Royal State Railways 2-8-2 Locomotives in Thailand

Class 301 (Locobase 15289)

Data from DeGolyer, Vol 72, pp. 274+. Works numbers were 56139-56140 in January 1923.

These first two Mikados were intended to travel on 24.8 kg/metre (50 lb/yard) rails, grades of 2 1/2%, and manage relatively gentle 180 m/590 ft radii (9 3/4 degree) curves. Each cylinder was supplied through an 8" (203 mm) piston valve.

They were relatively small even for the metre gauge. That they were followed shortly by four more with a third cylinder (Locobase 4413) suggests they might have been regarded as underpowered.

Class 303 (Locobase 4413)

Data from narrowmind.railfan.net and elevation and photograph from Railways of Thailand as advertised at [], supplemented by DeGolyer, Vol 78, pp. 382+. Works numbers were 58668-58671 in September 1925.

Required by the specifications to travel on 24.8 kg/metre (50 lb/yard) rails, grades of 2 1/2%, and manage relatively gentle 180 m/590 ft radii (9 3/4 degree) curves, these engines had the same boilers and grates as the earlier 2-8-2s shown in Locobase 15289, but sought more power by resorting to a three-cylinder layout--each with its own 8" (203 mm) piston valve--with a difference. The photos show an orthodox-looking straight-boilered Mike with an odd, thee-cylinder layout. The stroke lengths varied with the two outside rods traveling 22" and an inside rod going only 20". Varying stroke lengths in any design was very unusual -- another example was the much larger Union Pacific 4-12-2