SAR class GM
| SAR class GM | |
|---|---|
.jpg) Class GM No. 2298 in Krugersdorp , April 23, 1970
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| Numbering: | 2291-2306 |
| Number: | 16 |
| Manufacturer: | Beyer-Peacock |
| Year of construction (s): | 1938 |
| Retirement: | until 1975 |
| Type : | (2'D1 ') (1'D2') h4 (Garratt) |
| Gauge : | 1067 mm ( cape track ) |
| Service mass: | 177 t |
| Friction mass: | 117 t |
| Wheel set mass : | 15.2 t |
| Driving wheel diameter: | 1371 mm |
| Impeller diameter: | k. A. |
| Cylinder diameter: | 520 mm |
| Piston stroke: | 660 mm |
| Boiler overpressure: | 138 N / cm² |
| Grate area: | 5.9 m² |
| Radiant heating surface: | 26.1 m² |
| Tubular heating surface: | 258.7 m² |
| Superheater area : | 72.3 m² |
| Train brake: | Suction air brake |
The vehicles of the class GM of the South African Railways (SAR) were articulated locomotives of the Garratt design .
The locomotives were built for the route between Johannesburg and Zeerust , part of the route via Botswana to Southern Rhodesia . The rails laid there allowed lower axle loads than on many other routes, and the traffic was mostly handled with the light mountain locomotives of the class 19D , also with Garratts of the classes GE and GF as well as the single piece of the class 21 (wheel arrangement 1'E2 ') . However, none of these locomotives were powerful enough that they often had to be driven in pre-tensioning mode.
Two class 19D locomotives had proven to be the most economical variant. So it was decided to introduce a Garratt with the capabilities of two 19Ds. The somewhat shortened GL class boiler should serve as the basis . However, the first draft turned out to be too difficult, so the water supplies on the locomotive were greatly reduced. On the front bogie there was only a comparatively small water tank with a reserve of 7.2 m² for shunting trips; only the coal bunker was housed on the rear bogie. Most of the water supply was carried on an attached water tender (basically a simple tank car).
Even with this trick, the axle load was even higher than that of the locomotives already running on the route; the draft was nevertheless approved. In 1938 Beyer-Peacock delivered 16 locomotives. They spent most of their time on the route they were built for, and it wasn't until 1972 that diesel locomotives displaced them and stationed them in Pretoria and Pietersburg . In 1973 they were retired.
A little later there was a shortage of locomotives in Breyten , and three GM with the numbers 2301, 2303 and 2304 were overhauled and relocated there. From Breyten they drove on the route to Piet Retief for about a year and then did shunting service. Eventually the three reactivated locomotives were sold to coal mines. Two locomotives, No. 2301 and 2304, have been preserved.
The GM class was supplemented in the 1950s by the GMA / GMAM class with the same performance . Together, both classes belong to the five most powerful steam locomotive types that have been used in the southern hemisphere.
literature
- AE Durrant: Garratt locomotives of the world. Birkhäuser, Basel et al. 1984, ISBN 3-7643-1481-8 .