THE SUCCESSFUL B CLASS SADDLE TANK AND OTHER DHR LOCOMOTIVES
Only a few locomotives types were used on the DHR. The initial locos were 8 ton designs ordered fron Sharp Stewart in 1881. These were too small and weak to tackle the job of climbing 7000 feet in 50 miles and were soon sold off to other places within a few years. Then came the A class 0-4-0 10 ton locos with a wheel base of 4ft 6in ordered from 1885. These required some enhancements in the form of saddle tank water storage and coal bunkers in front of the cab to do their job (with these modifications the A class looked like a small B class loco). they could pull 25 tons up the hill. One of these survived till 1952.
By the late 1880s it was evident that more motive power was needed for the job and Sharp Stewart obliged with the B class loco which was built in batches from 1888 to 1927. The design was a simple 0-4-0 ST with wheelbase of 5ft 6in which could negotiate the 50ft radius curves of the line. Engine weight varied from 13.5 tons in 1889 (engine no 779 still running today!) to 15.5 tons (802, 804 etc 1927). These locos could pull a train of 45-50 tons up the hill.
A Beyer -Garratt loco was ordered in 1910 0-4-0, 0-4-0 with wheel base of 4ft 6 in. It wasnt a success on the DHR probably because it was an early prototype. Steam joints kept breaking down, maintenance was complex and coal consumption was double the B class though pulling power was only 50% more. It was roundly condemned by the DHR management and banished to the plains section of the DHR! No garratts were ever ordered again and the solitary example was scrapped in 1954.
Finally the plains section of the DHR from Siliguri to Kishenganj had three fine 4-6-2 pacific tender locos built by NBL in 1914. These were called the C class and were probably the worlds smallest pacifics then! One of these probably still survives at Gauhati in Assam.
Therefore the DHR is synonymous with "B" class locos. The design was so good that it has endured for more than a hundred years. It suited perfectly the unique needs of the railway in terms of size, wheelbase, pulling power, low maintenance and trouble free operation. These attributes enables them to survive until today in active service with the relatively low tech maintenance facilities at Tindharia. Spare parts havent been available for 50 years but the locos have kept going by improvisation and the loving care of the DHR staff at Tindharia works.
It is still an experience like no other narrow gauge steam railway when you travel on the DHR. For the first 18 km in the plains from New Jalpaiguri to Sukna the train goes at a gentle 16-20 km per hour and you hardly hear the engine puff along. As soon as Sukna station is passed the train begins to climb and the tiny engine is transformed into a big hearted one! The engineer opens the regulator to 85%-100% of the 160psi boiler pressure! As a result the smoke rises vertically from the chimney and the sound of the pistons becomes a tremendous hammering as if the loco was suddenly ten times bigger. Believe me none of the steam engines in restored UK steam railways sounds that wonderful! The DHR operates entirely by adhesion and goes at a max of 16 km per hour uphill. The slowness of the journey and the loud piston thrashing do not permit much conversation in the coaches but the fabulous views more than compensate. To date the mechanical components are kept in first class order because anything less than that would not permit the successful working of trains.
The success of the old B class has left modern diesels limp. Recent trials of a standard ng diesel failed because it couldnt negotiate the tight curves. More learned friends suggest that for very narrow gauges diesels develop less tractive power than steamers. Long may the B class live and I will look forward to the day when brand new ones with new boiler technology will run on the line.
