South African Class GH 4-6-2+2-6-4

Class GH at Monument Station, Cape Town, c. 1930

Type and origin
Power type	Steam
Designer	Maffei
Builder	Maffei
Serial number	5687-5688
Model	Class GH
Build date	1928
Total produced	2

Specifications
Configuration	4-6-2+2-6-4 "Double Pacific" Union Garratt
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Leading dia	30 in (762 mm)
Driver diameter	60 in (1,524 mm)
Trailing dia	30 in (762 mm)
Wheelbase	Total: 76 ft 7 in (23,343 mm) Engines: 6 ft 2 in (1,880 mm) bogie 10 ft 9 in (3,277 mm) coupled 25 ft 2 in (7,671 mm) total
Length	85 ft (25,908 mm)
Height	12 ft 11.4375 in (3,948 mm)
Frame	Bar frame, 39 ft 6.5 in (12,052 mm) between pivot centres
Axle load	18.1 long tons (18.4 t) on 1st & 3rd drivers
Adhesive weight	107.5 long tons (109.2 t)
Loco weight	304,700 lb (138.2 t) empty 184.75 long tons (187.7 t) w/o
Fuel type	Coal
Fuel capacity	13.5 long tons (13.7 t)
Water cap	3,650 imp gal (16,600 l) front 2,350 imp gal (10,700 l) underbelly
Firebox: • Firegrate area	60 sq ft (5.574 m²)
Boiler	6 ft 11 in (2,108 mm) inside diameter 13 ft 8 in (4,166 mm) inside length 8 ft 3 in (2,515 mm) pitch
Boiler pressure	180 psi (1,240 kPa)
Heating surface	2,655 sq ft (246.658 m²)
• Tubes	195 tubes 2.25 in (57 mm) diameter 43 tubes 5.5 in (140 mm) diameter 2,416 sq ft (224.454 m²)
• Flues	25 sq ft (2.323 m²)
• Firebox	214 sq ft (19.881 m²)
Superheater: • Heating area	665 sq ft (61.781 m²)
Cylinders	Four
Cylinder size	19.5 in (495 mm) bore 26 in (660 mm) stroke
Valve gear	Walschaerts

Performance figures
Tractive effort	44,490 lbf (198 kN) at 75% pressure

Career
Operators	South African Railways
Class	Class GH
Number in class	2
Numbers	2320-2321
Delivered	1928
First run	1928
Withdrawn	1958

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The South African Railways Class GH 4-6-2+2-6-4 of 1928 is an articulated steam locomotive.

In 1928 the South African Railways placed two Class GH 4-6-2+2-6-4 Double Pacific type passenger versions of the Class U Union Garratt articulated steam locomotive in service.^[1]^[2]^[3]

Manufacturer

The Class GH, the heavy passenger version of the Class U Union Garratt, was designed and built for the South African Railways (SAR) by Maffei in Munich, Germany. Two locomotives were delivered in 1928, numbered 2320 and 2321, and were erected at the Salt River shops in Cape Town. They were superheated and had Walschaerts valve gear and bar frames.^[1]^[2]^[3]

It has been surmised that, if the same classification practice as that which was used for Garratt and Mallet locomotives had been followed, the Class U and the Class GH should have been designated Class UA and Class UB respectively.^[4]

Truth is that during the design phase of the two Union Garratt types, they were designated classification letters in the regular SAR Garratt range as Classes GH and GJ. When orders were placed with the manufacturers, however, the Class designation of the Class GH was retained while that of the Class GJ 2-6-2+2-6-2 Double Prairie type was changed to Class U.^[5]

Characteristics

The Union Garratt was a hybrid locomotive, part Modified Fairlie and part Garratt. The front end of the locomotive was of a typical Garratt arrangement, with a water tank mounted on the front engine unit’s frame, while the rear end was constructed in the Modified Fairlie fashion, with the coal bunker mounted on a rigid extension of the locomotive’s main frame and with the pivoting rear engine unit positioned beneath the coal bunker.^[1]^[3]

Since the rear bunker carried only coal, an additional large underbelly water tank under the boiler compensated for the resulting diminished water capacity.^[3]

All its water was carried in the front bunker tank and in the underbelly water tank, with a combined capacity of 6,000 imperial gallons (27,000 litres), while the rear bunker had a coal capacity of 13.5 long tons (14 tonnes). The main frame therefore carried the smokebox, boiler, firebox, cab, coal bunker, as well as the underbelly water tank.^[1]

These were massive and powerful locomotives and, having been designed for passenger service, they were built for speed with their large 60 inches (1,524 millimetres) driving wheels. With their 60 square feet (5.574 square metres) firegrates, they were equipped with mechanical stokers of the duplex type. One reason that had been put forward for the construction of the rear end of the Union Garratts on the Modified Fairlie principle was actually to enable their coal bunkers to be rigidly in line with their boiler frames, to ensure a satisfactory arrangement for the installation of mechanical stokers.^[1]

Shortcomings

The Modified Fairlies and the Union Garratt variations of it were not successful in South Africa and they suffered from the same shortcomings.^[1]

On the Union Garratts, as on the Modified Fairlies, the frames were prone to metal fatigue and cracking, brought about by the long frame overhang at the rear beyond the engine pivot centre. The overhang, laden with the coal bunker of which about two-thirds extended beyond the rear engine unit’s pivot centre, was subjected to severe vertical vibration while the locomotive was in motion and this led to structural weakening of the frame.^[1]^[4]

In addition, as a result of the coal bunker that was mounted on the frame instead of on the engine unit, the rear pivot bearings were subject to quite rapid wear, since they carried a considerable additional vertical load compared to those on a pure Garratt. As was the case with the Modified Fairlies, this resulted in increased maintenance and, as a consequence, increased operating cost.^[1]^[3]^[4]

Service

The Class GH was acquired for working the named fast passenger trains of the era, the Union Express and Union Limited, and was initially stationed in Cape Town. The service career of the Class GH had a rough start, however, since on the first trip it was discovered that it exceeded the loading gauge in width. It returned to Salt River minus its steps and sundry fittings after having scraped the platforms of every station along its route. Considerable modifications had to be carried out before the two locomotives could be placed back in regular service.^[1]

The Class GH made several trips working the two Union trains out of Cape Town, but they were not as successful as had been hoped and they were soon taken off that duty. Their mechanical stokers also proved to be troublesome and were eventually removed. They were transferred to Natal and worked on the Natal mainline north of Glencoe for the rest of their service lives. Both were withdrawn from service by 1958.^[3]

Illustration

The main picture and the following illustrate both sides of the Class GH Union Garratt.

Class GH Union Garratt staged at Glencoe, Natal, circa 1950

References

1 2 3 4 5 6 7 8 9 Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 56–57. ISBN 978-0-7153-5427-8.
1 2 South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
1 2 3 4 5 6 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 93. ISBN 0869772112.
1 2 3 Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 31. ISBN 0715386387.
↑ Official Class U 2-6-2+2-6-2 drawing

Wikimedia Commons has media related to South African Class GH (4-6-2+2-6-4).

Locomotives of South Africa

Steam

7' ¼" gauge	East London Harbour 0-4-0 Table Bay Harbour 0-4-0ST Table Bay Harbour 0-4-0T Table Bay Harbour 0-4-0WT

4' 8½" gauge	Cape 0-4-0T Blackie Cape 0-4-2 Cape 2-4-0T CGR 0-4-0ST Aid Natal 0-4-0ST Durban Natal 0-4-0WT Natal Natal 4-4-0T Perseverance

3' 6" gauge Tank engines	CGR 0-4-0ST 1873 CGR 0-4-0ST 1874 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST 1902 CGR 0-6-0T 1876 Back-to-Back CGR 2-6-0ST 1900 CGR 2-6-0ST 1902 CGR 1st Class 0-4-0ST 1875 CGR 1st Class 0-4-0ST 1876 CGR 1st Class 2-6-0ST 1876 CGR 1st Class 4-4-0T 1875 CGR 2nd Class 4-4-0T 1882 CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack CSAR Railmotor DSWA Eight-Coupled Tank 2-8-0T Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth Harbour 0-4-0ST Kowie Railway 0-6-0T Kowie Railway 4-4-0T Metropolitan & Suburban 4-6-2T NGR 2-6-0T Durban & Pietermaritzburg NGR Class I 2-6-2T NGR Class K 0-4-0ST NGR Class K 0-6-0ST NGR Class K 2-6-0T NZASM 10 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese SAR 0-4-0ST 1903 SAR 0-4-0T no. 69 SAR Class A SAR Class B SAR Class C SAR Class C1 SAR Class C2 SAR Class D SAR Class E SAR Class F SAR Class G SAR Class H SAR Class H1 SAR Class H2 SAR Class J SAR Class K SAR Clayton Railmotor

3' 6" gauge Tender engines	CGR 1st Class 2-6-0 1876 Beyer, Peacock CGR 1st Class 2-6-0 1876 Kitson CGR 1st Class 2-6-0 1879 CGR 1st Class 2-6-0 1891 CGR 1st Class 4-4-0 1879 CGR 1st Class 4-4-0TT 1881 CGR 2nd Class 2-6-2TT 1875 CGR 3rd Class 4-4-0 1883 CGR 3rd Class 4-4-0 1884 CGR 3rd Class 4-4-0 1889 CGR 3rd Class 4-4-0 1898 CGR 3rd Class 4-4-0 1901 CGR 3rd Class 4-4-0 1903 CGR 4th Class 4-4-2 CGR 4th Class 4-6-0TT 1880 CGR 4th Class 4-6-0TT 1882 CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 DSWA Eight-Coupled Tender 2-8-0 NGR Havelock NGR Class I SAR Class Exp 1 SAR Class Exp 2 SAR Class Exp 3 SAR Class Exp 4 SAR Class Exp 5 SAR Class Exp 6 SAR Class S SAR Class S1 SAR Class S2 SAR Class 1 SAR Class 1A SAR Class 1B SAR Class 2 SAR Class 2C SAR Class 3 SAR Class 3A SAR Class 3B SAR Class 4 SAR Class 4A SAR Class 5 SAR Class 5A SAR Class 5B SAR Class 6 SAR Class 6A SAR Class 6B SAR Class 6C SAR Class 6D SAR Class 6E SAR Class 6F SAR Class 6G SAR Class 6H SAR Class 6J SAR Class 6K SAR Class 6L SAR Class 6Y SAR Class 6Z SAR Class 7 SAR Class 7A SAR Class 7B SAR Class 7C SAR Class 7D SAR Class 7E SAR Class 7F SAR Class 8 SAR Class 8A SAR Class 8B SAR Class 8C SAR Class 8D SAR Class 8E SAR Class 8F SAR Class 8R SAR Class 8X SAR Class 8Y SAR Class 8Z SAR Class 9 SAR Class 10 SAR Class 10A SAR Class 10B SAR Class 10C SAR Class 10D SAR Class 11 SAR Class 12 SAR Class 12A SAR Class 12B SAR Class 13 SAR Class 14 SAR Class 14A SAR Class 14B SAR Class 14C SAR Class 15 SAR Class 15A SAR Class 15B SAR Class 15C SAR Class 15CA SAR Class 15E SAR Class 15F SAR Class 16 SAR Class 16A SAR Class 16B SAR Class 16C SAR Class 16D SAR Class 16DA SAR Class 16E SAR Class 17 SAR Class 18 SAR Class 19 SAR Class 19A SAR Class 19B SAR Class 19C SAR Class 19D SAR Class 20 SAR Class 21 SAR Class 23 SAR Class 24 SAR Class 25 SAR Class 25NC SAR Class 26 Red Devil

3' 6" gauge Articulated engines	CGR Fairlie CGR Kitson-Meyer SAR Class FC SAR Class FD SAR Class GA SAR Class GB SAR Class GC SAR Class GCA SAR Class GD SAR Class GDA SAR Class GE SAR Class GEA SAR Class GF SAR Class GG SAR Class GH SAR Class GK SAR Class GL SAR Class GM SAR Class GMA SAR Class GO SAR Class HF SAR Class KM SAR Class MA SAR Class MB SAR Class MC SAR Class MC1 SAR Class MD SAR Class ME SAR Class MF SAR Class MG SAR Class MH SAR Class MJ SAR Class MJ1 SAR Class U

2' 6" gauge	Cape Copper 0-6-0T 1871 Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Class Cape Copper Condenser Cape Copper Scotia Class Namaqua Copper Pioneer

2' & 600mm gauges	ACR Class NG-G16A CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T DSWA Class Ha DSWA Class Hb DSWA Class Hc DSWA Class Hd DSWA Jung DSWA Zwillinge NGR Class N 4-6-2T SAR NG 0-4-0T 1899 SAR Class NG1 SAR Class NG2 SAR Class NG3 SAR Class NG4 SAR Class NG5 SAR Class NG6 SAR Class NG7 SAR Class NG8 SAR Class NG9 SAR Class NG10 SAR Class NG-G11 SAR Class NG-G12 SAR Class NG-G13 SAR Class NG-G14 SAR Class NG15 SAR Class NG-G16

Electric

Amcoal Class E38

Diesel

3' 6" gauge Diesel-electric	PRASA Class Afro 4000 SAR Class DS SAR Class DS1 SAR Class 31-000 SAR Class 32-000 SAR Class 32-200 SAR Class 33-000 SAR Class 33-200 SAR Class 33-400 SAR Class 34-000 SAR Class 34-200 SAR Class 34-400 SAR Class 34-500 SAR Class 34-600 SAR Class 34-800 SAR Class 34-900 SAR Class 35-000 SAR Class 35-200 SAR Class 35-400 SAR Class 35-600 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 TFR Class 35-800 TFR Class 39-200 TFR Class 43-000 TFR Class 44-000

2' gauge Diesel-electric	SAR Class 91-000

3' 6" gauge Diesel-hydraulic	SAR Class 61-000

3' 6" gauge Electro-diesel	Spoornet Class 38-000

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