The reference for locomotives and railcars


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Federated Malay States classes O1 to O4
Malayan State Railway classes 561 to 564
Malaysia | 1938 | 68 produced
O<sup>4</sup> No. 564.01 “Kangar”
O4 No. 564.01 “Kangar”
flickr/Historical Railway Images

To accommodate increased mail traffic, the meter-gauge Federated Malay State Railways ordered class O Pacifics from North British at the end of the 1930s. Due to individual batches built between 1938 and 1946, they were given the designations O1 to O4. They were built to achieve the greatest possible power with a permitted axle load of 11 3/4 tons.

These were the most advanced Pacifics in the FMSR. Lightweight construction was used in many places so that the boiler and engine could still be sufficiently dimensioned. The boiler pressure was chosen to be relatively high at 250 psi to increase power. Three cylinders were also used, which were enlarged by half an inch in the third and fourth series. Other special features were thermic syphons and a rotating valve gear.

They were successfully tested for possible high-speed traffic at 70 mph or 113 km/h, but were not actually used. Although these locomotives were later converted to run on oil, they were soon replaced by diesel locomotives in the fast mail service. They therefore continued to be used in freight transport for a long time.

VariantO1, O2O3, O4
Built1938-19391940, 1946
ManufacturerNorth British
Axle config4-6-2 (Pacific) 
Gauge3 ft 3 3/8 in (Meter gauge)
Dimensions and Weights
Wheelbase28 ft 3 in
Fixed wheelbase10 ft
Total wheelbase51 ft 7 in
Service weight133,280 lbs
Adhesive weight85,344 lbs
Total weight232,512 lbs
Axle load28,560 lbs
Water capacity4,119 us gal
Fuel capacity2,882 us gal (oil)
Power sourcesteam
Estimated power1,700 hp (1,268 kW)
Optimal speed49 mph45 mph
Starting effort22,135 lbf23,942 lbf
Power Plant
Driver diameter54 in
Boiler pressure250 psi
Expansion typesimple
Cylindersthree, 12 1/2 x 24 inthree, 13 x 24 in
Grate area27 sq ft
Firebox area385 sq ft
Tube heating area1,109 sq ft
Evaporative heating area1,494 sq ft
Superheater area218 sq ft
Total heating area1,712 sq ft
Calculated Values
steam locomotive
last changed: 02/2024

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