STREETERVILLE — Acrophobics, fear not: The engineer behind Tilt, the newest attraction at the John Hancock building's observatory, is not too keen on heights, either, so he made sure the glass encasement that tips 30 degrees toward the street is "very, very safe."
The Hancock building's answer to Willis Tower's Ledge took a year to develop, engineer John Peronto of Thornton Tomasetti said at a ribbon-cutting ceremony Thursday.
The attraction opens to the public Saturday, and will cost $5 on top of the normal $18 admission fee to the Hancock observatory on the 94th floor.
Lizzie Schiffman admits that she even chickened out a bit on Tilt. Hear about her experience:
"Designing a structure that's kinetic and can move this high up, at these wind speeds, that was a big challenge," Peronto said.
Three hydraulic pumps move the steel-framed glass box a little over 50 inches, tilting eight people at time at a 30-degree angle toward the ground. The full tilt happens in three phases over Delaware Place.
"Even thought there's structural laminated glass that's like the viewing panel, the system itself is a steel frame," Peronto said. "So the whole system stand alone steel frame with many layers of safety embedded in it. The occupant himself is encapsulated almost in the steel frame right at the viewing panel."
Riders brace themselves with steel handles on either side of each slot, and waistband harnesses will be added later "so you can lean on them and don't have to support your weight with your arms," Peronto said.
At its full extension, riders will lay flat against the glass unless they're holding the handrails or strapped in place.
Tilt wasn't built like ordinary windows.
"It's very special glass," Peronto said. "It's fully tempered, there's three layers of fully tempered glass with structural inner layer laminates, so it's very robust. The system itself is designed so that any two of the three panels can take the entire weight, and the third is just extra."
Downtown Aldermen Brendan Reilly (42nd) and Bob Fioretti (2nd) were on hand Thursday, as was Choose Chicago CEO Don Welsh, who said he hoped Tilt would help the tourism agency reach Mayor Rahm Emanuel's goal to bring 55 million tourists to Chicago by 2020.
