The 0-6-0 wheel arrangement with inside cylinders was a peculiarly British phenomenon. Great Britain literally had scores of 0-6-0 classes. Its railway men loved them for some reason, though their inside cylinders must have made maintenance rather difficult; even outside-cylindered six- wheelers were not all that popular in other countries. In the British Isles, they were built from the dawn of steam era till almost its very end when O.V.S.Bulleid, the Chief Engineer of the Southern Railway, was still designing these useful locos. It must have seemed like heresy when, during World War II, England had to accept outside-cylindered 0-6-0s from the U.S. War Department, the last six-wheeler design to run in that proud island. It is no surprise that locomotive engineers in the Raj - expatriate Britons, to a man - were specifying and buying 0-6-0s that could be mistaken for those running on lines in the mother-country. These old 0-6-0s lasted till the very end of steam traction in what became Pakistan and almost as equally long in India. They were maids-of-all-work that used to haul even prestigious mail trains in the early part of the 20th century.
The broad gauge 0-6-0 was one of the 2 standard types of locomotive in 1903 by the Engineering Standards Committee, the other type being the 4-4-0. The latter was based on a class which was already giving good performance in India. The 0-6-0 was for goods traffic and was designed with so that its boiler, cylinders, motion, rods, axles, axle-box guides, springs, etc., were identical with those of the 4-4-0, as far as possible. Both classes were to have slide valves and inside cylinders powered by saturated steam. The standards allowed for future increases in boiler size.
The first 0-6-0 designed to the new BESA standards was the SG Class which was built between 1905-13. It proved to be a useful and efficient and was built in large numbers. It was able to haul 1450 ton goods trains at 16-18 mph. With 61.5 inch drivers they often hauled troop trains at 30 mph hauling 25-30 cars. The 61.5" drivers were so sized as to be able to accept pre-existing tires. Its light axle load enabled it to run over all NWR lines. The SG Class also served on Eastern Bengal Railway lines.
SGC Class : (photo courtesy: L.T.Cerny) After 1927, some members of the SG class received superheaters and were called the SGC Class by the NWR. Another variant was the SGC3 on the EIR which had both superheating and Lentz rotary valve gear -- probably the only inside-cylindered engine in the world ever to use that valve gear!
SGS Class of the NWR was an SG Class variant that had 20" x 26" cylinders with piston valves, superheating and a 56 1/4" diameter boiler. The final SGS specimens built had 61.25" diameter boilers and 8 wheel double bogie tenders. The SGSC had round fireboxes unlike the Belpaire fireboxes of the SGS. Somewhat confusingly, the SGSC was later renamed SGC2. All of these highly similar engines were also frequently used to haul passenger and mail trains -- as evidenced by this pre-dawn photograph of the Frontier Mail taken during the early 1920s.
Owning Railways: NWR, EBR, EIR, ORR (collectively known as
Indian State Railways)
Builders: Vulcan Foundry, North British Locomotive Company, Robert Stephenson & Hawthorns
Numbers built (approx.): 486 SG, 362 SGS, 66 SG1
DIMENSIONS (SG Class)
Cylinders: (2) 18.5 x 26, 61.5" drivers
Boiler: 180 psig pressure, Grate Area: 25.3 sq.ft, 4'6" x 11' long boiler, 236 tubes of 1.75" dia., Heating surfaces (sq.ft): 1229.5 (tubes)+ 120 (firebox) + 25.3
Wheelbase: 15'3", 3000 gal/7.5 ton tender, 48 ton engine + 39.25 ton tender
Axle load: 16 tons
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