South African Class NG15 2 8 2

Manufacturers

As a result of heavy traffic demands on the Otavi Railway in South West Africa (SWA), three additional locomotives were ordered in 1931. The Class NG15 2-8-2 Mikado type narrow gauge steam locomotive was designed by the South African Railways (SAR) and built by Henschel and Son for the Otavi Mining and Railway Company. The company operated the 352 miles (566 kilometres) long narrow gauge Otavi Railway across the Namib Desert from Swakopmund on the Atlantic coast to Tsumeb and Grootfontein in SWA. The first three locomotives were delivered in 1931, numbered in the range from NG17 to NG19. They were followed by three more in 1939, numbered in the range from NG117 to NG119.

Ten more of these locomotives were built for the Otavi line by Société Franco-Belge and delivered in two batches of five in 1950 and 1953, numbered in the ranges from NG120 to NG124 and NG132 to NG136 respectively.

In 1958, five more of these locomotives, once again built by Henschel, were delivered to the Tsumeb Copper Corporation, numbered in the range from TC1 to TC5, for use by the SAR in terms of an agreement between the SAR and the Corporation. They were later renumbered in the SAR range from NG144 to NG148.

Forerunners

The Class NG15 2-8-2 locomotive was a development of the Class Hd and Class NG5 locomotives, which had been acquired for the Otavi Mining and Railway Company in SWA in 1912 and 1921 respectively. In the 1920s, one of the Class NG5 locomotives was sent to the Avontuur line in South Africa for trials, but since it jammed on the tighter curves in the Langkloof despite having one set of flangeless coupled wheels, it was returned to SWA.

The usual practice of the SAR in the steam era was to design locomotives in their own drawing offices and to then go out and find a builder. The drawing board work for the Class NG15 has been attributed to a Chief Mechanical Engineer of the Otavi Railway, a German engineer known in SWA as Mr. Peters, who was employed as a draughtsman by the SAR. Since the earlier trials with the Class NG5 locomotive, the sharpest curves on the Avontuur line had been eased and the experience gained in the process was taken into consideration during the design of the Class NG15.

Characteristics

Like the Class NG5, the locomotives were built on plate frames and their valves were actuated by Walschaerts valve gear, but they were fitted with piston valves instead of flat slide valves. While the sand boxes of the older locomotives were mounted on top of the boiler, aft of the dome on the Class Hd and ahead of the dome on the Class NG5, those of the Class NG15 were arranged on the running boards. The seats of the driver and stoker were mounted on poles, which allowed them to be swung around to outside the cab, and crews could often be seen riding outside. Similar swing-seats were used on the SAR's narrow gauge Garratts.

Their leading wheels were mounted in a Krauss-Helmholtz Bissel truck which was arranged in front instead of to the rear of the cylinders. The leading pair of coupled wheels of the Class NG15 have a limited amount of sideplay and are linked to the leading Bissel truck, while the axle of the leading coupled wheels still remain parallel to the other three coupled axles at all times.

This linking of a pony truck and coupled axle is known as a Krauss-Helmholtz bogie, an invention of Richard von Helmholtz who was the chief designer at the Krauss works in Munich from 1884 to 1917. On standard gauge railways in Europe, the inclusion of a Krauss-Helmholtz bogie has allowed the use of large 2-10-0 locomotives on sharply curved mountain sections. Some early electric locomotives also used Krauss-Helmholtz bogies.

Compared to the Class NG5, the Class NG15 had larger tenders with a working order weight of 31 long tons 4 hundredweight (31,700 kilograms), against the 25 long tons 11 hundredweight 3 quarters (26,000 kilograms) of the Class NG5's tender. The tenders had low-slung sides, with the bottom part of the water tank extending down to below axle level on either side of the tender bogies to lower the vehicle's roll centre on the narrow track gauge.

The original tenders were built as flat-sided box-shaped vehicles. A second tender version was delivered with the later batches of locomotives, with the coal bunker sides set inward for reasons unknown. The new shape made no difference to the crew's rearward field of vision and the only likely benefit was a reduced axle load as a result of the reduced coal capacity.

Service

In SWA, the Class Hd, Class NG5 and Class NG15 Mikado locomotives operated in a common pool. They were the most powerful non-articulated narrow gauge steam locomotives in SAR service.

In 1960, when all the SWA narrow gauge lines were widened to Cape gauge, the Class Hd and Class NG5 locomotives were withdrawn from service, while the 21 Class NG15 locomotives were all relocated to the Langkloof line between Port Elizabeth and Avontuur. In the Langkloof, the Class NG15 was nicknamed Kalahari, inappropriately so since its previous stamping ground was across the Namib desert, to the west of the Kalahari.

When it was first introduced on the Avontuur line, the Class NG15 was not allowed to work beyond Humansdorp from Port Elizabeth, because of a lack of turning facilities in the Langkloof. This was rectified by the construction of a triangle at the end of the line at Avontuur, something which had not been required until then since the Langkloof had been the domain of bi-directional Garratt locomotives.

In the last years of steam traction on the Avontuur line, the Class NG15 was the only non-Garratt steam locomotive working in the Langkloof. Outside the apple season, the Class NG15 became well known for hauling the Apple Express from the Humewood Road railway station in Port Elizabeth to Loerie and back every Saturday to cater for tourists. It gained further fame when the Apple Express instituted an annual train race marathon, where athletes could compete against an Apple Express train filled with spectators.

In 1973, steam traction in the Langkloof began to be replaced by diesel-electric power, upon the introduction of the General Electric-built Class 91-000 diesel-electric locomotive. Diesel and steam served the Langkloof together for some years, but by the mid-1980s, road transport had triumphed over rail transport on the apple route as well, and the narrow gauge steam fleet was withdrawn from service.

Works numbers

The builders, works numbers and SAR renumbering of the Class NG15 locomotives are listed in the table.

Current locomotive status

Since the preservation of heritage locomotives is always dependent on the attitude and disposition of the current incumbents of positions of authority, the current status as set out in the table should be considered as a snapshot of the situation at a point in time. The information was last updated on 17 December 2015.

Illustration

The main picture shows Franco-Belge-built no. NG124, equipped with smoke deflectors, crossing the Van Stadens River with the Apple Express on 26 October 1985.

Additional reading