Here are some questions you might have about the roof in advance of Sunday’s showcase:
IS THERE REALLY A BUTTON?
Not exactly, according to Mark Silvera, president of Uni-Systems Engineering, which designed and supplied the mechanization equipment for the roof.
“Everybody likes to say there’s a button (to open the roof),” he said in an interview with The Atlanta Journal-Constitution. “There’s sort of a button.
“At the operator control station, there is a PC where the operator interfaces with the control program that runs it. And through that PC, it’s mostly mouse clicks that you use to set up the moves.
“Once you get the moves set up,” Silvera continued, “there’s an infrared sensor that you put your finger in. That’s your actual button. The sensor is there so the operator is required to stay at the station. If he takes his hand out to go somewhere else, then the roof stops. It’s not a button that you depress; it’s just a sensor, a little cradle that senses (the operator’s presence).”
So the roof doesn’t actually operate with the push of a button?
“Click of a mouse, you could say,” said Silvera, who has been involved with the Mercedes-Benz Stadium project for almost five years. “But it’s really that sensor you put your finger into once the move is set up that initiates the move.”
HOW FAST WILL IT TYPICALLY OPEN?
Stadium officials and architects had long promised the roof would open and close in a maximum of 12 minutes. Last fall, it took about two hours. But in Wednesday's demonstration, the roof was opened in eight minutes and 10 seconds. It then was reclosed in just over seven minutes.
Those should be the norms going forward, said Mike Egan, an AMB Group senior vice president who has executive oversight of the stadium project.
“It’s designed now to be opened at eight-minute speed without undue wear on the propulsion system, so that’s what we’re going to do,” Egan said.
Silvera said closing is about a minute faster than opening because the roof reaches full speed faster on closing.
“When you open up the roof, you go slow to start off because you want to disengage the seals and slow near the end because you don’t want to run off the end of the roof,” Silvera said. “But when you’re coming from open to closed, you go straight up to full speed and then just have a slow zone at the (finish).”
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HOW OFTEN WILL IT BE OPEN?
The four other NFL teams with retractable-roof stadiums have chosen to play only about one-third of their games with the roof open. But the Falcons and Atlanta United insist they’ll exceed that ratio.
“Those (other) stadiums are not designed to be able to take water. We built an outdoor stadium and put a roof on it,” Egan said. “That allows us, if there is a 25-percent chance of precipitation, to be able to open the roof because we have drainage and because the electrical system and everything in this building is designed to be able to get wet. We’re going to open it as much as we can.”
Egan said “fan comfort will be the No. 1 priority” and that as a “very rough guideline,” officials will consider opening the roof when the temperature is between 50 and 85 degrees. He said a range of other factors also will be considered, including humidity, sun angle, wind and likelihood of precipitation.
WHY DID THE WORK TAKE SO LONG?
As Silvera and Egan described it, the roof didn’t function as designed until recently because its eight 500-ton pieces, called petals, weren’t flexible enough.
“The big key was getting the petal structures flexible, as they were intended to be,” said Silvera, whose company also engineered retractable roofs for the Dallas Cowboys, Houston Texans, Arizona Cardinals and Indianapolis Colts. “You need each petal structure to flex enough to allow it to share the load evenly across all those bogies (the two-wheeled mechanisms that carry the petals along railroad-like tracks).”
Without that balance, there would be too much drag on the propulsion system and the motors would burn out prematurely.
The remedy was to put “some movable joints, some hinges” into the petal structures, Silvera said, “to allow them to displace vertically and share the load the way they are supposed to.”
It took as long as it did -– contractors turned the roof over to the stadium staff July 14 -- because work had to be fitted around a heavy schedule of events in the building, Egan said. Uni-Systems “told us last summer exactly what we needed to do to fix it,” Egan said. “That’s exactly what was done.”
AMB Group hasn’t revealed how much the roof cost, only saying it is included in the stadium’s overall $1.5 billion price tag.
On Wednesday morning, hundreds of AMB employees -- including Falcons coach Dan Quinn, Falcons general manager Thomas Dimitroff, Falcons president Rich McKay and Atlanta United president Darren Eales -- gathered at midfield to watch the roof open.
A few hours later, during the media event, the 200-foot-long petals slid smoothly and surprisingly quietly along their tracks, opening the stadium to the sky and answering affirmatively the question many observers had asked over the past year: Will the roof ever work?