South African Class HF 2-8-2+2-8-2

South African Railways

Industry	Railway transport
Headquarters	South Africa
Products	Locomotives

South African Railways Class HF 2-8-2+2-8-2

The Class HF 2-8-2+2-8-2 steam locomotive was an articulated design introduced by the South African Railways in 1927.

During 1927, the South African Railways commissioned ten Modified Fairlie articulated locomotives of the Class HF series, featuring a 2-8-2+2-8-2T wheel configuration commonly known as "Double Mikado." A further unit was added to the fleet in 1928.

Manufacturer

The Class HF Modified Fairlie locomotive was engineered and produced by Henschel and Son according to the requirements set forth by Colonel F.R. Collins DSO, who served as the Chief Mechanical Engineer of the South African Railways (SAR). A total of ten units were constructed in 1926 and were assigned numbers from 1380 to 1389 upon their arrival in 1927. An additional locomotive, numbered 1390, was manufactured in 1927 and delivered by Henschel in 1928.

Although Henschel, based in Kassel, Germany, had previously produced several locomotive models for German South West Africa prior to the First World War, most of which were incorporated into the SAR fleet in 1922, the Class HF marked their inaugural locomotive class specifically built for SAR.

Characteristics

Designed primarily for mainline service, the Class HF was significantly larger and heavier compared to the Classes FC and FD Modified Fairlie locomotives used on branch lines during 1925 and 1926. It served as the Modified Fairlie counterpart to the Class GE 2-8-2+2-8-2 Garratt, sharing similarities both in dimensions and mechanical design. Under earlier classification conventions for Modified Fairlie types, it might have been designated Class FE; however, the inconsistent naming of Class HF—standing for "Henschel Fairlie"—was adopted instead.

These locomotives featured Heusinger-Walschaerts valve gear, incorporated bar frames, and were equipped with superheaters. Unlike previous Modified Fairlie versions that utilized Belpaire fireboxes, they had round-topped fireboxes. They also included a Parry soot-blower system that allowed cleaning of boiler tubes while the locomotive was operational. The driver controlled reversing through Hendrie's steam reversers from within the cab. Additionally, there was a mechanism enabling steam supply to be shut off to either engine unit during emergencies.

Exhaust steam from the rear engine unit was routed to the smokebox via a pipe positioned externally along the left side of the main boiler frame. Aligning with the left side of the smokebox, this pipe passed through the frame into the blast pipe. For the front engine unit, exhaust steam traveled through a pipe connected directly to a blast pipe featuring two separate openings. Both engine units were nearly identical and could be swapped with minimal adjustment to their steam pipe configurations.

The coupled wheels employed overhung springs, while each engine unit's leading Bissel and trailing carrier wheels allowed lateral movement of approximately 3⁄4 inch (19 millimetres) in either direction. The radial motion of each engine unit was restricted at both ends. Steam brakes were installed on each engine unit and automatically engaged alongside the vacuum train brake system. Furthermore, a screw-type handbrake was fitted on the rear engine unit and operated from the cab. Lambert sanding equipment with eight sanders was installed—four positioned ahead of four wheels on both directions of travel.

For illumination, Pyle National electric headlamps were mounted on brackets above each engine unit’s end buffer beam rather than atop the bunkers, enabling better alignment with track curvature. The turbo-generator supplying power to these lights was mounted atop the boiler, situated ahead of the safety valves.

Shortcomings

Initially, these locomotives did not perform satisfactorily and were consequently sidelined for a period while G. Ramsay, the Mechanical Engineer at the Durban workshops, experimented with adjustments to the blast pipe configuration. Following these successful alterations, their steaming efficiency increased enough to allow them to enter active service. Although they demonstrated considerable power comparable to the earlier Modified Fairlies, they did not achieve the same level of success as their Garratt counterparts.

They exhibited similar flaws to those found in the preceding Class FC and Class FD models. The extended rigid frame caused significant overhang issues on tight curves and was susceptible to metal fatigue and frame cracking due to the long extensions beyond the engine unit pivot points at both ends. These overhangs, which supported the water and coal bunkers, tended to oscillate vertically during motion.

The pivot bearings experienced accelerated wear because they bore a substantial additional vertical load concentrated at the center of the engine units. This was a result of mounting the water and coal bunkers on the main frame rather than on the engine units themselves, unlike the Garratt design. This design choice led to more frequent maintenance requirements and consequently higher operational expenses.

Service

The Class HF locomotives had a maximum axle load of 13 long tons 2 hundredweight, enabling them to operate on 60 lb/yd rail. They were deployed primarily on the Natal North Coast line as well as in the Witwatersrand region. These locomotives were withdrawn from service by 1951.

No further Modified Fairlie type locomotives were procured by the South African Railways after this class.

Knuckle couplers

Starting in 1927, the South African Railways began transitioning its Cape Gauge rolling stock from the Johnston link-and-pin coupling system, which had been standard since the Cape Government Railways' inception in 1873, to AAR knuckle couplers. Evidence from period photographs along with official SAR Locomotive Diagram Books and dimensional drawings—mostly reflecting original, unaltered designs—indicates that Class HF locomotives were delivered equipped with knuckle couplers from new. Other classes introduced in 1927 with similar fittings included Classes 18, GCA, GF, and U.

During this conversion phase, which spanned several years, both coupler types remained visible on rolling stock well into the late 1950s. To maintain compatibility during this overlap, locomotive knuckle couplers featured a horizontal gap and a vertical hole within the knuckle itself to accommodate a link and pin respectively. This design allowed coupling with vehicles still fitted with Johnston link-and-pin couplers.

Knuckle couplers had been introduced in South Africa over twenty years earlier by the Central South African Railways (CSAR), which fitted Gould knuckle couplers on its Limited Express and Imperial Mail passenger trains starting in 1904. The Limited Express ran between Pretoria and Johannesburg, while the Imperial Mail connected Pretoria with Cape Town. These early knuckle couplers also incorporated split knuckles to facilitate coupling with older Johnston-type link-and-pin couplers still used on CSAR locomotives. This ensured compatibility with their existing goods and older passenger rolling stock as well as with equipment from other connected railways.

Illustration

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  Class HF number 1386 stationed at Durban locomotive depot, circa 1950