Germany’s first mobile organ inaugurated at the Alpirsbach monastery
Pipes gliding on air cushions
Christmas 2008 saw Germany’s first mobile organ hover on air cushions through the Alpirsbach monastery church. To keep it on track, a mobile guide rail holds the monumental wood sculpture on course. The fischer group of companies of Waldachtal developed a unique anchoring construction for mounting and dismantling the guide rail in no time.
The Romanesque church is the largest of its kind in Baden-Württemberg, with most of the building still in its original state. Its excellent acoustics make it the perfect setting not only for worship but also for music. The monastic concerts at Alpirsbacher are renowned nationwide.
As the old organ had been in a rather sorry state, the Protestant parish members decided in 1992 to build a new organ. But, with disagreements about the location of the new organ, it took another sixteen years before the it was inaugurated in December 2008. The 900 year old church simply did not have the space. While the church historians wanted to see as little as possible of the new organ, the musicians wanted a centrepiece position for the instrument. After many protracted and heated discussions, the parties finally agreed on building a mobile organ sculpture. The contract for this demanding job went to the renowned organ builder’s firm of Winterhalter in Oberharmersbach in the Ortenau district and to the wood-carver Armin Göhringer.
The new instrument can now be moved from its “parking position” for everyday church music from the southern transept into two different concert positions in the direction of the intersection: stopped half way and rotated by about 35 degrees, it is now used for orchestral concerts with organ accompaniment. If it is turned by 90 degrees in the middle of the church, it can be played for organ concerts.
The 16.6 tonne instrument is twelve metres high, measures 4.8 metres in the square and has 2,182 different pipes. The steel frame on which the organ rests weighs three metric tonnes alone.
To move the giant organ sculpture without damaging it and to prevent the sandstone slabs underneath from crumbling, the frame rests on a total of 12 ring-shaped air cushions (40 cm in diameter) and on three legs. The organ is moved and lifted by means of a compressor which blows compressed air into the cushions developed by Nuremberg-based DELU GmbH (Deutsche Luftkissentransportsysteme). Wheels are then plugged on to the frame, the multi-sectional guide rail is mounted to the church floor and, finally, six cubic metres of air per minute are pressed into the air cushion with a pressure of 7 bar. The new organ can so be moved with ease to the desired position on a thin film of air along the guide rail.
The smooth “hovercraft action” of the organ requires an absolutely level surface of the sub-construction and secure mountings for the side guide rail. The sandstone floor slabs had to be taken out in the 12 metre travel range of the organ in the transept between the altar and the centre aisle. The section underneath was excavated at a length of 13 metres by 5 metres and filled with a load-bearing concrete floor plate. A levelling course was cast on top and the original sandstone slabs were put back in place.
Drill holes set with care
The last step involved setting the guide rail in this section. As this construction is only needed when the organ is moved, it is not permanently anchored in the floor. This is where fischer’s experts were called for: the guide rail is plugged into sleeves in the floor, with the sleeves spaced at a distance of about 1.5 metres.
“We had to be really careful when we drilled the holes for the sleeves”, says Thomas Held from the technical field service, Southern Region. After all, the holes had to be drilled through the sandstone, the levelling course and the concrete to a depth of 25 cm. The guide rails and the sleeves were then inserted and cast in place. “We used our FCS - Liquid Can System and the FIS VW 360 S injection resin which proved to be the most suitable products in tests we had carried out at our Denzlingen plant,” reported Thomas Held.
The fischer crew drilled the 12 holes at a depth of about 25 cm in the summer of 2008 and inserted the sandblasted stainless steel floor sleeves with a diameter of 5 cm. The anchor holes are protected by specially developed and numbered covers. “Bonding the sleeves into the floor also required ultimate precision,” recalls Christian Kroll, workshop manager of the organ builder’s firm. “But the fischer team did a really fine job.”