South African Class 25NC 4-8-4

South African Class 25NC 4-8-4
No. 3410 at Sannaspos, Free State, 4 July 1999
Type and origin ♠ Type EW1 tender - ♥ Type EW2 tender Power type Steam Designer South African Railways (L.C. Grubb) Builder Henschel and Son North British Locomotive Company Serial number NBL 27287-27296, 27311 Henschel 28731-28769 Model Class 25NC Build date 1953 Total produced 137
Specifications Configuration: ​  • Whyte 4-8-4 (Northern)  • UIC 2'D2'h2 Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 30 in (762 mm) Coupled dia. 60 in (1,524 mm) Trailing dia. 30 in (762 mm) Tender wheels 34 in (864 mm) Minimum curve 275 ft (84 m) Wheelbase ♠ 81 ft 4 11⁄16 in (24,808 mm) ♥ 95 ft 1 11⁄16 in (28,999 mm)  • Engine 38 ft (11,582 mm)  • Leading 6 ft 10 in (2,083 mm)  • Coupled 15 ft 9 in (4,801 mm)  • Trailing 5 ft 6 in (1,676 mm)  • Tender ♠ 32 ft (9,754 mm) ♥ 45 ft 10 in (13,970 mm)  • Tender bogie 10 ft (3,048 mm) Length: ​  • Over couplers ♠ 91 ft 6 9⁄16 in (27,903 mm) ♥ 107 ft 6 1⁄16 in (32,768 mm) Height 13 ft (3,962 mm) Frame type Cast Axle load 18 LT 14 cwt (19,000 kg)  • Leading 21 LT 2 cwt (21,440 kg)  • 1st coupled 18 LT 10 cwt (18,800 kg)  • 2nd coupled 18 LT 14 cwt (19,000 kg)  • 3rd coupled 18 LT 12 cwt (18,900 kg)  • 4th coupled 18 LT 9 cwt (18,750 kg)  • Trailing 22 LT 12 cwt (22,960 kg)  • Tender bogie Bogie 1: ♠ 51 LT 6 cwt (52,120 kg) Bogie 2: ♠ 54 LT 5 cwt (55,120 kg)  • Tender axle ♠ 18 LT 1 cwt 2 qtr (18,370 kg) Adhesive weight 74 LT 5 cwt (75,440 kg) Loco weight 117 LT 9 cwt (119,300 kg) Tender weight ♠ 105 LT 11 cwt (107,200 kg) Total weight ♠ 223 LT (226,600 kg) Tender type EW1 (3-axle bogies) EW2 (3-axle bogies) Fuel type Coal Fuel capacity ♠ 18 LT (18.3 t) ♥ 19 LT (19.3 t) Water cap ♠ 10,500 imp gal (47,700 l) ♥ 11,200 imp gal (50,900 l) Firebox type Round-top  • Firegrate area 70 sq ft (6.5 m2) Boiler: ​  • Type Domeless  • Pitch 9 ft 1 5⁄8 in (2,784 mm)  • Diameter 6 ft 4 1⁄8 in (1,934 mm)  • Tube plates 19 ft (5,791 mm)  • Small tubes 158: 2 1⁄2 in (64 mm)  • Large tubes 40: 5 1⁄2 in (140 mm) Boiler pressure 225 psi (1,551 kPa) Safety valve Ross-pop Heating surface 3,390 sq ft (315 m2)  • Tubes 3,059 sq ft (284.2 m2)  • Arch tubes 37 sq ft (3.4 m2)  • Firebox 294 sq ft (27.3 m2) Superheater: ​  • Type Melesco  • Heating area 630 sq ft (59 m2) Cylinders Two Cylinder size 24 in (610 mm) bore 28 in (711 mm) stroke Valve gear Walschaerts Valve type Piston Valve travel 7 3⁄8 in (187 mm) Loco brake Vacuum Couplers AAR knuckle
Performance figures Tractive effort 45,360 lbf (201.8 kN) @ 75%
Career Operators South African Railways Class Class 25NC Number in class 50 original, 87 rebuilt Class 25 Numbers 3401-3450, 3452-3510, 3512-3539 Delivered 1953-1954 First run 1953

External video

South African Steam: Trans Karoo Steam Finale: 2nd Last Run - March 1997 A short video featuring the second last run of steam on the Trans Karoo Express on 15 March 1997. The locomotives are Class 25NC no. 3422, a regular on the Trans Karoo, and Class 25NC no. 3407, a relatively rare engine on this train. The other two regular locomotives, nos. 3404 and 3476, were not available as they were being spruced up for the final run the following week. (Time 4:36)

External video

Class 25NC 3533, 5 October 2009 Rovos Rail's Class 25NC 3533, converted from a Class 25 condenser, enters Capital Park yard on 5 October 2009, in the process of turning The Pride of Africa around on the Capital Park triangle. (Time 1:00)

The South African Railways Class 25NC 4-8-4 of 1953 was a steam locomotive.

Between 1953 and 1955, the South African Railways placed fifty Class 25NC steam locomotives with a 4-8-4 Northern type wheel arrangement in service. The Class 25NC was the non-condensing version of the Class 25 condensing locomotive, of which ninety were placed in service at the same time. Between 1973 and 1980, all but three of the condensing locomotives were converted to non-condensing and also designated Class 25NC.

The Class 25NC non-condensing and Class 25 condensing 4-8-4 Northern type steam loco­mo­tives were designed by the South African Railways (SAR) under the direction of L.C. Grubb, Chief Mechanical Engineer of the SAR from 1949 to 1954, in conjunction with Henschel and Son of Kassel in Germany who designed the condensing apparatus and the condensing tender of the Class 25 sister locomotive. Between 1953 and 1955, eleven Class 25NC locomotives were built by the North British Locomotive Company (NBL) and numbered in the range from 3401 to 3411, while 39 locomotives were built by Henschel and numbered in the range from 3412 to 3450.

The Class 25NC was superheated and used piston valves actuated by Walschaerts valve gear. Timken roller bearings were used throughout, including on the three-axle tender bogies, the coupling and connecting rods as well as the crosshead gudgeon pins, while the locomotive's leading bogies and coupled wheels had Cannon-type axle boxes. Compared to earlier SAR practice, a novelty was the adoption of mechanical lubrication. A sixteen-feed lubricator was driven off the reversing link trunnion. The cylinders and frames were cast in one piece by Commonwealth Steel Castings Corporation in the United States of America. The steel cylinders and steam chests were fitted with cast iron liners. Being entirely mounted on roller bearings, very little effort was required to move these locomotives.

The Alligator type crossheads were split on the vertical centre line and clamped on to the end of the piston rods, which had three coned rings engaging in grooves in the crossheads. The original coupling rods differed from the usual in being three separate rods, thereby doing away with four knuckle joints and pins.

The multiple-valve superheater header was of the Melesco type. The boiler was fitted with four Ross-pop safety valves, each 2 ¹⁄₂ inches (64 millimetres) in diameter, and two Hopkinson boiler blowdown cocks on the firebox wrapper, one on each side. Feedwater was delivered to the boiler by two Friedmann vertical type non-lifting injectors, each with a capacity of 5,200 imperial gallons (23,600 litres) per hour.