Ketten Wälder lifts 24t "Solid Sky" into New York lobby

Two stainless steel, e-polished cromox chains were used for the project including chains with a 32mm-wire diameter for the circumferential chain, and 10 x 16m chains for the suspension.

The blue sphere, made from a 40-ton cuboidal block ‘Azul do Macaubás’,  was cut at Macaubás quarries in Brazil; and shaped into a sphere at the Silesian workshop of stonemason Josef Gajek in Ciasna, Poland.

Ketten Wälder has been developing and producing safety-relevant stainless steel chains and components under its brand cromox since 2005.

"The stone sphere with its strong physical presence (Ø 8' 2", 48,000 lbs) seems to deny gravity ..." Kwade said in her pitch for tender to win the project. “The huge heavyweight stone sphere really seems to cancel gravity.”  

"Although we are proud to realise extraordinary requests, this was a real challenge for us," said Franz Maximilian Wälder, MD, Ketten Wälder.

"The requirements not only regarding stability, strength, safety but also the aesthetics of the overall construction and in particular the connecting elements to the sphere were hugely demanding." 

Thanks to Roman Auer, the industrial engineer and technical head at Ketten Wälder, who managed this project, a single blue Azul do Macaubás sphere is now hanging from 10 stainless steel chains attached to the ceiling of the entrance hall.  

“What seems to be suspended in air in the foyer of the former Sony administration centre USA and AT&T, is a construction where it was clear right from the beginning that "extreme forces act on chain and sphere, " said Auer. Not only the enormous weight of the sculpture itself – 24 tons – but also the resulting forces which had to be secured.   

"The project involved numerous tests including 24-ton dynamic fatigue tests in our company-inhouse laboratory, as well as tensile- and bending tests, with achieved breaking strengths beyond 160 tons – the basis of reliable quality. The relevant requirements were predefined by Ingenieurbüro Art Engineering."   

Each chain member made from a primary basic material is individually bent in several steps and subsequently integrated into the chain itself. This is followed up by an automatic welding process. "Our chain members are welded together without any filler material in a highly precise process according to proven finishing methods," said Auer.  

Subsequently, the individual members are deburred and calibrated to size with a predefined force. The finished chain must be able to hold a multiple of the quoted load capacity – with a safety factor of at least 1:4.  

The static calculations, tests and trial suspensions showed, "that already one of the 16mm chains guaranteed sufficient stability. Not only the 20m long suspension chains were subjected to trial loads as well as a laser measuring under load in Bad Endorf, but the sculpture itself was also tested with the complete chain suspension at the workshop in Ciasna.  

Not only was safety of utmost priority. The overall appearance of the sculpture had to fulfil the highest aesthetic standards. The circumferential chain of the sphere should be as close as possible to the equator. A further task to solve concerned the points where the suspension and circumferential chains met and were linked. These special points of connection newly developed and manufactured by Ketten Wälder, had to be incorporated seamlessly into the overall design – milled, welded, ground, and polished. The interaction of highest surface quality, mechanical strength, tested quality and ambitious design fulfilled and surpassed the artist's requirements.  

The overall artistic impression of the sphere in the end was that of a baby in a gentle slumber in a bed of chains. As if gravity is of no importance...

Ketten Wälder will be exhibiting its CDAW-10, COSL-13 safety eye hook, CCH-200 chain hoist with trolley CHT-200 and chain sling size 18mm/26mm with safety eye hook at LEEA’s LiftEx from October 5-6, 2002 in Aberdeen.