XB Class

Tintin was seen riding; rather driving; the Pacific 4-6-2 locomotive in “Tintin in America”. His next adventure took him across the globe to the Egypt, the Middle East and India in the “Cigars of the Pharaoh”. Tintin had to take a flight to escape being shot by Colonel Fuad in the Middle East where he had been convicted as a spy to be shot by the firing squad. He escaped in a aeroplane which crashed in India. Here the villains had him declared a mad man to be confined to an asylum. Again, he escaped by boarding a train. The locomotive which was pulling this train resembles closes to the XB class locomotive of the Indian Railways.

The XB class was a broad gauge – 5′ 6″ (1,676 mm) – light passenger 4-6-2 steam locomotive used by the Indian Railways. These were an iteration of the 4-6-2 Pacific design. These locomotives were built by a number of British manufacturers like; Vulcan Foundry, Armstrong Whitworth, North British Locomotive Company etc. A total of 99 XB Class locomotives were introduced into the Indian Railways between 1927 and 1936. These locomotives were built as per the British Engineering Standard Association (BEAS) standards but had a mix of British and American design.

These locomotives had a wheelbase of 13′ 2” (4,013 mm) and an axle load of 17 tons. The driver wheel had a diameter of 6′ 2″ (1,880 mm) while the leading wheels were 3′ (914 mm) in diameter and the trailing wheels were 3′ 7″ (1,092 mm) in diameter. These locomotives could carry 10 tons of coal and 18,000 litres of water. Their boilers generated steam at 180 psi (12.41 bar). They had super-heaters to improve engine efficiency and two cylinders with bore x stroke of 21.5″ x 28″ (546 mm x 711 mm) to generate the motive power. The XB class was designed for a maximum speed of 72 mph (116 km/h) and a Tractive effort of 26,760 lb-ft (119.03 KN).

They had incorporated 3-point suspension from America. As with all other British locomotives of the time, the trailing wheels were mounted on Cartazzi trucks. To facilitate free movement between the engine and the tender, Goodall-type draw-gear was installed. All these three components had design flaws which made the XB Class unduly susceptible to track irregularities. This problem led to increasing number of derailments of these locomotives. The worst accident was a derailment in Bihita in Bihar state in 1937 which led to a 100 fatalities. Thereafter these locomotives were limited to a top speed of 45 mph (72 km/h). The XB Class were prone to frequent other failures like, frame fractures, coupling rod failure, boiler tube cracking etc.

After the accident a committee was formed which came up with a solution which included fitting stiffer leading and trailing bogies with better damping. This solution was successful in overcoming the design issues faced by the locomotive. These locomotives were thereafter successfully operated by the Indian and Pakistan Railways for 46 years. The last of the XB Class locomotive was retired from service in 1983.