After 18 months, The Schaeffler Group has now completed the manufacture of two giant spherical roller bearings for the world's tallest observation wheel, China's new Beijing Wheel.
Two giant-sized spherical roller bearings from Schaeffler Group have now been completed, ready for use on the world's tallest observation wheel, China's brand new Beijing Wheel.
In total, around 22 tonnes of steel has gone into producing the two hub bearings. Each bearing has an outside diameter of 3,200mm, an inner ring bore of 2,600mm and a ring width of 630mm. Each bearing incorporates 118 rollers, each of these weighing around 20kg.
The hub bearings for the Beijing Wheel will operate 108 metres above the ground. The Beijing Wheel will be 208m high and is designed to accommodate 1,920 passengers. One revolution of the wheel will take 20 minutes to complete, but will enable guests to see stunning views of the city of Beijing.
Schaeffler has plenty of experience developing bearings for super structures. Back in 2005, the company designed and manufactured hub bearings for London's Millennium Wheel, which back then was the world's tallest observation ride. The bearings for this wheel have an outside diameter of 2,600mm, so would fit precisely into the inner bore of the bearings for the Beijing Wheel.
But being chosen as a development partner for the Beijing hub bearings placed unique challenges both on the engineers at Schaeffler and on the bearings. Henri van der Knokke is head of Application Engineering at Schaeffler Group Industrial's Heavy Industries Division and was responsible for the overall project. He recalls: "When we received the dimensions and specifications from Great Wheel Corporation in black and white, at first, we couldn't believe our eyes. Looking closer at the designs, we realised that a spherical roller bearing of these dimensions and with these technical specifications had never been built before."
Although Schaeffler gained much experience from developing the hub bearings for London's Millennium Wheel, the Beijing Wheel presented new challenges. "The first thing we had to do was to find out if our production facilities could actually manufacture the bearings," explains Rainer Schrader, Design Engineer at Schaeffler Group's Spherical Roller Bearing Product Line.
Questions needed answering, including whether the machine tools at Schaeffler were suitable for machining such large dimensions. Or whether the hardening furnace was large enough. Could the crane in production support carry such loads? What would be the best method of transporting the bearings to China? And, once delivered to site, how could Schaeffler ensure that the bearings were installed correctly?
As van der Knokke states: "It was like a jigsaw with many thousands of separate pieces, which piece by piece, we had to complete. This was made possible only by close collaboration between our application engineering, design, calculation and production departments."
During this process, team members at Schaeffler had to continuously break new ground, improvise and coordinate time schedules. The bearing rings were forged in Italy. The barrel rollers were turned at Schaeffler's FAG plant in Eltmann, Germany, then hardened in Wuppertal and returned to Eltmann where they underwent a new grinding process. Finally, the bearings were manufactured and assembled by FAG's large bearing specialists in Wuppertal.
Despite decades of experience in producing large bearings, Gerd Benninghoven, Production Manager at the Fag plant in Wuppertal, said that the Beijing bearings created one or two surprises of their own. First, the outer ring only just fitted into the hardening furnace, but nobody could really predict how this process would affect the bearing material. Indeed, according to Benninghoven, the diameter of the bearing rings shrunk by about one centimetre during heat treatment. During final machining, however, accuracy in the micrometre range had to be restored, which provided a unique challenge with such large parts. "Just imagine the challenge during the machining process. During a single machining cycle, the tool covers a distance of more than 20km as it cuts through the metal," says Benninghoven.
Once delivered to site, the two hub bearings had to be mounted, which required the erection of a 100-metre tower. In order to lift the bearings to their mounting position, bores for the eye bolts were also required. Technicians at Schaeffler had to verify that the threads on these eye bolts were safe and could withstand such high loads.
Henri van der Knokke concludes: "We learned so much during this project and will soon be able to use this valuable experience in other customer applications." Indeed, Schaeffler Group has recently secured further bearing orders from Berlin and Orlando for similar observation wheels.
For more information on Schaeffler's FAG range of spherical roller bearings, please visit www.schaeffler.co.uk or telephone the marketing department on 0121 351 3833.
With a total of 66,000 employees at over 180 locations around the globe and group sales of 8.9 billion euros (fiscal year 2007), the Schaeffler Group is one of the world's leading rolling bearing manufacturers and automotive component suppliers. The corporate group includes the INA Group with headquarters in Herzogenaurach, the FAG Group based in Schweinfurt as well as the LuK Group, with headquarters in Buhl.
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