In the desert areas of the Karoo and Kalahari, the large water requirements of powerful steam locomotives posed a major problem for the SAR. The contract for the development of a 4-8-4 locomotive and a condensation tender went to Henschel in Kassel. At the same time, the class 25NC was developed without a condenser. The prototype was built by Henschel and taken to North British in Scotland, where the rest was built. For the conditions of the Cape Gauge, these locomotives were very large and powerful.

In order to provide sufficient draft for the fire, the blower had to be particularly powerful. This did not work with a steam jet as usual, but with a fan driven by a turbine. When running under load, no exhaust beats could be heard, but instead the whine of the turbine.

In order to protect the fan from damage caused by solid objects in the smokebox, it was provided with a banjo-shaped extension. The fan still had to be changed later because it wore out very quickly. Instead of an injector, a turbo pump had to be used to feed the boiler because the condensed water was still at a very high temperature.

View with banjo-chaped cover on the smokebox

https://www.flickr.com/photos/144395184@N08/49340807001

Timken roller bearings were installed everywhere, which caused problems in the early days. Oil was thrown from the bearings on the coupling rods against the underside of the boiler, which then dripped onto the wheel tires and made the locomotive more prone to slipping. This could only be remedied after the bearings on a large part of the locomotives had been replaced with ones from SKF and after Timken had repaired the remaining bearings.

The operations took place on the non-electrified lines in the desert areas in front of all types of trains. All in all, the locomotives achieved a range of around 500 miles or 800 km with one water filling, but at the expense of extensive maintenance. The fans in the smokebox and on the tender were particularly important here.

Therefore, between 1973 and 1980, 87 of the 90 class 25 locomotives were rebuilt into Class 25NC. The long tenders with a round water tank and no condenser were now called “Worshond Tender” because of their appearance, which stands for “Dachshund” and literally means “sausage dog”. They were retired around 1990 when all remaining steam locomotives were replaced by diesel and electric locomotives.