SAR class 23

SAR class 23
SAR class 23
Numbering:	2552-2571, 3201-3316
Number:	136
Manufacturer:	Henschel , BMAG
Year of construction (s):	1936-1939
Retirement:	1970s
Type :	2'D1 'h2
Gauge :	1067 mm ( cape track )
Length over coupling:	26,575 mm
Service mass:	112.7 t
Service mass with tender:	218.6 t
Wheel set mass :	19.1 t
Driving wheel diameter:	1,600 mm
Cylinder diameter:	610 mm
Piston stroke:	711 mm
Boiler overpressure:	155.0 N / cm²
Grate area:	5.85 m²
Train brake:	Suction air brake

The class 23 locomotives of the South African Railways (SAR) were steam locomotives with the wheel arrangement 2'D1 '( Mountain ). The class was the heaviest and most powerful of the numerous mountain classes of the SAR and also the one with the largest drive wheels. With 136 copies, the class was also one of the most numerous steam locomotives in South Africa.

delivery

The locomotives were developed in 1936 for passenger and freight train service on main lines. The original plan was to purchase a small series of 20 locomotives for testing purposes, but because of the worsening political situation in Europe, 116 more were ordered before they were delivered. The first 20 received the track numbers 2552-2571, the others the numbers 3201-3316. Manufacturers were the Henschel-Werke (98 pieces) and the Berliner Maschinenbau AG (38 pieces).

The last copies were put into operation in August 1939, less than a month before the outbreak of war.

technology

The locomotives were an enlarged version of the classes 15E and 15F , which were initially also built by Henschel and BMAG ; Cylinder dimensions and boiler ( standard boiler 3B ) were identical, but the boiler pressure was 10.3 N / mm² (15 psi ) higher, which resulted in a higher pulling force in spite of the enlarged coupling wheels from 1,524 to 1,600 mm. As with the class 15F, a Walschaerts control was installed instead of the Caprotti valve control of class 15E.

Although classes 15E and 15F have slightly smaller wheels, the middle of the boiler in class 23 is a few centimeters lower, so that the chimney could be correspondingly longer. The reason for this is that Class 23 was originally planned with even larger wheels (1,676 mm), but this was changed in a late construction phase so that tighter curves could be negotiated. Even with the 1,600 mm wheels, however, the fixed wheelbase was still so large that the first coupled axle had to be provided with lateral play.

The locomotives were the first SAR series locomotives to receive six-axle tenders in order to be able to use them more efficiently on routes in the arid Karoo . It was planned to provide some of the locomotives with streamlined cladding, but this was not done primarily for weight reasons.

With an operating weight of 112.7 t (without tender), class 23 in South Africa - apart from articulated locomotives - was only outbid by classes 18 and 25. The total weight including the tender was 218.6 t. The machines are among the world's largest non-articulated steam locomotives for Cape Gauge .

Use and whereabouts

First, the class 23 locomotives were used on the routes between Touws River and Beaufort West as well as De Aar and Klerksdorp , where they carried the main load of the operation. With the appearance of the classes 25 and 25NC from 1953 and the electrification of some route sections, many class 23 locomotives were relocated to Bloemfontein , from where they were used to Kimberley and Kroonstad .

Cracks in the frame, caused by poor quality steel, which had to be used in construction because of the looming war, led to the entire class being retired in the 1970s. Some of the tenders continued to be used on machines of the class 15F, which was originally only equipped with four-axle tenders.

One locomotive (No. 3300) was kept in service by the SAR and used for special trips. Another example, No. 2556, has also been preserved and is a monument locomotive in a park in Touws River. Two machines (No. 3286 and 3311), which had been parked for a long time in the Millsite depot near Krugersdorp , were only scrapped in 2008, which sparked protests from railway enthusiasts because they were intended for preservation and marked accordingly.

literature

Leith Paxton, David Bourne: Locomotives of the South African Railways. A Concise Guide. C. Strui (Pty) Ltd., Cape Town 1985, ISBN 0-86977-211-2 .
John N. Middleton: Railways of Southern Africa. Locomotive guide. 5th edition. Beyer-Garratt Publications, Rickmansworth 1994, ISBN 0-620-18548-1 .