This involved the installation of ground source heat pumps and an under-floor heating system. The decision was made to use the opportunity to replace the existing dais with an electromechanical alternative which could be raised and lowered on demand – courtesy of a lifting system supplied by Drive Lines.
The Cathedral Architect, John Prichard, of Lloyd Evans Prichard Architects approached Drive Lines Technologies Ltd for assistance in specifying a suitable drive system for the lift. As experts in supplying screw jack based lifting solutions, Drive Lines had previously supplied such a system for a lifting dais in Lichfield Cathedral.
The dais was to consist of two independent platforms – the main octagonal dais and a smaller adjacent rectangular one. Working with the structural engineers, Drive Lines specified and supplied both of the independent drive systems.
Ian Carr, Drive Lines Managing Director, explains: “The development project was the perfect opportunity to update the cathedral with a modern, lifting dais. We were asked to specify and supply a solution which would offer reliable, efficient service for many years with minimal maintenance. As part of our service we are able design complete lifting systems. We help engineers to source high quality components from some of Europe’s best manufacturers.”
The drive systems were incorporated in the framework attached to the underside of the two platforms. Each system uses four Grob translating screw jacks which apply an axial force against floor pads embedded in the bottom of the pit to lift the complete load of stonework, framework and, of course, the weight of anybody occupying the dais. The system is designed to lift a full load to the required height of 190mm. Of course, a large safety factor was designed in when sizing the screw jacks: in total the system is capable of supporting up to 40 tonnes.
As well as the screw jacks, Drive Lines supplied the brake motors, Graessner bevel gearboxes and R+W line shafts to complete the drive trains. The power transmission specialist also specified and supplied combined bearings for the vertical linear guidance to keep the complete system steady as it moves, and to prevent any side loading on the lifting elements.
Working with controls partners, Awtec Control Systems, and the Cathedral electrical contractors, Drive Lines’ technical team were able to supply the complete electrical control system. This proved challenging due to the available power supply in the Cathedral. A suitable inverter was employed to ensure the current draw was kept below the 32A available whilst still being able to supply enough power to operate both platforms simultaneously if required. This restriction also dictated the design and location of the control cabinet in order to keep the cable runs to a minimum.
The finished result is visually stunning. When the dais is in the lowered position the quality and accuracy of the stonework is such that there is barely a noticeable gap between the dais and the surrounding floor. The dais is regularly lifted for important ceremonies and gained national recognition during the 100th anniversary of the Battle of the Somme, when the BBC broadcast a live service from the Cathedral with the choir occupying the raised dais.