IDC Develops First Retractable Crane Windsail to Maximise Productivity

IDC has helped Select Plant Hire develop an innovative new windsail solution for luffing jib cranes facing tough space and safety restrictions in urban environments. This new windsail technology has meant that Select’s cranes have been able to achieve a smaller parking radius whilst retaining the full operational wind speed limit. With a smaller park radius, contractors can also install more cranes on a single site, dramatically increasing productivity. IDC not only designed the windsail, but took it right through the development process to production; manufacturing windsail systems in IDC Models’ production unit.

Steve Bradby, Select’s engineering leader explained the background to the challenge. ”It is common in the UK that cranes are not allowed into the air space above an adjacent property, an issue especially prevalent in city centres and next to high-rise urban developments where space is at a premium. In these instances, luffing jib cranes are often the only solution. Luffing cranes have jibs that can be raised and lowered enabling them to manoeuvre within a site boundary or around nearby obstacles such as buildings or other cranes etc. When the crane is not being used, it is critical, in order to limit the stresses on its structure and achieve increased heights, that the upper part can rotate freely – to ‘weather vane’. The windsail is essential to generate the force required for the crane to weather vane correctly when the jib is parked at a steeper angle and ensure the crane is left safely overnight.

Until now, luffing crane windsails have been made from rigid materials such as steel. Unfortunately, a large fixed sail can make the crane difficult to manoeuvre in windy conditions and we recognised that if these windsails were made retractable, the cranes would have much greater productivity.”

Select approached IDC with the challenge, asking them to consider solutions and develop a new retractable windsail solution. IDC’s first step in the development was to brainstorm ideas and explore potential concepts. Risk analysis was an important early consideration to understand how the windsail would react at varying windspeed and loading. Once a concept was selected, the engineering team produced detailed CAD models, selected materials and undertook finite element analysis to understand the stress resistance of the design and ensure the system was able to withstand large forces. This was further tested using a full-sized prototype of the windsail, subjected to wind speeds exceeding 100 km/h.

IDC Models played a key role in this project, producing 3D printed SLA models, followed by a full scale prototype of the system. The production engineers then went on to manufacture and assemble ‘windsail kits’ - each comprising around 3,000 components, controls electronic and aluminium extrusions of up to 8.6m length - for installation into jib sections by Select at their depot in St Neots, Cambridgeshire. IDC used its global network to influence the design and manufacture of required components.

The new windsails have already been seen in Manchester and are currently in use at sites in London. At one site on London’s south bank where 21 cranes will be used, 17 will require retractable windsails. On the exceptionally tight site, utilising this many cranes would have been impossible without the retractable windsail.

IDC has manufactured 32 individual windsails to date, for four different models of Terex crane. Demand for additional systems remains high with further production runs programmed.

IDC’s Director, Ryan Fenton, comments, “We’re delighted to have developed a product which has such a powerful impact on the productivity of cranes. This project relied on expertise across the whole of IDC and demonstrates how diverse our capabilities are, from design and engineering, right through to prototyping, testing and production. The new product has already been shortlisted for a British Engineering Excellence Award and we look forward to seeing further success commercially.”