A second attempt to lift the world’s biggest ferris wheel, the 1,500t London Eye, is to be made this month following an aborted first lift on 10 September, writes Adrian Greeman. The delay will be about four weeks.
Project director Mace is working with Dutch fabricator Hollandia and heavylift contractor Mammoet to re-design temporary cable anchorages on the wheel rim. Unlocking of these wedge and plate assemblies forced the first lift to be called off during final 110% load tests on the day of the lift. Failure of the lift was a major embarrassment as television crews from around the world had gathered to record the spectacle.
Mammoet is using a temporary A-frame – taken from its massive MSG-50 II lifting device – mounted with four large strand jacks to haul the wheel, together with the wheel’s permanent A-frame support, from a horizontal assembly position to a 65O ‘vertical’ where it will be stayed on permanent cables. The wheel will then be fitted with passenger cabins and angled on the A-frame to a true vertical.
The 135m-high observation wheel, designed as a tourist attraction to give passengers views over London, has been assembled on piles in the river Thames just downstream of the Westminster bridge, Big Ben and Parliament.
When upright, the London Eye will be London’s fourth highest structure. It is being built as part of the UK’s millennium celebrations.
“The wheel rim is linked to a spindle and hub by tension cables, like a bicycle’s spokes,” explained project director Tim Renwick. “But for the lift there are additional temporary cables running from the top of the spindle to the rim.” It was two of these which came loose at about 4pm when the loading was at about 90% on the tied down wheel. Corinne Hall, one of the many public spectators who had gathered since morning with cameras and videos, said she heard a crack and saw the cables splash in the water “followed by others around the rim”. The spindle dropped back.
“Cables are threaded into an anchorage assembly welded to the rim,” explained Renwick, “and held by a split plate arrangement and wedges. The grip tightens with compression.” But the cable must be properly perpendicular to the assembly, he said, and to make sure of that, the front of the assembly rotates. “But that did not happen fully because of a friction problem,” he said.
Since the aborted first lift the team has spent several weeks reanalysing the anchorages and modifying them to push the rotating section back “which will increase the bending moment on them and therefore help overcome friction”.
British Airways, the wheel’s sponsor, remains confident that the London Eye will be ready for its 31 December opening date. The programme was already tight, said Renwick, but he thought it might be possible.
Previously the world’s biggest ferris wheel was in Yokohama, Japan, standing at 114m.
