Cedar Point guest hit by Top Thrill Dragster part while in queue

cmwein said:
I'm not exactly certain what Hagrid's uses for it's positioning, but it most likely has some kind of encoder tape and scanner along the busbar. But again, cost. I cannot see how TTD would benefit being fitted with this type of system. Hagrid's on-ride effects made that type of system be the better choice for the ride.

My understanding is Hagrid's also has onboard computers on the trains to help with sound, effects, etc. I do not believe Top Thrill has anything like that on the trains - basically, they are strictly mechanical vehicles. If the train has onboard computers, it can say to the ride control system "I'm here at this spot", but if it doesn't, that is a bit more challenging to do.

Being on a track, I doubt anything on the train is related to control, it's all for the show system. An impressive example of something onboard would be Mickey & Minnie's Runaway Railway, where four individual trackless cars move around like a "train" at the start and end of the ride. It's insanely impressive when you see it the first time.

I rode Remey’s Ratatouille Adventure last week and watching trackless cars dance around each other is still so cool. At the end of the ride the four vehicles exit the show area and pause to let four additional cars at the unload platform move out of the way. Seeing 8 cars move about is really neat. Especially right now since the ride is so new because the cars have yet to wear down a track path.

Were you at the cast preview last week? I was there that day for lunch! Our VIP assholder day is a week from Saturday. Really looking forward to it.

I have a sense that I need to clarify some of my own comments. Let me point out this, something I think I have been clear on all along, but I want to be *especially* clear about it...

I understand how various roller coaster systems and control concepts work. I know the requirements for a blocking system, and I listened carefully to what the ODA investigator said in his news conference. I am *not* intimately familiar with the systems used on Top Thrill Dragster, nor am I entirely familiar with the changes made to that system since the ride was built. I mean, some are obvious, like the installation of the catch-car braking system, the safety cage around the rope idler bullwheel, even the positioning flag system on the catch car engagement system. I know that early on there were problems reliably catching some sensors on the ride, and while I know that some of the switches were upgraded to faster models, it's mere speculation on my part that the targets were also changed out.

As for the signal flags themselves, it certainly does look like they're on both sides of that car in SteveWoA's photo. Which surprises me if they are using those flags for check-in and check-out as the ODA investigator described. I'm also surprised to find that they are on at least two cars of the train, as the shop photo shows the back of a car which is not the last car of the train. My expectation is that the check-in/check-out flags would only be on the ends of the train. What we are learning is that does not appear to be the case.

Also, while most of the check in/check out activity happens at low-speed points on the ride, there are block ends which would be in high speed locations, particularly to catch a train coming back down the hill, or a train successfully completing the run and entering the trim brakes.

--Dave Althoff, Jr.

1) Jeff, may I ask you to elaborate on what about the brake fin grouping doesn't make sense.

2) Dragster seems to be one of the most overly-complex rides there is. A basic design principle is KISS: Keep It Simple Stupid. I figure that whatever system they use to launch a train to 120 MPH, it is going to be complicated, but it just seems to be that they made Dragster way more complicated than it needs to be.

I did see in a POV, Dave, that the top-o-the-ride block sensor appears to be in the middle of the track, so I assume it works like those you'll find around the kicker wheels. Total speculation on my part.

The rollback brakes rise from the track in groups, I dunno, maybe 30 feet at a time, after the train passes over them. In that 30 feet, there are let's stay 10 individual brake fins on each side, for a total of 20. Each one has its own piston (I think they're spring loaded to be up when there is no air pressure), and there is a switch on each end of the fin, so 40 switches being monitored in that track section. That's so many moving parts and switches!

Instead, why not have a 30-foot-long brake section that's on a bracket on rocker supports (think of the way the collapsible railings on various rides work, top of this photo), with a single piston to hold it down. When pressure releases, the bar goes from a parallel position below the track to a parallel position above it. The only accommodation you need to make to the track structure is that the cross members would have to be lower, for whatever distance of travel for the bar. You've now reduced the number of moving parts and sensors exponentially. And for the record, I might be imagining this because I've seen it on a real ride.

Not being a designer, I have to wonder again if it has something to do with reliability and potential failure. With dragster as it is right now, should a given section of brake fins fail to rise for whatever reason, With what you describe above, should a section fail to rise, for the "group" you've lost 10% of the braking. In the scenario you describe, you'd lose the entire section. I'm sure somewhere in the design there is an ability of the coaster train to stop properly if x brakes do not rise properly. I honestly have no idea though what x might be.

Yep, totally get that, but as anyone who has witnessed a rollback knows, you would need an awful lot of brake fins to not deploy before it was a problem. And really, disregard what I'm saying, because I'm working under the constraint that the overall approach for braking is correct. A clean sheet design may have a far more elegant solution for all of it, including the launch.

In software, we try to build the most simple, smallest thing first, get that to the customer fast, then iterate. People are quick to say that you can't do that with physical engineering, but then, if you watch SpaceX, especially with Starship, they're doing exactly that. They've blown up a lot of stuff for the data, and iterate quickly. You could do that with ride engineering as well, and mostly with virtual tools before you start cutting steel.

Jeff said:

Were you at the cast preview last week? I was there that day for lunch! Our VIP assholder day is a week from Saturday. Really looking forward to it.

Yeah. A good friend of mine was a designer on the ride so I was excited to see the finished product. It's a really fun ride and the overall theme/scenic inside and out is great. I absolutely love the soundtrack. There is enough stuff going on that it took multiple rides for me to really see what all was going on. I am really looking forward to the new crepe restaurant in there too. I was reading the menu on one of the tables and I don't think there was a single item I wouldn't eat.

Jeff said:

A clean sheet design may have a far more elegant solution for all of it, including the launch.

That's what I was suggesting a page back. That type of change requires taking a step back and approaching the whole concept with a fresh approach.

This is a chance to (perhaps) rethink it. The whole thing.

Wow Jeff, I didn't know that Disney paid people to hold your ass!

You misunderstood. I have to hold it myself! Nothing is free at Disney.

Unless you add the Assholding+ option to your ticket media

I should probably clarify the joke. It reads pretty strange without context.

OhioStater said:

That's what I was suggesting a page back. That type of change requires taking a step back and approaching the whole concept with a fresh approach.

This is a chance to (perhaps) rethink it. The whole thing.

See Red Force at Ferrari Land.

In that design the hydraulic system has been completely abandoned, but I don't know if anything changed on blocking and number of trains. I know they made some changes to King da ka based on what they learned on TTD.

I learned at WCO that there was some serious upgrades to the computer system and the hydraulics for the launch part of TTD. If I understand, the PLC system only controls positioning and blocking of trains outside of the launch. Then the launch part is its own system. There is some sort of handoff between the two that is done.

I think the window of starting with a clean sheet has passed based on scope of this last upgrade. Again, this info came from my conversation with maintenance, so it could be a telephone game. It seems some news articles confirm the upgrade that was done.

BrettV said:

Unless you add the Assholding+ option to your ticket media

and now the upcoming mobile app enhancements will give you guidance on how best to hold it for maximum enjoyment

Yes, I will agree that the design of the rollback brakes is needlessly complicated. Making something along the lines of what you described with fewer sensors and fewer moving parts seems like it would have been a better and more reliable way to design the ride. Two possibilities that I can think of off the top of my head:

1) The lateral force on the brakes would be too great with one large moving piece.

2) There isn't a lot of interdepartmental cooperation when designing the ride. Perhaps the mechanical engineer designed the braking system in the way that was easiest from the structural perspective without any regards to how complicated it then makes the control system.

In most machinery, your major safety concern is in keeping the people away from the machinery. On an amusement ride, the entire point is to put the people *on* the machinery.

I have seen "incidents*" where one or more brake fins malfunctioned. The nature of such a malfunction is that it's a minor enough failure that the ride can continue to operate even if a single brake fin won't function reliably. Management of risk involves reducing the probability, severity, or both, of a hazardous event. I can see that individual brake actuation very likely increases the probability that one brake fin will fail, but the failure of a single brake fin is a much less severe hazard than the failure of ten brake fins. It may be more acceptable to allow for the more likely, but less severe hazard than to allow for an only slightly less likely, but more severe hazard. The individual brake system may allow for 10x the failure points, but the probability of a single failure should be about the same...which means combining a bunch of brake fins onto a single assembly might easily be considered to be a less-safe solution...because if each combined assembly is at least as reliable as the individual assemblies, they are just as likely to fail...with a greater severity when it happens.

So you choose your poison. Do you want a statistically higher likelihood of a failure that has virtually no impact on the operation of the ride, perhaps a 1% reduction in emergency braking force, or a simpler system with fewer points of failure, but not necessarily less prone to failure, whose failure reduces your emergency braking by, say, 10%?

Oh, and that's also worth noting: when the brakes on the launch track actually engage with the train, it means *something else* has already gone wrong. Remember, that's a safety system!

--Dave Althoff, Jr.

* "Scare quotes" because these weren't really incidents in the usual sense; just minor failures that most riders or observers...often including me...wouldn't even notice.

If a bolt, or bolts were still in the train, considering that they are flathead bolts, then they would have to have broken off. It could be possible that one bolt became loose and fell out and the other broke off. Had they both become loose, the bracket would have sagged and taken out one of the proximity sensors before becoming totally detected.

I went back and looked at the supposed photo of the bracket and you can see the witnesses mark next to the bolt hole. So, the visual inspection would have revealed a loose fastener.

Not doubting Rideman, but there certainly has to be a better way to sense the position of a train than that huge bracket. A magnetic sensor counts the 7 fins of a turbocharger impeller spinning about 20,000 rpm on a locomotive engine.