South African Class 23 4-8-2

South African Class 23 4-8-2
No. 2556 in Gideon Joubert park, Touws River, 8 January 2010
Type and origin ♠ Locomotive numbers 2552-2271 ♥ Locomotive numbers 3201-3316 Power type Steam Designer South African Railways (W.A.J. Day) Builder Berliner Maschinenbau Henschel and Son Serial number Berliner 10738-10744, 10816, 10985-10999, 11001-11015 Henschel 23742-23754, 24155-24239 Model Class 23 Build date 1938 Total produced 136
Specifications Configuration: ​  • Whyte 4-8-2 (Mountain)  • UIC 2'D1'h2 Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 34 in (864 mm) Coupled dia. 63 in (1,600 mm) Trailing dia. 34 in (864 mm) Tender wheels 34 in (864 mm) Minimum curve 300 ft (91 m) Wheelbase ♠ 77 ft 8 1⁄2 in (23,686 mm) ♥ 78 ft 2 1⁄2 in (23,838 mm)  • Engine 37 ft 1⁄2 in (11,290 mm)  • Leading 7 ft 2 in (2,184 mm)  • Coupled 16 ft 6 in (5,029 mm)  • Tender 30 ft 8 in (9,347 mm)  • Tender bogie 8 ft 8 in (2,642 mm) Length: ​  • Over couplers 87 ft 2 1⁄4 in (26,575 mm) Height 12 ft 11 1⁄2 in (3,950 mm) Frame type Bar Axle load ♠ 18 LT 17 cwt (19,150 kg) ♥ 18 LT 14 cwt (19,000 kg)  • Leading ♠ 20 LT 7 cwt (20,680 kg) ♥ 20 LT 17 cwt (21,180 kg)  • 1st coupled ♠ 17 LT 16 cwt (18,090 kg) ♥ 17 LT 12 cwt (17,880 kg)  • 2nd coupled ♠ 18 LT 17 cwt (19,150 kg) ♥ 18 LT 14 cwt (19,000 kg)  • 3rd coupled ♠ 18 LT 15 cwt (19,050 kg) ♥ 18 LT 13 cwt (18,950 kg)  • 4th coupled ♠ 17 LT 16 cwt (18,090 kg) ♥ 17 LT 11 cwt (17,830 kg)  • Trailing ♠ 17 LT 8 cwt (17,680 kg) ♥ 17 LT 15 cwt (18,030 kg)  • Tender bogie Bogie 1: ♠ 54 LT 14 cwt (55,580 kg) ♥ 53 LT 17 cwt (54,710 kg) Bogie 2: ♠ 54 LT (54,870 kg) ♥ 53 LT 17 cwt (54,710 kg)  • Tender axle ♠ 18 LT (18,290 kg) ♥ 17 LT 19 cwt (18,240 kg) Adhesive weight ♠ 73 LT 4 cwt (74,370 kg) ♥ 72 LT 10 cwt (73,660 kg) Loco weight ♠ 110 LT 19 cwt (112,700 kg) ♥ 111 LT 2 cwt (112,900 kg) Tender weight ♠ 104 LT 5 cwt (105,900 kg) ♥ 107 LT 14 cwt (109,400 kg) Total weight ♠ 215 LT 4 cwt (218,700 kg) ♥ 218 LT 16 cwt (222,300 kg) Tender type EW (3-axle bogies) Fuel type Coal Fuel capacity 18 LT (18.3 t) Water cap ♠ 9,200 imp gal (41,800 l) ♥ 9,500 imp gal (43,200 l) Firebox type Round-top  • Firegrate area 63 sq ft (5.9 m2) Boiler: ​  • Model Watson Standard no. 3B  • Type Domeless  • Pitch 9 ft (2,743 mm)  • Diameter 6 ft 2 1⁄4 in (1,886 mm)  • Tube plates 22 ft 6 in (6,858 mm)  • Small tubes 136: 2 1⁄2 in (64 mm)  • Large tubes 36: 5 1⁄2 in (140 mm) Boiler pressure 225 psi (1,551 kPa) Safety valve Ross-pop Heating surface 3,400 sq ft (320 m2)  • Tubes 3,168 sq ft (294.3 m2)  • Arch tubes 26 sq ft (2.4 m2)  • Firebox 206 sq ft (19.1 m2) Superheater: ​  • Heating area 676 sq ft (62.8 m2) Cylinders Two Cylinder size 24 in (610 mm) bore 28 in (711 mm) stroke Valve gear Walschaerts Valve type Piston Valve travel 7 1⁄2 in (191 mm) Couplers AAR knuckle
Performance figures Tractive effort 43,200 lbf (192 kN) @ 75%
Career Operators South African Railways Class Class 23 Number in class 136 Numbers 2552-2571, 3201-3316 Delivered 1938-1939 First run 1938 Withdrawn 1983

The South African Railways Class 23 4-8-2 of 1938 was a steam locomotive.

In 1938 and 1939, the South African Railways placed 136 Class 23 steam locomotives in service. The Class 23 was the last and the largest 4-8-2 Mountain type locomotive to be designed by the South African Railways.

The Class 23 4-8-2 Mountain type steam locomotive was designed by W.A.J. Day, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1936 to 1939. It was intended as a general utility locomotive, capable of operating on 80 pounds per yard (40 kilograms per metre) rail, and was built in two batches by Berliner Maschinenbau and Henschel and Son in Germany. The original order in 1938 was for twenty locomotives, of which Berliner built seven, numbered in the range from 2552 to 2558, and Henschel thirteen, numbered in the range from 2559 to 2571.

At the time, the urgency brought about by the rapidly deteriorating political climate in Europe led to a further 116 locomotives being ordered even before the first batch could be delivered and tested, contrary to usual SAR practice. Ordering this quantity of a new class of engine before any had been tried out constituted a record for the SAR. Of this second batch, Henschel built 85, numbered in the range from 3201 to 3285, and Berliner 31, numbered in the range from 3286 to 3316. The last locomotive of this second order was delivered in August 1939, just one month before the outbreak of the Second World War.

Berliner-built locomotive no. 3301 received an out-of-sequence works number, Berliner no. 10816 instead of no. 11000, since works number 11000 was reserved for the new Class 01.10 4-6-2 Pacific type locomotive for the German State Railways.

In general appearance and power, the Class 23 locomotive is very similar to the Classes 15E and 15F. As originally designed, the locomotive would have had 66 inches (1,676 millimetres) coupled wheels which would have required a newly designed boiler to accommodate the extra length brought about by the long coupled wheelbase. The increasing political turmoil in Europe and the resulting urgency, however, prohibited time being spent on designing a new boiler. As a result, the existing Watson Standard no. 3B boiler was incorporated in the design with an extra long smokebox which was extended by 1 foot 6 inches (457 millimetres) to partially compensate for the shorter boiler. This boiler was one of the range of standard type boilers which was designed by Day's predecessor as CME, A.G. Watson, as part of the latter's standardisation policy. To maintain approximately the same tractive effort as the Class 15E, the boiler pressure was raised to 225 pounds per square inch (1,551 kilopascals), at the time the highest yet used on the SAR since the SAR loading gauge did not permit horizontal cylinders of greater bore diameter than 24 inches (610 millimetres) with normal cylinder spacing.