Sending riders skyrocketing up 240 ft or dropping them in a free-fall the same distance was a challenge that only pneumatics could solve for ride designers of Cedar Point’s Power Tower. For the third installment in Design World’s Summer Tech Vacation video series, Editorial Director Paul Heney speaks with Monty Jasper, Corporate Vice President for Safety & Engineering for Cedar Fair about the engineering behind the Power Tower, a 300-ft tall steel structure that shoots riders up 240 ft or thrusts them downward at 50 mph. Featuring four cars, the ride offers two towers that lift riders and two that drop them. The ride acts something like a flagpole, Jasper said, in that you have a cable that goes over a top of a sheave, with vehicles attached to that cable-and-sheave system. The cable is attached to a pneumatic cylinder’s piston rod, and the piston is moved up and down with compressed air, which is supplied by four 200-hp compressors. The piston and cylinder are both about 10 in. in diameter, so no air can get past the cylinder, which forces the piston to shoot up through the cylinder. While operating pressure is about 100 psi on the ride, only about 40 psi is required for use in the cylinders, said Jasper. “When they load the people on the ride, we’ll weigh them, and calibrate how much air we want to thrust into the cylinder to make the ride move,” he said.
The ride works simply. The piston is at the top and the vehicle at the bottom and when pressurized, the piston shoots earthward, moving the vehicle at speeds up to 50 mph to the top. It traps the air in the bottom of the cylinder, acting like a spring, recoiling and giving the rider a bungee-cord type of feeling. Dropping riders works the same way, except in reverse. While the ride is something of an energy hog, pneumatics is the only technology that could really accomplish shooting vehicles earthward at speeds greater than gravity. “There are many drop rides, but this one is a drop ride on steroids,” Jasper said. Not only does the air cylinder’s piston act as the thrusting force, it can also act as a brake, said Jasper. The cylinder is designed with small holes at the top, so when the ram passes over these holes, they are exhaust the air. “It essentially blocks off the escape to the air and the air at the top of the cylinder acts as a brake,” Jasper said. “It compresses and it slows the vehicle down. So air not only launches you but it also slows you down. And then once it gets to a point where the air is compressed enough and you’re stopped, it shoots you back earthward again.” Watch our on-site interview to learn more about this simple, high-speed technology. And stay tuned for all five videos in the Summer Tech Vacation series, with looks at the variable speed drives on the Gatekeeper, the linear induction motors on Wicked Twister, hydraulics on Top Thrill Dragster, and cable lift technology on Millennium Force.
The drive system with the cable loop and cylinder is almost identical to the system we used to drive crash sleds. It works very well and with good pressure control it is very repeatable.
BUt I would caution folks that the operation is a “Ballistic Fling”, meaning that after the launch there is no such thing as an emergency stop, since the expanding air will keep on driving even if the supply valve is closed. This became a real issue when one european customer started complaining that the system was unsafe because there was no emergency stop feature. We explained that there are several interlocks such that the failure of any two system elements could not result in an unintentional launch, and that any single failure of a system element would inhibit the progress of the launch preparation sequence. The system was safe because the launch required multiple deliberate actions from the operator, who was responsible for verifying that the area was secure.
I am considering riding the Power Tower at Cedar Point on the Space Shot Tower going up fast. When you go down on that side how does the speed going down compare to the fast drop side of Power Tower? From the You Tube videos it appears to go down fast on both sides.