Horizontal Assembly of a Cable-Tensioned Wheel
Erecting a 135-metre wheel upright from the start would have required extensive temporary falsework to hold each rim section in place while the spoke cables were installed and stressed in sequence. The horizontal method removed that dependency entirely.
The response was to assemble the entire structure flat — rim, hub, spindle, and all spoke cables — on piled platforms in the river. The cables were tensioned before the lift began. By the time the strand jack system engaged, the wheel was already a fully assembled, cable-tensioned structure lying on its back in the water. It also allowed construction to proceed simultaneously across multiple locations, reportedly cutting the overall programme by around half.
† Reported figures — not confirmed in primary project documentation.
The Two-Phase Strand Jack Rotation
The lift was carried out in two phases. A strand jack system operating via a temporary A-frame — reportedly around 90 metres tall, erected on the foundation plinths — rotated the structure at roughly 2 degrees per hour. It reached 65 degrees and stopped. Engineers held it there for approximately a week. The project record indicates the two-phase approach was introduced to allow the stabilisation system — the arrangement of cables and winches controlling the wheel against rotation — to be reconfigured at that point, giving better control through the final arc to vertical.
The sequence was understood to address load management as much as anything else. A 1,700-tonne structure rotating about a fixed support generates continuously changing reactions across the A-frame, the foundation, and the backstay system — and the stabilisation demands change with them.
Temporary Works Under a Cantilevered Support Condition
The wheel also cantilevers over the Thames — in its final position the spindle is supported on one side only. That support arrangement meant the temporary works needed to address wind loading on a partially-rotated structure at an intermediate angle, not just at the final position.
The horizontal assembly method, the two-phase rotation, and the hold at 65° were not incidental details of the build. They were the governing logic of the erection sequence — shaped by the cantilever condition of the permanent structure, the load path through the temporary A-frame, and the limits of what the backstay and stabilisation system could manage continuously through the full arc.
Frequently Asked Questions
Erecting a 135-metre wheel upright from the outset would have required extensive temporary falsework to support each rim section while the spoke cables were installed and stressed in sequence. Assembling the entire structure flat on piled platforms in the Thames removed that dependency. It also allowed construction to proceed simultaneously across multiple locations — reportedly cutting the overall programme by around half.
The two-phase lift was introduced to allow the stabilisation system — the arrangement of cables and winches controlling the wheel against rotation — to be reconfigured at the 65° hold position. This gave better control through the final arc to vertical. The hold also addressed the continuously changing load distribution: as the 1,700-tonne structure rotated about its fixed support, the reactions across the A-frame, foundation, and backstay system shifted throughout the arc.
Mammoet acted as heavy lift contractor, working for Hollandia, the Dutch main design and construct contractor. The strand jack system used in the rotation was manufactured by Enerpac. Mace was responsible for overall construction management, with Tony Gee & Partners as consulting engineers for the foundation works.
A strand jack is a hydraulic tensioning device that grips and pulls high-strength steel strand in incremental strokes, capable of lifting or rotating very large loads with precision. On the London Eye, the strand jack system was mounted at the top of a temporary A-frame approximately 90 metres tall, erected on the foundation plinths. The jacks pulled cables attached to the wheel rim, rotating the entire 1,700-tonne structure from the horizontal at roughly 2 degrees per hour.
The London Eye is cantilevered — the spindle is supported by an A-frame on one side only, with the wheel extending over the Thames on the other. This arrangement meant the temporary works had to address wind loading on a partially-rotated structure across a range of intermediate angles, not only at the final vertical position. The cantilever condition of the permanent structure was the primary factor shaping the load path through the temporary A-frame and backstay system throughout the rotation.