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CHAPTER FOUR
1945 - 1965 The Development of Mechanisation
Contents
The Repeal of the Essential Work Order 1941 - Experiments in Mechanisation - The Eimco Compressed-Air Rocker-Shovel - The Robbing of Pillars - Buccleuch Quarry Closes - The Introduction of Swedish Concentrates
The Repeal of the Essential Work Order 1941
The end of the war brought with it the inevitable lifting of the
Essential Work Order,
and with it the realisation by the Company
that many optants would eventually wish to return to their peacetime jobs, leaving around half of the former labour force to load ironstone at the face.
In addition, the hardened miners were ageing, and
few young men were coming forward to take their place. The era of the traditional ‘navvy’ type miner
was dwindling fast, and as early as the autumn of 1944 the Company had begun to
investigate ways of maintaining production with fewer men.
This could only be achieved by developing
some form of mechanical loading of the ore, as suggested by Professor Henry
Louis many years previously.
Unfortunately, however, the amount of ore ‘got’ at the face in one operation by
the present methods would not warrant the cost of introducing mechanical
loaders.
Tunnels wider than 13 feet (4 m.), which could provide a greater tonnage, were not considered advisable in view of the
need to keep a safe roof span; the alternative was to drill more holes in one
operation, and to drill deeper than the usual 4‘6", (1.37 m.) which would achieve a
greater tonnage at each firing.
‘
Experiments in Mechanisation
On Monday, 30 October 1944, three new tunnels
were developed near Chapman‘s Corner, (fig 1)
away from the normal working districts. Here drilling experiments were carried out during 1945.
It would be nearly two years, however, before the procedures for a mechanical system were established and finally put into
practice; during that time 25 experimental rounds had been fired.
The first attempts at a revised drilling
pattern used the hand-held electric drills already employed by the normal face
workers, but they were very soon found to be unsuitable on two counts.
Firstly, they could not stand up to the strain of continuous, and deeper, drilling; they were constantly ‘burning out’,
requiring a costly rewinding of the armatures.
Secondly, the men could not stand the physical strain of continuous
drilling throughout the whole shift.
The Company proposed, therefore, to experiment with the use of one of the nine old
Blackett drilling rigs which had been bought in 1920; it was brought to the
surface, for overhaul, before being used to assist in future drilling.
During the closing days of 1944 it was fitted with an A.C. motor to replace the existing power source.
These machines, originally driven by D.C. electric motors, powered from batteries towed behind, had been produced by
Blackett Hutton of Guisborough for the Cleveland mines, but due to their size they were found to be too cumbersome for the
pillar and stall workings there, and went out of use.
At Irthlingborough, too, that model had gone out of use, for the reasons given in Chapter Two, but owing to the persistence
of Mr. Andrew Turnbull, the Undermanager, who orchestrated the introduction of
mechanisation at Irthlingborough, they were now modified and given a further
lease of life. (They were still in use when the mine closed in 1965 and it is
interesting to note that the scrap merchant who eventually bought them has said that
he later sold them on to a mine, but did not have a record of their destination).
Representatives from Messrs. Gibbs & Gibbon, experts in explosives, were brought in to
experiment and advise on the type and amount of dynamite to use;
by December 1944 they had fired 4 complete rounds.
The first two rounds of ‘bulk’ firing, each now using 12 to 14 holes, yielded 18¾ tons and
28½ tons of ore respectively, but the drilling had taken rather longer than expected.
In March 1945 the Company decided to purchase 19 Consolidated No. 3b ‘Little
Giant’ hand drills, to supplement the existing 15 Black & Decker and Wolf hand
drills.
These new machines were more durable, and were used to drill the ‘box-cut‘, a square pattern of four holes
drilled in the middle of the face about 4‘ 6" (1.37 m.) apart, and drilled to taper inwards
towards each other to form a wedge.
When detonating the round these four would be fired first to produce a cavity.
The remaining eight or nine holes would be
drilled around them using the Blackett drill.
This system was soon discontinued, however, with the Blackett now being
used to drill the whole face with a standardised pattern of 12 holes.
By April the amount of ore ‘got’ in one round
had been well established at 30 tons, enough to justify the introduction of a
mechanical loader.
The holes were drilled to a depth of 7‘ 6" (2.29 m.) for the ‘box-cut’ and 6‘ 6" (1.98 m.) for the remaining eight
holes of the round, giving an advance of the tunnel of 6 feet (1.83 m.) at each firing. Even as late as the autumn
of 1947 the firing sequence had not been finally established.
In a Paper given by the Mine Agent, Mr. W.E. Davies, to a Meeting of the
Institute of Mining and Metallurgy on the 8 January 1948 he described the
procedure as follows:-
Soon after this, or perhaps even before the
Paper was read, and on the recommendation of the explosives experts, the need
for the shot-firer to re-enter the heading to charge and fire the five
remaining upper holes in the old manner, using blue sump-fuse, was abandoned; this
had entailed the miner entering a fume-laden and smoky atmosphere and climbing
the heap of already fallen stone to carry out his task. It was much simpler, although a little more
costly, to charge and fire these upper holes, using a further delay, at the
time of the initial blast.
Later on, however, the miners found that, due to the extra cost to themselves of the electrical
delayed-action detonators, it was just as effective, and cheaper, to put 4‘ 6"
(1.37 m.) holes in the top of the seam, charge them and light them using the sump-fuse,
then to leave the heading quickly so that they could fire the rest of the round,
using a Schaffler exploder, before the top holes detonated.
Later, each team was supplied with a Beethoven Multi-Shot Exploder, considered to be an improvement.
The explosive used in the early years was
Nobel‘s Explosive 704, ammonium nitrate TNT type, packed in cartridges 1¼ "
(3.18 cm.) diameter by 4" (10.16 cms.) long, and weighing 8 oz. (0.23 kg.)
By using 13 lbs. (5.9 kg.) of dynamite for each round the approximate cost was 5d
(2 p.) per ton.
One of the problems with bulk firing was the density of fumes produced.
In December 1946, and again in March 1947, fume tests were carried out,
and it was confirmed that 704 was the best type of explosive to use in this
situation.
Because the daily weight of explosives was
now of the order of 40 lbs. (18.14 kg.) for each team, the shot-firer could not be expected
to carry that weight from the Steps Entrance to the working faces; it was therefore
conveyed from Irthlingborough Works in boxes loaded into empty wagons or placed
on the loco. It was not unusual for
maintenance workers and surveyors, wishing to gain easy access to the working faces,
to sit on these boxes with sparks falling around their ears from above as the
collecting pole of the loco passed through the overhead hangers.
This procedure was eventually discontinued, perhaps at the instigation of the Mines
Inspector, and a special enclosed wagon was
built, with lockable sliding doors, for this purpose.
Eventually the explosives magazine at Finedon
was closed and the, by now redundant, A.R.P. post above the Irthlingborough adit was converted to
this use in February 1953.
A further consideration, in 1945, was the number of tunnels to be driven concurrently,
based on the number of ‘working places’ which could be drilled in one shift. The Weekly Report of 30th. April of that year
confirms the management‘s thinking at that time.
By May 1945 two Blacketts were in use, each
operated by two men.
The Company considered that it took about a
month for a worker to become proficient in the use of this machine. The ore was being loaded away
by hand, there being no mechanical loader in the mine at this time.
By early December, however, things were progressing satisfactorily, and on 21 December 1945 the first
three
‘Eimco’
mechanical loaders were delivered.
Because the loaders were not suitable for working on bends, the old ‘pillar and stall’
layout (see Chapter Two, figure 1) was redesigned with tunnels on 60 foot
(18.29 m.) centres, 13 feet wide (3.96 m.), intersected by 9 feet (2.74 m.) wide crosscuts, at intervals of
370 feet (112.78 m.), made for ventilation purposes (fig.2).
Because the distance between crosscuts would
be quite long, refuge holes were dug into the side of the tunnels to protect
the shot-firer when exploding the round; as it happened, this was only done in
three tunnels before the procedure was abandoned and the crosscuts were
standardised at 220 feet (67.06 m.) apart.
It was also decided, at this time, to drive eight tunnels for each Blackett/loader
team, rather than the six originally suggested.
When designing the number of holes and their layout, and the amount of
explosives to be used in each face, consideration was given to the fragmentation and
‘throw’ of the ore.
It was important that the ore should be of a size which could be handled by the mechanical loader, and
that it was not thrown too far from the face. Figure 3 shows a good example of a
satisfactory round where 46 tons has been ‘pulled down’.
The considerable amount of ‘fines’ produced was now no longer a problem as these could be accepted by
the Sinter Plant.
With the final decision made on the pattern of holes (fig. 4), each team was
supplied with a template made of conduit steel tubing; its guide arms gave the correct angular
alignment of the holes. These were not used
for long, however; after a short time the drillers found that they could place
their holes without the aid of this rather cumbersome device.
In any case, as it was found later,
where the thickness of workable iron ore varied, some change in the number and placing
of holes had often to be made.
Mr. W.E. Davies, in his Paper issued on the 8 January 1948, and mentioned
above, gave the following reasons for the finally-adopted length of tunnels
between crosscuts:-
Before the new loaders could be put to use
a compressor had to be installed (fig. 6) as near
to the working faces as
possible, along with all its associated electrical wiring, switch gear and pipe work.
For this, the Company chose
Ingersoll Rand
compressors, each producing 284 cubic feet (8 cu m.) per minute at 100 p.s.i., (689,475 Pa.) driven by a
Metrovickers
motor supplied with electricity at 3,300 volts.
This should have been capable of serving two
loaders, although men using the machine complained that this was not so, and,
if both loaders were working flat out and lifting stone at the same time, one
of the buckets was likely to drop, a
distinctly hazardous occurrence.
The compressor was air-cooled by a fan suspended from the roof.
The pipes, which were of the 4 inch (10.16 cms.), 12 feet (3.66 m.) long Carlton type, were laid as near to each working face as possible.
To allow the loader,
which normally ran on the 3 foot (0.91 m.) gauge track, to move forward into the heap, a telescopic device
was constructed in the workshops (fig. 7).
On this, the machine could run in the grooves of extra rails laid on their sides.
After a tunnel had advanced two rounds (12
feet (3.66 m.)) the road-man would lay two further sets of 35 lb. (15.88 kg.) rail and add another 12
foot (3.66 m.) length of compressor pipe.
It was soon realised that the loader was only able to fill the wagons to a capacity of
2 tons 18 cwt. (2.95 tonnes), after which, to secure the required tonnage, the operator had
to stop and add large rocks manually, as the hand miners would do.
This was time-consuming, and compromised the
efficiency of the loader.
In January 1946 an experiment was carried out in which a wagon‘s sides were modified by
welding ¼ inch (0.64 cms.) metal plate, 9 inches (2.29cms.) deep, to their top edges.
It was found that this allowed the operator
to fill the wagon to a capacity of 3tons 10 cwt. (3.56 tonnes) without the need to stop and hand fill; a proportion of the fleet of
wagons was then modified in this manner, and the tipplers at the surface were adapted
to accommodate the conversion.
The Eimco Compressed-Air Rocker-Shovel
The first three Eimco rail-mounted compressed-air rocker-shovels (fig. 8), produced in Salt Lake City, in the U.S.A., arrived in December 1945. They were accompanied by a Demonstrator from the Ingersoll Rand Company who stayed for
ten working days to give the miners tuition in the use of the machine. The
operator stood on the footplate and the Shovel was operated by two
levers.
One rocked the bucket, digging it into the heap of stone which was thrown over the machine into a wagon behind; another
propelled the machine backwards and forwards along the rails.
The bucket could be swung from side to side manually to reach stone on either side of the 3 foot (0.91 m.) gauge track
on which it ran.
This
silent video
(although not filmed at Irthlingborough) gives a good idea of its operation.
Unfortunately, being silent, it gives no idea of the accompanying din; note that the operator is not wearing ear protectors,
as was also the case at Irthlingborough.
No doubt today this would not be allowed, if only to ensure that the Management
were not sued for loss of hearing in later life.
In February 1947 a further two rocker-shovels
were delivered by rail, followed eventually by five more.
They proved to be extremely robust machines and,
with very little maintenance, were in continual use until the closure of the
mine, when nine of the ten machines purchased were found to be in working order.
(It was reported
that in December 1946 the first machine, which had been put to work on production in February that year, had loaded, during
that time, approximately 30,000 tons (30,481 tonnes) of ore, requiring no replacements of parts or
major repairs, and showing no signs of deterioration).
By the end of January 1946 three men
had become proficient in operating the machine, and it was planned to compose three
individual teams, each responsible for a particular set of eight tunnels.
The arrangement for each team of six men, which became
standard for many years, was as follows :-
Two drillers, operating the Blackett drill, who could drill 2 or 3 faces in a shift
(fig. 9). One shot-firer, who would be responsible for placing and igniting the explosives
(fig. 10).
One loader-operator, assisted by a
hose-boy who would hold the flexible hose clear
of obstacles (fig. 11).
One road-man, who would advance rails and compressor pipes as the tunnels advanced
(fig. 12).
The shot-firer placed the explosives into
each hole with a wooden stemming rod and tamped them in with clay ‘pug’
sausages made from the drillings.
He was the only man who was required to be a qualified miner; the hose-boy could be a young
school leaver on his first job, while the road-man might
be an older worker no longer able to stand up to the rigours of hand-mining.
In addition to this team there were many men
acting in support. A tractor driver
kept the loader-operator supplied with empty wagons and hauled the loaded ones to
sidings ‘out-bye’.
There were electricians extending cables as the tunnels advanced, fitters regularly servicing the
compressors and blacksmiths at the surface sharpening drills (fig. 13).
With very few modifications, except for detailed adjustments to working practices as conditions
in the mine dictated, the mechanical operations continued until September 1965 when the mine was closed temporarily and put on a ‘care and maintenance’ basis. It was, in fact, never to open again.
At some time during the period from 1946 to
1965 several of the Eimcos were modified by welding a strengthening rib to the
bucket (fig. 14), when it was
found that the weight of the iron ore was causing
it to buckle .
I.C.I. often produced modified 704 type explosives, and constantly carried out fume tests in an attempt to reduce the
noxious effects of bulk firing.
Once a viable system had been formulated it became essential to adjust the rates of pay for the
‘mechanical’ teams, taking into consideration the greater tonnage that could now
be produced. Tests on the potential output were carried out in early 1946 when there were sufficient men with
proficiency in each operation.
In order to keep the amount paid to the mechanical teams comparable to that earned by the hand miners, their rate of
pay per ton was reduced.
Considerable interest in the new mechanical system was shown by the media, and as early as 11 December 1946 the local Evening Telegraph published an article entitled
"Robots Brought in to Speed our Constant
Drive for Iron". In the national pictorial magazine, "The Picture Post", there appeared an
article in June 1948 asking "Can We Save Our Iron Mines ?".
On the BBC Third Programme, in the spring of
1951, David Keir spoke of his journey into the underground mines of
Irthlingborough in a programme entitled "The Bright Dark", in which he showed great
interest in the employment of foreign workers; this will be the subject of
Chapter Five.
At the same time mining engineers and students were among the many groups invited to tour the mines and
see the new machines in operation for the first time in Britain.
The Robbing of Pillars
By Hand-Mining
In parallel with the mechanical
loading of ore, hand-miners were still employed in producing an
equivalent tonnage
by ‘robbing’ pillars
left after previous ‘first-working’.
It was the constant concern of the management that too large an area of iron ore was being left unextracted in pillars, and
mechanical mining made this problem much worse.
‘Robbing’ was carried out by driving secondary tunnels into the existing
pillars, and then working backwards removing as much as possible of one wall
(the rib) of each tunnel, at the same time supporting the roof as necessary
with a ‘forest’ of props (fig. 15) and leaving mere 9 foot (2.7 m.) square pillars.
The props were subsequently withdrawn remotely, using a
‘Sylvester’
tool (fig. 16), whereupon
the roof would collapse, resulting in subsidence at the surface.
By Mechanical Mining
It was at first considered that the robbing of the mechanically mined districts should only be carried out
by experienced hand-miners, as it was not advisable to use mechanical loaders
where the noise would prevent the men from hearing any roof movement.
In the quieter environment of hand-mining, the distinct warning sound of ‘squeezing’ could be heard from the wooden ‘capping
pieces’ wedged in the top of the pit props.
Later, (fig. 17) however, a system of secondary working of the mechanical
districts was devised whereby tunnels were driven between, and parallel with,
the existing ones and then, finally, further tunnels were driven across at an
angle of 45º, thereby extracting as much ore as possible.
Although by this method less ore could be extracted from a given area than by
hand-mining (where extraction rates were of
the order of 92%), mechanical mining, nevertheless, produced overall a greater
output.
During the period from 1945 to 1965 tonnages increased from year to year with a much slimmer labour force. In October 1943 the output had been 29,458 tons with a total labour force of 530, compared with 37,707 tons in October 1958, when manpower stood at 322, now resulting in more than double the output per man employed.
Buccleuch Quarry Closes
Buccleuch Quarry ceased production in May 1946 and in 1948 the 4140
Ransomes & Rapier
face shovel was dismantled by six employees from Ebbw Vale for transport
to another site; it may well have been destined for either the Trefil or Ystrad limestone quarries in South Wales.
In any event it was loaded into railway wagons towards the end of July for transport to Wales.
The 5360 Ransomes & Rapier stripper, however, stood in the open ‘end gullet’ for many years (fig. 18) until,
in 1954, it was dismantled and transported by rail to Blisworth (fig. 19),
where the Company
was in the process of re-opening an iron ore quarry.
This ore was destined for the Company‘s
Redbourn Steel Works at Scunthorpe.
Buccleuch Quarry had produced over 2 million tons in seven years. When the Irthlingborough mine closed its portals in September 1965 a total of 10,056,106 tons (10,217,507 tonnes) had been extracted from its underground workings.
The Introduction of Swedish Concentrates
In June 1950 the Company began to import high grade ore (Swedish Concentrates) from
Kiruna,
in Swedish Lapland, with an iron content of over 60%.
This would arrive in Irthlingborough after a four day, 3,000 mile (4828 km.) journey to Britain during the summer months, when the Arctic seaport of Narvik was open.
It was deposited in heaps at Irthlingborough (fig. 20) and used to add to the burden in the Sinter Plant in an effort to improve the quality of the sintered ore.
In early 1954 concentrates from Kiruna were no longer available so an alternative supply from the Sydvaranger mine in northern Norway was considered.
This material was much finer in texture so experiments were carried out at the British Iron & Steel Federation’s Station at Redcar. Eventually in July 1954 tests were carried out at
Irthlingborough which proved to be satisfactory and this material was used thereafter.
It must have already occurred to the Company that it was uneconomical to bring this material so far inland, rather than to
use it in steel works nearer the coast.
It was ultimately, however, the exorbitant cost of converting the comparatively
low grade Northamptonshire ore to iron, during the mid 1960‘s oil crisis, that was to
deal the final blow to an industry which had started in Irthlingborough with
such high expectations half a century before.
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