Since the debut of the Ferris Wheel in 1893 at the Chicago World's Fair, these engineering marvels have been getting larger and larger. But the monster wheel now on the drawing boards at the Great Wheel Corp. in China is in a league of its own, with a diameter of more than two football fields.

The 682-foot-high wheel is scheduled to open in Chaoyang Park, Beijing, China, just in time for the 2008 Olympics. It will give up to 5,760 passengers per hour a fantastic view of the city and surrounding area. Each of the wheel's 48 capsules holds 40 people who can enter and exit while the wheel is in motion. Boarding stations — synchronized with the Great Wheel's tangential velocity — are located on both sides of the capsules.

The contract to power the wheel, recently awarded to Bosch Rexroth AG, includes drive, control, and safety functions. The drive system will consist of a powerful and almost maintenance-free hydraulic power unit. Hydraulic motors will drive 32 tires that will contact, under pressure, the 650-foot-diameter wheel, causing it to rotate at a constant speed of three revolutions per hour. A backup system ensures reliable operation if a fault develops in the main circuit. Bosch Rexroth is responsible for project engineering, shipment, and installation of the drive and controls system, as well as automation of the boarding stations.