PROJECTS

What have GPS, a ladder and a rubber dinghy got in common? Mike Simpson explains

The London 2012 Olympics has given the UK a unique opportunity to show off its best design and newest technology. Given that contracts for the venues were resolved more than three years ago, the challenge was to make sure that what was specified wasn’t outdated by the time it came to installation. For example, the park-wide external lighting was to have been the latest compact white light source but during the procurement stage a number of lanterns were updated to LEDs.

Access to the park was tightly controlled and required every visitor to hold a Construction Skills Certification Scheme card. First everyone had to undergo a park-wide induction and then each venue had its own induction. For the main stadium, special training in the use of harnesses and working at height was also required. If you didn’t visit the site for three weeks, your pass expired and had to be reactivated.

Missing broadcasting brief

Another challenge was the lack of a broadcasting brief. Most venues are designed on the specifications used in Athens and Beijing. While this was all right in principle, production techniques have moved on in the past four years with more focus on high definition, slow motion replays and the beginning of 3D. All of these affect the lighting.

Lighting was considered at an early stage in the design of the main stadium to ensure that the correct aiming angles would be achieved for broadcasting. This was to set the overall height of the roof on which the lighting towers were to be mounted. The main stadium uses 536 2kW floodlights on 14 towers which achieve 200 lux on the vertical. Half of these were hot restrike and would come on instantly if the power failed.

Access to floodlights was high but well designed which made the commissioning easier. We used GPS positioning to set out the aiming points, significantly speeding up installation. All towers were aimed within four working days, which we believe is a record for a stadium of this size.

'During the procurement stage, a number of lanterns for the park were updated to LEDs' Mike Simpson

The velodrome presented its own challenges with its low roof that hugs the side of the venue. The floodlights were attached to a suspended containment from the roof. But there wasn’t enough height or load capacity to use a walkway, so floodlights were set to the correct angle before being hoisted up by riggers on ropes. All floodlights are standard, and can run from an uninterruptible power supply if the power fails.

A total of 356 1kW floodlights achieve 2,000 lux on the vertical. When taking readings we had to use a ladder laid on the track to reach points where it banked steeply. This building will stay open after the Games, so the design had to provide eight different switching steps (2,000 lux, 1,000 lux, 2 x 750 lux, 4 x 300 lux). The multiple steps at lower levels were to extend lamp life, so no floodlight could appear in more than one switch mode. This, together with the need to balance load across phases and mix light evenly between phases, proved a challenge for the electrical and lighting designers.

The aquatic centre was a unique design by ZHA. The event lighting comes through holes or ‘bubbles’ in the roof. These bubbles contained between two and 14 1kW floodlights with just under half hot restrike. A total of 420 1kW and 122 400W floodlights achieve 2,000 lux on the vertical. How do you take light meter readings over a swimming pool? With a boat. We got a small inflatable dinghy and tethered it with ropes so it could be pulled into place to take the readings.

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