The surface plant and the underground pumps near the pit shaft were almost exclusively powered by d.c. motors, which were however slightly less ancient than some I had seen at Chanters Colliery. There had been a power station including turbo-generators, but these had long gone when I arrived, and the source of d.c. power was a large motor convertor, which had been purchased second-hand from the Manchester Corporation Traction Dept. It was another Edwardian electrical oddity which in general worked well. It had idiosyncrasies in that when it had been shut down for a few days it would start up sometimes with the positive and negative polarities reversed. This only happened occasionally, but the only way we ever found to put this right was to jab a car battery onto the field coils just prior to starting up, this would usually do the trick.
The motor convertor obtained its power from the adjacent Stuart Street power station at 6 k.V 3-phase. Eventually the d.c. drives were reduced to one d.c. motor driving a large pump. This pump derived its power from a mercury-arc rectifier, the motor convertor having long been scrapped.
There was one big electric drive which is worthy of mention, rated at 600 b.h.p. on a 500 v. d.c. supply. It was located at the bottom of No.1 pit, and used to haul 10 tons of coal at a time up an incline of 1 in 3 over a distance of 1 mile at a fast rate.
On this steep incline, known as the "South Dip" there were normally 2 trains of 22 tubs each at any one time, such that the one set of empty tubs was lowered as one set of full tubs was hauled up the incline. This arrangement operated for 2 shifts per day.
Bottom of No2 Pit with shunting loco and Mine car tippler
One afternoon the driver was about to land a heavily laden train at the top of the incline, when he had to stop for some reason, he brought the machine to a halt and applied the brakes. After a few moments he noticed that the train of tubs was beginning to creep backwards. He screwed the hand-wheel of the brake downwards but this too failed to hold. He wound the brake handle to and fro several times, and became so confused that in the end he didn't know whether he was applying the brake or taking it off, he then panicked. The train was now running away down the incline at ever increasing speed.
When the motor was running at about three time its normal speed the driver felt that his only hope was to apply electric power in the reverse direction.
The resulting electrical explosion sounded the death-knell for the d.c. system at Bradford Colliery, the haulage motor was damaged beyond repair and was scrapped. The replacement motor was an a.c. 3-phase type running at 2 kV, and took about 3 weeks to fit.
One of the geological problems at Bradford Colliery was the steepness of the coal measures which were about 1 in 3 of a south-sloping gradient. This tunnel, known as the South Dip, sloped downwards from near the pit bottom for a distance of well over a mile, and over the years, because of ground movement, this tunnel was little more than 4ft. high. At the end of each shift a "man train" was hooked on to the haulage system to wind men up and down at shift change, but between shifts the climb and the descent were very tedious and certainly kept one fit. It was difficult to keep one's feet when going downhill.
Over the decades, however, a device had been developed which could be made as a favour in the carpenter's shop and was known as a "Horse". It consisted of a piece of hardwood about 5ins. square, and about three quarters of an inch thick, rivetted to a piece of steel channel which fitted snugly onto the tub rail (where the coal tubs ran). You needed two rails about 2ft. apart which happened to apply through British coal mines
You put the Horse onto the tub rail and you put your left haunch on it, you then put your left instep about 2ft. in front of you, and your right instep on the adjacent rail to your right, ------ and slid. It took a bit of practice because you could slide very fast, and you were meant to brake by pulling your left foot towards you. I don't think this practice would have been allowed by the Coal Mines Act if they had known about it. It would only work on these steep gradients, and it had the disadvantage that it wouldn't come uphill.
With a bit of practice it worked fine and the old hands could slide on a brick or even a spanner, but I understand that the latter could get a bit hot.
The idea was the No.2 shaft would be used for raising coal in the future, and that a metal skip capable of holding 12 tons of coal would be used. The two skips, one full, one empty, would be connected by a locked-coil winding rope, passing round a Koepe wheel instead of a conventional drum (the German influence). Two d.c. motors at 2,000 h.p. each were used to drive this Koepe wheel, and would be supplied with power at 1,000 volts derived from a large motor generator set located in a power station about 800 yards away. The two generators were rated at 2,000 h.p. each and driven by a motor rated at 3,100 kW.
Bradford Colliery Truck From Truck Netuk.com
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