#News
THE STORY OF GIANT WHEELS - 4 PART 4: THE STAR OF NANCHANG
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PNR
21006 dated 02.02.2018
Published by
Alberto Fabbri
Source
NATIONAL GEOGRAPHIC
2006, STAR OF NANCHANG, 160 m.

Another huge problem that observation wheels have to face is to make their structure strong enough to withstand the strong winds and keep the wheel stable even in worst conditions.

This problem has been already faced by chinese engineer building the Star of Nanchang, the 160 meters Chinese giant wheel, built after the London Eye. Chinese engineers had to find a way to keep the wheel stable in strong winds.

In 2006 the chinese officials of Nanchang wanted to build something that showed the power and efficiency of chinese economics and come to the idea to build the world’s biggest sky wheel. They wanted to build something that stands like a beacon during night-time.

But the light structure of London Eye with its thin spokes and rim offer but little surface in which to attach lights. So the designers opted for a bigger surface structure, with strong struts replacing the thin spokes. And providing room for many lights. This created also a problem: the winds had more area to push against, creating so much pressure on the legs.

Designers so created a computer model of the whole structure and examined the behaviors of every single strut during heavy winds, optimizing the size of all them to allow winds of up to 100 km/h to pass through it without being too weak or too heavy.
This allowed the structure to have the room to put more than 6000 lights, visible from far and wide.
 
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In Singapore the wet weather can make storms of up to 140 km/h appear from nowhere. Engineers of Singapore Flyer had to design a wheel that could withstand this fury of nature

Strong winds, flowing around the two cylindrical legs, create small tornados that can make the legs oscillate and vibrate, creating metal fatigue that could cause the steel structure to fail.

Engineers had so to find a way to stop the legs from rocking back and forth, finding a genial solution: the use of “mass dampers”, heavy masses that oscillate against the main oscillation, slowing it down.

They put big masses inside the legs in a shape of big pendulums, damped by big shock absorbers to increase the efficiency. When a leg moves in one way, the damper moves in the other, making the legs to slow down.

Big ladders inside the legs allow engineers to access the dampers, each of about 500 kg blocks of steel.

The next challenge that the Singapore Flyer had to face was the problem of the evacuation of People: if something goes wrong, they must get the people down.

On 23 December 2008, while 173 passengers are riding the Singapore Flyer, suddenly the wheel grinds to a halt. An electrical fire in the electrical control room cuts the power of the motors, so engineers started the backup generator, but this is routed to the same control room on fire so this also fails. This left the operators no way to operate the wheel and get the passengers back down. Trapped in the glasses cabins with no air conditioning, passengers become desperate.

After 6 hours operators take the drastic decision to evacuate the passengers with ropes. Police order to close the wheel.

The Flyers’s management ordered to quickly create an engineers task force with the purpose to make the Singapore Flyer the safest wheel in the World. First engineers installed a complete separate backup power supply; this bypasses the control rooms and is routed directly to the drive wheels. In case both power supplies fail engineers installed on high tech wheel one additional backup system: a low technology winch.

At night, when the wheel is closed to the public, the safety team practice the emergency drills, connecting the cable of the emergency winch to the rim of the wheel, slowly pulling the wheel around.

To make sure that passengers are confortable while they turn the wheel in case of emergency, they also installed each cabin very unusual emergency bags, with water, food, urinal bags end even playing cards to keep people occupied.

Having faced their demons, the Singapore Flyer reopens on 26 January 2009, after an incredibly fast reassessment of the whole emergency system.

So far emergency system has been used once, but is kept ready just in case.

After Singapore Flyer, world’s highest sky wheel record has been taken for only 2,6 meters by Las Vegas High Roller, 167.7 m, that is still the highest wheel in the world, waiting fro New York Wheel and Dubai Eye to open.