Big wheel keeps on turning

The British Airways London Eye is one of the most spectacular and popular attractions in the world.

The British Airways London Eye is one of the most spectacular and popular attractions in the world.

Since opening in 2000 it has completed more than 30,000 rotations at 0.26m/s, and has welcomed more than 20 million visitors on board for the half-hour ride.

The 32 capsules can carry up to 15,000 visitors per day.

An exceptional piece of modern engineering, the London Eye is still moving safely thanks to a number of specially made components.

The two main spindle bearings installed in the hub of the Millennium Wheel are large-sized FAG double row radial spherical roller bearings with pin-type cages.

They are located on the wheel axis as a locating/ floating bearing arrangement and have to withstand the load of the 135m high wheel and 1700t of steel.

The spindle and hub alone weigh over 330t.

The locating bearing has an outside diameter of 2.66m, weighs 6.3t and is firmly mounted on the shaft in axial direction.

The floating bearing has an outside diameter of 2.62m, weighs 5.2t and can move on the shaft in order to compensate for longitudinal expansion.

As these are considered safety-relevant components, the bearings have to undergo regular inspections.

During the second of these inspections, which took place in early 2004, the bearings were found to be as good as new.

The lubricant was free of any contamination and wear particles and no abrasion or wear could be detected.

As lubricant was found in the roller bore, future wear of the pins can almost certainly be ruled out.

This is good news for the Schaeffler Group which has also supplied two large-sized INA Elges spherical plain bearings in the base of the wheel.

These were originally required for slewing the wheel from its horizontal mounting position over the Thames into its vertical operating position.

The bearings now help to compensate for wind induced micro movements that would otherwise have an adverse effect on the not very flexible steel construction.

The bearings in the base of the wheel have an outside diameter of 6m and weigh 194kg each.

The outer ring is firmly fixed to the housing, whereas the inner ring can move on the shaft.

This makes it possible to compensate for heat expansion.

The spherical plain Elges bearings are coated with Elgoglide, a low-friction, maintenance-free material.

This is a PTFE, commonly known as Teflon, and fabric composite that has been developed by INA FAG to meet the demanding long-term, maintenance-free requirements of the architectural and construction industry.

The special coating increases the life span of the bearings considerably even at the high load of 362N/mm2.

During the slewing procedure the bearings even had to take a load of more than 450N/mm2, which they withstood without problems.

Life span of the bearings has further been increased by sealing them on both sides to eliminate contamination.

Without these bearings, the design of the wheel would have to have been changed into something much less elegant than the London Eye as we know it today.

The popularity of the London Eye has sparked ideas for similar projects around the world.

Planning has already started for the construction of giant Ferris wheels in Singapore, Melbourne, Beijing, Shanghai, Hong Kong, Dubai and Berlin.

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