Oct. 31--When Nik Wallenda makes his way across the Chicago River on Sunday, he'll be 600 feet in the air on a tightrope made of sturdy, 100 percent steel, securely tied in place by his father and uncle.
The tedious job of connecting the 750-foot wire from the west tower of Marina City to the Leo Burnett Building across the river was to begin Thursday night. Wallenda arrived in Chicago on Thursday afternoon to help, though his dad -- Terry Troffer, the chief rigger -- said he wishes he would stay home and get some rest.
"I don't like to see him out there so much because he'll want to work right alongside everyone else," said Troffer, who has been rigging tightropes since he was 17 and works as his son's safety coordinator. "But I understand. He wants to see it done right. If he sees it himself, I don't have to do so much convincing when it's time for him to walk."
On Thursday evening, the city was to close off the surrounding sidewalks as about 40 workers begin running a large spool of wire -- three-quarters-of-an-inch thick, or about the size of a nickel -- along the bridge at Dearborn Street down Wacker Drive. About three hours later, the city will shut down Wacker Drive to traffic as workers, positioned on top of the buildings, use capstan winches to hoist the steel wire up the side of the buildings.
They expect to work through most of the night, according to Troffer, making sure the wire does not touch or damage the buildings.
Once the wire is brought to the top of the buildings, the workers will tie it down to standing structures already on the roof using a braided nylon sling. On the west Marina City tower, the wire will be tied to a tall concrete tube that formerly held communications antennas. On the east tower, they plan to bolt big steel plates in pre-existing holes. And on the roof of the Leo Burnett Building, the wire will be wrapped around a large structural beam.
The tightrope was designed by Wallenda's uncle, Mike Troffer, the chief engineer who works closely with his brother to make sure the integrity of the tightrope isn't compromised.
Months before, Mike Troffer, a mechanical engineer, runs all the numbers to determine exactly what cable wire should be used for the tightrope and how much tension should be placed on it. Dynamometers will be attached to the cable to make sure the exact amount of tension is reached.
Guy wires will be attached to concrete barriers on the ground to prevent the tightrope from swinging too wildly.
"A lot of engineering goes into place with this," said Troffer, who married into the Wallenda family. "Every walk is different, and there are lots of challenges being in a downtown metropolis. There are lots of obstacles to be aware of and we have to do our part to make sure it's safe."
On Friday, workers will install about 100 feet of wire for the second trek, from the east to west towers of Marina City.
City officials asked the Wallendas to install the bigger tightrope Thursday night rather than waiting until Friday, when the downtown area will likely be busy with Halloween revelers. The Wallendas have security in place to ensure that no one tampers with the wire once it's installed.
There's little chance the wire will break under the pressure of Wallenda's weight. The first wire can hold up to 70,000 pounds and the second one, up to 42,000 pounds.
If all goes as planned, Wallenda will complete the first walk, take the elevator down, cross the river and head to the top of the east Marina City tower to begin his second walk.
The event will be broadcast live by the Discovery Channel. Viewers also can watch at SkyscraperLive.com.
Wallenda will have a rare opportunity to view Chicago's stunning skyline up close. Now, thanks to the Discovery Channel, thrill-seekers can take a virtual tour of what Wallenda will see up there before he steps onto the rope.
For the narrated virtual tour of the tightrope, go to skyscraperlive.com to get a 360-degree view from Wallenda's vantage point.
dglanton@tribune.com
