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Skelmorlie ROC Post

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Skelmorlie ROC post open day, 2004
Skelmorlie post open day
© Unknown

Skelmorlie ROC Post lies in a fenced compound on low mound in the corner of a field to the west of an unnamed minor road, adjacent to the gated entrance to the field. This road sits on the hill above the A78 coast road between Skelmorlie and Largs. The post was operated by the Royal Observer Corps and was open between April 1965, and September 1991.

The post has been fully restored by former personnel and supporters, with most of the work being completed between 2003 and 2004, and can be visited by arrangement. It is also usually open to visitors during the annual Doors Open Days programme. At all other times, the post is locked and all equipment is removed and placed in storage, both to protect it from the dampness from which most posts suffer, and for security.

Open Day 2009

The post was visited on September 5, during the 2009 Doors Open Days event. Although poor weather on the day meant that the usual outdoor exhibition of larger items belonging to the post had to be cancelled, underground visits and displays were unaffected.

When first acquired, the post was empty, and part of the restoration work involved tracking down surviving examples of the contents which could be used to populate the interior.

Monitoring room west, 2009, Fox
Monitoring room west

The photographs of the monitoring room do not portray the normal service view, which would have been much sparser, but show numerous artefacts related to monitoring operations. The large map to the left is a standard Ordnance Survey item of the time, while the map to the right shows all the ROC posts in the Prestwick sector, which Skelmorlie lay within. The console with the telephones visible in the corner below the OS map is not a post item, but is part of the related communication system which would have been installed within police stations to provide communication with the sector posts, and was acquired from a redundant police station. This area would normally have contained the rechargeable 12 volt batteries which would have been used to the power the room lighting, with candles as an alternative, and any other electrical equipment. Early posts had small vehicle lightbulbs fitted for illumination, while later posts used more effective fluorescent lights, similar to those used for camping and caravanning, and able to operate from the low voltage supply. A clockwork timer was fitted to the light switch, so that the light could not be left on when the post was not in use, and drain the batteries. The post was equipped with a small diesel generator in order to charge the batteries. This had to be hauled to the surface when needed, and the post had to be open when charging was being carried out, due to the poisonous exhaust fumes from the generator, and the potentially explosive gases produced by the battery during charging operations.

The instrument table carries a display of assorted dosimeters which would have been used to measure and record the individual dose of radiation received by each observer, together with examples of other equipment used for monitoring and observer training.

Certain posts were designated METAR, and provided meteorological weather reports which would have been used to plot and predict the path of radioactive fallout following a nuclear attack, and the table contains examples of anemometers, barometers, and whirling hygrometers. Prevailing weather conditions would also have been observed and reported, such as cloud cover and type.

The grey boxes above the clock were part of the system which received the GPO telephone wiring, and filtered out the signals which the normal telephone lines carried, but which were only detectable using the WB1401 carrier receiver with WB1410 filter unit. On the table below, but almost hidden behind the pot, is the blue and yellow Tele-talk, which is what the observers would have used to make contact with other posts, as they were not provided with normal telephone style handsets. Communications between posts and Group Headquarters was by GPO telephone lines, and in 1964 the conventional headset and microphone were replaced by the Tele-talk which contained both the microphone and amplifier. In case of emergencies, all Group HQs and one post in each cluster, such as Skelmorlie, were equipped with VHF radios and telescoping pump-up aerial masts, and were known as master posts. Evidence of such a mast can be seen in the west room photograph, where the handle of the pump is just visible to the left of the police station console.

Monitoring room east, 2009, Fox
Monitoring room east

The large white dial to the right of the communications equipment is the BPI (bomb power indicator), which measured the pressure of the bomb blast as it passed the post. A 1-inch tube connects the indicator to a surface, and is topped with baffle plates to protect the indicator, which is fitted with a mechanism to record the maximum or peak pressure, and can then be reset in readiness for the next blast.

Below the BPI are samples of the food issued to the crew, while the pot sits on top of a small solid fuel stove. The cupboard to the right would have contained much of the consumables and materials needed to run the post, such as charts, cleaning materials, government issue (hard) toilet paper, and similar.

Not visible in the photograph is a much larger tube in the ceiling, which leads to the surface. This larger tube can be seen clearly in the accompanying external photographs. The was for the FSM (field strength monitor) which was basically a Geiger counter, or radiation meter, which allowed the exterior radiation level to be measured and reported. This had a novel method of changing the sensitivity. The large tube was fitted with a thin tubular housing into which the radiation sensor could be pushed from below. This provided very little shielding, so the monitor operated with high sensitivity and could record very low radiation levels. In the event of an attack, the sensor would be withdrawn and dropped until it was enclosed by the pipe, in which case it was shielded by the wall of the metal pipe, reducing its sensitivity and allowing much higher levels of radioactivity to be recorded.

The radio set on the shelf above the cupboard is a genuine ROC post radio but the Skelmorlie Post never actually had one, although inspection of the smaller surface vent shows this carries the brackets and fitting for the pump up mast, and the dome which contained the terminations for the aerial cables.

The far east end of the room provided an area for the for a bunk bed, where the two off duty observers could relax while the third was on duty. On the top bunk are the dismantled parts of the GZI (ground zero indicator) which would have been fitted outside the post, on the mounting point adjacent to the access hatch. The GZI is effectively four pinhole cameras in one unit, with the pinholes aligned to the cardinal points of the compass. Within the unit, specially prepared photographic paper charts record the air detonation of nuclear bombs, with the size of the recorded flash indicating the size of the bomb, and its position on the chart giving its elevation and bearing relative to the post. As with the other results from the FSM and BPI, these figures are reported to headquarters. The white cylindrical cover of the GZI can be seen on top of two boxes on the top bunk, and this cover contains the four pinholes, and had a blackened interior to minimise internal reflections. To the right is the blackened internal mounting for the photographic recording chart paper. One chart would have been mounted to the curved carrier, behind each pinhole, and the yellow S indicates where the south facing paper would have been fitted.

Monitoring room east end, 2009, Fox
Monitoring room east end

On the end wall, above the bunk bed, is the shutter for a ventilation shaft which leads to the small surface vent (where the telescopic aerial mast would have been fitted). Just below this is a grey unit with a handle which is a hand cranked ventilation filter system. Although this was acquired from another Ayrshire post, it was not actually fitted to the Skelmorlie post, and was actually relatively rare, reportedly being less than effective in use. Not visible in the interior photograph (although the corresponding surface vent can be seen in the exterior photographs), is the second ventilation shaft which ran alongside the large access shaft, and was supposed to provide a through path for (unfiltered!) surface air for the observers. Various filters and forced ventilation systems were tried, including a number of home-made systems assembled by the observers themselves, but none were really considered successful or practical.

The three observers on duty at any one time were numbered 1, 2 and 3. No 1 Observer was in charge of the post and was responsible for reading and accessing the information from the GZI and the BPI. No 2 Observer was in charge of communications, checking the GZI and BPI readings, reading the FSM, filling in the post log and reporting the readings and observations to group headquarters. No 3 Observer had the unenviable task of changing the photographic paper in the GZI, and was responsible for the domestic side of the post.

The floor at the base of the access shaft was provided with a shallow sump covered by a metal grill. This collected any water that leaked into the shaft from the access hatch above, together with any condensation which collected within the post, or leaked in from any cracks in the structure. A manually operated sump pump was provided on the shaft wall, which the observers would operate by hand to drain the sump, which discharged through a small pipe which emerged above ground, from the side of the access shaft.

A small utility room was also provided at the base of the access shaft, and this served as a storage cupboard and toilet, containing an Elsan chemical toilet.


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