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| Overhead cranes for fabrication of the composite aircraft wings  To meet the exacting needs for the production of composite aircraft wings, Bombardier Aerospace, Belfast is using overhead cranes from Street Crane Company. These are some of the most elaborate and sophisticated ever built in the UK. To support fabrication of the composite aircraft wings there are three cranes of five tonnes safe working load. Two are of 20 metre span between the crane rails and one of 25 metre span. Exceptionally, crane rails are an integral part of the roof structure, rather than being attached to the building columns or supported on gantries. Moreover, each of the cranes has cantilevered extensions to the crane beam to give extended reach. This necessitated that crane construction be underslung from the tracks and hoists in turn underslung from the crane bridge. This results in a compact crane that operates in a confined height envelope with the ability to traverse the load beyond the track line. A key requirement was to keep the production area unobstructed and completely free of crane supports. All three cranes use Street Crane's ZX64 hoist and have a six metre height of lift. The single beam crane bridge is of box girder construction to give the strength and rigidity required. In the main production area a most unusual wide span single girder 20 tonne four axis crane has been installed with several unique features The bridge is equipped with hoists of 15 and 10 tonnes SWL. Known as the jiggle crane, the first hoist takes most of the weight of the wing and the second provides lateral adjustment allowing the wing to be rotated by 600mm with an additional plus or minus 300mm rotation around the beam axis. This multi-span crane has four suspension points and an overall span of 64 metres including an additional cantilever at each end. The box beams are pin-jointed to give flexibility of movement to the crane beam so that it accommodates movements in the roof structure which is designed to deflect under the combined loading of the crane, wind and snow. Hinged, multi-span cranes of this type are unusual, but are a requirement in aircraft production facilities where wide bays are needed for unobstructed production. Roofs of wide span bays are of light construction and designed to flex in response to wind loading, requiring hinged cranes of similar flexibility. Street has developed this moonbeam technology over 25 years with similar installations at British Aerospace, Princess Yachts and a number of military installations. Even more unusually, in the assembly area Street has installed an eight tonne double girder underslung turntable crane with twin rotating hoists. The innovative design permits the suspended wings to rotate by 200 degrees at the same time as being transported across the full 52 metre bridge which is also of a pin jointed design. The turntable is in effect a small double girder crane running on a circular track rail mounted on a five metre wide trolley. Street Crane managing director Andrew Pimblett says, "There is certainly not another crane of this design in the UK and I doubt if there is another anywhere in the world. There is an 80 metre span double girder underslung crane at Heathrow Airport. This was one of the most unusual cranes that Street has ever built, but the Bombardier crane is in a class above anything ever done in suspended crane systems." Throughout the installation international standards have been adopted for safety, stability and precision control. For safety, all cranes have a special safe load capacity restrictor, amber flashing lights to warn of their approach and audible warnings. Hoists and travel motion speeds are variable from twenty metres per minute to 400 millimetres per minute with sensorless current vector control for smooth movement and accurate positioning. All the cranes are remote radio controlled for operator safety with maximum flexibility, but have the additional safeguard of a push button pendant for back-up. write your comments about the article :: © 2012 Construction News :: home page |