Engineering the Fear: Inside Disney’s Tower of Terror

The night is October 31, 1939.  Five guests at the Hollywood Tower Hotel are riding in the elevator as lighting strikes the building.  The elevator tumbles into a free fall, the hotel soon closes down, and the guests are never to be seen again.

This is the narrative behind Walt Disney World’s famous attraction, the Tower of Terror.  Opened in 1994, this engineering feat was inspired by the popular 1959-1964 TV series The Twilight Zone.  Riders move through the eerie hotel in a ride vehicle and experience exciting drops in the hotel’s broken elevator.  The towering front exterior of the hotel houses two tall elevator shafts where the thrilling drop sequences happen.  The rear of the building, which is not quite as tall or menacing, contains the dark ride component, queue, loading and unloading areas, as well as four shorter elevator shafts connected to the main two by horizontal passageways.  

Exterior of the Hollywood Tower Hotel, Fig. 1

At the rear of the building, on the second floor, guests board a ride vehicle located in one of the four elevator shafts.  The ride vehicle is whisked up to either the third or fourth floor, dependent on which shaft it is in, for riders to view the first show scene.  The elevator door opens, and riders gaze down a long corridor where five hologram-like guests seem to appear out of thin air.  The figures then disappear and the hallway goes dark.  Stars light the dim scene and all thats left illuminated is a single window at the end of the corridor.  In order to create this show scene, Imagineers used two tools: forced perspective to make the corridor appear longer than it actually is and an optical illusion known as “Pepper’s Ghost” to create the projections.

Show Scene, Fig. 2

The show scene ends ominously, and the ride vehicle is lifted to the fifth floor where guests enter the “fifth dimension,” a horizontal passageway full of visual effects and stars.  This spooky passageway takes guests to the main elevator shaft.  While moving through the “fifth dimension,” the ride vehicle, a wire-guided AGV or automated guided vehicle, moves on a trackless system.  The movement of the vehicle for this portion of the ride is comparable to that of a line-following robot.  The vehicle has sensors near its bottom which pick up on radio signals transmitted from wires in the passageway’s ground.  By following these wires, the vehicle navigates through the hallway.

“Fifth Dimension” Diagram, Fig. 3

After exiting the “fifth dimension,” the ride vehicle enters the main elevator shaft for the part of the ride that guests have been anticipating: the drop sequences!  A computer randomly selects one of four preprogrammed drop sequences for the ride vehicle to experience. Regardless of the selected sequence, each ride has one full drop at a height of about 27.4 m.  Before the big drop, at the top of the ride, the elevator doors open, giving guests an aerial view of Hollywood Studios.

The ride system used for the drop sequences was developed by the Otis Elevator Company.  Two large induction motors positioned in a mechanical room above the shafts accelerate riders up and down.  Each motor is connected to two cable drums with solenoid brakes on the end of each drum.  The first drum holds two cables which support the elevator car from above.  While a single cable would be more than sufficient for this job, two are used for precautionary reasons.  The second drum holds another two cables which are wound in the opposite direction than those of the first drum and are connected to a counterweight.  The counterweight itself has two more cables coming out of it, which loop around the bottom of the shaft to attach to the bottom of the elevator car.  Because of this closed loop of cables, the motors can pull the elevator car downwards.  This added downward force means that guests can experience an acceleration faster than free fall! 

Mechanical Room, Fig. 4

To ensure guests safety while on this ride, many redundant safety systems were engineered.  The first layer of safety is the solenoid brakes.  In the extremely unlikely case that these fail to work, emergency friction brakes are in place along the elevator shaft’s rails, and a similar system is on the counterweight.  Should the cables break, which is again highly unlikely, there are a set of emergency brakes which prevent the car from falling.  Shock absorbers are also situated on the shaft floor.  The ride was over-engineered to ensure guests safety.

After the drop sequence is complete, the ride vehicle moves to the first floor and travels through another horizontal passageway back towards the rear of the building.  At the unloading area, the vehicle makes a 90 degree turn to let riders off.  While the ride is in this stationary position, an inductive charging system in the floor recharges the onboard battery of the ride vehicle, and the vehicle is ready to slickly maneuver itself through the Hollywood Tower Hotel again so another set of riders can experience the thrills and haunts of the attraction.

 

 

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