Taking the Duel Out of the Dragons

Universal Orlando recently announced a major operating change for the Dragon Challenge roller coasters. Let’s look back at how this incredible thrill ride pioneered the control system technology enabling dueling coasters to consistently time their near-miss collisions.

Art of the Duel

Dueling roller coasters offer a thrilling element not typically found on single track rides: the near-miss collision. Two trains travel directly toward one another often at a combined speed in excess of one-hundred miles per hour, seemingly on a head-on collision course, only to turn away at the last breathtaking second, narrowly avoiding the other train by a few inches. But how do two trains on two completely separate tracks arrive at the same point hundreds or thousands of feet into their layout time after time?

Without perfect synchronization these near-miss collision elements are useless and defeat the point of building an expensive dual ride if they are not timed up exactly. On most coasters, after the point of release from the highest point on the ride there is no way to control the speed of the trains until the end (or a mid-course brake run). Dueling coasters work by weighing the trains and then by using past performance data to determine which train to release from the lift first and how much of a head start to give it.

On most iron coasters, small differences in speed and duration of the ride do not matter. However, they can greatly affect the ride experience on a racer or dueler. Near misses can only be achieved if the vehicles are exactly the same. In the real world, this is impossible. Each train will have a different weight due to number of passengers; some wheels will be more worn than others, and so on. So what do you do to consistently ensure perfect synchronization? The engineers design the ride where the variables such as aerodynamics and rolling resistance can be controlled as much as possible.Dueling Dragons - Islands of AdventureThe main variable to compensate for is weight. But how do you weigh a fully loaded coaster train? The solution is actually pretty simple. The weight of the trains can be determined by measuring the current draw on the lift hill motors (or LIMs in the case of a launched ride). This can be done because the weight of the loaded train is directly proportional to the power needed to pull the train up the lift hill. For example, say you know the weight of an empty train. You can measure the current draw on the motor as the train proceeds up the lift. Next, add a few water dummies with a known weight to the train and take another current measurement. Now we can interpolate between those numbers in order to determine other unknown weights using the current draw alone.

The next issue is how do you know how much of a delay to release the second train relative to the first? The goal is for the second, faster train to catch up to the lighter, slower train at the desired location. Several factors which influence the speed of each train include: aerodynamics (surface area), rolling resistance, wheel condition (worn), track condition (greased or not), condition of tires, bearing condition, wheel alignment, etc. All of these factors can cause a faster or slower than expected ride and the tricky part is that they are different for every circuit of the course. Wheel wear may not be an issue in the morning but by the end of the day, after hundreds of circuits, the train may be performing much differently than just a few hours before.

This problem is solved by graphing a train performance curve which will constantly be updated. Any change in the tire’s rolling resistance or vehicle aerodynamics is instantly compensated for. In theory, the near-miss collisions should get better and more closely timed as the day goes on and as more data points are added to the performance curve. The computer can take real time data and combine it with past performance results. Similar performance curves may be implemented on launch coasters such as Top Thrill Dragster. That data can help determine how much power needs to be applied to the motor in order to launch the train over the hill.

Most dueling coasters contain multiple near-miss elements but there is often no way to adjust the speed or timing of the trains after they are released from the lift hill. Therefore, every near miss cannot be controlled exactly. In this case, the designers have to pick which element they want to have the best duel. On Dragon Challenge, this may have been where the two trains came together in the loops. Battlestar Galatica at Universal Studios Singapore (pictured below) has the additional challenge of one train being floorless while the other is inverted.

Battlestar Galactica - Universal Studios Singapore
In review: as the trains are pulled up the lift, the control system measures the weight of each train by determining the amount of current drawn on the motor. Sensors tell the computers where the trains are on the lift. The computer calculates which train to release first based on a performance curve of data which is updated after every circuit. The lift hill motors are adjusted accordingly. Dueling roller coasters have increased the thrill and excitement level by using a control system which allows two trains on separate tracks to simultaneously arrive at the same near-miss location over and over again.

Taking the Duel Out of the Dragons

Dragon Challenge at Universal’s Islands of Adventure Theme Park in Orlando, Florida pioneered the dueling control system technology. Unfortunately, after two incidents involving loose articles this past summer it has been announced that the ride will never duel again. A full explanation was never given for the change though foul play on the part of a guest is suspected. If foul play was a factor it’s a shame that one or two people had to ruin it for everybody, considering there has probably been more than ten million riders who have ridden it without incident.

What is also interesting about this situation is that another solution wasn’t even attempted. Why couldn’t they have just installed a plexi-glass wall or a small mesh net between the loops (assuming that is where the incident took place)? Then, the near-miss effect could still be seen, but a wall or net could have stopped any loose articles from hitting the other train. What about all riders being provided with protective eyewear?

Many theme park goers are hoping this doesn’t set a precedent for other parks across the country with similar rides. Hopefully, we won’t see a change in policy of letting racing coasters actually race each other. Can you imagine Cedar Point’s Gemini or Kennywood’s Racer without the hand slapping around the turns? Will they no longer release Battlestar Galatica trains at the same time too? In hindsight, it was a good idea to take the word “duel” out of the name of the ride. Perhaps somebody saw this coming?

The decision to never duel the dragons again is tragic news for roller coaster enthusiasts everywhere. It’s just sad that one of the most unique rides in the World with one of the most innovative control systems is now just two ordinary roller coasters standing really close together. At least we’ll still have our photos and memories.

Photo Credit – Image 1: coastercritic, Image 2: johnnyhann