| South Australian Railways R & Rx class | |
| Powertype: | Steam |
| Builder: | Dübs & Co (6) James Martin & Co (24) Islington Railway Workshops (14) North British Locomotive Company (15) Walkers Limited (25) |
| Builddate: | 1885-1916 |
| Totalproduction: | 84 |
| Rebuilder: | Islington Railway Workshops |
| Rebuilddate: | 1899-1913 as Rx |
| Numberrebuilt: | 30 to Rx |
| Whytetype: | 4-6-0 (2′C 3) (2′C 2′2′) |
| Leadingdiameter: | 2feet |
| Driverdiameter: | 4feet |
| Length: | 49feet |
| Axleload: | (R) (Rx) |
| Locoweight: | 400NaN0 (R) |
| Tenderweight: | 220NaN0 (R) |
| Locotenderweight: | 65LT (R), 880NaN0 |
| Fueltype: | Coal |
| Fuelcap: | (R), (Rx), (Rx 6 wheel tender) |
| Watercap: | (R) (Rx), (Rx 6 wheel tender) |
| Boilerpressure: | 1450NaN0 (R) 1750NaN0 (Rx) |
| Firearea: | (R) (Rx) |
| Tubearea: | (R) (Rx) |
| Fireboxarea: | . (R) (Rx) |
| Superheaterarea: | (Rx) (not fitted to some locos) |
| Cylindercount: | 2 |
| Cylindersize: | 18x |
| Valvegear: | Allan Straight Link |
| Valvetype: | Piston |
| Tractiveeffort: | 177002NaN2 (R) 214202NaN2 (Rx) |
| Factorofadhesion: | 3.49 |
| Operator: | South Australian Railways |
| Operatorclass: | R/Rx |
| Numinclass: | 84 |
| Fleetnumbers: | 5, 9, 10, 15, 20*, 25*, 48, 55, 56, 91*-96*, 102*-107*, 138*-153*, 155, 158, 160, 190-203, 206-235 (* originally built as R class) |
| Firstrundate: | 10.2.1886 |
| Lastrundate: | 5.9.1969 |
| Withdrawndate: | 1927-1969 |
| Preservedunits: | Rx 5, Rx 55, Rx 93, Rx, 160, Rx 191, Rx 201, Rx 207, Rx 217, Rx 224 & Rx 231 |
| Scrapdate: | 1928-1974 |
| Disposition: | Ten preserved, remainder scrapped |
The South Australian Railways R class engine, later upgraded to Rx Class engine is a class of 4-6-0 steam engines operated by the South Australian Railways.
In 1886, Dübs and Company of Glasgow delivered the first six R class of engine. A further 24 engines had been built by James Martin & Co by November 1895. From 1899, all engines were rebuilt with higher powered Belpaire boilers and reclassified as Rx class engines. A further 54 locomotives were built as Rx class by the Islington Railway Workshops, North British Locomotive Company and Walkers Limited with all engines in service by May 1916.[1]
The R class engines were the predominant locomotive used on broad gauge main line services in South Australia from their introduction. After the introduction of the large Webb engines they were relegated to secondary lines and services such as shunting and hauling goods trains and passenger trains. A large group of Rx class locomotives, mainly early builds, were withdrawn from service in 1934, however the remainder continued to serve into the mid 1960s.[1]
Several Rx class locomotives, including one original R class engine (Rx93), survive to this day in various states of preservation.