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S headstock c1890 -s02

 South headstock  circa 1888  (JST)

N headstock c1890 -s

 North headstock  circa 1888  (JST)

The early headstocks at both shafts were pitch-pine and wrought iron structures with the raking legs (back-stays) resting on corbel stones built into the end walls of the engine houses.  The original corbel stones of the South pit headstock can still be seen and those of the North pit are believed to be still in-situ below the present pit-top surface level.

DSC01241a -s

 Dismantling the old North pit wooden headstock   May 25th 1901 (JST)

 Corbel stones for the old South pit wooden headstock thrust-legs

 South pit corbel stones for the old wooden headstock raking-legs

These headstocks were erected in 1877-78.  The front legs were cast iron columns fastened to pitch-pine main legs by a wrought-iron lattice-frames, nearly semi-circular in shape, and two cross-girders fastened to theses frames carried the detaching plates.   The main legs were 16 inches square at the bottom and tapered to 12 inches square at the top, the height was 60 feet and the difference in width being only 7 feet less at the top made them appear to be nearly vertical.  The back legs were also made of pitch-pine, 18 inches square at the bottom, tapering to 12 inches square at the top and were placed parallel.  Shoes resting on large stones in the wall of the engine-house received the lower ends with two cast-iron columns supporting the middle of the legs.

Originally, the North (downcast) shaft was the only coal winding shaft and was arranged to allow simultaneous decking at two levels. In 1888, in order to increase the output, the South shaft was fitted up with cages, initally two deck and later three deck.  The winder and cages were on a smaller scale than those at the North pit and sequential decking was operated. The headstock was partially enclosed but had no air casing. A nearby  building may have been the weigh-cabin.

pleasley-1899-25in-detail#5a

 North heapstead circa 1898

south pit-top 1899

 South heapstead circa 1898

The South pit was the upcast shaft and the top  was closed by two wooden “bonnets” with padded leather seats. These were raised and lowered by the cages. This method was commonly used in the 1800s at collieries where there were only two winding shafts although it was usually preferred not to wind coal at the upcast.

The early types just had a heavy wooden or iron lid which was raised by the cage, but the weight of the lid plus the air pressure on it created constant shock loading of the winding rope and gave rise to rapid damage.    In addition, a serious leakage of air occurred whilst the cage was  coming to decking level.

An improved version designed by Mr Galloway at the Llanbradach Colliery utilised a modified cover assembly. A wooden cone with its top diameter large enough for the detaching hook to pass through sat over a larger hole in the wooden lid.  The top of the cone was covered by a flat disc which allowed only the rope to pass through it.  For some distance below the surface the shaft was divided by wooden partitions into two chambers, each only slightly larger than the cage.

DSC01280a -s

 Improved upcast shaft closure lids at Llanbradach Colliery.

When the cage neared the surface a rubber buffer positioned above the rope cap raised the disc and released the air pressure, minimising as far as possible the shock loading whilst the close fitting partitions prevented serious leakage of air.

When the former arrangement was used, the size of the cage would be  limited by the relative narrow spread of the suspension chains due to the need to keep the size of the hole in the shaft cover as small as possible.

This may account for why the original South pit cages only carried one tub per deck, although the size of the winding drum would have limited the rope size and hence the maximum load.

(Surprisingly, this method of closing the upcast shaft was still in use as late as 1934 at Gresford Colliery - opened in 1911 - where they were known as “butterfly boards” or “policemen”).

By the late 1890s the wooden headstocks were deteriorating badly and with the decision to upgrade the South shaft to full coal winding a new headstock was installed there in 1900.  The new headstock was built in-situ and,  with the installation of a more powerful winding engine and boilers, this took several months, being completed in May of that year.  In addition to the new headstock at the South shaft, the wooden bonnets closing the top of the shaft were replaced by a two-level brick-built air-casing, with extended air-locks suitable for full coal winding  and with double-glazed windows for daytime illumination.

A capstan-engine and small winding frame was erected for use in case of accident at the downcast shaft, and the South pit’s output was absorbed by two shift working at the North shaft during the changes. 

Pleasley-1916-25in-detail#6 a

 South heapstead circa 1916

South headgear pre 1919 1 -s

 South headstock air-casing circa 1916 (FoPP/JST)

In 1901 the back-stay legs of the North headstock were in a very poor condition and it was decided to replace it by the same type of steel-girder structure as that at the South pit. The layout of the surface and pit bottom haulage roads  precluded the use of the South shaft for winding all the coal and it was decided to erect the new headframe on the pit-top in line with the shaft and then winch it into place.

The new headframe took several months to assemble but the dismantling of the old headstock, moving into position of the new one and fitting the sheaves only took about 48 hours. Preparatory work on the pit-top had been going on for over a week, however, and the re-installation of the decking, weighing and tram roads took about another week. Even so, only about 6 days actual coaling were lost - pretty impressive given the scale of the undertaking.

North pit headgear move -s02

 Moving the North headstock into position May 26th 1901 (JST)

The men seen each side at the front are inserting cast-iron rollers beneath the headgear base-frame to allow it to be moved along two sets of  heavy timbers covered with lengths of iron boiler-plate.

new headstock in place -s

 The new North headstock in position May 30th 1901 (JST)

The corrugated iron sheets of the top-deck covering are yet to be fitted. The top deck shaft-side frame and the weighing cabin can be seen. The building immediately behind contained the tipplers feeding the North screen.

North pit heapstead 1900 - 05

 New North headstock in operation 1901 - 04 (FoPP)

The new headstocks were amongst the first to make use of the wider girders which had recently become available from steelworks following the introduction of  larger rolling mills.  Most of the headstocks installed around this time used either iron/steel lattice work or  fabricated box-section  members.  Pleasley’s headstocks took a radical new line by using a girder construction with special fabricated strengthening for the legs.  

The construction consists of two lengths of large I section girder, but-jointed together and reinforced by lengths of steel plate riveted along both flanges. Each side plate is connected to its neighbour with a simple riveted but-joint and additional bracing pieces are fitted between the plates and the web on each side.

All connection between the structural elements is made using riveted angle-iron with the main joints also reinforced by gusset plates.  Support for the sheaves and detaching plates is provided for by smaller H section girders.

headstock raking leg 102

North headstock raking leg cross bracing

headstock joint 2 -m02
headstock plate joint

North headstock side plate but joint

headstock joint 1 -s

North headstock inter-member connection showing gusset plate reinforcing

An unusual aspect of the Pleasley headstocks was the use of foreign steel for the main girders.  These were manufactured by the Burbach Steelworks of  Saarbrucken in SW Germany and display the Burbach name and the (metric) web size. 

burbach 1

Manufacturers rolling mark - North headstock steelwork

Although the raking leg  girders are in two sections (and probably the other legs too), each section is a good length and, whilst much of the journey would have been by water, the final overland leg  would have provided an interesting spectacle.

Only one other example of this type of headstock has so far been identified and this was at the downcast shaft of Creswell Colliery - the upcast there being of a lattice construction.  Who the engineer was who designed the headstock and why and how the steel was transported all the way from Saarbrucken remains a complete mystery. 

The designer may have been German although the headstocks are unlike those in use at German collieries at this time.  One possibility is that the Managing Director of Stanton Ironworks, J.A. Longden, who was educated in Germany, may have had contacts there, or it may be that this was the only source available of steel of these dimensions.

south pit-top 1975 -s bw02
south pit-top 1975 -s bw

South headgear spring 1975  (FoPP / JST)

In 1975 both of the headstocks were found to be in a very poor condition due to corrosion of the steelwork, giving rise to serious doubts about their structural integrity. Emergency remedial work was immediately put in place whilst  longer term solutions were organised

At the South pit, during the summer holidays, a new bell platform with a concrete ring beam and a 6 inch concrete slab were installed and stronger, Ormerod detaching bells fitted.  The brick air-casing in the vicinity of the bell platform was strengthened with new brickwork and supporting steelwork and a main cross-tie girder within the air-casing which had been removed at some time in the past was replaced by a steel-reinforced concrete beam.  Missing bracing rods between the raking-legs were also replaced.

new Sth pit detaching bells 1971 bw

Installing the new Ormerod detaching bells  - summer 1975 (FoPP / JST)

At the end of August, following a more detailed inspection, the factor of safety calculations indicated that the headstocks were in a such a bad state that they could collapse under rope-break conditions. This gave rise to very serious concern at a high level within the National Coal Board and complete replacement of the headgear in twelve months time was considered. 

Remedial work commenced on the North headstock which by now was only used for emergency egress. The main legs and cross-girders were encased in reinforced concrete, a badly corroded main member at the winding platform was replaced and the main cross-member in the raking legs taking the thrust from the pulleys was reinforced.  The access stairs and landings were also properly fixed and made secure.  Consideration was given to the de-rating of the North shaft facilities but after analysis this was not found to be cost-effective.

The proposed strengthening of the South headstock rear main legs by welding steel joists along the webs was rejected due to the possible interference with production. Instead, it was decided to partially encase them in reinforced-concrete as a temporary measure and this was completed by the end of the year.

During the spring of 1976,  new reinforced-concrete walls were constructed on the east and west sides as far as the bell platform and were tied into the concrete reinforcement of the rear legs. A new reinforced-concrete emergency airlock tied into the side walls and supported on concrete columns was also constructed on the south side of the headstock. The end result was a complete integral structure supporting the entire load with the rear legs becoming largely superfluous. The old brick air-casing between the main-legs inside the new casing was then demolished during the summer holidays.

Sth headstock W -s bw
Sth headstock E -s bw02

South headgear concrete air-casing

As part of the remedial work at the South headstock it was also decided to install Bennet overwind catches to limit the amount of fall-back of the cage in case of a high speed overwind.  Exactly why this was decided upon is unclear, possibly a result of the recommendations made following the Markham colliery winding disaster a few years earlier, but more likely as a means of reducing the stress on the structure imposed by fall back of a fully loaded cage, which could amount to as much as 10 ft in the case of a high speed overwind.

In order to provide access to the overwind backout switches and catch reset facilities, the disused  north side high-level air-lock was re-opened and a two-level access platform constructed behind the empty-side overwind catches. The upper level contained the manual hydraulic pumps for the catch release and the lower level held the control panels for overriding the headgear limit switches.  These panels were normally locked and access to the key was restricted.

Overwind catches -s

Sth headgear full-side overwind catches

Sth shaft lower overwind platform -s02

Sth headgear overwind backout control platform

Overwind catch reset platform

Sth headgear overwind catch reset platform

Overwind lower platform -s

Sth headgear overwind backout switch panels and communications unit

On the South side, the brick emergency escape air-lock was replaced with a new reinforced concrete structure supported on concrete legs on either side of the lower air-casing.  This consisted of a tall access chamber allowing egress from both decks of an over-wound cage together with an air-lock opening onto the South roof of the brick air-casing from where descent was made via a metal stairway.

 

Bibliography

  • Trans. Fed. Inst. Min. Eng 1901 - 02
  • Trans. Fed. Inst. Min. Eng 1907
  • NCB Correspondence File  1976

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