THE FOOTBALL PITCH IN THREE PIECES WEALTH CREATION

Tottenham Hotspur is part of a regeneration project that has transformed the stadium and surrounding area. As well as being home to Tottenham Hotspur Football Club, the stadium will host NFL games in the UK, and to accommodate both sports, the stadium boasts the world’s first dividing sliding pitch. Science journalist Richard Gray asked Danny Pickard, lead engineer at SCX, RETRACTABLE PITCHES AROUND how the pitch was developed. THE WORLD While the Tottenham Hotspur Stadium now has the first retractable pitch that divides into sections before it is rolled away, it is not the first stadium in the world to have a removable grass field. In 1998, the first major sports stadium to get a so-called ‘convertible pitch’ was the GelreDome in , . Home to the football club Vitesse Arnhem, a huge concrete tray that contains the turf can be pushed out through an 85-metre For 118 years, , will be played on the world’s opening under the south stand to make way for concerts and home of Tottenham Hotspur first dividing, retractable other sporting events. It takes around three and a half hours to Football Club, has been one of grass football pitch. Mounted move the enormous slab and it is usually left outside the stadium the most famous addresses in in three enormous trays, the in the wind, rain and sunshine so that the grass can grow. football history. The stadium grass surface can be rolled In 2001, retractable pitches were installed at both the Arena hosted some of the team’s away beneath the south AufSchalke football stadium, which is now known as the Veltins- most dramatic moments, from stand to reveal an artificial Arena, in Gelsenkirchen, , and at the Dome in famously picking apart the NFL American football Toyohira-ku, . The 11,000-tonne playing field at the Veltins- formidable Polish side Górnik field beneath. The Premier The football pitch at the new Tottenham Hotspur Stadium hides an artificial NFL field underneath. The pitch slides over in three metal trays, each weighing over Arena, home of the Bundesliga side FC Schalke 04, can take six 3,000 tonnes, which are stored beneath the stands when not in use © Tottenham Hotspur / SCX Special Projects Zabrze in its first ever European League Club already has a to eight hours to move in or out of the stadium. Four hydraulic Cup appearance in 1961 to 10-year contract with the presses push the lawn about half a metre at a time in what can defeating Inter Milan during its NFL to stage a minimum of be a 340-metre round trip. first Champions League outing two games a season, using The Sapporo Dome primarily hosts and football in 2010. In total, Spurs played the artificial surface. The games for the Nippon-ham Fighters and Consadole 2,533 competitive games at retracting pitch means that Sapporo FC. The pitch here is the world’s first ‘hovering football the North stadium the stadium can quickly stage’, where the 8,300-tonne field partly floats on a cushion before demolition work began convert from hosting a of air as it moves, reducing the weight that the 34 wheels in May 2017 to make room for football match on the grass underneath have to carry. To convert the stadium, the artificial THE FOOTBALL a new 62,062 seat stadium. This pitch to an NFL game on baseball field rolls away and a bank of seats are retracted into the redevelopment, rumoured to the artificial field in just walls. The pitch rolls into the arena and rotates 90 degrees along cost around £850 million, has a few hours. The - with a revolving bank of seats until moved into place, and the not only almost doubled White wearing artificial surface also retractable seats move back into place. In total, the whole process Hart Lane’s previous capacity, means that the stadium can can take four or five hours. but has also turned it into one of host other events, such as Most recently the 63,400-seat University of Phoenix Stadium PITCH IN the most flexible major venues concerts, without damaging in Glendale, just west of Phoenix, Arizona, opened in 2006. It in the world. At the very heart the grass. For most football makes use of the space outside the stadium, rolling the 9,300- of the stadium, the pitch has grounds hosting concerts tonne grass playing surface out through an opening at one been transformed from a simple and other events involves end in around one hour. This has allowed the stadium to host patch of grass into an ambitious putting thick matting onto events as diverse as motorsports, wrestling matches, NFL games, engineering project. the pitch, which can quickly international football matches and concerts by acts including Matches at the new kill the grass and requires Beyoncé, Taylor Swift and U2. THREE PIECES Tottenham Hotspur Stadium new turf to be laid before the

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The whole pitch weighs over 9,000 tonnes, more than the Eiffel Tower in Paris. Each of the three sections need to fit together seamlessly so that fans watching football games, and footballers taking part, cannot tell that matches are happening on trays mounted 1.6 metres above solid ground

grow. The team initially used a observes the pitch’s progress. Once it has stopped, a parking the inside edge of this structure device similar to a pizza cutter to Moving the pitch sections brake – similar to the one in a can be lifted or lowered using slice between the sections, but requires both operators to car – is applied to clamp the hydraulic actuators. it left noticeable damage when continually press down their structure in place. The outer Once the pitch is in place, the pitch was reassembled later. safety buttons. An automatic sections then move inwards to hydraulic cylinders raise the Instead, it found that the best slow-down system is triggered meet the centre of the pitch sidelines before the flaps are approach was to simply let the as the huge pitch sections trip with the help of 32 hydraulic lowered to rest on the edge turf tear naturally as the sections sensors when the sections cylinders on the steel structure of the turf. Ramps in each pulled apart, allowing it to split are 75 centimetres apart. This underneath. corner of the pitch also pivot along its own weak points. slows the movement down There needs to be enough upwards with the touchlines To ensure that each section to the tenth of its top speed space to allow this to take to give access from beneath would line up, the first tray – just seven centimetres per place, so the team created the stands. Then the entire module in each was surveyed minute – before triggering a touchlines that move too. structure is locked into place. At into place to make sure it second and third sensor that Along the length of the pitch, the north end of the stadium, a was correctly aligned, before brings the whole structure to touchlines are mounted on top third set of flaps hides a series Extensive testing of the sliding pitch prototype was undertaken at Tottenham Hotspur’s training centre in Enfield © Tottenham Hotspur / SCX Special Projects the other trays were bolted a halt. The motors themselves of a huge steel structure with of growlights and sprinklers alongside. When complete, can be used to slow and brake artificial turf bonded to the that can be wheeled out over next match can be played. This single entity, as has been done and cooling, caused by the the trays were lined with a the pitch while it is moving. surface. Six-metre-wide flaps on the pitch between games can take days, if not weeks, for with other retractable pitches JOINING THE PITCH welding, making the steel waterproof layer before matting, most . around the world [see box on The whole pitch weighs over buckle and bow in different gravel and soil were put on top. The football club turned to the previous page]. Instead, SCX 9,000 tonnes, more than the ways. The team built a test Then the turf itself was rolled out Sheffield-based engineering opted to split the pitch into three Eiffel Tower in Paris. Each of site at Tottenham Hotspur’s over the top. firm SCX to help deliver the lengthwise sections that divide the three sections need to fit training centre with a section retractable pitch. SCX specialises roughly along the outer edges of together seamlessly so that of movable turf to experiment in complex kinetic architecture the penalty box. fans watching football games, how the pitch would fit ON THE MOVE having previously created the Once this concept had and footballers taking part, together. With a length of Sixty-eight electric motors enormous retractable roof over been agreed, the club tasked cannot tell that matches are 21 metres and a width of 3 power every second tray in each Centre Court and No.1 Court its Head of Moving Structures happening on trays mounted metres, this gave the team a section, with the ones on the at Wimbledon. It also built a Nick Cooper FREng and his 1.6 metres above solid ground. more manageable replica of centre rail doing most of the 900-tonne section of removable team with designing and fully Ensuring the accuracy required the edges to experiment with. work, and the motors on the turf at Ascot racecourse that integrating the moving pitch, to get this kind of join along The team discovered that the outside rails powering opposing is wheeled out of the way to surrounds and supporting the entire 118-metre-long best way of ensuring a reliable wheels, running diagonally reveal an access road to the services into the stadium build edge was one of the most and repeatable joint was to have opposite. Together, they give paddocks in the centre of programme. difficult aspects of the project the trays ‘touch’ via a three-ply each section a top speed of the track so that vehicles do Each section is mounted on for the engineering team. Each rubber strip running down the seven metres per minute. Once not damage the race course. rails that are hidden beneath section, composed of 33 metal entire length of each section the goals, advertising boards However, despite this previous the NFL pitch, which allow trays welded together from of pitch, just beneath the turf. and pitch surround are removed, experience, the stadium’s new them to be rolled in and out of 16-millimetre-thick steel plates, Alternatives included a plastic it takes two people just 25 retractable pitch has been one position through a complex set needs to line up perfectly mesh that would allow the roots minutes to roll the pitch away. of the most challenging projects of manoeuvres from under the when brought together. to knit through over time. The To switch from one event the firm has undertaken. south stand. First the central During fabrication, the engineers at SCX also tested to the other can take just four The columns that support the section rolls in and then the trays were bolted together how best to pull the pitch apart hours. As the pitch is rolled terracing underneath the south outer sections pull alongside in the exact same order and again as, when the sections are away, one operator walks in stand meant that the pitch could and move inwards to meet the under the same conditions to joined, the grass can become front of the moving section A computer-generated image shows how the three trays carrying the pitch will slide over the artificial NFL field below not roll out from beneath as a central piece. control the effects of heating entangled as roots and leaves while another, the ‘watcher’, © Tottenham Hotspur / SCX Special Projects

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leap to make a save, or the way the ball bounces, and would have interfered with the whole game. The team fitted a series of accelerometers around a football field during a game to monitor vibrations and find out how a normal pitch behaved. Engineers also tested a movable pitch at the University of Phoenix Stadium in Glendale, Arizona, during a match between Real Madrid and LA Galaxy to work out what the optimal resonant frequency should be. Widening the main structural beams allowed the engineers to tune the pitch to the right frequency, so that it When the NFL pitch is in use, the touchline structure lowers to ground level and the flaps sit flush on the side of the artificial pitch. When the pitch sections are feels like solid ground. ready to be rolled in, the flaps can be raised into a vertical position at the touch of a button © Tottenham Hotspur / SCX Special Projects While the structure The integrated grow lighting system at the new stadium is a moving structure that weighs approximately 120 tonnes with 864 individual lights covering a total of 7,525 square metres. It is lifted hydraulically onto rails needed to be solid, it also fitted with steel scrapers and to prevent it from becoming too mounted permanently on the east and west pitch trays and then seamlessly rolls from one end of the pitch to the had to be flexible. Changes in brushes to clear the rails of any hot, cold or damp. other. This enables full coverage of the pitch without equipment ever coming directly into contact with the grass surface © Tottenham Hotspur / SCX Special Projects temperature could cause the dirt or debris that might get steel frames to expand and washed down onto the rails. to give the grass some extra been installed. Each motorised can be swapped if there is contract, meaning the pitch While a waterproof liner seals ALWAYS PREPARED light and water. There are six module has been wired a failure. can grow or shrink by up to the pitch trays to prevent any Over the years, SCX has learned giant trusses, each carrying together in a way that helps 45 millimetres in all directions. sand or soil spilling down onto that an ‘over engineering’ 126 growlights, that span the prevent the structure from To cope with this constantly the rails, bad weather can wash strategy is the key to success in entire width of the pitch and becoming stuck. Module 2, for FLEXIBLE BUT changing size, engineers debris under the pitch, meaning this sort of large moving project, weigh just under 20 tonnes example, connects to module STABLE designed the 598 wheels that this cleaning mechanism because it is hard to know each, which can be rolled out 12 rather than the next one in With something of this size support the pitch sections so is essential. An integrated exactly what obstacles might on a rail hidden underneath line so that if there is a power raised off solid ground, there that they do not slip off the watering and drainage system need to be overcome when it is the touchline. Hydraulic ramps failure in module 2, it does not was a danger that it could rails as it moves. Each section in the pitch ensures that the operating. It pays dividends to on either side allow the height affect the motor beside it and behave very differently from of pitch runs on three rails, and grass can get the nutrients have extra capacity in hand. of these to be adjusted so that the sliding mechanism will still standard football pitches. the wheels on the central rail it needs to grow without SCX finished installing the the amount of light the grass work. Meanwhile, there are Running on a large steel pitch in October 2018 – just have a flange on both sides making the ground beneath The retractable pitch passes its first tests in May 2018 during the building receives can be tuned. movable dummy powerlines structure suspended above to keep the trays running in waterlogged. The systems can over six years since it first of the stadium © Tottenham Hotspur / SCX Special Projects To cope with any behind the movable touchlines the ground will cause it to a straight line. However, the be quickly disconnected when started working on the project – unexpected failures, the entire that run from east to west, so bounce, so the team faced wheels running down the outer the pitch needs to be moved. and the first matches are set to BIOGRAPHY project has large amounts of that if the power system fails on the challenge of making sure rails have no flange, allowing When the pitch is stored under be played in 2019. Danny Pickard joined SCX Special Projects as a design engineer extra capacity engineered into one side, it can be run from the the whole structure did not them to move left and right the stands, LED lights provide This feat of engineering may after graduating in 2007. He has delivered a wide range of the structure. For example, just other. The hydraulic cylinders turn into a giant trampoline. A across the rail as the weather the grass with just enough light mean that the stadium will mechanical handling and specialist crane solutions. 20 motors are needed to move that are needed to lift the flaps bouncy pitch could affect the conditions shift. to stay alive but not enough to become almost as famous for the pitch into place, less than a and the touchlines are also way that players move or jump The front wheels of each cause it to grow. A ventilation its world-first pitch, as it is for its To watch how the pitch works, please visit third of the number that have interchangeable, so that they for a header, how goalkeepers pitch section have also been system also pushes air over it football team. www.youtube.com/watch?v=JmeljNpIV1k

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