Designed around the heartline?

I think people find this revolutionary because old Arrows hurt...B&M's do not.

Also, I think that you are correct in saying that (on sitdowns and such) the riders begin above the parabola and are rotated under it and above it again-and vice versa for inverts. I wonder if they did it that way to mimic the feeling of being swung, laterally, around the track.

Ever ride Dueling Dragons? At one point in the que line, you get a view of Ice's zero G roll that shows the lateral shift of the track as well as the slight valley in the middle of the top of it-which would suggest (to me anyway) that the rotation of axis is further from the track than the nub of the first car. Maybe not necessarily the chest area either. But definitely not the nub of the first car.

I thought I would input a couple of pictures from Medusa W. From these pictures you can see that around the base of the seat appears to be where the center of gravity. It looks like the track actually twist around the rider (that's how it feels too.)

Picture one: http://www.sfmwzone.com/random/sfmwtrip17%20004.jpg

Picture two:www.sfmwzone.com/random/medusatwist1.jpg

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Parker - http://www.sfmwzone.com/p_coastercount.htm>>My Coaster Count
www.SFMWZone.com
*** This post was edited by GoliathKills 10/16/2003 3:00:48 AM ***
*** This post was edited by GoliathKills 10/16/2003 3:02:46 AM ***

I don't think center of gravity is the term you're looking for. Probably axis of rotation. Additionally, the track doesn't twist around the rider. Because the axis of rotation is between the rider and the track, the track actually twists opposite the rider. How did people get so sloppy with their terminology?

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Be polite and ignore the idiots. - rollergator
"It's not a Toomer" - Arnold Schwartzenkoph
"Those who know don't talk and those who talk don't know." -Jeff
*** This post was edited by ApolloAndy 10/16/2003 10:09:52 AM ***

Hey man, it was late... I was just trying to give some input.

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Parker - http://www.sfmwzone.com/p_coastercount.htm>>My Coaster Count
www.SFMWZone.com

The best Heartline Rolls I can think of are those on Chiller. You are totally weightless, but perhaps that just the lapbar talking.

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If I was part of a coaster, I would be an upstop pad on an Arrow Mine Train.
MAGNUM HAD MY BABY!

The short version is that the curves, whether they be banked turns, zero-g rolls or corkscrews, are designed to be as structurally sound as possible. The easiest way of accomplishing that is to ensure that, as the train passes over any point on the coaster, it's exerting a force onto the track that is evenly distributed and easily supported.

Think about it a bit -- the track cross-section remains the same through the ride, right? There is no extra bracing in the track ties at the curves. To minimize the stress on those members, it's necessary to ensure that the force exerted upon those ties is the same everywhere in the coaster -- that is, half the weight of the train is supported by one rail and half by the other.

By designing around the train's center of gravity, it's possible to minimize the lateral forces the train exerts on the track (as well as the other way around, thanks to Newton) and ensure uniform loading. The result for us, as riders, is that we experience very few lateral forces and a smoother ride. Really, think about how many B&M coasters have strong lateral forces and you'll see that there aren't many. The result for the engineers, though, is that it's easier to support the track because most of the force acting upon it is normal to plane of the rails.

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--Maddie--
What do I Listen-To?
Hot stuff.

Sorry to bump this old thread, but I was reading it and disagreed with some of Maddie's "final" comments.

1) track tie density and cross section do vary through out the ride. Spine depth and distance between ties, specifically.

2) Rotating about center of mass of train does not translate into smooth ride for riders. If the riders' centers of mass are the same as the CoM for the train, than it would, but the riders' CoM is different, they will be flung around when the train rotates about its own CoM.

Interesting topic. Even though it's a year old, I think there are still some definite loose ends. I doubt I'll clear it up; probably just add the the confusion in the end. :)

The way I see it, they are indeed designed around a rider's "heartline". Heartline may not mean chest level, it may be the centroid point (centre of mass/gravity), or it might well actually be the axis point of the restraints. I'm liking this last one because logic tells you that if a coaster is going to hurt, this is where it will hurt, so design around this point. To reduce confusion, I'll continue to refer to it as the heartline.

However, I don't think designing around this heartline has too much correlation with the "twist" of the train. Let's say a B&M called for a section of track that banks to one side (perhaps a trick-track), which also must keep this nub at. At no point should this nub exhibit any lateral movement or vertical movement, just rotating about its centre as the track banks. The movements of the track and train will indeed be skewed slightly depending on the side it banks to, so from above it'll appear to curve slightly to one side, directly proportional to the rate of banking (dθ/dx)

The transitions in and out of this banking will need to be graduated at an amount appropriate to the heartline; else "roughness" will occur. If it's a sitdown, it'll need less transition than say a floorless, which will need less than a standup which will presumably need less than an inverted, because the length of the arc that they move will be based on the distance they are off the track.

So, this would be designed around the heartline, no? Yet the (eloquently named) nub is exhibiting absolutely no movement, other than that around its axis, which is identical to the rate of banking, dθ/dt.

Transferring this idea to a hugely complex element like the zero-g-roll would be difficult, but let’s see how it goes.

The nub may well remain centred, aside from its vertical movement, which one would thus deduce, given the nature of the zero-g-roll and the path riders take, would be appear from side-on to be following a slightly smaller parabolic + sinusoidal (where the sinusoid is pretty much negligible given the size of the parabola) path.

The riders will follow a path that's vertically parabolic. That's the only thing we need to satisfy for the zero-g-roll to provide the 0G sensation. Because we're keeping the nub free of any lateral movement, the train will consequently curve slightly outwards (and the track too in the opposing direction) - from above it will again be sinusoid. The transitioning (back to dθ/dx) will need to be gentle enough to cause no noticeable forces laterally, and above all has nothing that effects the parabolic path of the heartlines (i.e. a vertical force component).

In theory, you could throw in a 90º turn to the left on a parabolic hill. Provided we can ensure this turn creates no vertical force component and the length of track doesn't change, the exact same feeling of weightlessness / 0Gs / "Goliath hill" is felt.

Above all I think it's interesting that someone somewhere said it was designed around the heartline (back to heartline as the level where that thump-thump think sits). I doubt anyone here could really say for certain, but it's just become gospel on the Internet. Who says? Do we need a letter with B&M's letterhead to categorically denying any knowledge of any such "heartline designing", a la Drachen Fire? ;)

The rolls on B&M inverts are very parabolic when viewed from a position perpendicular to the track. If you take a parabolic curve and cut off its peak horizontally, that's what the track looks like. Combine that with the twist and the rider continues to arc through the parabolic curve even though the track does not.

Looking at it from a plan view, it's still a parabolic curve that the rider follows, but it begins on one side of the track and ends on the other.

The "heartline" expression comes indeed from Werner Stengel who developed this design feature in the seventies.
The first rides with this innovation were Shockwave and Mindbender in SFOT and SFOG.

You can see the so-called "Heartline paradoxon" in the way the track bends in the opposite direction before going into a curve.

The imaginary line is not exactly at the riders heart, usually a little bit lower to reduce the forces on the riders neck which is the weakest spot to withstand strong and sudden lateral forces.

Has it occurred to anyone that it is *silly* to design a coaster element around the rider's 'heartline', that is to say, the center of the chest cavity? First of all, that position is going to be different for every rider. Second, putting your point of rotation there isn't going to accomplish much.

There are two points on the rider where it DOES make sense to base your point of rotation, though. One is easy to find, the other is not, but you can guess.

If you want to do a real "zero-G" roll, then your point of rotation should not be anywhere near the rider's head, the track, or the chest cavity, it should be at the rider's center of mass, which is located perhaps 6"-8" above the seat cushion. In fact, the manufacturer who may have come closest to designing elements around this point is actually Arrow, because their looping coaster train sits down between the rails, actually putting the lowest point of the seat bench very close to track level. Remember, the center of mass is the point where all of the various forces pulling on an object resolve to an equivalent single point. For most seated humans, that point is very close to the waist line, roughly halfway back on a line between the navel and the tailbone.

The other sensible location to use to guide a design is the rider's head. That will vary from person to person, but as someone else suggested in this thread, you could estimate it with the position of a shoulder bar pivot. If you can minimize the translation of that point, you can minimize the headbanging. Of course, the width of the train is an issue then, as you aren't running the axis of rotation through the rider's head, but rather a point between the riders' heads, meaning that nobody's head is actually on the point of rotation...and seating riders 4-across will put half of them even further away, increasing the lateral translation, and thus the head-thwacking.

--Dave Althoff, Jr.

auscoaster - Interesting. That actually makes a ton of sense.

I'm not so sure that the reasoning behind B&M's smoothness isn't that their track design is that different from Arrows, but maybe it stems from other areas of their designs. For instance, B&M uses spring loaded wheels where Arrow did not (in the past), and B&M also places these wheels on a turntable I believe so that they are capable of steering. Obviously, the track design is different too, I'm not sure Arrow worried too much about transisitions. However, the biggest difference could be a combination of wheels, banking, etc...

B&M does make their elements much more spread out, and I believe their track fabrication is superior in many ways to what Arrow's was in the past. I say "in the past" because I hear that the newer rides were fabricated better.

But the cross-section of B&M track definitely does change throughout the ride. You can see it get thicker in some spots and smaller in others. Intamin's is much more obvious.

Back in the old days, Arrow didn't have parabolic curves anywhere, they were all fixed-radius. I don't know if the later rides (Top Gun, Tennessee Tornado) changed this or not, but I would assume so.

^ If you check the photos of TTs turn into the brake, it certainly looks that the track is not just bent around the main beam. There seems to be a higher axis of rotation.

http://www.rcdb.com/installationgallery534.htm?Picture=4

In this picture it looks like there is the typical slight "sway" in the track (shortly before it rises into the brake).
This is either the typical sign for a heartlined design, or a trick of perspective :)

http://www.rcdb.com/installationgallery534.htm?Picture=11