Four clock movements have been constructed, one for each side of the tower. The central elements are two shafts that support the hour and minute hands, driven by servomotors. The motor for the minute hand switches on 15 seconds before the top of the minute, moving the 22-metre (approx. 72 feet) minute hand forward 60 times an hour, 1,440 times a day, 525,600 times a year.
"The very low shaft speeds and extremely high loads mean classic bronze bearing solutions with grease or oil lubrication would soon reach their limits under these conditions," explains Stadlmayr. "These heavily loaded bearings are expected to operate maintenance-free over decades in spite of extremely difficult conditions."
Following successful year-long trials at Perrot that included lightning strike tests, the first of the four movements was installed in late summer 2010. At that time only one of the four sides of the fibre-reinforced concrete tower had been completed. All construction work has now been completed. All four movements of the world's largest tower clock are now ticking in sync.
Clock Tower Facts
- At 601 metres (approx. 1,969 feet), the clock tower is six times higher than Big Ben's clock tower in London
- The dials on the four sides of the tower have a diameter of 43 metres (approx. 141 feet)
- The minute hands are 22 metres (approx. 72 feet) long and weigh around 7.5 tonnes each
- The hour hands are 17 metres (approx. 55 feet) long and weigh around 7.5 tonnes each