South African Class GCA 2-6-2+2-6-2

South African Class GCA 2-6-2+2-6-2
No. 2615 at Greyville, November 1971
Type and origin ♠ First order - ♥ Second order Power type Steam Designer South African Railways (Col F.R. Collins DSO) Builder Friedrich Krupp AG Serial number 970-982, 1042-1068 Model Class GCA Build date 1927-1928 Total produced 39
Specifications Configuration: ​  • Whyte 2-6-2+2-6-2 (Double Prairie)  • UIC 1'C1'+1'C1'h4t Driver 3rd & 4th coupled axles Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 42 3⁄4 in (1,086 mm) Trailing dia. 28 1⁄2 in (724 mm) Wheelbase 56 ft 8 in (17,272 mm)  • Engine 17 ft 8 1⁄4 in (5,391 mm) each  • Coupled 8 ft (2,438 mm) each Pivot centres 29 ft 8 in (9,042 mm) Length: ​  • Over couplers 64 ft 9 in (19,736 mm) Height 12 ft 7 in (3,835 mm) Frame type Bar Axle load ♠ 11 LT 16 cwt (11,990 kg) ♥ 11 LT 14 cwt (11,890 kg)  • Leading ♠ 10 LT 2 cwt (10,260 kg) front 10 LT 17 cwt (11,020 kg) rear ♥ 10 LT 10 cwt (10,670 kg) front 10 LT 9 cwt (10,620 kg) rear  • 1st coupled ♠ 10 LT 19 cwt (11,130 kg) ♥ 10 LT 16 cwt (10,970 kg)  • 2nd coupled ♠ 10 LT 12 cwt (10,770 kg) ♥ 10 LT 19 cwt (11,130 kg)  • 3rd coupled ♠ 10 LT 12 cwt (10,770 kg) ♥ 10 LT 19 cwt (11,130 kg)  • 4th coupled ♠ 11 LT 2 cwt (11,280 kg) ♥ 11 LT 13 cwt (11,840 kg)  • 5th coupled ♠ 11 LT 2 cwt (11,280 kg) ♥ 11 LT 14 cwt (11,890 kg)  • 6th coupled ♠ 11 LT 16 cwt (11,990 kg) ♥ 10 LT 16 cwt (10,970 kg)  • Trailing ♠ 8 LT 8 cwt (8,535 kg) front 8 LT 16 cwt (8,941 kg) rear ♥ 8 LT 14 cwt (8,840 kg) front 9 LT 6 cwt (9,449 kg) rear Adhesive weight ♠ 66 LT 3 cwt (67,210 kg) ♥ 66 LT 17 cwt (67,920 kg) Loco weight ♠ 104 LT 6 cwt (106,000 kg) ♥ 105 LT 16 cwt (107,500 kg) Fuel type Coal Fuel capacity 7 LT (7.1 t) Water cap 2,000 imp gal (9,090 l) front 1,000 imp gal (4,550 l) rear Firebox type Round top  • Firegrate area 34 sq ft (3.2 m2) Boiler: ​  • Pitch 7 ft 4 3⁄8 in (2,245 mm)  • Diameter 5 ft 2 in (1,575 mm)  • Tube plates 11 ft 3 5⁄8 in (3,445 mm)  • Small tubes 141: 2 in (51 mm)  • Large tubes 24: 5 1⁄2 in (140 mm) Boiler pressure 180 psi (1,241 kPa) Safety valve Pop Heating surface 1,388 sq ft (128.9 m2)  • Tubes 1,225 sq ft (113.8 m2)  • Arch tubes 21 sq ft (2.0 m2)  • Firebox 142 sq ft (13.2 m2) Superheater: ​  • Heating area 331 sq ft (30.8 m2) Cylinders Four Cylinder size 14 in (356 mm) bore 23 in (584 mm) stroke Valve gear Heusinger Valve type Piston Couplers AAR knuckle
Performance figures Tractive effort 28,470 lbf (126.6 kN) @ 75%
Career Operators South African Railways Class Class GCA Number in class 39 Numbers 2190-2202, 2600-2625 Delivered 1927-1928 First run 1927 Withdrawn 1975

The South African Railways Class GCA 2-6-2+2-6-2 of 1927 was an articulated steam locomotive.

In 1927, the South African Railways placed thirteen Class GCA Garratt articulated steam locomotives with a 2-6-2+2-6-2 Double Prairie type wheel arrangement in branch line service. Another batch of twenty-six locomotives was acquired in 1928.

The Class GCA 2-6-2+2-6-2 Double Prairie type Garratt steam locomotive was built to the specifications and design of Colonel F.R. Collins DSO, Chief Mechanical Engineer of the South African Railways (SAR), based on the design of the Class GC Garratt. Thirteen locomotives were ordered from Friedrich Krupp AG of Essen in Germany, who delivered them during October 1927, numbered in the range from 2190 to 2202.

A second order for another 26 locomotives was placed with the same manufacturer in 1928. These were numbered in the range from 2600 to 2625 when they were delivered during August in that same year.

The Class GCA had the same tractive effort and main dimensions as the Class GC, but was built on bar frames instead of plate frames. They also differed in general appearance by having round-topped fireboxes, compared to the Belpaire fireboxes of the Class GC, and with water tanks and built-up coal bunkers of a different shape. The second batch of locomotives differed slightly from the first and were 1 long ton 10 hundredweight (1,524 kilograms) heavier. Like the predecessor Class GC, they were all superheated and had Walschaerts valve gear.

The Class GCA proved to be good locomotives, although some trouble was experienced with coupling rods breaking, much of which was attributed to running them at excessive speed to maintain schedules with their small coupled wheel diameter of only 42 ³⁄₄ inches (1,086 millimetres).

Experience showed that the performance of these locomotives could have been better if they had been fitted with somewhat larger cylinders since their boilers still had an appreciable margin of capacity.

The first batch of locomotives were placed in service on the Natal South Coast line and shedded at Greyville, while the second batch were distributed wherever their services were required. These could be found working around Pietermaritzburg on the Donnybrook to Underberg and Greytown to Mount Alida branch lines, while some ended up at Nelspruit in the Eastern Transvaal Lowveld for service on the Graskop branch line. They were even tested on the South West Africa System.