Why do coasters shuffle?

Monday, February 23, 2004 6:01 PM
Because they want to play cards.

Sorry.

I keep hearing thata one of the reasons that Arrow $ Vekoma coasters are so rough is because those two builders place the guide wheels on the inside of the rails, while Intamin & B&M coasters place them on the outside. This really doesn't make myush sense to me because it seems to me that it shouldn't matter so long as the coasters are built to adequate tolerances. In fact, IIRC, wooden coasters are built this way, and (usually) people don't complain if those shuffle. Can someone explicate this? Thanx

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Monday, February 23, 2004 6:05 PM
It actually has nothing to do with whether the wheels are on the outside or the inside, it has to do with the wheel assemblies. B&Ms, Intamins, etc have what could be considered "spring loaded" wheels assemblies so that all three sets of wheels make solid contact with the rails at all times. Arrows, Vekomas, etc do not have this....their side and under wheels have massive gaps between them and the tracks, and therefore can "slam" into the rail on a turn or a peak....it is a key ingredient of the roughness. Ride a Vekoma SLC and look up....you can watch the wheels slam into the track and they are forced to go from not spinning to 50mph in a fraction of a second.
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Monday, February 23, 2004 6:06 PM
Well Intamin and B&M have spring loaded type wheels, so that all three wheels remain in constant contact with the track at all times. Most (if not all) Arrow and Vekoma's don't have these which means all three wheels aren't in constant contact with the track at all times, thus the shuffling occurs.

EDIT: Peabody beat me too it. *** Edited 2/23/2004 11:07:39 PM UTC by CoasterDude316***

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Monday, February 23, 2004 11:08 PM
Have a look here for some theories about it...

--Dave Althoff, Jr.

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Tuesday, February 24, 2004 12:58 PM
why would a designer do that? it must be cheaper, because that is just common sense, if they don't touch, it would bang. also, doesn't that banging cause the wheels that are not moving, that suddenly start moving to slow the ride down due to friction
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Tuesday, February 24, 2004 1:26 PM
Also would that "shuffling/banging" of the wheel assemblies actually increase the need to replace the wheel assemblies?
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Tuesday, February 24, 2004 1:49 PM
Spring loaded bogies aren't the answer here. Intamins have shuffle to them also, and sometimes a B&M can as well. Shuffle is caused purely by not all wheels being in contact with the track. The more room to move, the more room to bang into the track and bounce off. All wooden coasters shuffle (except maybe the Intamin plug and play).

Shuffling can be minimized though by maintaining 2 things: Track Gauge and Wheel Gauge. If the track gauge was perfectly even all the way through the ride (or altered where needed depending on how the wheels are set up, which we will ignore for now) and the wheels stayed the same distance apart then there would be no problems and a perfectly smooth ride. However we know that there is play in how far the wheels move. Some manufactures allow for more play than others (Vekoma). Park maintenence must also play their part and keep adjusting the wheels to the proper gauge so that they stay put. Even the smoothest B&M could suffer if someone wasn't making sure that spring was tight and the wheels were held close to if not on top of the track at all times.

-Ride_Op

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Tuesday, February 24, 2004 3:04 PM
B&Ms also shuffle - or better "vibrate".
Two examples of this are "Scream" and "Silverstar".
I still wonder what makes them shuffle though - must be a resonance between the springs on the wheels, the wheel rotation or some other thing with the train.
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Tuesday, February 24, 2004 3:10 PM
Or maybe a derterioration of the polymer that is used to wrap the wheels. But then again, what do I know!
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Tuesday, February 24, 2004 4:55 PM
It could also be caused by the durometer(hardness) of the wheel treads as well.

A harder wheel(higher durometer) would bounce a bit more than a softer one...vekoma uses a harder wheel (to increase durability) on the SLC's & the gap is there to prevent the train from binding in the curves.

It doesn't matter much though if the wheels are contacting the rails at all times,instead the transitions & radius of the curves is more of a factor....look at Togo's stand up or Premiere's launchers,on both of these rides all three wheel sets are touching the rails at all times & yet they're still rough.

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Tuesday, February 24, 2004 6:06 PM
I don't really believe that the gaps in the guide wheels is the entire cause of the problems. Am I right in suggesting that Giovanola use fixed guide wheels on their two hypers? I remember that they were fixed upstops, and I'm pretty sure that they're fixed guide wheels. Meanwhile, you've got a coaster that certainly equals any other manufacturer for smoothness. Both Titan and Goliath are some of the most twisted coasters I've been on, yet they seem to hold up just fine, with quite basic trains.

I think most of the problem lies with the designing of the rides. What Vekoma and Arrow couldn't do, presumably because of inadequate technology and/or design processes is design a track that is as calculated and graduated as what was brought to the scene by our Swiss friends. The gap is of course a problem, but it could be made insignificant with a good track design - isn't Tennessee Tornado said to be B&M smooth, despite having the same trains as every other Arrow looper?

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Tuesday, February 24, 2004 6:25 PM

BATWING FAN SFA said:
It could also be caused by the durometer(hardness) of the wheel treads as well.

A durometer is the actual instrument that measures the hardness, not a unit of measure. You don't weigh an object and then say it weighs ten scales, do you?

-Nate
*** Edited 2/24/2004 11:26:16 PM UTC by coasterdude318***

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Tuesday, February 24, 2004 11:31 PM
Nate: That's true, but it seems that when you talk to companies that make this stuff, they refer to a particular 'durometer' material. Inaccurate, as it should be 'durometer rating' or something like that, or better still, "stiffness", but that's how it sometimes comes out. Probably because the stiffness is rated based on the durometer reading, which, if I remember correctly, is an arbitrary value, not an actual unit of measurement.

On the ride, even if there is a gap between the guide wheel and the track, that doesn't mean you have to have shuffle. Consider, for example, the second hill on Mean Streak, or Son of Beast (I think they are both about the same). When the front of the train hits that high-banked curve, the train doesn't shuffle; the outboard guide wheels stay 'stuck' to the outside of the curve and the train goes around quite nicely, until about half the train goes through. At that point, the train is moving slowly enough that (I suspect...) gravity overcomes the lateral force on the curve and slams the car sideways into the inboard (lower) rail.

The presence of a gap isn't necessarily a bad thing. Take a ride on Gemini sometime and watch the back of the other train, and notice that on straight track, frequently, NEITHER of the guide wheels are touching! Why should they be? It's straight track! Accordingly, if the designer tweaks the curve to bring the rail gently in to the guide wheel, that 'bump' at the point where the axle starts to turn can be minimized.

The worst shuffle, of course, is going to happen on an improperly trailered train where the cars are literally fighting each other to go through the curve. Mercifully, there are only two of these left that I can think of right now: Predator at Darien Lake, and the Lil' Dipper at Camden Park.

--Dave Althoff, Jr.

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Tuesday, February 24, 2004 11:51 PM
Dave...what makes those 2 trains improperly trailered? Sorry if I'm overlooking an obvious answer. Was Hercules like that too?
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Wednesday, February 25, 2004 6:28 AM
Peabody, the link Dave posted earlier covered that point nicely. :)
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Wednesday, February 25, 2004 9:06 AM
My brain hurts after reading that...

God bless people like you Dave, cause if it were up to me having to build amusement rides, there's just be a big hill, water and a Slip N' Slide (or Wet Banana if that's your druthers) and a ramp into a big mudpuddle at the bottom of the hill.

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Wednesday, February 25, 2004 9:19 AM
Yeah - kind of funny how focussing on unfamiliar complex ideas can make the brain hurt.
Once they become familiar though, the pain stops unnoticed.

*** Edited 2/25/2004 2:19:26 PM UTC by superman***

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Wednesday, February 25, 2004 10:16 AM
Good call, auscoasterman, that was kind of the whole point of that link was to explain why that kind of trailering doesn't work...

In a nutshell, think of it this way:
Consider a two-wheel trailer, such as a boat trailer. If you pick that trailer up by the tongue, and translate the tongue left or right, the trailer will rotate on a vertical axis positioned right in the middle of the axle.

If you weld a hitch ball onto the back end of the trailer, and attach an identical trailer to that hitch ball, something strange will happen. When you translate the tongue of the lead trailer to the right, the trailer rotates clockwise on its axle. The hitch ball on the back will actually translate to the LEFT, causing the second trailer to rotate COUNTER-clockwise on its axle! And if you add a third trailer in the same fashion, the third trailer will match the motion of the first one!

Well, that would be a nightmare going down the road. Put it on a track, and things get downright nasty because the trailers can only rotate so far before the guide wheels catch. A ride on the Lil' Dipper demonstrates quite well what can happen (I think I have a good piece of video here someplace that shows it...).

That's how PTC's trailered trains (don't) work.

You can fix the problem with the trailers by moving either the axle or the hitch balls. If the hitch is positioned directly over the axle, that is, at the point of rotation, then when you translate the front of the first trailer, the second *won't move at all*. Which, since on a track you want the train to follow the track, is pretty much exactly what you want.

And that is exactly how Prior, GCI, Arrow, Vekoma, Schwarzkopf, and B&M do it.

--Dave Althoff, Jr.

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Thursday, February 26, 2004 4:24 PM
But to save the shuffling between the rails, why don't they just make, or aim for, all wheels touching at all times? is it a friction reason?
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Friday, February 27, 2004 7:34 AM
Don't forget about Intamin hyper trains.
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