Feel the burn: designing the London 2012 Olympic Torch

After years of dedication, sacrifice and the proverbial blood, sweat and tears that go with it, athletes across the world are gearing up to take part in the 2012 Olympic Games. It's a sporting spectacle without equal and one symbolic of human endeavour of all stripes and colours.

But while these sportsmen and women have been diligently pushing themselves to the limits of human capability in intense training sessions, the Olympic Torch, itself an instantly recognisable symbol of the Games, has also been subjected to a grueling series of trials and tests.

Sequestered away from expectant eyes and cheering crowds at BMW Group's state-of-the-art Energy and Environmental Test Centre (ETC) in Munich, the torch was put through its paces. On an ordinary day the ETC's three wind tunnels and two climatic test chambers are used to evaluate the company's flagships cars and motorcycles. Designed to replicate hostile environments such as the Arctic Tundra and the Sahara desert, the facility can create environments with ambient temperatures ranging from -20°C to 55°C, 280km/h hurricane-strength winds, and altitudes of up to 4,200m above sea level – almost half the height of Mount Everest.

Road-testing the Torch

In a series of tests designed to emulate the worst the British weather could throw at it, the torch endured temperatures ranging from -5°C to 40°C and 50mph gusts of wind, as well as simulated downpours and snow storms. It was also dropped onto both ends in computer simulated worst case scenario tests. Throughout it all the flame stayed alight.

Central to this success was the burner. This was designed and manufactured by Birmingham-based LPG gas specialists Bullfinch who were given the brief after one of their previous projects, a series of 250 beacons running the length of Hadrian's Wall installed in 2010, caught the eye of LOCOG-appointed torch engineering partners Tecosim.

"We weren't initially presented with a final design so we were allowed some leeway," says Christopher Andrews, technical manager at Bullfinch. "We were asked to work within the space environment that we were given and found it was almost impossible. We needed some minor adjustments in both the shape and the height of the fitting. There's a solid aluminium bezel at the top and we needed some slight modifications in that to ensure that we got our burner system in place."

The 800mm, 800g Torch comprises an inner and outer skin, made from an aluminium alloy developed for the aerospace and automotive industry, and a cast top piece and base into which the burner fits. It was created by east London designers Edward Barber and Jay Osgerby, who won the honour following a competitive tender run by the London 2012 Organising Committee and the Design Council.

Central to the design are the 8,000 holes perforating the torch's external skin, each one representing one of the 8,000 bearers carrying the torch on its 70-day tour of the UK. It's an elegant enough metaphor perhaps, but it was also the source of a potential problem in that it makes the flame a lot more likely to be blown out by an errant gust of wind.

"That was a considerable worry to us," Andrews explains. "In the past the torches, around the flame area, have been fairly solid which presented a nice protection for the flame. One of the other considerations that we had is with a perforated skin with the ambient temperature and any wind, particularly cold wind, could affect the operating temperature of the cylinder of the burner itself."

Keeping the flame alive

The solution involed the use of a liquid offtake system.

"In a cylinder of propane, butane or any mixture of the two, the gas is stored under pressure as a liquid," says Andrews. "In normal circumstances you would fill that two-thirds to three-quarters full and the space at the top of the cylinder would then be filled with gas. The minute you release the pressure the gas flows out and the liquid beneath it needs to boil to produce more gas and maintain the cylinder pressure.

"Butane boils at 0°C and propane boils at -42°C. In very cold conditions an appliance operating on butane will not light as the liquid cannot turn into a gas, which is why industrial products are normally propane and domestic products are normally butane.

"For the process of the liquid to turn into gas it needs heat so it draws any residual heat it needs from the atmosphere which is why on large road-marking operations with 47kg orange cylinders you can sometimes see ice forming even on a very hot day," Andrews continues. "That is because the cylinder is trying to produce as much gas as it can to power the burners that are being used.

"There's also an evaporation coil which takes the liquid from the regulator up around the main burner both inside the inner cage and outside that cage and inside the outer shield. Then, back down to the injector."

From an aesthetic point of view it was also important for the burner to replicate the rich yellow flame of the pitch-soaked rag used in traditional torches. LOCOG also specified that it must be visible for at least 200m allowing the spectators gathered to get a clear view. Eventually engineers at Bullfinch chose a burner system running on a 60 per cent propane/40 per cent butane mix which would give a flame of the desired height and colour and also operate at an appropriate temperature.

And of course another key consideration was the consistency of the flame.

"Within this burner there is a pressure regulator which controls the outlet pressure of the liquid to two Bar, and that gives us a very consistent flame," says Andrews. "In very windy conditions the flame will reduce down in size and it will become more blue because of the introduction of extra oxygen but the important thing is that it remains alight and then when the wind drops the flame then goes back to the very soft, yellow flame you see on the torch normally."

The flame started its 70-day torch relay around the UK at Land's End on 19 May after being lit in a symbolic ceremony at the Temple of Hera in Greece. It is currently making its way across the country and will finish at the Olympic stadium on the eve of July 27. The Olympic Cauldron will be lit among the Maypoles, Morris dancers and farmyard animals of Danny Boyle's 'green and pleasant land' opening ceremony and will continue to burn until all races have been run and all games played.

Throughout this 8,000 mile journey the torch has had to endure one of the wettest, dreariest summers Britain has seen for the last 100 years. And despite the careful design and rigorous testing, the flame was briefly snuffed out in Exeter, Devon, while being carried by wheelchair user David Follett.

Andrews maintains this was down to human error, noting that all the torches were tested before leaving the factory. In fact, the burner in question was returned to the company after this mishap and found to be in perfect working order. Regardless of what happened and who was to blame, the torch has unquestionably ignited a feeling of excitement and anticipation ahead of the Games wherever it has travelled. And that, after all, is its primary purpose.

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