company (NBL) and 39 locomotives (3412 – 3450) were built by Henschel.

The class 25NC was superheated and used piston valves actuated by Walschaerts valve gear. Timken 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. Compared to earlier SAR practice, a novelty was the adoption of mechanical lubrication. A sixteen-feed lubricator was driven off the expansion link trunnion. The cylinders and frames were cast in one piece by Commonwealth Steel Company in the United States. 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.

The locomotives were fitted with type EW1 tender which was equipped with a mechanical stoker. The tank had a water capacity of 10,500 imperial gallons and the coal bunker a capacity of 18 long tons. 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.

Soon after entering 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, 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.

When new, the tapered Timken crankpin roller bearings soon became notorious for throwing their lubricant onto the underside of the boiler, from where it ran down to the lowest point and dripped onto the coupled wheel tyres along the way and was one of the reasons for the reputation of the class being slippery. Timken managed to resolve the problem before all their bearings had been replaced, but by then about two-thirds of the locomotives had already been fitted with redesigned coupling rods with SKF crankpin ball bearings.

The class 25NC initially served on the unelectrified mainlines from De Aar via Kimberley to Welverdiend. They were pooled from their introduction and were run through from De Aar to Welverdiend and vice versa, recoaling at Warrenton. After electrification was extended from Welverdiend to Klerksdorp, they ran from there to De Aar, still recoaling at Warrenton. Later they also worked from Kimberley via Bloemfontein to Harrismith in the Free State while some were employed on the line from De Aar via Beaufort West to Touws River.

With the reallocation of some steam locomotives following the introduction of diesels on the line south from De Aar between 1973 and 1974 the class 25NC locomotives which were then relocated to Bethlehem in the Free State.

Between 1953 and 1955 90 class 25 locomotives entered service with the South African Railways. The North British Locomotive Company built 89 (3452 – 3540) of these and Henschel & Son of Kassel in Germany the other 1 (3451). They were as the class 25NC apart from being condensing steam locomotives which were built because of difficulties in obtaining water in some regions of the country. It was claimed that these locomotives could run for 700 miles without the need for fresh water. The condensing apparatus for these engines and their condensing tenders were designed and patented by Henschel.

On the condensing locomotive, spent steam was recycled and condensed back to water for repeated use. Since the steam wasn’t expelled up the chimney the smokebox contained a steam turbine-driven fan beneath the chimney to keep the draught going, with deflector plates that were supposed to prevent char from causing excessive wear on the fan blades.

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.

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 water-bottom 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).

Between 1979 and 1981 3450, the last class 25NC to be built, was rebuilt at the SAR workshops at Salt River, 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, 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. The locomotive was painted in a red livery and was given the name Red Devil.

Preservation

A number of North British Locomotive Company locomotives have been preserved in South Africa. There are also some built by Henschel & Son in Germany but they are not included.

One locomotive built by the North British Locomotive Company is preserved as a class 25 locomotive. This is works number 27371 3511 which is included under class 25.

North British Locomotive Company – Works No 27290 3404

North British Locomotive Company – Works No 27291 3405

North British Locomotive Company – Works No 27293 3407

North British Locomotive Company – Works No 27296 3410

North British Locomotive Company – Works No 27311 3411

North British Locomotive Company – Works No 27314 3454

North British Locomotive Company – Works No 27317 3457

North British Locomotive Company – Works No 27327 3467

North British Locomotive Company – Works No 27331 3472

North British Locomotive Company – Works No 27336 3476

North British Locomotive Company – Works No 27340 3480

North British Locomotive Company – Works No 27342 3482