Top Thrill 2 faces extended closure for modification

I’m just here to drop my guess.

I think the center of gravity is just a little too high, and the laterals during the straight-away were underestimated along the way. For such a long straight section of track, with zero lateral support structure its’ entire run… I think that “shuffling” is creating a few issues that will be discovered over time.

- I could see the stators being banged up as these lateral forces take their toll

- I could see potential structural fatigue ala Fury 325

- I could see issues with wheel compounds not holding up due to intense and rapid variations in positive lateral/vertical forces.

But also, it’s also possible that the brake fins could be being scraped again 🤷🏻‍♂️

After what happened, I think pretty much any of these reasons are suffice to stop everything & re-evaluate. Can’t have even a slightly similar repeat situation, or it’s all over.

To be honest, I’ve always suspected that even Top Thrill Dragster had unresolved lateral force issues that contributed to the incident. If you raise the center of gravity, that will only exacerbate those lateral forces, and without something to dampen them, I only see more problems in the future for TT2.

I think we all whom have ridden it, have enjoyed the ride layout & extended sections of speed so much, that we really did not want to think of all that “shuffling” as being a potential issue at some point. But… cmon, it crossed most of your minds! 🤷🏻‍♂️ There is just not enough lateral brace.

I suspect they are trying to start conservative to find method to alleviate at least this specific symptom they are having at this time, and get through the season. I do believe there will be more symptoms to come, all stemming from the bigger issue, “shuffling”, which will have to be dealt with at some point, hopefully between seasons. If Kingda Ka opened with lateral support through that straight-away section, only 2 years after Top Thrill Dragster, even Intamin recognized there was a flaw there; and again, with trains sitting at a much lower center of gravity than these.

I was not consciously looking for it, but I did not notice any shuffling on either of my laps. So maybe?

There are no lateral forces. It's entirely linear until the pull outs.

I've had 2 total rides, both in the last row. Yes, the shuffling was very noticeable. I'm sure the back and forth of this shuffle are the lateral forces being referenced.

Whether or not the "shuffle" is the reason the ride is closed I don't think has been made public, but it wouldn't surprise me if this was the case.

Jeff:

There are no lateral forces. It's entirely linear until the pull outs.

Are you sure?

Lost Gravity at Walibi Holland had an issue in it's seemingly straight section of track due to oscillations after the train passed, as seen in this video:

They eventually added a tuned mass damper to remedy this problem... There is no curve or laterals expected here, as it's a a straight bunny hop... But add in train induced loading/vibration, the structure can excite in directions you don't expect.... Basically vibrational modes being excited.

That could certainly have propagated from uptrack downward spiral just before that from the highest point in the ride. More to the point, the straight track on TT2 doesn't wiggle. And even more to the point, no force is acting laterally on the train. The only force acting on the train is straight, in line with the track.

The non-flat pull up track wiggles, yes, and that's not surprising because that's a lot of energy pushing on it with some awfully long supports under it. That's why I said it was linear until the pullouts. Ignoring for a moment the mass of the train on the level(-ish) track, the vector is parallel to the track for the duration of the launch. When it hits the pullout, it's not. (Sidebar: It shook a lot more with the old system, and someone had a theory that the energy of the very heavy catch car coming to a stop was likely to generate a "wave" through the track, a phenomenon you can see on many coasters down track of their final brakes. That seems plausible. KingDa Ka has more conventional A-frame supports under that track, interestingly enough.)

The end of Kingda Ka's launch track is also a bit higher off the ground than the end of TTD/TT2's launch track. Kingda Ka has no lateral bracing on the valley after the drop, and that track shakes violently every time a train goes over it. If they launch trains back-to-back that track will still be swaying from the first train when the second train hits the valley.

Regarding lateral forces, are we only talking about the straight sections of track?

PhantomTails:

Maybe they figure it's not worth the effort. The number of people who are going to make an informed decision as to whether to visit a park by referencing a site such as queue-times has got to be minimal.

To boot, it may actually help encourage people to visit on less crowded days. I have visited thrill data in setting up a plan for theme park visits. I completely realize I am a small subset of a small subset of park visitors.

Bakeman31092:

Regarding lateral forces, are we only talking about the straight sections of track?

That's where the shuffling occurs.

Those are absolutely lateral forces acting on the train.

What is pushing the train from the sides?

So that was somewhat the point of my previous post, that if you excite structural modes even on a straight section of track, you could get lateral movement. When you excite structural modes, you'd get movement in X/Y/Z axis. It would not just be in the normal direction. It wiggles, bends and twists.

Sure, the train is not going along a curve and getting 'direct' lateral forces, but that shuffling and possibly movement of the structure from being under-constrained could cause lateral loading situations. Usually you just need to stiffen some stuff.

I have a large A36 steel test stand I designed at work being used to support a rocket fairing for an acoustic test... As beefy as the thing was initially designed (and overkill for the loading), once we ran our acoustic models with input from the customer on those acoustic energy levels, those excited structural modes required some hefty redesign/stiffening to prevent all the movement in all types of directions. It's very difficult to simulate that type of stuff without doing the testing itself (acoustic, vibe and shock tests) on the hardware/structure. In our case, the customer was doing their own testing and reporting back the vibe/shock levels we had to design around.

Not sure if they get to that level of requirements with these structural firms doing the support/foundation work? I know at Universal they had done a bunch of vibration testing on the Velocicoaster trains and the fiberglass coverings/mounts and all that, but still had issues after the fact in the real world.

At the end of the day, the vibration/structural modes will do some funky stuff. Many rides get tweaked after the fact because of the unknowns not being accounted for because it's so difficult to account for it all. Many rides have had structural mods once built likely for this reason... I'm sure when designed they accounted for what they needed statically, but dynamically I wonder how much goes into that?

That being said, I'm no structural or civil engineer.

Any left-right imperfections in the track or its alignment will apply lateral forces to the train when those deviations alter the direction of the train. Any offset between forces applied to the train (either from the track or the LSMs) and the train's center of gravity will result in a torque/rotation, which could also be resolved through lateral forces applied to the train. Whether or not those unintentional lateral forces are significant enough to be considered in the design of the track or train is unclear to me, but they are certainly there.

Movement isn't force, that's what I was getting at. Yes, any bump in the track would deflect the train off-axis, but in the context of this discussion and whether or not it's causing any harm, that kind of "force" seems pretty insignificant.

I don't know enough about the LSM firing sequence to really speculate on anything, but one thing I do wonder is whether or not they are active on every car in the train, and if so how that works with the trailered configuration of the cars. Because if you have a trailer, you always want to be pulling it; you don't want to push it from behind because it can become unstable at the hitch point. It seems like this would be a problem that's already been solved by all the prior magnetic launch coasters since all modern trains are trailered, but maybe there's a gotcha in there that Zamperla just wasn't aware of. I can see how a little bit of lateral shuffling would be intolerable due to the tight air gap between the stators and the fins.

Jeff:

Movement isn't force, that's what I was getting at. Yes, any bump in the track would deflect the train off-axis, but in the context of this discussion and whether or not it's causing any harm, that kind of "force" seems pretty insignificant.

I agree, I doubt the forces causing the (apparent) lateral movement of the train are any higher than what the track/train experience by design on the twists. I also doubt I'd want to be stuck between a wall and whatever force is causing the multi-ton train to shuffle.

As others have speculated, I wonder if the issue is due to a lack of force between the guide wheels and the track, i.e., the train is unable to apply the force needed to resist lateral shuffling that results from imperfections in the track and variable centers of gravity. If the LSMs have indeed been nicked by the trains, I understand why the park would choose to shut everything down and address the matter before it becomes a more significant issue.

That's the most plausible theory I've heard. But it's still based only on the fact that we've seen the trains wiggle a little.

I tend to agree. The springs and hardware used on the wheel bogies just look kind of small and insignificant from the pics I've seen. I know these are lighter trains, but I remember someone commenting early on when seeing the Lightning trains that they really don't have much of a suspension on them.

I'm not an aerodynamic engineer, but I do push buttons on machines designed by them. ;)

If I had to guess, I'd say a combination of what TylerWS said above, aerodynamics, and weight distribution.

The trains can only be so aerodynamic when you have uneven weight distribution from 20 guests of all heights and weights placed randomly throughout the train leading to unbalances. You also have the uneven forces caused by some hands being up, some heads sticking up further than others, etc etc. All this could, I assume, lead to aerodynamic buffering.

Going backwards it doesn't look like there's much aerodynamic-ness to the rear of the trains at all. I'm sure some was designed in, but you've still got seat backs, head rests, the aforementioned unbalanced weight of riders. All this moving at 100mph, which is faster than most of us have ever driven a car.

Wiggle… a little…?

I think it’s a lot bigger of a deal than it’s being played out to be. I see the base frames of the seats being modified lower to reduce the center of gravity of riders.

As you can see from this video clip from CoasterStudios, it’s a lot more than a wiggle. This has gotta be causing issues all down the launch and brake runs. Seeing as though misalignment issues contributed toward the former coasters demise, I would say modifications needed made sooner than later.

But I do think this is the issue and I’m willing to take bets on it. 😀