The delay means that project manager Mace will not receive a bonus for completing the project on time. “Bonuses that might have been paid won’t now be paid,” said a source. The amount is estimated to be in the region of £300 000.
The decision not to allow passengers on board the wheel was taken by Mace, and not by the Health and Safety Executive, as some reports claimed.
Mace made the decision on 30 December, a day before the official opening, because of uncertainty over why the clutch, which helps to keep the capsule stable, had failed. “At the time, it couldn’t be confirmed whether the problem was only with the clutch,” said wheel designer David Marks of David Marks Julia Barfield Architects.
He added: “The instruction to disengage the clutch was given remotely, so it was not clear if it was the clutch itself or if the computer or software controlling the clutch was at fault.”
The problem was discovered during one of the 200 commissioning and safety tests carried out on the wheel before it could open to the public.
The problem is being investigated by Mace, client’s engineer Allott & Lomax and the clutch manufacturer. “It could be as simple as a bit of rust or something in the clutch,” said Mace project director Tim Renwick.
The capsules, which accommodate 32 people, are mounted outside the wheel’s 150 m diameter rim. They are supported by two 4 m diameter steel ring bearings that ensure the pods remain level as the wheel turns.
This design means the capsules have a low centre of gravity that makes them unstable if the passengers move around inside the pod. To compensate for this, each capsule is fitted with a mechanical levelling system to ensure they remain horizontal.
However, in a test carried out on 30 December, the clutch seized up in the “on” position. This could result in the capsule tipping upside down as the wheel turned.
Marks played down the the clutch problem. “It is not something that is required under normal operation; the clutch would only have to be disengaged if a motor fails,” he said.
Delays in raising the wheel and the tight construction programme were responsible for the team missing the deadline. “We just ran out of time to complete the testing regime,” said Marks. “The problem was a disappointment to all concerned.”
Renwick added: “If we’d had another 24 hours we could have sorted it. We could even have taken the faulty capsule out of commission.”
The wheel is due to open to the public in the middle of February.