In January 2004, The All England Lawn Tennis and Croquet Club announced plans to build and construct a fully retractable and weatherproof roof over its famous Centre Court in readiness for the 2009 Wimbledon Championship.
The new roof, three years in the making and five years in the planning, is a retractable 5,200 sq metre folding fabric concertina, made from a revolutionary translucent, waterproof material called tenara, which allows natural light in when the roof is closed.
The design and build of the roof was commissioned by a chosen consortium of companies which included, Sheffield based Street Crane Xpress (SCX), whose role int he build was to focus on the mechanisation and control of the roof, enabling it to open and close depending upon weather conditions.
42 bespoke electric linear actuators have been manufactured and supplied to create locking devices, 36 of which operate when the roof opens and closes. Specialised engineered solutions for this challenging application play an integral part in improving playing conditions on centre court and contribute generally to a more pleasant spectator environment at this unique and historic venue, whatever the weather! The roof, measuring 80 metres long, is divided into two sections with a total of nine bays of structural fabric, four bays in one section and five in the other. Each of the nine bays is clamped on either side by prismatic steel trusses. Altogether there are 10 trusses spanning 77 metres across the court. At the end of each truss there is a set of wheels that glide until the two sections overlap, giving the equivalent coverage of 7,500 open umbrellas!
Much of the roof’s working life will be parked in the open position. When the roof is ready for closing, one section is parked in its folded state at the north end of the court while the other is parked at the south end. Again a combination of actuators and arms form the mechanism for closing the roof at a maximum speed of 214 mm per second. The mechanism moves the trusses apart and, at the same time, unfolds and stretches out the fabric between the trusses over the court until the two sections meet in an overlapping seam above the middle of the court. At this stage 36 linear actuators lock each section of the roof in place.
These linear actuators used for locking and unlocking the roof segments were specially for the Wimbledon roof using 3D design technology to optimise the design process and integrate with SCX. The actuators design is based on the Type-A Rolaram technology which has been used worldwide invarying industry sectors including automotive, medical, steel and nuclear. Each of the Wimbledon Rolaram’s is designed to have a peak load rating of 160kN to withstand forces exerted by nature. They operate at 1500mm/min over a 400mm stroke with the use able stroke set by limit switches integrated into the actuator. Drive for the actuator is provided by an electric brake motor with an IP66 weatherproof enclosure. Both the motor and the limit switches connect to the electrical control and power systems via plug-in connectors for quick and easy installation. The completed Rolaram actuator is mounted in the roof using a trunnion to clevis type arrangement that allows the actuator to pivot through an arc as it operates. Just like the players below the actuators are finished in a classic white paint especially for Wimbledon.
With the roof closed over the court the arch shape to the tops of the trusses helps the structure to withstand loading from elements such as snow and wind. The shape also assists in providing 16 metres clearance sufficient for even the highest of lobs.
A key element of the design has been to allow natural light to reach the grass, while an airflow system removes condensation from within the bowl to provide the optimum internal environment for the comfort of spectators and players when the structure is closed.
The roof has been designed to close in under 10 minutes. If the roof is being closed forrain, court covers will protect the grass in the usual way while closure is in progress. After the roof has been closed, play can resume in approximately 20 minutes, depending on climatic conditions, allowing television companies to be able to broadcast almost unbroken coverage of play on every day.
The benefits of having a moving roof are clear to see. No longer will there be unpredictable and long-lasting rain, which in the past stopped play during prestigious games. It will also enhance the Wimbledon Centre Court with-out compromising on its long standing design.
The project is now complete and on May 17th 2009 the official inauguration and testing of the roof, was held on Centre Court. On the day under the watchful eyes of four grand slam players and 15,000 spectators, the roof closed in 7 minutes and 4 seconds to a rapturous applause from all who witnessed this historic event. Daniel Salthouse, Project Manager for SCX, said “Reliability was always the key issue when considering which equipment suppliers to use on the roof. We chose Power Jacks both as a result of the numerous successful projects that we have used their equipment on in the past and because of their ability to mee tour demanding specifications”.