Data from South African Rys & Harbours 8 -1941Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange collection; "South African Class 24 2-8-4" in Wikipedia at [], last accessed on 19 September 2022; and A E Durrant (1972). Works numbers were 23313-24312 in 1949-1950. (3675 was the 2,000th locomotive delivered by NBLC to South African railways, a benchmark celebrated by naming it Bartolomew Dias.)
Designed by Chief Mechanical Engineer (CME) Dr. M M Loubser over a ten-year period, these were only Berkshires on the SAR. Many were concentrated in the SouthWest Africa area. Impressive engines running on 45-lb/yard (22.5 kg/m) rail. (As big as they were Locobases 3839, 3842-3843 (Japan), 4329 (Kenya) trailed tenders, 6480 (Chile), and 3722 (Argentina). In most dimensions, these were half-size versions of the Class 23 Mountains.
Baldwin's General Steel Castings plant in Eddystone, PA supplied the cast-steel main frames with integral cylinders and the six-axle tender's Buckeye bogies. Firebox heating surface included 16 sq ft (1.49 sq m) of arch tubes.
Although the 24s delivered good steam power, dieselization and electrification considerably shortened their likely service lives to an average of 15 years or less. The upside for posterity soon appeared as 23 of the 24s wound up in displays or operational heritage operations in South Africa. In addition, the 3620 traveled across the Pacific to New Zealand's Main Line Steam Trust in 1997.
Four years later, it crossed the Tasman Sea to Cairns, Australia1. Not long after it began service, 3620 was idled for restoration for 13 years. Russell Newman posted the following update on 7 March 2021:
"After 13 years out of action the ex South African Railways Glasgow North British Locomotive Company built Class 24 2-8-4 No. 3620 has successfully completed its test runs at the Bellarine Peninsular Railway in Victoria State. During the locomotive's restoration, several major changes and additions have been made to No. 3620 which is now equipped with air brakes and oil firing, along with a bell, smokebox headlight and front numberplates being fitted at its owner Mr Ian Welch's request."
The engine then re-entered service to pull the six light-blue carriages on the Q Train's "Rail Restaurant".
Principal Dimensions by Steve Llanso of Middle Run Media | |
---|---|
Class | 24 |
Locobase ID | 2923 |
Railroad | South African Railways (SAR) |
Country | South Africa |
Whyte | 2-8-4 |
Number in Class | 100 |
Road Numbers | 3601-3700 |
Gauge | 3'6" |
Number Built | 100 |
Builder | North British |
Year | 1948 |
Valve Gear | Walschaert |
Locomotive Length and Weight | |
Driver Wheelbase (ft / m) | 13.48 / 4.11 |
Engine Wheelbase (ft / m) | 31 / 9.45 |
Ratio of driving wheelbase to overall engine wheelbase | 0.43 |
Overall Wheelbase (engine & tender) (ft / m) | 65.26 / 19.89 |
Axle Loading (Maximum Weight per Axle) (lbs / kg) | 25,761 / 11,685 |
Weight on Drivers (lbs / kg) | 100,127 / 45,417 |
Engine Weight (lbs / kg) | 163,296 / 74,070 |
Tender Loaded Weight (lbs / kg) | 126,673 / 57,458 |
Total Engine and Tender Weight (lbs / kg) | 289,969 / 131,528 |
Tender Water Capacity (gals / ML) | 5399 / 20.45 |
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 9.90 / 9 |
Minimum weight of rail (calculated) (lb/yd / kg/m) | 42 / 21 |
Geometry Relating to Tractive Effort | |
Driver Diameter (in / mm) | 51 / 1295 |
Boiler Pressure (psi / kPa) | 200.20 / 1380 |
High Pressure Cylinders (dia x stroke) (in / mm) | 19.02" x 25.98" / 483x660 |
Tractive Effort (lbs / kg) | 31,360 / 14224.67 |
Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.19 |
Heating Ability | |
Tubes (number - dia) (in / mm) | 76 - 2.52" / 64 |
Flues (number - dia) (in / mm) | 24 - 5.512" / 140 |
Flue/Tube length (ft / m) | 17.75 / 5.41 |
Firebox Area (sq ft / m2) | 138.96 / 12.91 |
Grate Area (sq ft / m2) | 35.95 / 3.34 |
Evaporative Heating Surface (sq ft / m2) | 1636 / 151.99 |
Superheating Surface (sq ft / m2) | 380 / 35.30 |
Combined Heating Surface (sq ft / m2) | 2016 / 187.29 |
Evaporative Heating Surface/Cylinder Volume | 191.49 |
Computations Relating to Power Output (More Information) | |
Robert LeMassena's Power Computation | 7197 |
Same as above plus superheater percentage | 8565 |
Same as above but substitute firebox area for grate area | 33,106 |
Power L1 | 11,454 |
Power MT | 1008.79 |