The cauldron was re-lit to beating drums and resounding cheers in The Overflow Park on Olympic Boulevard. The stainless steel bowl will stand as a permanent reminder of the success of the Games. The project was conceived and designed by Barry Webb, Iain Clark and Fiona McVicar of Barry Webb & Associates, with Show Technology’s architectural products manager Jonathan Ciddor assisting with the configuration, control and integration. Installer Beyond AV was responsible for the co-ordination, installation and programming of the lighting system.
The cauldron sits upon a concrete slab at ground level and beneath it is a large chamber, 5 metres deep, housing the lighting equipment, pumping and gas controls, and a large water tank. On the ceiling of the pit are 22 Clay Paky Golden Scan 3s arranged in two rings - 16 on the outer and six on the inner. The scans project light up through 220mm round glass portholes. As well as their excellent positional capabilities, the Golden Scans were chosen for the HMI 1200W lamp, which can effectively cover the distance to the cauldron and its support structure, and the water flowing down from above. The beams remain static and usually white in colour, with the colour-changing option reserved for special occasions. "Because the beam angle is quite wide and the porthole quite narrow in diameter, it was very difficult to get the beams to line up properly," explained Beyond AV’s Con Andrews. "Consequently, movement of the beam is virtually impossible."
Fiona McVicar spent some considerable time ray tracing the beams to ensure that they would achieve an even light distribution across the whole of the cauldron and water flow. To accommodate the requirements, Show Technology and Clay Paky provided a special wide-angle lens combination to increase the beam angle from the standard 16° beam angle out to 23°, enabling more uniform coverage of the cauldron.
The control system is based around Martin Pro’s LightJockey PC-based system, which now has real-time scheduling thanks to a software upgrade. The whole Olympic precinct’s exterior lighting was controlled by a conventional Clipsal CBus control system, including the Overflow Park, so it was essential that a simple interface allow the pre-programmed cauldron shows to run reliably and in co-ordination with the park lighting. The Martin AD-DA interface for LightJockey allows multiple external triggers to activate whole cue sequences. This way CBus provides a contact closure and initiates the show.
Andrews described the significant components of the system: "With 22 luminaires operating in an industrial environment, five metres off the deck, and below ground, with high pressure water and gas piping running all over the pit, the DMX is via individual opto-isolated runs through LSC splitters. This way, if there is a cabling fault it is very fast and easy to locate. We also had to co-ordinate the power-up of the scans. Striking 22 1200W HMI lamps pull a significant current that would have required excessive power engineering. Using DMX to drive standard mains electrical contactors, the scans are turned on and off in a sequence and are ready for each show."
Jonathan Ciddor confirmed that these were significant issues identified during the design stage and were easily solved by Show Technology and Clay Paky recommending the GS3s for the project.
