120 mph?

Monday, October 23, 2000 3:46 PM
I've heard that there is a momenum limit of 120 mph? Is this true? (I hope it isn't.
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Monday, October 23, 2000 4:35 PM
Yes, I'm pretty sure that 120 mph is the limit on a coaster, but if it's not, the actual maximum velocity is not far from it. Once you reach this speed the wind resistance that is exerted as the train moves along becomes equal to the amount of energy possessed by the train, preventing it from reaching higher speeds.
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Monday, October 23, 2000 5:03 PM
Of course not. With LIMs, you can always have over that, just not for very long...
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Tuesday, October 24, 2000 5:22 AM
Once again this topic emerges.... Sigh.

People constantly refer to "Maximum velocity" or "terminal velocity" when talking about the maximum speed of a roller coaster. And, they always peg this number at around 120-130 MPH. This is due to the fact that the terminal velocity of a skydiver is right around those speeds. This number takes into account for air friction, but only in the "spread eagle" position of the diver. In reality. there are "speed" divers who consistantly reach speeds of 300 MPH. They do this by wearing a rubber suit, and actually diving, as opposed to laying down in the air.

So what's my point?

My point is that a roller coaster train, due to its mass and aerodynamics, can and does have a higher terminal velocity than skydivers do. Therefore, the limit is higher than 120 MPH. However, the heights needed to attain those speeds is much more than the current 300 feet. The faster an object is moving, the more space it needs to accelerate.

There are more factors and information, but I've already bored you long enough....
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Tuesday, October 24, 2000 1:00 PM
actually, (and yes, ive said this befroe too, this is another topic that wont die)
no roller coaster train would have an area that small except for some funky strap yourself to a flatbed on the track coaster launched by LIMs... :::rushes to drawing board:::
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Wednesday, October 25, 2000 3:47 AM
Huh? Could you clarify that response, please?

Not trying to be a smartarse, but I'm not sure what you mean....
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Wednesday, October 25, 2000 1:05 PM
Hey Don Lacey, there's also friction on the track.
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Wednesday, October 25, 2000 1:36 PM
Giga: First of, a skydivers 'jumpsuit' is actually designed to increas surface area and thus induce more wind drag. Vehicles can be designed to minimize that drag, such that a 120+mph speed could be generated from a freefall, though the height needed would be MUCH more than your run of the mill coaster.

As for the LIM's part, that's very easy to do, IF you have a long enough plot of straight land to accelerate on. There already is a vehicle much bulkier than your ordinary coaster train which uses magnets and runs on rails (sort-of) it is France's Train de Grand Vitesse (TGV=Train of Great Velocity). It reaches over 180+ http://www.railway-technology.com/projects/frenchtgv/index.html
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Wednesday, October 25, 2000 1:36 PM
the skydivers go 300 mph by presenting their shoulders as the area of resistance, no their bodies, and a coaster train is larger, so more resistance.
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Wednesday, October 25, 2000 1:38 PM
but thats a train, not a coaster, the limit we were talking about was with out constant acceleration.

riiight...
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Thursday, October 26, 2000 4:00 AM
Yes, there is more surface area on a coaster train than a human being. But, coaster trains also are aerodynamically designed, unlike humans.

But, there is also more inertia. What this means is that although the accelleration of gravity is constant, regardless of an object's mass, objects with more mass can reach higher speeds during freefall than objects with lesser mass and similar forces of friction.

Remember, the definition of inertia is "A body at rest tends to remain at rest unless acted upon by some force. A body in motion tends to remain in motion unless acted upon by some force."

In this case, the forces are gravity and friction.

And, yes I do know there is friction between the rails and wheels, hell, even within the wheels themselves, there is still a lot of inertia. This is one of the areas Arrow missed on the Steel Phantom. When first built, there was too much speed going into the loops. This is because they didn't give the train enough 'uphill' to lose its momentum (inertia).

As a related side note, inertia is what causes trains to be able to go through loops. There really is no such thing as centrifugal or centripetal force. These are terms to describe inertia at work. It only feels like you are being forced down into your seat, when in reality, the seat is being forced up into you. Because of your inertia, you tend to move in a straight line. The train forces you to move in another direction.

I can hear all of you snoring now......
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Thursday, October 26, 2000 12:49 PM
yea, i forgot to mention the mass thing... i think the point of the matter is that for a coaster to get to and sustain 120 mph is only currently possible (feasible) using a launch system.
Think how easy it would be to make a mf clone minus the lift. I bet it would be much less expensive...
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Thursday, October 26, 2000 6:32 PM
You also have to think about g-force. If higher heights are needed to obtain speeds faster than 120 mph, the g-forces would be way too high for anyone to withstand.

-------------
Parks for 2000: CP, Great Escape, Great Adventure, SFA, Islands of Adventure, Kennywood
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Friday, October 27, 2000 4:13 AM
Not true, Korn.

Fact is, if you create higher hills, in order to compensate for the higher forces, you create a larger radius curve at the bottom of the hill.

The larger the radius, the less G force exerted on the object. Think about how loops are designed (clothoid loops). At the top of the loop, you will find a smaller radius than where the trains enter and exit the loops. The reason for this is that due to the smaller radius, the train does not need to be moving as fast to get through the loop. There are other reasons, but from a physics standpoint, this is the main reason.

One of the other reasons is that if a loop were constructed using a constant radius, people would black-out due to inertia. The human body is much more suited to withstanding short high g force bursts than sustained g forces. For instance, you can probably withstand a half-second 9g burst, but probably not withstand a 6 second 6g run without beginning to black out.

Back to the point, though. :)
The higher the hill, the larger the radius of the 'valley'.

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