Proper calculation of even the strongest Vuvuzela crescendos

Polyurethane nubbed belt CONTI SYNCHRODRIVE^® N10 used in wind tunnels

20:30 hrs CET. 11. July 2010. Johannesburg / South Africa. Soccer City Stadium. The referee's whistle sounds, the final of the 19th FIFA football championship in South Africa is underway. 80,000 spectators fill the stadium. The notorious Vuvuzelas (horns typically blown in South African stadiums) start their ear-shattering noise. Billions watch the match on TV or listen to the radio. About 8,500 kilometres away, in Birkenfeld/Württemberg, employees of the Wacker Ingenieure Wind Engineering Consultants GmbH established in 1992, relax in front of their TV's. What they have computed during the last few years in their wind tunnels in Birkenfeld with respect to wind loads, vibrations, wind comfort and room ventilation, during many weeks of trial configurations, has finally proven itself in practice.

After all, in the wind tunnel in Württemberg, everything was checked, tested and optimised on a scale model, that could possibly be encountered in terms of wind and vibration and their static effects on the huge Soccer City Stadium in Johannesburg.

View into the boundary layer wind tunnel with the model installation face open. The characteristics of the 2.05 x 1.85 m cross section correlates to an open rural area, allowing speeds of up to 20 m/sec. Bernd Reinhard, responsible aerodynamics engineer at Wacker Ingenieure and „Lord of the wind tunnels and models“ as well as Dipl.-Eng. (FH) René Preßler from the Mulco partner Hilger u. Kern Antriebstechnik, Mannheim, are certainly also following the match and observing the stadium. In close cooperation, they made an approximately 3,200 mm long and 30 mm wide Polyurethane nubbed belt „Conti Synchrodrive N10“, which played a decisive role in the drive of a high-precision rotary table at the end of a wind tunnel.

Nubbed pulley intermeshing with the nubbed belt CONTI SYNCHRODRIVE N10 at the carrier rim accommodating the models to be examined. „Ultimate high-precision“, this is how Bernd Reinhard terms the combination of the nubbed belt Conti Synchrodrive N10-PAN HF (produced by the Mulco partner company ContiTech Antriebssysteme) and the pulley, here termed nubbed pulley instead of simply a pulley, driven by a stepping motor. The belt glued with a special adhesive to a type of steel rim horizontally and freely moving on rollers, with the nubs facing outward, drives a pulley. This pulley supporting the models to be tested, can be rotated through 360° and controlled in 4,000 precision increments.

Wacker employee Arne Blitzer preparing a test series in the wind tunnel.. The pictures shows him bundling the system of small tubes and hoses at the measuring points. Bernd Reinhard and René Preßler describe their thoughts that eventually led to this drive design: „A positive locking, self-guiding drive was needed. Knowing that the nubs of the Conti Synchrodrive N10 feature a harmonious intermeshing behaviour in both directions, maximum precision and synchronisation are guaranteed. Moreover, the structure's centre had to be open to provide room for the hoses led through and connecting the measuring points of the model“.

Conversation at the wind tunnel model of the Johannesburg Soccer City Stadiums: Aero-dynamic specialist Bernd Reinhard (left) from Wacker Engineers, and Dipl.-Eng. (FH) René Preßler, Hilger u. Kern, Mannheim. The Conti Synchrodrive N10 permits the physical flow examinations to be carried out in exactly defined steps and the achievement of very precise measuring data. „On the nubbed pulley, the nubs move along a perfect circular arc“, explains Mr. Preßler. The constant belt tension and the high performance are guaranteed by the production method using abrasion and wear resistant Polyurethane with reinforcing steel tension members. The system is self-guiding and needs no flanges.

„Solutions such as the nubbed belt Conti Synchrodrive N10 are a good match to our innovative way of operating since the foundation of our company“, says Bernd Reinhard, describing how the trial series in the wind tunnels are prepared for the measurement of wind loads or person induced vibrations. For the wind tunnel trials, for instance, hundreds of measuring points containing hairline tubes at defined points of the models are connected by a system of hoses, and the data obtained is evaluated by Wacker's own software programs.

„Wind Engineering“ is the term for what Wacker Ingenieure are doing world wide, with only one competitor in the market. The list of references is impressive, encompassing tests with city profiles and high-risers as well as famous buildings, through to the stadiums accommodating the Football World Championships 2010 in South Africa: New Durban Stadium, Port Elizabeth, Greenpoint Cape Town and Soccer City Stadium Johannesburg with the opening match and the final. „Without us and our tests, the building could not have been started and finalised from the statics point of view“, says Bernd Reinhard not without pride.

The large hall houses three wind tunnels for boundary layer tests and aerodynamics as well as wind speeds of up to 100 km/hour. They allow the Wacker wind engineers to test all buildings, city plans or bridges world wide exposed to wind, thermal and dynamic effects.

Wacker Ingenieure is serviced by the Mulco sales partner Hilger u. Kern. „The accompanying engineering, such as during this drive project, is highly appreciated. The intensive involvement in the design idea from an early stage is very important for us“, says Bernd Reinhard commenting on the close cooperation.

What is behind the view of the gigantic football stadium filled with 80,000 enthusiastic fans from mid-June 2010, in terms of technical construction and static requirements and effort, will only be imagined. However, the Lords of the Wind in Birkenfeld have known the details for a long time. Their lengthy and precise work formed the basis for the convincing statics of the large building. „Are you feeling uneasy in any way?“, we ask Bernd Reinhard before leaving: „No, not in the slightest“.

Mulco-Europe EWIV
5th of May, 2010