South African Class GL 4-8-2 2-8-4
The locomotives of the class GL of the South African Railways (SAR ) are the largest Garratt steam locomotives ever built for South Africa, and with a force of more than 40 tons of the most appealing steam locomotives of the Southern Hemisphere.
Electrification has already been decided for the main route between Durban and Cato Ridge 1914. This was delayed by the First World War, and the work did not begin until 1922. The first section was taken in 1925 in operation. For the heaviest freight trains three locomotives of Class 1E were used in multiple traction. On the not yet electrified section between Pietermaritzburg and Durban, these trains were pulled by two 2'D1' - steam locomotives of Class 14. Since the track was a bottleneck, it was decided to procure to bridge the time until the completion of electrification Garratt locomotives that could replace three locomotives of Class 1E or two of class 14 and would thus avoid the prestressing operation.
As the planned locomotive would be 50 % more efficient than all the existing and the tank diameter would be more than double the track, which led to concerns about the stability, only two locomotives were initially ordered from Beyer- Peacock. The first was put into service in October 1929 and tested extensively. The locomotive exceeded with a heavy freight train not only the performance of three locomotives of Class 1E, but also showed good running characteristics. After seven weeks of testing, therefore, a further six locomotives were ordered.
Pending the completion of electrification work in 1938 the locomotives were on their regular route in use; then they were used before coal trains between Glencoe and Vryheid, where they had on slopes up to 20 ‰ in 1200 t pull heavy trains - more than the power required in the design of locomotives.
Also, this line was electrified until 1968, and the GL came on the distance between Stanger and Empangeni. There, however, they were underutilized and were replaced by the smaller Garratts Class GMA / GMAM. After a bawanced gravity hump operations did not materialize, the locomotives were retired in 1972.
Two specimens (Nos. 2351 and 2352 ) have been preserved. The No. 2351 was still operational until at least the late 1990s; No. 2352 is in the Museum of Science and Industry in Manchester.
The GL class has been called the wheel arrangement ( 2'D1 ') ( 1'D2 '), also called " Double Mountain". Cylinder and driving wheel diameter had been taken over by the class 14. The locomotives were fired on a stoker coal. 12.2 tons of coal and 31.8 cubic meters of water could be carried.
The locomotives were designed for difficult curvature ratios. In addition to a minimum radius of 83.8 m, it was on the track and to 114 mm excessive counter- curves without intermediate straight. For this reason, the pivot of the front motor bogie was made spherical in order to avoid distortion of the 27.6 m long locomotive.