So months after the opening of Tower of Terror I get a call in Glendale from the engineers in Florida. They have noticed that the Lift Cab is overshooting the 5th floor when it parks. They try describing the details but I really wanted to see its characteristics. I asked them to shoot a video of it so I can see it firsthand. During the installation we had put markers on the yellow drum that the cable rolls up on and also a mark of the blue brake which is stationary. This visual gives you a perfect view of how the Lift Cab is parking at each location.
So the video below is a clip of what they sent me. I did get one for each Drop Lift designated as Lift E and Lift F. In 1994 this was on a VHS tape that was over-nighted to me. I recently found this tape in a pile of VHS home movies.
We start on the Unload floor. The blue piece on the right is 1 of 8 brakes that like drum brakes in a car clamp into the four corners on one of the two drums. The background sound is all the fan (blowers) for the motor drives and the motor itself. It is hard to talk to one another in this equipment room above the 13th floor. The motor, motor drive, brakes, brake control cabinets, and Ride Control electronics cabinets are there (two sets of each for two Drop Lifts). In fact the room is so small, when sitting at the computers you can turn around and see what is in the picture (actually you can touch it).
The next sound you hear are large contactors closing supplying electricity to the motor and all 8 brakes opening. Then you see the yellow drum start spinning. It spins many times to reach the 5th floor. What you see is it overshoot the 5th floor by a few inches and then come back down and park. Then you hear the brakes close and contactors open.
No guest would notice this but it adds a fraction of a second which lowers the ride capacity over a day. I really laughed when I saw there message. The next part of the video shows the Lift Cab heading to the 13th floor, the fake drop and then the freefall and then it parks on the unload floor. I could see that the parking there was not perfect either.
A few days later I flew to Florida and made a change to the software that allowed each floor to have its own position servo parameters and then we retuned the parking position servo for each floor. Previous and usually the parameters for each floor could be the same. This made a good system better and this fixed the overshoot problem for good.