The Falkirk Wheel's dramatic thought provoking shape is the result not of the five years of planning and design that preceded tenders for its construction, but of a hectic three weeks brainstorming session after a preferred contractor had been chosen, and involving a 20 strong multidisciplinary team of engineers and architects.
The tendered exemplar design was scrapped. Participants were ordered to arrive at meetings with only a blank piece of paper and a clear head. And the emergent solution is a genuine rare example of design integration between architects, steelwork designers and engineers of several disciplines - civil, structural and mechanical.
'Collaboration like this has to be the way forward this century, ' claims one of the main players, director with architect RMJM Tony Kettle. 'We must have design without ego; no ivory towers, just teamwork with a common aim.'
'Total surprise and amazement' was the reaction from everyone on the preferred contractor team on the day in August 1999 when British Waterways summoned them to a meeting. Forget about the structure you have spent six weeks tendering for, they were told, and instead come up with totally new ideas for a showpiece wheel more befitting the 21st century.
But unanimous was their delight that the client was abandoning the Victorian style ferris wheel that it now appears no one, including BW, really wanted. 'Unattractive and likely to have been a disaster', is how Kettle sums up the original option.
Though a design and build contract, all four sets of tenderers had priced only this exemplar design. BW's desire for alternatives seems not to have reached the bidders which, given an unusually short tender period plus firm cost ceiling from the client, spent all their time proving and refining the ferris wheel.
'But now nothing was ruled out so long as we could call it a wheel, ' recalls Butterley Engineering director Colin Castledine. 'And when reference to the dictionary indicated that a wheel did not need spokes and a rim, we all started again from first principles.'
Preferred contractor, a Morrison-Bachy Soletanche JV, had already appointed Butterley to design, fabricate and erect its originally priced wheel, so the steel specialist's own team of civils consultant Tony Gee and mechanical engineer Bennett Associates was included in brainstorming sessions from the outset. RMJM, also brought in by the JV, arrived with an architectural team and, for once, design by committee paid dividends.
'We provided the possible building blocks - curved box beams, gate design and number of gondolas, ' explains Bennett managing director Nick Cooper.
'And in just a week the architect came up with what became the final solution.'
Kettle's own team had, though, already doodled through inclined planes, giant seesaws, tipping balloon structures half full of water and even a vast cylindrical wall of water disguising within it a simple lift.
'I started with the large scale, celebrating the rejoining of Scotland's severed spine of canals, ' says Kettle. 'And the chosen double curved profile emerged from shapes varying from a nodding donkey oil pump to a Barbie doll.'
Such architectural speak was however not transferred to Butterley's team. Though claimed as a simple engineering concept, the structure's stress analysis is anything but.
Under load the central axle bends causing its massive arms to tilt fractionally inwards at the top and out at the bottom. As the wheel turns, most of these steel elements face repeated 100% stress reversals as they alternate between tension and compression.
Equally complex are the gondolas which bend like simply supported bridge decks, exerting 1000N/mm 2forces on circular rail lines fixed into the rim of each arm and around which the gondola wheels run.
'Forces are transferred around the wheel between both structural and mechanical elements, ' explains Tony Gee senior engineer Richard Prosser. 'We have had to accommodate thermal and solar movements, boat impact into the gates and even ice forces if water in the gondolas were to freeze.'
There are no structural codes for boatlifts, and Prosser had to source a dozen international guidelines varying from Norwegian offshore specifications to Germany's ice codes.
Five distinct interfaces between mechanical and civils design were established within the boatlift. For example, the outer 3m ends of each gondola, containing drop gates, seals and hydraulics, were designed by Bennett, with the central 19m section the responsibility of Tony Gee.
'It was essential to work as an integrated team, with both sets of engineers needing an understanding of the other's problems, ' says Cooper. 'If civil and mechanical design had been sublet as separate packages, there was no way we could have met the timetable.'
Client: British Waterways Scotland Main contractor: Morrison-Bachy Soletanche JV Structural consultant: Arup Architect: RMJM Wheel subcontract (designer, fabricator, erector): Butterley Engineering Civils consultant: Tony Gee & Partners Mechanical consultant: Bennett Associates
Funding for the £78M Millennium Link is led by a £32.2M grant from the Millennium Commission;
£18.7M from Scottish Enterprise; £8.6M from the European Union with £9.3M from British Waterways, £7M raised by seven local councils and £2.4M from the private sector.