South African Class 18 2-10-2

South African Class 18 2-10-2
Builder's picture of the Class 18, c. 1927
Type and origin Power type Steam Designer South African Railways (Col F.R. Collins DSO) Builder Henschel and Son Serial number 20787-20788 Model Class 18 Build date 1927 Total produced 2
Specifications Configuration: ​  • Whyte 2-10-2 (Santa Fe)  • UIC 1'E1'h3 Driver 3rd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 30 in (762 mm) Coupled dia. 57 in (1,448 mm) Trailing dia. 33 in (838 mm) Tender wheels 34 in (864 mm) Minimum curve 320 ft (98 m) Wheelbase 67 ft 7 3⁄4 in (20,618 mm)  • Engine 38 ft 2 1⁄4 in (11,640 mm)  • Coupled 21 ft (6,401 mm)  • Tender 20 ft 5 in (6,223 mm)  • Tender bogie 6 ft 2 in (1,880 mm) Length: ​  • Over couplers 76 ft (23,165 mm) Height 13 ft (3,962 mm) Axle load 19 LT (19,300 kg)  • Leading 7 LT 9 cwt (7,570 kg)  • 1st coupled 18 LT 6 cwt (18,590 kg)  • 2nd coupled 18 LT 18 cwt (19,200 kg)  • 3rd coupled 19 LT (19,300 kg)  • 4th coupled 18 LT 4 cwt (18,490 kg)  • 5th coupled 18 LT 2 cwt (18,390 kg)  • Trailing 14 LT 12 cwt (14,830 kg)  • Tender bogie Bogie 1: 33 LT 18 cwt (34,440 kg) Bogie 2: 38 LT 16 cwt (39,420 kg)  • Tender axle 19 LT 8 cwt (19,710 kg) Adhesive weight 92 LT 10 cwt (93,980 kg) Loco weight 114 LT 11 cwt (116,400 kg) Tender weight 72 LT 14 cwt (73,870 kg) Total weight 187 LT 5 cwt (190,300 kg) Tender type HT (2-axle bogies) Mechanical stoker Fuel type Coal Water cap 6,000 imp gal (27,300 l) Firebox type Round-top  • Firegrate area 60 sq ft (5.6 m2) Boiler: ​  • Pitch 8 ft 6 in (2,591 mm)  • Diameter 6 ft 3 3⁄4 in (1,924 mm)  • Tube plates 20 ft 7 in (6,274 mm)  • Small tubes 160: 2 1⁄4 in (57 mm)  • Large tubes 34: 5 1⁄2 in (140 mm) Boiler pressure 215 psi (1,480 kPa) Safety valve Pop Heating surface 3,231 sq ft (300.2 m2)  • Tubes 2,945 sq ft (273.6 m2)  • Arch tubes 21 sq ft (2.0 m2)  • Firebox 265 sq ft (24.6 m2) Superheater: ​  • Heating area 850 sq ft (79 m2) Cylinders Three Cylinder size 21 1⁄4 in (540 mm) bore 28 in (711 mm) stroke Valve gear Outer Walschaerts - Inner Gresley Valve type Piston Couplers AAR knuckle
Performance figures Tractive effort 53,650 lbf (239 kN) @ 75%
Career Operators South African Railways Class Class 18 Number in class 2 Numbers 1360-1361 Nicknames Henschel Giant Delivered 1927-1928 First run 1927 Withdrawn 1951
The 3rd & 4th coupled axles had flangeless wheels

The South African Railways Class 18 2-10-2 of 1927 was a steam locomotive.

In December 1927 and January 1928 the South African Railways placed two Class 18 three-cylinder steam locomotives with a 2-10-2 Santa Fe type wheel arrangement in service on the Witbank-Germiston coal line.

The Class 18 2-10-2 Santa Fe type steam locomotive was designed by Colonel F.R. Collins DSO, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1922 to 1929, and built by Henschel and Son in Germany. Two locomotives were delivered in 1927 and 1928, numbered 1360 and 1361.

They were very powerful three-cylinder locomotives. At the time, three-cylindered locomotives were being built in appreciable numbers in Europe and America. Factors in their favour were their more even turning moment, improved balancing and better distribution of crank-pin thrust. Drawbacks were increased complexity and higher repair cost.

When delivered, the third cylinder was clearly visible, but plating was subsequently added beneath the smokebox and hid it from view. These were the most powerful non-articulated steam locomotives to see service on the SAR, with a tractive effort of 53,650 pounds-force (239 kilonewtons) at 75% boiler pressure and capable of hauling loads of 1,800 long tons (1,829 tonnes) over the ruling gradient of 1 in 100 (1%) on the Witbank-Apex section.

Contemporary Henschel publicity appropriately referred to them as the "Henschel Giants". They were larger in most respects than Deutsche Reichsbahn's new Standard gauge Class 44 three-cylinder 2-10-0 locomotives. Although their all-up locomotive weight was almost the same, when considering the fact that the SAR's Cape gauge Class 18 had shorter axles and frame stretchers, saving weight that could then be built into other items such as the firebox, the Class 18 was the larger locomotive.

The Class 18 had a round-topped firebox with a combustion chamber and with arch tubes supporting the brick arch. It was fired by a Duplex D.4 type mechanical stoker, operated by a four-cylinder steam engine on its Type HT tender, which had a coal capacity of 14 long tons (14.2 tonnes), a water capacity of 6,000 imperial gallons (27,300 litres) and a maximum axle load of 19 long tons 8 hundredweight (19,710 kilograms).