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July, 1947

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For the benefit of senior N.C.B. officials of all areas of the Northern Division, demonstration running of the new Hunslet 100 b.h.p. six-wheel diesel locomotive at Blackhall colliery took place over a special surface test track at that pit on May 8 and 9.

This particular locomotive is intended for the haulage of man-riding trains over gradients as steep as 1 in 17, in the region of a down throw fault. The test track was laid out with gradients of 1 in 35 and 1 in 15. Though this 15-ton locomotive can operate over rails weighing 35 lb. a yard, or 28 lb. under exceptional circumstances, the Blackhall rails were considerably heavier than this, and were not the type normally found underground. The test train was made up of new man-riding cars with a nominal seating capacity of 24 each, and which, like the locomotive, were fitted with Westinghouse air brakes.

Underground, the locomotive is to haul trains carrying 192 men, and at speeds up to 15 m.p.h. on level and favourable sections. The special underground man-riding track of 2 ft. 8½ in. gauge, about 1,800 yards long, at Blackhall, has a general grade of 1 in 30, and over this two Hunslet 50 b.h.p. diesel locomotives have been working trains carrying 150 to 180 men successfully for three years, but not as yet over the 1 in 17 grade, which is in a new extension. Speaking of these smaller locomotives, Mr. E. Chicken, the Blackhall manager, has said:

"I installed two diesels at Blackhall Colliery and, after 18 months running over a straight road one mile in length with an average gradient of 1 in 30 and a maximum gradient of 1 in 22 and carrying 168 men (sometimes 180) in seven cars, I am delighted with the results. The cost of spare parts has only amounted to a few shillings and I get approximately 8 miles to the gallon of fuel. The gauge of 2 ft. 8½ in. seems rather unusual, but it was fixed from the existing gauge at Horden; 40 lb. rail section is used with 4 ft. 6 in. X 7 in. X 4 in. sleepers every 3 ft., but no sleepers are used under rail joints. Special cars are used; brakes are tried regularly and the train can stop within the length of the locomotive. All told, I can report 12,000 miles of successful running. The curve shunting is of 60 ft. radius. In three months time I hope to extend the mile travel by a further 900 yards. The CO content from the exhaust never exceeded 0.05 per cent., the flame trap being brought to bank every day and the intake trap once a month. I can confidently recommend the use of diesel locomotives underground."

On test the 100 b.h.p. locomotives have shown a steady drawbar pull of over 8,000 lb. on starting in first gear, which is sufficient to start a 32-ton trailing load on a 1 in 15 gradient. However, of greater interest at Blackhall is the ability to climb a 1 in 17 gradient at over 6 m.p.h. in second gear with the present train and 192 men, and the main reason for the installation is to get the higher speeds uphill with the same load of men hitherto hauled by the four-wheel locomotives.

Four gear steps are available on this locomotive, corresponding to track speeds of 4, 6¼, 9½ and 14½ m.p.h., with top engine revs.; and the demonstration runs showed the ease with which the locomotive climbed the 1 in 15 grade in third gear, starting the grade at 8 m.p.h. and surmounting it without speed, falling below 7 m.p.h. The accompanying graph shows the speed-tractive effort curves, and gives an indication of the great hauling capacity when this type of locomotive is used for coal trains.

Braking downhill was remarkably effective. Descending the 1 in 15 grade at a speed of 8½ to 9 m.p.h., the air brakes pulled up the train in a distance of 22 to 26 ft., with a normal full application, that is, without the automatic sand delivery feature of an emergency application. On the level, a distance of only 45 to 50 ft. is needed to pull up from 15 m.p.h. With air-braked man-riding cars the weight of train does not measurably affect the stopping distance. Braking performances of the above orders were obtained repeatedly, but with locomotive and cars in a new condition. After working underground for some time, and with equipment bedded-down and a good standard of adjustment, the general performance probably would be 5 or 8 per cent, better than these values. Manual braking tests from speed were not undertaken, but the hand screw brake on the locomotive could hold the complete train at rest on the 1 in 15 test track.

There was detailed examination of the locomotive by the visitors to check how it would meet underground track and working conditions. In particular, there was close investigations as to the way the locomotive would run over badly aligned track. The advantages of the compact construction, with a length of 14 ft. 3 in. over buffer beams, were evident for the vertical curves present on the test track, and the special coupling allowed extra movement in a vertical or horizontal plane. These features are becoming increasingly important with the spread of diesel locomotive haulage to tracks and levels not specially laid out for them; and the consensus of opinion at Blackhall was that all the requirements had been fully covered in this locomotive.

Commendation also was given to the compact arrangement of the Westinghouse air brake equipment. The main and auxiliary reservoirs, triple valve, piping and other details are arranged above the gearbox, just in front of the driving position. After loosening four pipe connections and a few holding down studs, the whole of this equipment and its containing framework can be lifted off en bloc.

A full information service as to capacities, limitations, spares, inspection and maintenance schedules, driving instructions, and methods of lowering down shafts, was available throughout the two days of the demonstration, and opportunity was taken to give guidance to the Blackhall drivers and fitters in the differences between this locomotive and the 50 b.h.p. size which they have handled hitherto.

Drawings and Photographs accompanying the article