Mechanic's Grab Bag: Ride Q&A Volume I

Today's post introduces a new feature on our blog: a Q&A where we highlight and answer your questions about rides and how they work. In this series, I will break down complex mechanical topics into more accessible language. If you’d like to ask a question, please email us at amusementodyssey@gmail.com.

I will do my best to answer every question I receive. If a question is common or intriguing enough to warrant further exploration, I may feature it in a later blog post. I aim to keep each response brief yet informative, even as many topics may be expanded upon in future posts. Let’s get started!

Question 1. from Rob: How don't the wires for the lights on spinning rides get all tangled up?

That's a great question that I think is a mystery to a lot of readers. You see it everywhere. There's a spinning ride going round and round all day long in the same direction. Of course all of the light bars require electrical power for the bulbs to light up. But how do the wires not get tangled around the center hub and finally snap off?

There are actually no wires that connect the power at the ground to the spinning "hub" of the ride. In-between these two items is typically an assembly known as a slip ring. A slip ring is essentially just a stationary ring made of copper or other conductor that is bolted to a center pole, boom arm, or other fixed point. Connected to the ring is a wire that travels back to the ride's electrical source. On the rotating portion on the ride is a brush holder with a series of brushes or contacts. As the ride rotates, there is pressure held onto the slip ring(s) by the brushes, creating a constant electrical contact point as the brushes never leave the ring.

Following the brush holder are the wires that go to each light bar, secured to each sweep or light panel. Since most of these light bars are connected in series or "daisy chained" to each other, the wires never have to travel from the rotating portion of the ride to the ground. The electricity travels from the stationary slip ring, to the rotating brush, through the light bars, and back to a neutral or ground brush.

Slip rings are used virtually everywhere where rotation or oscillation may be involved. Pendulum rides, Wave Swingers, Carousels, Top Spins, kiddie rides, and the list goes on and on. Slip rings aren't just used for lighting purposes, but many rides have complex slip ring assemblies with several rings, with a lot reserved for control power and feedback from sensors that may rest on rotating components. Even your car's steering wheel functions are controlled by slip rings.

The following image is a product offered by United Equipment Accessories, an industrial supplier of slip ring assemblies:

Question 2. from Peter S.- What is the most difficult repair you've had to do in the field?

I've had many difficult repairs, however not all of them are difficult in the same aspect. Each job is unique and has its own set of challenges to mitigate. Some jobs are just plain physically tolling on the body. Others don't give many clues and there are countless hours of troubleshooting involved, causing mental exhaustion.

Some of the worst jobs to do involve lift chains, sprockets, and bearings in that area. Given the nature of the beast, everything on a lift assembly is large and heavy. If you think about the weight that a ride has to pull to get a train up the hill it makes complete sense.

Sprockets often ride on very large shafts with large bearings that don't like to move if they've been in place for a long time. I've done bearings on the top of coaster lifts that required great physical effort. There's usually a lot of heavy lifting involved, swinging hammers, and finding ways to lift on shafts or other objects with chain hoists or hydraulic rams. Just getting all of the tools and equipment to the top of the lift takes a lot out of you.

One set of bearings we did involved splitting the lift chain, securing it to the structure, pounding out a solid shaft that was almost 6" around, lowering the sprocket with a chain hoist, pressing out the old bearings, pressing in the new bearings, and reassembling everything... TWICE while over 200 feet in the air on a work platform. It might not sound like too difficult of a job, but everything weighs an extreme amount and fights you every step of the way. Our water ride lifts were almost just as bad as you had to fight the rust and corrosion caused by the chlorinated water.

Gearboxes (whether large or small) also were a challenge. Almost every gearbox is unique, even if it comes from the same family or even the same supplier. Very few gearboxes at our park came with detailed drawings. In fact, you were lucky if you got a replacement parts list. A lot of working on gearboxes required taking notes and pictures, keeping all of the parts together, and determining what required replacement. Due to the nature of complex moving parts that must mesh perfectly, most gearboxes have specific shims in them to set distances. If you didn't remember what shims went where, it was a nightmare trying to get things back together perfectly. This is coupled with the fact that you have a lot of movement going on and a lot of pressed components together in a tight space.

I watched one mechanic take apart a gearbox in a very destructive way. He set it aside for months while waiting for his bearings to show up. Finally, when he decided to put it back together, he had lost all of the shims and decided just to slap it back together. A couple of months later, the gearbox blew apart internally because the lack of shims caused a shaft to slip off a gear mesh and it destroyed all of the teeth. Since the gearbox was not in production anymore, we had to find a suitable replacement, which was extremely expensive because the replacement ended up being a custom design to fit where we needed it to.

Question 3 from Brody: How do you make sure that magnetic launch fins are aligned right?

Very carefully! Magnetic brakes (and launches for that matter) are great because they are a non-contact way of accelerating or decelerating a train. Manufacturers are moving to these solutions because magnets can last a really long time with less maintenance than is required with friction brakes. The one caveat is that trains and track design have to be kept to much tighter tolerances.

Magnet assemblies work the best when the air gap between the magnets is kept to a minimum. When magnets are closer together, naturally they generate a stronger field. When it comes to roller coasters, this becomes an issue given that trains vary from cycle to cycle exactly where they will track from side-to side. In order to avoid a complete disaster from happening, the alignment of the fins and magnets become critical.

We had one launch coaster with LSM-style fins. In this orientation, the magnets were bolted to the bottom of the train, and the launch fins were on the track. The launch fins were static, and aligned by the manufacturer when they put the ride in. We monitored the fins for rubbing or damage visually on a daily basis. Annually, we used a jig that they supplied with the ride to slide along the track to verify that the fins were within spec. If not, they required adjustment or shimming to correct, possibly even replacement of a fin if it had been damaged.

As far as the train went, it was important to keep the guide wheels in proper adjustment so that the magnets would not get too close to the launch fins. The wheel bogies actually had jack bolts that allowed you to move the guide wheels tighter or looser to the track. Just like with the launch track, we had a cut out jig for the train that we used to align it side-to-side when rehabbing it.

Another coaster at our park had the opposite configuration. The brake magnets were located on the track, and each car had two brake fins. In this case, you had to adjust all aspects of the train height to center the fins in the brakes. This included adjusting the height of the road wheels, since they rode on cammed pins, and shimming each brake fin properly. At the beginning of the season, we set the train height from the track by measuring from the track to the bottom of the frames, and setting the wheels first. Then, you would bolt the brake fin on and measure its height from the track. Each of the three mounts was a different length, and each one had to be shimmed accordingly.

After you got all of the heights equal for the brake fins, we backed the train into the brakes to verify its height. One mechanic got headstrong one year and thought that because he had measured everything twice that he could skip this step. Well, the train made it to the brake run when there was a huge crash. One of the brake fins was set way too high and destroyed both the brake fin and the magnet assembly, both costly repairs.

This attraction was so finicky that it became a weekly inspection to park it in the brakes and check all of the heights. Even a minor issue like a worn wheel could throw everything off requiring readjustment. In fact, whenever we had to change a road wheel, we had to double check everything or risk a brake hanging up on the train. There were only a couple of millimeters to play with, because not only did the train have to slide through the small air gap, but the brakes oscillated to open and close, giving you even less clearance. Trying to get about 50 mounts shimmed perfectly within 1-2 mm is a very long and difficult process. Some brake fins needed to be adjusted 2-3 times during assembly to get them perfect.

Question 4. from Mikayla: How are block systems tested to make sure they work? Have you ever seen one fail?

Block systems are one of the most critical aspects allowing for multiple unit operation on an attraction. They should be tested on a daily basis for proper function if an attraction is utilizing multiple units. Each block system is unique in operation and function, but the law remains the same: only one unit may occupy a block zone at a time, and a unit may not advance until the following block is cleared.

In the morning, rides usually go through a "block reset mode." This mode either verifies train positions or clears empty blocks within the control system. In its safest mode, the ride will automatically occupy all blocks, since at that point nothing can move forwards. Block resets may actually take more than one person to perform, as the task of clearing blocks is one of the most safety critical for a ride. Usually you want a block reset button located right next to or near a block zone to verify that there are no trains present. This was the issue with The Smiler at Alton Towers, where a block was cleared where a train had valleyed, and the ride had no way of knowing.

A portion of a block where the train can actually stop is called the "control point." Whether it's a drive tire, friction brake, or other means of parking a train, the area containing the control point is usually littered with sensors. If a sensor is flagged, intentionally or not, it should set the block automatically as a failsafe. One of the Gerstlauer coasters I am familiar with typically cleared blocks by itself during morning startup. It was the job of the technician to verify that the blocks presented on the screen were actually set or clear, and push a button to acknowledge the info. This likely was the issue with The Smiler, since if the ride did not see a train at a control point, and the processor cleared the block upon a system reboot, the valleyed train was ignored by the ride, since the technician failed to verify the block status.

When trains begin to stop in blocks because the following blocks are occupied, this is called a block setup or cascade. Operations staff must keep ride vehicles moving efficiently so that trains don't keep piling up in brakes, waiting to move forward. Oftentimes, when rides setup they will go into an E-stop mode and require a full system restart. This requires maintenance or operations to clear blocks, and begin getting trains to move forward.

Some parks require maintenance to test blocks in the morning, some parks rely on operations to do so. It all depends on the company, as I have worked at one of each in regards to this system. One park I had worked at had a lot of modern control systems with touchscreens. There were actual block check modes built into the program. Essentially the operators would come in in the morning and begin starting the ride. They activated the lift chain, station area, drive tires, blocks, and whatever else the ride required. Then, as they began running cycles there were three options of a block check, A, B, and C. Depending how many cars were running on the track, that determined which combination of block checks were necessary. Once all of the vehicles setup on the track, it could be reset. This was on a Wild Mouse attraction where there were a maximum of 10 possible vehicles active at a time.

I know that a park like Cedar Point allows operations staff to have a lot more trust, with the ability for them to transfer trains on and off by themselves without maintenance present, which makes me pretty weary. Now, that goes to say that Cedar Point's control systems are probably a lot more advanced than most parks, with several more safeties in place and specific transfer modes that disable a lot of safety critical features. For instance, most of the coasters at my park required manually moving trains with jog functions. Our parent company did not like this very much, and preferred that we installed features that automatically moved and transferred trains with the push of a single button. However, we were grandfathered in and the plans never really came to fruition.

The other park I worked at required us to test the blocks ourselves. Basically, you would stop a train in a block, and ensure that the train following it would not violate the block rules and proceed forwards. Simply put, for a typical two train and three block ride, that would mean parking a train on the lift and trying to dispatch from the station, parking a train in the brakes and ensuring the preceding train stopped on the lift, and seeing that a train in the brakes would not proceed into the station if occupied. We also attempted to dispatch coasters "every possible way incorrectly" that we could. This meant trying to send the train if the gates were open, restraints were not locked, chain wasn't running, etc. This just verified that all of the permissives and conditions in the logic were active and working properly.

As for if I have ever seen a block system fail... I cannot think of a scenario where I have during normal operation. Rides monitor so many variables and are able to compute logic so quickly that they will shut down in a split second if something is amiss. There have been a couple of RARE cases where mechanics have been troubleshooting issues and flagged a bunch of sensors manually out of sequence, causing strange issues to arise. We had two trains literally dispatch themselves out of the station and brake areas on one ride because somebody thought it would be a good idea to flag a set of sensors with a pipe without thinking about the consequences. Luckily, somebody was at the panel to E-stop the ride within seconds, and no riders were on the trains, but it was still a scary moment. In most cases, a bad proximity sensor or other feedback device going bad or falsely flagging would immediately cause a block violation and shut the ride down, even if there is not an actual violation actively happening.

There were a couple of rides where dispatching too quickly would actually cause a block setup and stop trains at the top of lifts. To prevent this from happening, timers were installed into the logic prohibiting a dispatch before a certain interval. So even if the operators were ready to send a train in a very quick time, the ride would prevent an actual dispatch until the timer was met, and a setup was not possible.

Block systems and their function will certainly be covered more in-depth in a later piece! Thank you for reading, and feel free to submit questions to amusementodyssey@gmail.com.