South African Class 91-000

South African Class 91-000

Numbers 91-003 and 91-009 on the limestone train from Loerie PPC to New Brighton

Type and origin Power type Diesel-electric Designer General Electric Builder General Electric Serial number 38603-38622 Model GE UM6B Build date 1973 Total produced 20

Specifications AAR wheel arr. B-B UIC class Bo'Bo' Imperial class Bo-Bo Gauge 2 ft (610 mm) narrow Wheel diameter 838 mm (33.0 in) 915 mm (36.0 in) Bigfoot Wheelbase 7,290 mm (23 ft 11.0 in) 7,314 mm (24 ft 0 in) Bigfoot  • Bogie 2,108 mm (6 ft 11.0 in) 2,082 mm (6 ft 10.0 in) Bigfoot Pivot centres 5,232 mm (17 ft 2.0 in) Length: ​  • Over couplers 10,580 mm (34 ft 8.5 in) Width 2,564 mm (8 ft 4.9 in) Height 3,632 mm (11 ft 11.0 in) Axle load 12,000 kg (26,000 lb) Adhesive weight 48,000 kg (106,000 lb) Loco weight 48,000 kg (106,000 lb) max Fuel type Diesel Fuel capacity 1,600 litres (350 imp gal) Prime mover Caterpillar D-379 RPM range 650-1,365  • RPM idle 650  • Maximum RPM 1,365 Engine type 4-stroke diesel Aspiration Schwitzer 4ME 455 turbocharger Generator 6 pole GE 5GT-601C1 Traction motors Four GE 5GE-778AI DC 4 pole Two GE 5GE-761-A13 DC 4 pole Bigfoot  • Rating 1 hour 410A, 665A Bigfoot  • Continuous 395A @ 14 km/h (8.7 mph) 655A @ 15 km/h (9.3 mph) Bigfoot Cylinders V8 Gear ratio 13:68:1 double reduction MU working 3 maximum Loco brake 28-LV-1 with vigilance control Train brakes Westinghouse 4CD2UC compressor/exhauster Air reservoir cap 500 litres (110 imp gal) Compressor cap 0.036 m3/s (1.3 cu ft/s) Exhauster cap 0.072 m3/s (2.5 cu ft/s) Couplers Willison AAR knuckle (Bigfoot)

Performance figures Maximum speed 50 km/h (31 mph) Power output: ​  • Starting 520 kW (700 hp)  • Continuous 480 kW (640 hp) Tractive effort: ​  • Starting 108 kN (24,000 lbf) @ 25% adh.  • Continuous 86 kN (19,000 lbf) @ 15 km/h (9.3 mph) Factor of adh.:  • Starting 25%  • Continuous 20% Loco brakeforce 60% ratio @ 345 kPa (50.0 psi) Dynamic brake peak effort 85 kN (19,000 lbf) @ 14 km/h (8.7 mph)

Career Operators South African Railways Spoornet Transnet Freight Rail RRL Grindrod Class Class 91-000 Number in class 20 Numbers 91-001 to 91-020 Delivered 1973 First run 1973

The South African Railways Class 91-000 of 1973 is a narrow gauge diesel-electric locomotive.

Between September and December 1973, the South African Railways placed twenty Class 91-000 General Electric type UM6B diesel-electric locomotives in service on its narrow gauge Avontuur Railway line, between Port Elizabeth in the Eastern Cape and Avontuur in the Western Cape. Some of them later also worked on the Alfred County Railway line, out of Port Shepstone in KwaZulu-Natal.

The Class 91-000 GE type UM6B diesel-electric locomotive was designed and built for the South African Railways (SAR) by General Electric (GE) in Erie, Pennsylvania. Twenty locomotives were delivered between September and December 1973, numbered in the range from 91-001 to 91-020. It was designed for 2 ft (610 mm) narrow gauge and is the largest two foot gauge diesel-electric locomotive in the world, at an average weight of 44,000 kilograms (97,000 pounds).

The usual practice was to have locomotive builder’s works plates attached to the locomotive’s frame below the cab windows. The Class 91-000 locomotives, however, had their works plates mounted on each side of the long hood. With the exception of numbers 91-001 (GE 38604), 91-002 (GE 38603), 91-016 (GE 38619) and 91-017 (GE 38618), the Class 91-000 works numbers are in sequence with their running numbers. It is very likely, however, that this was the result of body panels being swapped between locomotives during overhauls.

As a result of the severe clearance problems presented by the two foot gauge, it was not possible to follow the usual practice of axle-hung traction motors. Special bogies had to be designed, with the traction motors mounted between the axles, with one traction motor on each side of each bogie.