South West African Zwillinge

Swakopmund-Windhuk Staatsbahn

Company type	State railway
Industry	Railway transport
Founded	1897
Headquarters	Swakopmund , German South West Africa
Area served	German South West Africa (Namibia)
Products	Railway transportation services

South West African Zwillinge 0-6-0T Steam Locomotive

The South West African Zwillinge 0-6-0T was a narrow gauge steam engine introduced in 1898 during the period of German South West Africa.

From 1898 through 1905, the Swakopmund-Windhuk Staatsbahn (Swakopmund-Windhoek State Railway) received over fifty pairs of these twin Zwillinge 0-6-0T locomotives. By the year 1922, only two units remained active and were incorporated into the South African Railways' inventory.

Swakopmund-Windhuk Staatsbahn

On 11 September 1897, the initial contingent of the German Feldbahn-Baukommando (field railway construction unit) reached Swakopmund in German South West Africa (GSWA). Their mission was to construct a narrow gauge railway traversing the Namib Desert from Swakopmund to Windhoek, passing through Jakkalswater and Karibib. This 382-kilometre-long (237-mile) route, known as the Swakopmund-Windhuk Staatsbahn, was later referred to as the Northern State Railway or Nordbahn. It commenced operations officially on 1 July 1902, nearly five years after construction began.

Originally designed for provisional military purposes, the railway was intended to be powered by animals such as Argentine mules or Cape donkeys; however, steam locomotion was soon introduced. The railway utilized steel sleepers with rails weighing 19 pounds per yard (9 kilograms per metre). The line featured very tight curves and steep inclines. For instance, ascending from the Khan River gorge involved a gradient of 1 in 19 (approximately 5¼%) combined with curves having a radius of 180-foot radius (55-metre).

In 1905, a branch line spanning 14-kilometre-long (9-mile) was built from Karibib on the Nordbahn to Onguati near Usakos, linking with the newly established Otavi railway extending from Swakopmund to Tsumeb. This connection provided an alternate route from Windhoek to the Atlantic coast during periods when flooding affected the Khan River gorge segment. Subsequently, the section of the Nordbahn between Swakopmund and Karibib was abandoned. Between 1911 and 1913, the 119-mile-long (192-kilometre) stretch from Karibib to Windhoek underwent regauging to Cape gauge.

Manufacturers

The earliest locomotives deployed on the Nordbahn were Zwillinge, a class of compact paired steam engines with a 600 millimetres (23.6 inches) narrow gauge and a 0-6-0T wheel arrangement. These units were produced in Germany during the late 19th and early 20th centuries specifically for military railways within Germany and its empire. Between 1898 and 1899, the first substantial shipment of Zwillinge locomotives arrived in Swakopmund. By 1905, over fifty pairs—either new or second-hand—had been supplied to the Swakopmund-Windhuk Staatsbahn.

Six manufacturers were responsible for producing these locomotives: Krauss and Company, Henschel and Son, L. Schwartzkopff, Egestorf, Machinenbau Anstalt, and Arnold Jung. These so-called Feldbahn engines, originally designed for military use, were also employed in other German colonial territories; several were acquired second-hand for GSWA operations.

The last set of four pairs of Zwillinge locomotives designated for the Swakopmund-Windhuk Staatsbahn was manufactured by Krauss in 1903. These bore works numbers 4875 through 4878 and carried engine numbers 179 to 182 A and B respectively.

Characteristics

True to their name Zwillinge (twins), these locomotives consisted of two distinct units engineered to be semi-permanently coupled cab-to-cab, enabling a single crew member on the footplate to operate and manage both engines simultaneously. Each locomotive pair was assigned a shared manufacturer's works and engine number, with the individual units identified as A and B. The A units featured elevated cabin roofs compared to the B units, allowing the roofs to interlock when joined, thus enhancing crew protection. Although primarily designed to function as a coupled pair, each unit was fully equipped with independent controls for standalone operation. When operated singly, these locomotives were often referred to as Illinge.

The concept of utilizing two tank locomotives connected semi-permanently at their cabs was originally patented in 1855 by the English locomotive manufacturer Robert Stephenson and Company.

The Zwillinge were capable of handling curves with a radius as tight as 66-foot radius (20-metre), and could pull loads up to 32 long tons (32.5 tonnes) on gradients of 1 in 25 (4%). Their chimneys were equipped with balloon-style spark arresters, and they operated on coal imported from Germany. The steam regulator was positioned externally on the high steam dome. Some models featured two sandboxes mounted atop the boiler—one before and one behind the dome—while others had two small cylindrical sandboxes affixed to the smokebox. The locomotives employed flat Murdoch's D slide valves controlled by Stephenson valve gear, which were mounted outside the 5⁄8-inch thick (16-millimetre) plate frames.

By the onset of the First World War, a total of 182 pairs of Zwillinge had been manufactured for use across various German territories. Production ceased a few years after 1901 following the introduction of the larger 0-8-0T Brigadelok as the new standard military locomotive in Germany. Between 1901 and 1904, at least twelve of these Brigadeloks, constructed by Krauss and numbered from 101 to 112, were also delivered to the Swakopmund-Windhuk Staatsbahn.

Service

Zwillinge close to Pforte in 1898

Soon after the initial deployment of the Zwillinge locomotives, it became evident that the tank engines' fuel and water reserves were inadequate for the extensive distances encountered in the German African colonies. This was particularly true for the challenging terrain of the Namib Desert, which lay between Swakopmund and Windhoek. To address this limitation, a four-axle water tender was coupled to the twin locomotives. This tender not only increased water capacity but also provided seating accommodations for armed guards. The image alongside clearly shows the bench on top of the water tender along with the connecting water pipe between the tender and locomotives.

When the German authorities initiated regauging of the railway line linking Windhoek and Swakopmund, most Zwillinge units were withdrawn from service in GSWA. A majority were sold to Japan, while a smaller number were acquired by the Otavi Railway, where they served primarily as construction locomotives.

Locomotive No. 169B arriving at Bellville Quarry

Following 1922, when South African Railways (SAR) assumed control over all rail operations in South West Africa (SWA), none of the SWA locomotives underwent reclassification or renumbering; they retained their original German designations until retirement. Among these, Illinge numbers 154A and 169B are documented as the only Zwillinge locomotives incorporated into the SAR inventory.

Locomotive No. 154A served as a departmental engine without revenue duties in Windhoek and was withdrawn from operation in 1939 after accumulating approximately 371,000 miles (597,000 kilometres).

Constructed in 1904 by Maschinenbau-Anstalt Humboldt, No. 169B was transported to Cape Town post-World War I and assigned to non-revenue duties at the Bellville quarry situated on the slopes of the Tygerberg.

Preservation

The only remaining Zwillinge locomotive, number 154A, is currently displayed under a protective shelter outside Windhoek Station. This unit was originally one half of a pair manufactured by Henschel in 1900, bearing works number 5376. It entered GSWA service secondhand in 1904 and is listed in Henschel’s production records as initially built for Deutsche Feldbahnen in 1900 as one of seven paired locomotives numbered from 148A&B through to 154A&B, with works numbers ranging from 5364 to 5377. Its first deployment location remains unknown.

Initially, this locomotive was exhibited at the Railway College located at Esselen Park in Kaalfontein near Kempton Park within Transvaal. In the late 1950s, it was repatriated to SWA and has since been mounted on a plinth at its current site in front of Windhoek’s station building.

Commemoration

On 2 August 1985, a set of four commemorative stamps was released in South West Africa (SWA), featuring the Zwillinge locomotives as a tribute to the pioneering narrow gauge engines that established the region's railway network. The artwork for these stamps was created by the acclaimed stamp artist Koos van Ellinckhuijzen.

The locomotives illustrated on the stamp were the second pair from GSWA, identified as units 2A and 2B. The station name displayed on the nameplate in Fraktur lettering reads Otjimukoka. This station was renamed Johann Albrechtshöhe in 1903 to honor Duke John Albert of Mecklenburg, and was later shortened to Albrechts. Additionally, the SWA postal service used a front-facing silhouette of an Illinge locomotive as a special cancellation mark for Swakopmund on the day of issue. The first day cover issued alongside these stamps showcased the stamp itself, the commemorative postmark, and another depiction of the Zwillinge locomotives.

Other locomotive types

Besides the Zwillinge, other locomotive models operated on the Nordbahn, though records about them are limited. In addition to twelve Brigadeloks, a different class of small twin locomotives, referred to by crews as Pugs and likely utilized for shunting tasks, were introduced in 1901. These units were manufactured by Machinenbau Anstalt from Breslau, with boilers produced by Krauss and Company.

The Pug twin engines featured a shared water tank positioned between their frames and were equipped with chimneys fitted with balloon-style spark arresters. While their precise wheel configuration remains unknown, technical specifications include a boiler pressure of 176 pounds per square inch (1,213 kilopascals), a boiler heating surface totaling 154 square feet (14.3 square metres), and a firegrate area measuring 3.65 square feet (0.339 square metres). Their tractive effort at half boiler pressure was calculated at 2,150 pounds-force (9.6 kilonewtons). The boilers sat at a pitch height of 3 feet 7+5⁄16 inches (1,100 millimetres), and each engine weighed approximately 7 long tons 0 hundredweight 3 quarters (7,150 kilograms) when operational.

Later in 1901, Machinenbau Anstalt delivered a second pair of these twin locomotives, which featured larger boilers and omitted the balloon-type spark arresters.

Illustration

• 
  Zwillinge 0-6-0T units 167 B & A, circa 1920
• 
  Unit no. 154A displayed at Windhoek Station, 2006
• 
  Commemorative plaque on no. 154A, photographed in 2013
• 
  Rear view of unit no. 154A from 2013