1 10 1 https://d1y502jg6fpugt.cloudfront.net/21127/archive/files/f49ad8cba9dec79d7e69876fa7f68f86.pdf?Expires=1781740800&Signature=qG8vVb6GZR7BX4vcOJ5hT2IhaLpsM-PnFadpw72iAao0FjoqqLNAj%7EnkPimFGGaudmp3rVLjahwcRFGaaypxHJVuqReAMFJee83G7l5etrWROd1zLSTGEVeAxUB-AxRN8zMZ%7E929ucEoDJPg6IUKMMOGB9F%7EvKPxIniBDmqi2uYg6GqgzMoFiiktLXFNQMJhCVbfIRnwfSv-ejlK2omStE%7Ei4l774MX2RSyYTXpwmXIBPqD2uR34mybRgRamj8VBxcXc7UuP9JYeldlACCP%7EwrHRNS-RrGLx6zzToHetedF-aebxb7oxMz8tQm8I1PUWrRgerV1M2UhdxYDA-5kyIQ__&Key-Pair-Id=K6UGZS9ZTDSZM e27d5a8cbc18b54de5550a5c5e4ef01d PDF Text Text Conservation of the aerial tuning inductor from Rugby Radio Station, Warwickshire, UK Diana McCormack, National Museums Scotland, National Museums Collection Centre, West Granton Rd, Edinburgh EH5 1JA d.mccormack@nms.ac.uk Marta Leskard, Science Museum Group, Red Barn Gate, Wroughton, Swindon, SN4 9LT marta.leskard@sciencemuseum.ac.uk Keywords: Rugby Radio; tuning coil; conservation; reassembly; cable; Tufnol; polymer; safety; open display. Abstract On January 1st 1926 the Very-Low-Frequency (16 kHz) transmitter came into service at Rugby Radio Station, Warwickshire, to transmit telegraph messages to the Commonwealth. The aerial tuning inductor from the transmitter installed at Rugby is now the centrepiece of the Information Age gallery at the Science Museum, London. The fine tuning assembly, together with supporting framework, now standing in the gallery is only a portion of the original operating apparatus. The object was donated to the museum by BT and partially dismantled for removal to the storage site at Wroughton, Wiltshire. Museum curatorial and conservation staff advised on how much of the object would be taken into the collection, and worked with BT staff to deconstruct and transport the object to get it safely to its new home. Conservation work was then begun on the components of the object, to clean, repair and stabilise it so that it could be safely and effectively exhibited on open display to the public. Museum conservators worked with the heavy-lifting contractors from Constantine to rebuild the tuning coil at the centre of the gallery, in advance of other installation works. Conservators worked with the curator to ensure the object was displayed in a meaningful way and to retain as much as possible of the visible functionality of the assembly. Background In 1923, with the purchase of 920 acres of land at Rugby in the West Midlands of England, the General Post Office of Great Britain began the building of Rugby Radio in order to provide a Government station equal in power to any other in the world. This was partly for strategic purposes and partly to prevent an absolute monopoly by the Marconi Company who had applied a few years earlier for licences for the construction of eighteen wireless stations throughout the British Empire. The Hillmorton site was approximately 340 feet above sea level and was chosen to accommodate 12 250metre high masts, each of which was placed a quarter of a mile apart in an irregular octagon surrounding the station buildings. Twentyseven miles of copper wire in total formed two aerial sections which could be connected within the station buildings for extreme power. The system had an efficiency of about 29% at 16 kHz. 1 �Showing the Hillmorton site in Warwickshire. The tuning coils of the transmitter were wound with Litzendraht cables consisting of 6,561 strands of No 36 SWG copper wire, each strand insulated with enamel and one covering of cotton or silk. The formers were hex-frames of American white-wood (Liriodendron tulipifera), the external side being 7ft 9in (2.325m) in the largest former, and the turns were 6in apart. Five formers of eight turns each formed the aerial coil, three formers of four turns each the primary, and one former of two turns the coupling coil. The transmitter itself was designed to operate at a frequency of 16kHz, with a wavelength of 18,750 metres. Rugby Radio Station began transmitting very low frequency (VLF) signals worldwide on 1 January 1926 using the call sign GBR. Its VLF waves could follow the curvature of the Earth to travel very long distances, enabling one-way communication via Morse code. It transmitted wireless telegraph messages from the British Foreign Office, standard time signals from Greenwich, news bulletins, personal telegrams and Christmas greetings. With the advent of war in September 1939 and the suspension of most radio telephone overseas services, the transmitter became of vital importance to the Navy and other shipping interests. In later years Rugby Radio Station played an important role in both the Cold War and the Falklands War, as its very low frequency signals could be picked up by submarines. The VLF transmitter also broadcast time signals twice daily and, in 1951, added the transmission of reference Modulated Standard Frequencies (MSF). The tuning coil was damaged by fire in 1943 when the woodwork on the roof of the main station housing the VLF Transmitters became ignited due to the radiation effect from GBR. Because of its importance to the Navy, it was rebuilt and operational again within six months. There were very minor changes from the original design with American Whitewood (Poplar) used to reconstruct the formers. In 1965-67, the transmitter was rebuilt to broadcast more stable MSF but Sitka Spruce was substituted for the Whitewood as it was more easily available and had almost the same essential straight grain structure. The trunnion 2 �frameworks and formers were pegged together with heavy duty polymer dowels as metal dowels would have interfered with the long wave reception. On 1 April 2003 at 00.21 hrs the 16 kHz very-low-frequency transmissions from Rugby ceased as BT (British Telecom - the successor to GPO) lost the contract to transmit the MSF signal. A year later the twelve masts were demolished. BT Heritage and Archives circulated details of the tuning coil and the Science Museum accepted the donation after site visits in September and October 2004 were made by John Liffen, Curator, and Marta Leskard, Conservation & Collections Care Manager, to determine whether it would be possible to both store and eventually re-erect the coil for display. Showing the aerial tuning inductor as seen in situ by Science Museum staff. Acquisition of the object Dismantling of the coil was undertaken by BT high riggers and Science Museum conservators through November and December and the parts were transported to the Wroughton storage site in January 2005. The aerial lead-out frame and two longitudinal support beams which supported it and the two trunnion frameworks remained at Rugby as the aerial lead-out frame was still in use. It was decided in 2011 that the Rugby tuning coil (RTC) should be re-erected as the centrepiece landmark exhibit in the Information Age Gallery. Owing to the restricted height of the gallery (approx. 7m) it was accepted that the lower support trestles would have to be omitted. The lowest part would therefore be the two longitudinal beams which meant another trip to Rugby for Conservation staff. The two beams, no longer being used by BT, were retrieved but despite a stellar attempt, the aerial lead-out frame had to be left behind. 3 �Trial reassembly for display Two trial reassemblies were also required to ensure that the coil could be erected in the gallery; one to confirm the measurements of the total height and one to find a way to lift the formers onto the axles which were supported by the trunnion frameworks. While the measuring was carried out in the hangar where the RTC parts were stored, the trial reassembly was done in Wroughton’s Conservation facility (the Engineering Building) where the ceiling height was barely higher than that of the gallery. The trial reassembly was carried out by staff from Constantine Ltd. who were contracted to install all the large objects on gallery, supervised by Conservation staff. Despite having an overhead gantry in the conservation work space, only equipment that could be used on gallery was employed in the reassembly, to make sure that it was possible to lift the formers up and onto the axles. Only one former was installed during the trial. Showing trial reassembly in progress in the Engineering Building at Wroughton. While the trial was successful in ensuring that the RTC could be erected in the tight gallery space, the exercise revealed potential issues, with splits occurring along the grain of the wood forming the hex-frames and loss of strength in the polymer dowels. The brittle insulating tape covering the cotton-wrapped copper wire was damaged and shedding large fragments when the cables were moved around. 4 �Conservation Breaking down the coils Each of the formers comprised a cable/cables wound into the hexagonal framework, resembling a spider’s web. The cables were covered in insulating tape and then a hard insulating cover was tied around this. The formers had been stored in the partially dismantled state in which they had been removed from the radio station building. This was with a onethird section of the hexagonal formers removed, leaving the cables attached to the remaining two-thirds framework, but trailing on one side. The trailing portion of cable on each former had of course been stripped of its hard covers in order to remove it from the framework. Although they were not in storage for that long, the cables had sagged and the hard covers had begun to distort and become set into a slightly bent shape. The team from Constantine came to Wroughton to break down the partially dismantled formers into their component parts, as they would be transported to the gallery. It was important that they be a part of this process alongside the conservators as it was their task to reassemble the large frameworks on gallery, so both teams needed to understand the structure as much as possible. Once broken down it was then possible to spot weak points and damage to the woodwork that could be repaired in the workshop, before transporting the pieces to gallery. The cables were individually wound onto pallets and notes and drawings were made of how each had been attached to its framework. Labels were added at appropriate marker points to be used as points of reference on gallery, to ensure that all formers were reassembled and hung in the correct orientation. Showing the team breaking down a coil, winding the cable onto a pallet. The hard covers were made from a material known commercially as Tufnol (Godwin 2014), which comprised a paper pulp moulded in resin into a half-pipe shape with a semi-circular cross-section. The covers were used in pairs to cover the cabling and tied into position with many regularly-spaced string bundles, passed around the Tufnol in a double loop and knotted on top. The covers and the string lashing had become very dusty and dirty, discoloured in places, and faded by the light. The Tufnol had also broken and split in many places, particularly on the sections of cable that had remained in the frame during storage. It was 5 �noted that the covers stripped from the cables before storage were altogether straighter and had fewer points of damage from stress under the weight of the cable. In order to clean and repair the covers, they all had to be stripped from the cables. As so many of them had effectively re-set into a slightly bent shape, and as the length of each portion of cable varied slightly from frame to frame, it was important that covers should be replaced in the same positions from which they were removed. For this reason each pair of covers was carefully labelled after removal and laid out on pallets labelled clearly to show which former they belonged to. This required more working space in the laboratory but saved time in the long run, especially for reassembly on gallery. The knotted strings holding them in place had to be cut, as it could not be untied and successfully cleaned and re-used. The string was saved in sample bags for the purposes of colour-matching with new string, and for the sake of preserving original material. Conservation of the Tufnol covers The covers were very dirty and the grime was slightly greasy in nature, but in effect ‘baked on’ by the relatively high temperatures created during the working life of the object. The cleaning process was large in scale, so a detergent was selected that could be used at a fairly low percentage concentration in water, that was environmentally sound and could safely be used and disposed of in large volumes. A solution of Vulpex at 1:7 in water was selected for its ability to effectively remove the dirt quickly, with one wash. The covers were first dampened with a moist cloth, then the detergent applied, and then rinsed twice with water alone to neutralise the surface. Care was taken not to saturate the covers entirely, and they were then laid out (still in order)to dry overnight. This process also allowed the conservator to gain familiarity with cracks and breakages in each cover, and these were noted for repair at a later date. Showing typical state of Tufnol covers before conservation, still attached to cable. There were two types of breakage that occurred in the Tufnol covers: the first was simply a failure of old adhesive that caused pieces to separate at the joints with collaring pieces; the second was a stress fracture where the material itself had given way, leaving a sharp ragged edge with a very thin surface area. The former was much easier to repair, while the second type required some further support to be put in place around it. The failed joints were readhered using HMG Paraloid B72, and held with soft clamps overnight. To add extra support to breaks discreetly, a number of new collaring pieces were cut from spare Tufnol tubes and 6 �adhered over the breakage, allowing a much greater surface area for the adhesive to make purchase on. As there were a few sections of cable that had lost their Tufnol covers, a few entirely new covers were also cut from spare tubing. This material stands out a little as it is much cleaner and straighter than the used covers, but has the benefit of being made from original BT spares, of exactly the same material as the rest, and should age to blend in with the used covers over time. Some replica covers were also made from polypropylene pipe, cut in half lengthways, and painted on the exterior with an airbrush to mimic the mottled brown colouring of the originals. These were kept aside for use in case of any further breakages or failure of repairs when the object was being reassembled on gallery – as the covers would not be under the full strain of the cable weight until this point there was still a risk that the repairs may fail at the critical point. As the original strings securing the covers had to be replaced, a new supply of acid-free, unbleached cotton twine was acquired at the same thickness as the original, and dyed to match the old string. This was done so that the string would not stand out as being new against the used covers, and appear age-appropriate. Repairs to the woodwork During the breaking down of the object some minor damage was noted to the wooden structure and it became necessary to make some repairs. The cable had been held securely in the former with the aid of a wooden Litz clamp and wedge at each point where it crossed an arm of the frame. A Litz clamp is a small wooden block of about the same width as the cable, with a concave curving hollow to allow the cable to fit into it. The ends of the formers had suffered some chipping and cracking, and many of the Litz clamps were split in two and had only been held in position by tension. Breaks were repaired with a PVA adhesive and held in G-clamps until set. However, as there was a large supply of spare parts from BT, a number of ‘new’ Litz clamps were used to replace badly broken ones, as these were much more stable. The broken and degraded originals were boxed and labelled for storage. Showing repair of wooden former in progress, clamps in place. 7 �At the centre of each former the six arms came together around a hexagonal block and were joined with wooden dowels. During the dismantling process several of these became weakened or damaged, so it was necessary to strengthen the central joins with new dowels in some places. The new dowels used were again material supplied by BT as spares. In two of the formers the breakages were considered to be a risk to the structural integrity of the object and new dowels were inserted at extra points. This was an invasive procedure but necessary for the stability of the overall structure. Showing new dowels being inserted around the central joints of one former. Where the wooden beams had heavy deposits of greasy soot, bird droppings or footprints, this was cleaned with a mild detergent in distilled water. This was not a complete cleaning of the wooden framework, but brightened the surface and removed any disfiguring marks and dirt that could be transferred to other components. Conservation of the cables The cables had originally been covered in an insulating tape, similar to modern PVC electrical insulation tape. This had become very hard and brittle and was cracked, broken and flaking in many places, with large areas of loss. 8 �Showing the original yellow insulating tape with large areas of loss and shed fragments. It was necessary that the cables be bound in order for them to fit properly into the frames, as this tape provided the tension needed to hold the cable together and stop the cotton-covered copper strands from unwinding. The original tape could not be preserved for the most part as it was too brittle and degraded. It was necessary to find a similar material that could be used to replace this tape, but replacing like-for-like was not considered a desirable option, given that PVC tape would emit harmful gases over time and degrade in a similar fashion. A selfamalgamating butyl rubber tape was selected as the best option. This was selected because it would not bond to the object itself, and as it is based on polyisobutylene it would not cause corrosion of the copper wire, leave deposits on the object or give out harmful emissions to the gallery. Synthetic rubber is much more durable than organic rubber and withstands a much wider range of temperatures before becoming hard or embrittled. It had the added benefit of being an insulating tape, so although it no longer needed to perform this function, it was in line with the function of this layer on the cable and suitably thin but strong enough to perform this task. It is accepted, however, that given the lack of suitable environmental control in the gallery, the rubber tape will inevitably degrade over time (Williams 1997), but it was also considered likely that by the time the tape had degraded to the point where it no longer supported the cables, the object would most likely have been taken off display and disassembled, allowing either its removal or replacement as desired. This tape was also black in colour so could be used discreetly without drawing attention where it was visible between Tufnol covers. 9 �Showing the black self-amalgamating tape being applied over bare areas of cable. Cable 1 and cable 4 were found to have suffered from a fungal attack on the cotton bindings of the copper wire, causing powdering and disintegration of the cotton. This was most likely due to water ingress in storage affecting some parts of the cables that came into contact with it. Cable 1 was in worse condition than cable 4, but both required treatment with pure IMS to kill mould. Tests were done to consolidate the damaged areas to prevent loss of the cotton bindings, but the damage was too extensive and the powdery fragments had to be removed with a brush and vacuum in the worst-affected areas. A 5% Klucel G in isopropanol was used to consolidate as far as possible in areas around the damage to prevent further loss. The cables were then bound in self-amalgamating tape as done elsewhere. Showing cleaning of affected areas (left) and damage to cable (right) from mould. 10 �Repair of guide poles One of the six guide poles was broken into three sections at the joints and needed to be repaired. Due to the length of these pieces it was necessary to dowel the break with steel rod, which was held in place with an epoxy putty. This pole was also placed into the lowermost position at the base of the coils, to ensure that if the joints were to fail again there would not be any damage to the object as a whole. Twelve replica parts were manufactured from Perspex to replace missing or broken guide plates. These were fastened to the ends of the former arms in pairs, and had a large central hole through which the guide poles were slotted. These ensured that the formers remained on an even orientation during use or when the coils were repositioned. The replica pieces were painted brown to match the originals, but given a matt finish so as to be easily distinguishable from the originals in future. Showing the placement of polymer plates on ends of formers (before poles installed). Replacing the polymer fixings The original polymer dowels were replaced with steel bolts to give the structure strength, as it was not known whether the polymer could withstand any strain. The dowels could have been subjected to strain tests to find their breaking point, but it was considered much safer to simply replace them with steel, as the structure was to be on open display and safety considerations were paramount. The original material was labelled and packed in storage. It was, however, important to disguise the steel because the original object could not have functioned with this material in its structure. Any steel would have interfered with the signal and upset the fine tuning. All the new steel was therefore painted in exposed areas with an enamel paint to match the brown colour of the nylon polymer. During reassembly some of 11 �this paint was inevitably chipped by tightening the nuts with spanners, so it was necessary to touch-in these areas once the object was assembled. A note on environment and monitoring The conditions in the hangar storage were of a much higher relative humidity (RH) than was desirable, and so the object was moved to the Engineering Building workshops to allow it to acclimatise to more mid-range conditions there, before going to gallery where the environmental conditions were generally warm and dry. The acclimatisation period was approximately one year. A Hanwell Woodwatch WW01sensor was attached to one of the beams of the larger tower when it was moved to the Engineering Building, in order to monitor whether the drier conditions would cause the object any distress. The sensor is designed to record acoustic emissions as an indicator of deformation by micro-damage within the wood structure. As an unfortunate consequence of moving the object to the workshop, the increase in background interference noise was also significant, rendering the data rather opaque. It was also intended that the monitoring would be continued on gallery once the object was reassembled, but unfortunately the base-build conditions produced so much vibration, noise and dust that the monitoring was not possible during this period, when most change would be expected to occur in the structural material. This exercise perhaps demonstrates that other methods of observing such changes should be researched further. Transport to gallery The various components of the object were transported to the gallery on a number of pallets by Constantine Ltd. Smaller parts or fragile pieces were transported by conservation staff along with the necessary hand tools and personal protective gear. An area at the centre of the gallery was cordoned off for the reassembly work, as the basebuild was in progress at this time making the gallery effectively a building site. Reassembly on gallery An area at the centre of the gallery was cordoned off to allow for safe working and reassembly of the object. The object was to be positioned on a copper floor plate, which was already installed, and covered with plywood boarding so that it would not be marked by the ongoing work. The end tower was carefully positioned by measuring the length and spacing required for the complete object within this copper-floored area, and this tower was not moved from this position once work began. The three trunnion beams were then positioned and the opposite end tower moved into position to complete the basic framework. It was of course necessary to remove the second tower every time a former was added to the object, and then replace the tower to secure the structure while the next former was being prepared. The floor space allowed only for two formers to be laid out at any one time, so the formers had to be added in this manner, one at a time, rather than all six being prepared before assembly began. One former was assembled and one assembled former was dressed at any one time. 12 �Showing the working area on gallery, with one former complete and one in progress. In order to support the trunnion beams when the tower was removed, the central T-support was placed in position; once the tower had been replaced, the T-support was removed, and the former moved along the trunnion to its proper position. Once the first three formers were in position, the T-support was replaced and did not have to be removed each time another was added. This T-frame supported the trunnion beams at the centre of the object, spreading the weight of the formers and stopping the frame from sagging in the middle. A copy of the T-frame was also made by Constantine and two other prop beams, for use when the frame was carrying the weight of four and five formers, as extra support was needed at this stage when removing the tower. Once a former was assembled it was dressed by first winding the cable into position. Where it crossed an arm of the frame, the cable was held by a Litz clamp and a wedge. The wedges were tapped into place with a mallet to secure the clamps, taking care not to force them too far or split the clamps from too much force. Once the cable was fitted the next step was to dress the cable. It was at this point that the Tufnol covers were re-attached in their pairs, and tied into place with the string that had been prepared in the workshop. The covers retained faded marks showing where the string had originally been positioned, allowing just the right number and spacing of ties to be added. The guide plates were then attached the ends of the arms in pairs, and the former was ready to be raised onto the frame. Each former was first braced at the centre by placing a custom-fitted wooden board around the blocks, to support the structure as it was raised. This measure was introduced after the trial reassembly showed that the central joints came under too much tension in the lifting process. It was then lifted on the gantry and brought vertical, before the brace could be 13 �removed and the former hung on the trunnion beams. The second tower was then put back in place and slings were then used around the former to draw it along the trunnions to its proper position. Showing the first completed former with cable being raised and hung on the framework. When all six formers were in place the guide poles could be inserted to complete the object. As the base-build works were to continue for several months before the work would become dust-free, the object was covered with two large tarpaulins to protect it from the worst of the working dust. When building works were finished the tuning coil was un-sheeted and dusted before the gallery opened. Display Considerations Configuration of the formers The formers were spaced according to their positions as shown in a photograph of the object in their last working configuration, in accordance with how the curator wished for the object to be presented. In order to move the formers along the trunnion beams they were slung around the central point and manually pulled and pushed into place. The height restrictions in the gallery meant that the wheels to which the cables were originally attached could not be displayed, as these were supported by the lower trunnion beams that were excluded. This meant that the cable ends had to fall loose, and it was decided to allow them to drape to the floor and be gathered beneath the object. The ends were lifted onto mounts so as not to sit in contact with the copper sheeting. This had the added bonus of keeping the loose ends out of reach of the public. 14 �Design echoing lost components Once works were complete, the copper floor beneath the tuning coil could be uncovered without fear of damage. This floor was incorporated into the design to echo the copper ceiling plate at Rugby that was positioned above the apparatus after the fire in 1943. A further design measure introduced was the kerbed edge on the copper floor, which made a clear perimeter around the object to discourage the public from approaching too close to the object on open display. Showing the finished object on display in the Information Age gallery. Conclusion The reassembly of the tuning coil was achieved by close collaboration with a team of heavylifting handlers from Constantine Ltd, and required some compromises in terms of conservation. These mainly concerned safety requirements and ensuring the stability of a large structure on open display to the public. It was attempted to make these compromises invisible to the public by making the object appear as it did when in its working state. Although the object as it now stands is only a portion of the apparatus at Rugby, it represents the almost-complete fine tuning coil assembly. It is hoped that this communicates to the public a sense of the larger site works and instils an interest in the history of Rugby Radio Station as a whole. The object stands floor-to-ceiling at the centre of the Information Age gallery, which was opened to the public in October 2014. 15 �Acknowledgements The authors would like to thank the Information Age project team at the Science Museum, particularly: Dr Esther Beeby, Conservator; Mr John Liffen, Curator; the Wroughton staff; and, the team from Constantine Ltd. The authors also gratefully acknowledge the support of the Clothworkers’ Foundation, National Museums Scotland and the Science Museum for aiding the delivery of this paper. Biographies Diana McCormack entered conservation from a background in archaeology and research, studying at Durham University as an Objects Conservator and training with the Wiltshire County Council Conservation & Museums Advisory Service. She has subsequently worked as a Project Conservator, for English Heritage, the Science Museum, and National Museums Scotland. Marta Leskard is Conservation & Collections Care Manager for the Science Museum Group at the Wroughton storage facility. She is also a doctoral student at the University of Bath, studying the use of innovative materials in effective environmental control for museum storage buildings. References Godwin, R. 2014. A History of Tufnol, accessed 2014, http://ahistoryoftufnol.org/index.html Hancock, M. 2011.The Official History of Rugby Radio Station, © British Telecommunications plc., accessed 2015, http://www.subbrit.org.uk/sbsites/sites/r/rugby_radio/indexr69.shtml Williams, S. 1997. Care of Objects Made from Rubber and Plastic: CCI Notes 15/1, Canadian Conservation Institute. 16 � https://d1y502jg6fpugt.cloudfront.net/21127/archive/files/b0f9a1fc1da9f3153f50228e9744a31e.pdf?Expires=1781740800&Signature=PqyI2mAxE1uIap8mDrCZny3J4LO0FUyKDdPdVDtb0jhhZwx3Ne%7E354sbf3TiEv9irbobleicWbnMMzZK7VrZE-tBxfpKD2xeclAT64Xk61h-z41nRIk9DW6xI8MVWqqIKCl7KHa75yXSRNv-bZe7w60atQLhoaI7ZOz65f7zWMCxk386jTP8FRxLnReMPkqH1SZtdf6JeyDkxD243TqRO2PlyrUKSfABbDB3vo7OZ4VBgq8GIFefj3KpGRX1jtpt1wPh7sHXFxCAeZvEMcVLL5Idnt3JAixTaF2abYsF39fNSjiCvEg1gOmRkL%7EVyaxdDtUHHDvGu0EjUtZaGfDL2Q__&Key-Pair-Id=K6UGZS9ZTDSZM e27d5a8cbc18b54de5550a5c5e4ef01d PDF Text Text Conservation of the aerial tuning inductor from Rugby Radio Station, Warwickshire, UK Diana McCormack, National Museums Scotland, National Museums Collection Centre, West Granton Rd, Edinburgh EH5 1JA d.mccormack@nms.ac.uk Marta Leskard, Science Museum Group, Red Barn Gate, Wroughton, Swindon, SN4 9LT marta.leskard@sciencemuseum.ac.uk Keywords: Rugby Radio; tuning coil; conservation; reassembly; cable; Tufnol; polymer; safety; open display. Abstract On January 1st 1926 the Very-Low-Frequency (16 kHz) transmitter came into service at Rugby Radio Station, Warwickshire, to transmit telegraph messages to the Commonwealth. The aerial tuning inductor from the transmitter installed at Rugby is now the centrepiece of the Information Age gallery at the Science Museum, London. The fine tuning assembly, together with supporting framework, now standing in the gallery is only a portion of the original operating apparatus. The object was donated to the museum by BT and partially dismantled for removal to the storage site at Wroughton, Wiltshire. Museum curatorial and conservation staff advised on how much of the object would be taken into the collection, and worked with BT staff to deconstruct and transport the object to get it safely to its new home. Conservation work was then begun on the components of the object, to clean, repair and stabilise it so that it could be safely and effectively exhibited on open display to the public. Museum conservators worked with the heavy-lifting contractors from Constantine to rebuild the tuning coil at the centre of the gallery, in advance of other installation works. Conservators worked with the curator to ensure the object was displayed in a meaningful way and to retain as much as possible of the visible functionality of the assembly. Background In 1923, with the purchase of 920 acres of land at Rugby in the West Midlands of England, the General Post Office of Great Britain began the building of Rugby Radio in order to provide a Government station equal in power to any other in the world. This was partly for strategic purposes and partly to prevent an absolute monopoly by the Marconi Company who had applied a few years earlier for licences for the construction of eighteen wireless stations throughout the British Empire. The Hillmorton site was approximately 340 feet above sea level and was chosen to accommodate 12 250metre high masts, each of which was placed a quarter of a mile apart in an irregular octagon surrounding the station buildings. Twentyseven miles of copper wire in total formed two aerial sections which could be connected within the station buildings for extreme power. The system had an efficiency of about 29% at 16 kHz. 1 �Showing the Hillmorton site in Warwickshire. The tuning coils of the transmitter were wound with Litzendraht cables consisting of 6,561 strands of No 36 SWG copper wire, each strand insulated with enamel and one covering of cotton or silk. The formers were hex-frames of American white-wood (Liriodendron tulipifera), the external side being 7ft 9in (2.325m) in the largest former, and the turns were 6in apart. Five formers of eight turns each formed the aerial coil, three formers of four turns each the primary, and one former of two turns the coupling coil. The transmitter itself was designed to operate at a frequency of 16kHz, with a wavelength of 18,750 metres. Rugby Radio Station began transmitting very low frequency (VLF) signals worldwide on 1 January 1926 using the call sign GBR. Its VLF waves could follow the curvature of the Earth to travel very long distances, enabling one-way communication via Morse code. It transmitted wireless telegraph messages from the British Foreign Office, standard time signals from Greenwich, news bulletins, personal telegrams and Christmas greetings. With the advent of war in September 1939 and the suspension of most radio telephone overseas services, the transmitter became of vital importance to the Navy and other shipping interests. In later years Rugby Radio Station played an important role in both the Cold War and the Falklands War, as its very low frequency signals could be picked up by submarines. The VLF transmitter also broadcast time signals twice daily and, in 1951, added the transmission of reference Modulated Standard Frequencies (MSF). The tuning coil was damaged by fire in 1943 when the woodwork on the roof of the main station housing the VLF Transmitters became ignited due to the radiation effect from GBR. Because of its importance to the Navy, it was rebuilt and operational again within six months. There were very minor changes from the original design with American Whitewood (Poplar) used to reconstruct the formers. In 1965-67, the transmitter was rebuilt to broadcast more stable MSF but Sitka Spruce was substituted for the Whitewood as it was more easily available and had almost the same essential straight grain structure. The trunnion 2 �frameworks and formers were pegged together with heavy duty polymer dowels as metal dowels would have interfered with the long wave reception. On 1 April 2003 at 00.21 hrs the 16 kHz very-low-frequency transmissions from Rugby ceased as BT (British Telecom - the successor to GPO) lost the contract to transmit the MSF signal. A year later the twelve masts were demolished. BT Heritage and Archives circulated details of the tuning coil and the Science Museum accepted the donation after site visits in September and October 2004 were made by John Liffen, Curator, and Marta Leskard, Conservation & Collections Care Manager, to determine whether it would be possible to both store and eventually re-erect the coil for display. Showing the aerial tuning inductor as seen in situ by Science Museum staff. Acquisition of the object Dismantling of the coil was undertaken by BT high riggers and Science Museum conservators through November and December and the parts were transported to the Wroughton storage site in January 2005. The aerial lead-out frame and two longitudinal support beams which supported it and the two trunnion frameworks remained at Rugby as the aerial lead-out frame was still in use. It was decided in 2011 that the Rugby tuning coil (RTC) should be re-erected as the centrepiece landmark exhibit in the Information Age Gallery. Owing to the restricted height of the gallery (approx. 7m) it was accepted that the lower support trestles would have to be omitted. The lowest part would therefore be the two longitudinal beams which meant another trip to Rugby for Conservation staff. The two beams, no longer being used by BT, were retrieved but despite a stellar attempt, the aerial lead-out frame had to be left behind. 3 �Trial reassembly for display Two trial reassemblies were also required to ensure that the coil could be erected in the gallery; one to confirm the measurements of the total height and one to find a way to lift the formers onto the axles which were supported by the trunnion frameworks. While the measuring was carried out in the hangar where the RTC parts were stored, the trial reassembly was done in Wroughton’s Conservation facility (the Engineering Building) where the ceiling height was barely higher than that of the gallery. The trial reassembly was carried out by staff from Constantine Ltd. who were contracted to install all the large objects on gallery, supervised by Conservation staff. Despite having an overhead gantry in the conservation work space, only equipment that could be used on gallery was employed in the reassembly, to make sure that it was possible to lift the formers up and onto the axles. Only one former was installed during the trial. Showing trial reassembly in progress in the Engineering Building at Wroughton. While the trial was successful in ensuring that the RTC could be erected in the tight gallery space, the exercise revealed potential issues, with splits occurring along the grain of the wood forming the hex-frames and loss of strength in the polymer dowels. The brittle insulating tape covering the cotton-wrapped copper wire was damaged and shedding large fragments when the cables were moved around. 4 �Conservation Breaking down the coils Each of the formers comprised a cable/cables wound into the hexagonal framework, resembling a spider’s web. The cables were covered in insulating tape and then a hard insulating cover was tied around this. The formers had been stored in the partially dismantled state in which they had been removed from the radio station building. This was with a onethird section of the hexagonal formers removed, leaving the cables attached to the remaining two-thirds framework, but trailing on one side. The trailing portion of cable on each former had of course been stripped of its hard covers in order to remove it from the framework. Although they were not in storage for that long, the cables had sagged and the hard covers had begun to distort and become set into a slightly bent shape. The team from Constantine came to Wroughton to break down the partially dismantled formers into their component parts, as they would be transported to the gallery. It was important that they be a part of this process alongside the conservators as it was their task to reassemble the large frameworks on gallery, so both teams needed to understand the structure as much as possible. Once broken down it was then possible to spot weak points and damage to the woodwork that could be repaired in the workshop, before transporting the pieces to gallery. The cables were individually wound onto pallets and notes and drawings were made of how each had been attached to its framework. Labels were added at appropriate marker points to be used as points of reference on gallery, to ensure that all formers were reassembled and hung in the correct orientation. Showing the team breaking down a coil, winding the cable onto a pallet. The hard covers were made from a material known commercially as Tufnol (Godwin 2014), which comprised a paper pulp moulded in resin into a half-pipe shape with a semi-circular cross-section. The covers were used in pairs to cover the cabling and tied into position with many regularly-spaced string bundles, passed around the Tufnol in a double loop and knotted on top. The covers and the string lashing had become very dusty and dirty, discoloured in places, and faded by the light. The Tufnol had also broken and split in many places, particularly on the sections of cable that had remained in the frame during storage. It was 5 �noted that the covers stripped from the cables before storage were altogether straighter and had fewer points of damage from stress under the weight of the cable. In order to clean and repair the covers, they all had to be stripped from the cables. As so many of them had effectively re-set into a slightly bent shape, and as the length of each portion of cable varied slightly from frame to frame, it was important that covers should be replaced in the same positions from which they were removed. For this reason each pair of covers was carefully labelled after removal and laid out on pallets labelled clearly to show which former they belonged to. This required more working space in the laboratory but saved time in the long run, especially for reassembly on gallery. The knotted strings holding them in place had to be cut, as it could not be untied and successfully cleaned and re-used. The string was saved in sample bags for the purposes of colour-matching with new string, and for the sake of preserving original material. Conservation of the Tufnol covers The covers were very dirty and the grime was slightly greasy in nature, but in effect ‘baked on’ by the relatively high temperatures created during the working life of the object. The cleaning process was large in scale, so a detergent was selected that could be used at a fairly low percentage concentration in water, that was environmentally sound and could safely be used and disposed of in large volumes. A solution of Vulpex at 1:7 in water was selected for its ability to effectively remove the dirt quickly, with one wash. The covers were first dampened with a moist cloth, then the detergent applied, and then rinsed twice with water alone to neutralise the surface. Care was taken not to saturate the covers entirely, and they were then laid out (still in order)to dry overnight. This process also allowed the conservator to gain familiarity with cracks and breakages in each cover, and these were noted for repair at a later date. Showing typical state of Tufnol covers before conservation, still attached to cable. There were two types of breakage that occurred in the Tufnol covers: the first was simply a failure of old adhesive that caused pieces to separate at the joints with collaring pieces; the second was a stress fracture where the material itself had given way, leaving a sharp ragged edge with a very thin surface area. The former was much easier to repair, while the second type required some further support to be put in place around it. The failed joints were readhered using HMG Paraloid B72, and held with soft clamps overnight. To add extra support to breaks discreetly, a number of new collaring pieces were cut from spare Tufnol tubes and 6 �adhered over the breakage, allowing a much greater surface area for the adhesive to make purchase on. As there were a few sections of cable that had lost their Tufnol covers, a few entirely new covers were also cut from spare tubing. This material stands out a little as it is much cleaner and straighter than the used covers, but has the benefit of being made from original BT spares, of exactly the same material as the rest, and should age to blend in with the used covers over time. Some replica covers were also made from polypropylene pipe, cut in half lengthways, and painted on the exterior with an airbrush to mimic the mottled brown colouring of the originals. These were kept aside for use in case of any further breakages or failure of repairs when the object was being reassembled on gallery – as the covers would not be under the full strain of the cable weight until this point there was still a risk that the repairs may fail at the critical point. As the original strings securing the covers had to be replaced, a new supply of acid-free, unbleached cotton twine was acquired at the same thickness as the original, and dyed to match the old string. This was done so that the string would not stand out as being new against the used covers, and appear age-appropriate. Repairs to the woodwork During the breaking down of the object some minor damage was noted to the wooden structure and it became necessary to make some repairs. The cable had been held securely in the former with the aid of a wooden Litz clamp and wedge at each point where it crossed an arm of the frame. A Litz clamp is a small wooden block of about the same width as the cable, with a concave curving hollow to allow the cable to fit into it. The ends of the formers had suffered some chipping and cracking, and many of the Litz clamps were split in two and had only been held in position by tension. Breaks were repaired with a PVA adhesive and held in G-clamps until set. However, as there was a large supply of spare parts from BT, a number of ‘new’ Litz clamps were used to replace badly broken ones, as these were much more stable. The broken and degraded originals were boxed and labelled for storage. Showing repair of wooden former in progress, clamps in place. 7 �At the centre of each former the six arms came together around a hexagonal block and were joined with wooden dowels. During the dismantling process several of these became weakened or damaged, so it was necessary to strengthen the central joins with new dowels in some places. The new dowels used were again material supplied by BT as spares. In two of the formers the breakages were considered to be a risk to the structural integrity of the object and new dowels were inserted at extra points. This was an invasive procedure but necessary for the stability of the overall structure. Showing new dowels being inserted around the central joints of one former. Where the wooden beams had heavy deposits of greasy soot, bird droppings or footprints, this was cleaned with a mild detergent in distilled water. This was not a complete cleaning of the wooden framework, but brightened the surface and removed any disfiguring marks and dirt that could be transferred to other components. Conservation of the cables The cables had originally been covered in an insulating tape, similar to modern PVC electrical insulation tape. This had become very hard and brittle and was cracked, broken and flaking in many places, with large areas of loss. 8 �Showing the original yellow insulating tape with large areas of loss and shed fragments. It was necessary that the cables be bound in order for them to fit properly into the frames, as this tape provided the tension needed to hold the cable together and stop the cotton-covered copper strands from unwinding. The original tape could not be preserved for the most part as it was too brittle and degraded. It was necessary to find a similar material that could be used to replace this tape, but replacing like-for-like was not considered a desirable option, given that PVC tape would emit harmful gases over time and degrade in a similar fashion. A selfamalgamating butyl rubber tape was selected as the best option. This was selected because it would not bond to the object itself, and as it is based on polyisobutylene it would not cause corrosion of the copper wire, leave deposits on the object or give out harmful emissions to the gallery. Synthetic rubber is much more durable than organic rubber and withstands a much wider range of temperatures before becoming hard or embrittled. It had the added benefit of being an insulating tape, so although it no longer needed to perform this function, it was in line with the function of this layer on the cable and suitably thin but strong enough to perform this task. It is accepted, however, that given the lack of suitable environmental control in the gallery, the rubber tape will inevitably degrade over time (Williams 1997), but it was also considered likely that by the time the tape had degraded to the point where it no longer supported the cables, the object would most likely have been taken off display and disassembled, allowing either its removal or replacement as desired. This tape was also black in colour so could be used discreetly without drawing attention where it was visible between Tufnol covers. 9 �Showing the black self-amalgamating tape being applied over bare areas of cable. Cable 1 and cable 4 were found to have suffered from a fungal attack on the cotton bindings of the copper wire, causing powdering and disintegration of the cotton. This was most likely due to water ingress in storage affecting some parts of the cables that came into contact with it. Cable 1 was in worse condition than cable 4, but both required treatment with pure IMS to kill mould. Tests were done to consolidate the damaged areas to prevent loss of the cotton bindings, but the damage was too extensive and the powdery fragments had to be removed with a brush and vacuum in the worst-affected areas. A 5% Klucel G in isopropanol was used to consolidate as far as possible in areas around the damage to prevent further loss. The cables were then bound in self-amalgamating tape as done elsewhere. Showing cleaning of affected areas (left) and damage to cable (right) from mould. 10 �Repair of guide poles One of the six guide poles was broken into three sections at the joints and needed to be repaired. Due to the length of these pieces it was necessary to dowel the break with steel rod, which was held in place with an epoxy putty. This pole was also placed into the lowermost position at the base of the coils, to ensure that if the joints were to fail again there would not be any damage to the object as a whole. Twelve replica parts were manufactured from Perspex to replace missing or broken guide plates. These were fastened to the ends of the former arms in pairs, and had a large central hole through which the guide poles were slotted. These ensured that the formers remained on an even orientation during use or when the coils were repositioned. The replica pieces were painted brown to match the originals, but given a matt finish so as to be easily distinguishable from the originals in future. Showing the placement of polymer plates on ends of formers (before poles installed). Replacing the polymer fixings The original polymer dowels were replaced with steel bolts to give the structure strength, as it was not known whether the polymer could withstand any strain. The dowels could have been subjected to strain tests to find their breaking point, but it was considered much safer to simply replace them with steel, as the structure was to be on open display and safety considerations were paramount. The original material was labelled and packed in storage. It was, however, important to disguise the steel because the original object could not have functioned with this material in its structure. Any steel would have interfered with the signal and upset the fine tuning. All the new steel was therefore painted in exposed areas with an enamel paint to match the brown colour of the nylon polymer. During reassembly some of 11 �this paint was inevitably chipped by tightening the nuts with spanners, so it was necessary to touch-in these areas once the object was assembled. A note on environment and monitoring The conditions in the hangar storage were of a much higher relative humidity (RH) than was desirable, and so the object was moved to the Engineering Building workshops to allow it to acclimatise to more mid-range conditions there, before going to gallery where the environmental conditions were generally warm and dry. The acclimatisation period was approximately one year. A Hanwell Woodwatch WW01sensor was attached to one of the beams of the larger tower when it was moved to the Engineering Building, in order to monitor whether the drier conditions would cause the object any distress. The sensor is designed to record acoustic emissions as an indicator of deformation by micro-damage within the wood structure. As an unfortunate consequence of moving the object to the workshop, the increase in background interference noise was also significant, rendering the data rather opaque. It was also intended that the monitoring would be continued on gallery once the object was reassembled, but unfortunately the base-build conditions produced so much vibration, noise and dust that the monitoring was not possible during this period, when most change would be expected to occur in the structural material. This exercise perhaps demonstrates that other methods of observing such changes should be researched further. Transport to gallery The various components of the object were transported to the gallery on a number of pallets by Constantine Ltd. Smaller parts or fragile pieces were transported by conservation staff along with the necessary hand tools and personal protective gear. An area at the centre of the gallery was cordoned off for the reassembly work, as the basebuild was in progress at this time making the gallery effectively a building site. Reassembly on gallery An area at the centre of the gallery was cordoned off to allow for safe working and reassembly of the object. The object was to be positioned on a copper floor plate, which was already installed, and covered with plywood boarding so that it would not be marked by the ongoing work. The end tower was carefully positioned by measuring the length and spacing required for the complete object within this copper-floored area, and this tower was not moved from this position once work began. The three trunnion beams were then positioned and the opposite end tower moved into position to complete the basic framework. It was of course necessary to remove the second tower every time a former was added to the object, and then replace the tower to secure the structure while the next former was being prepared. The floor space allowed only for two formers to be laid out at any one time, so the formers had to be added in this manner, one at a time, rather than all six being prepared before assembly began. One former was assembled and one assembled former was dressed at any one time. 12 �Showing the working area on gallery, with one former complete and one in progress. In order to support the trunnion beams when the tower was removed, the central T-support was placed in position; once the tower had been replaced, the T-support was removed, and the former moved along the trunnion to its proper position. Once the first three formers were in position, the T-support was replaced and did not have to be removed each time another was added. This T-frame supported the trunnion beams at the centre of the object, spreading the weight of the formers and stopping the frame from sagging in the middle. A copy of the T-frame was also made by Constantine and two other prop beams, for use when the frame was carrying the weight of four and five formers, as extra support was needed at this stage when removing the tower. Once a former was assembled it was dressed by first winding the cable into position. Where it crossed an arm of the frame, the cable was held by a Litz clamp and a wedge. The wedges were tapped into place with a mallet to secure the clamps, taking care not to force them too far or split the clamps from too much force. Once the cable was fitted the next step was to dress the cable. It was at this point that the Tufnol covers were re-attached in their pairs, and tied into place with the string that had been prepared in the workshop. The covers retained faded marks showing where the string had originally been positioned, allowing just the right number and spacing of ties to be added. The guide plates were then attached the ends of the arms in pairs, and the former was ready to be raised onto the frame. Each former was first braced at the centre by placing a custom-fitted wooden board around the blocks, to support the structure as it was raised. This measure was introduced after the trial reassembly showed that the central joints came under too much tension in the lifting process. It was then lifted on the gantry and brought vertical, before the brace could be 13 �removed and the former hung on the trunnion beams. The second tower was then put back in place and slings were then used around the former to draw it along the trunnions to its proper position. Showing the first completed former with cable being raised and hung on the framework. When all six formers were in place the guide poles could be inserted to complete the object. As the base-build works were to continue for several months before the work would become dust-free, the object was covered with two large tarpaulins to protect it from the worst of the working dust. When building works were finished the tuning coil was un-sheeted and dusted before the gallery opened. Display Considerations Configuration of the formers The formers were spaced according to their positions as shown in a photograph of the object in their last working configuration, in accordance with how the curator wished for the object to be presented. In order to move the formers along the trunnion beams they were slung around the central point and manually pulled and pushed into place. The height restrictions in the gallery meant that the wheels to which the cables were originally attached could not be displayed, as these were supported by the lower trunnion beams that were excluded. This meant that the cable ends had to fall loose, and it was decided to allow them to drape to the floor and be gathered beneath the object. The ends were lifted onto mounts so as not to sit in contact with the copper sheeting. This had the added bonus of keeping the loose ends out of reach of the public. 14 �Design echoing lost components Once works were complete, the copper floor beneath the tuning coil could be uncovered without fear of damage. This floor was incorporated into the design to echo the copper ceiling plate at Rugby that was positioned above the apparatus after the fire in 1943. A further design measure introduced was the kerbed edge on the copper floor, which made a clear perimeter around the object to discourage the public from approaching too close to the object on open display. Showing the finished object on display in the Information Age gallery. Conclusion The reassembly of the tuning coil was achieved by close collaboration with a team of heavylifting handlers from Constantine Ltd, and required some compromises in terms of conservation. These mainly concerned safety requirements and ensuring the stability of a large structure on open display to the public. It was attempted to make these compromises invisible to the public by making the object appear as it did when in its working state. Although the object as it now stands is only a portion of the apparatus at Rugby, it represents the almost-complete fine tuning coil assembly. It is hoped that this communicates to the public a sense of the larger site works and instils an interest in the history of Rugby Radio Station as a whole. The object stands floor-to-ceiling at the centre of the Information Age gallery, which was opened to the public in October 2014. 15 �Acknowledgements The authors would like to thank the Information Age project team at the Science Museum, particularly: Dr Esther Beeby, Conservator; Mr John Liffen, Curator; the Wroughton staff; and, the team from Constantine Ltd. The authors also gratefully acknowledge the support of the Clothworkers’ Foundation, National Museums Scotland and the Science Museum for aiding the delivery of this paper. Biographies Diana McCormack entered conservation from a background in archaeology and research, studying at Durham University as an Objects Conservator and training with the Wiltshire County Council Conservation & Museums Advisory Service. She has subsequently worked as a Project Conservator, for English Heritage, the Science Museum, and National Museums Scotland. Marta Leskard is Conservation & Collections Care Manager for the Science Museum Group at the Wroughton storage facility. She is also a doctoral student at the University of Bath, studying the use of innovative materials in effective environmental control for museum storage buildings. References Godwin, R. 2014. A History of Tufnol, accessed 2014, http://ahistoryoftufnol.org/index.html Hancock, M. 2011.The Official History of Rugby Radio Station, © British Telecommunications plc., accessed 2015, http://www.subbrit.org.uk/sbsites/sites/r/rugby_radio/indexr69.shtml Williams, S. 1997. Care of Objects Made from Rubber and Plastic: CCI Notes 15/1, Canadian Conservation Institute. 16 � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Big Stuff 2015 Creator An entity primarily responsible for making the resource Alison Wain Date A point or period of time associated with an event in the lifecycle of the resource 03.09.2015 - 04.09.2015 Paper A paper presented at a conference or a workshop Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Conservation of the aerial tuning inductor from Rugby Radio Station, Warwickshire, UK Creator An entity primarily responsible for making the resource Diana McCormack & Marta Leskard cable conservation open display polymer radio reassembly safety Tufnol