Power Out

I remember discussing the power out at CP, but not what happens to MF's brakes. They are not friction and require electricity to operate. So what would happen?

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Millennium Force - world's first and greatist gigacoaster!

Unless I misunderstand something, MF's brakes are simply rare earth magnets...no electricity involved, even during normal operation.

If the train were on the course when a power outage occured, than it should stop at the brakes. The brakes are powerful earth magnets not electro-magnets, so they will stop the train with or without electricity. Unless the second brake set, the movable ones, are at rest when they are in their lower position.

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Monster Ride Host for 2 Years
3 Years Total @ CP

Millennium Force's brakes do not require power to operate, but the advancing wheels do. But the advancing wheels are connected to their motors via a reducing gearbox. Because it is not a planetary gearbox, the moving train is not going to push that wheel at all. I think the moveable brakes are counterweighted to stay up; in any case, I think they are bistable...that is, air pressure is needed to raise them, but air pressure is also needed to lower them.
The bottom line is that like virtually all the other rides in the park, Millennium Force fails to safe when the power goes out.

--Dave Althoff, Jr.

I read in one of the engineering trade rags at work (we publish them) that the retractable brakes are retracted by some kind of pneumatic device, and are normal in the closed position.

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Jeff
Webmaster/Guide to The Point
Millennium Force laps: 50

That certainly makes sense. I just don't know how they are accomplishing it. On Superman: Ride of Steel at Darien Lake, the final brakes are quite clearly counterweighted so that if the pneumatic cylinder fails, the brake will literally fall into its "set" position. On Millennium Force, however, I am not seeing any counterweights. I wonder if the actuating cylinder is spring loaded or something.....

--Dave Althoff, Jr.

How could it stop if the current never changed? You need to push as it approaches and push as it passes, don't you?

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Millennium Force - world's first and greatist gigacoaster!

No, JT, you're thinking in terms of a linear synchronous motor. LSMs use magnetic coils to alternately attract and repel a permanent magnet. The brakes on Millennium Force have more in common with a linear induction motor, in which the moving magnetic field coming from the motor coils induces a current...and hence a reaction field...in the reaction plate, propelling it forward. In this case, instead of an 3-phase AC moving magnetic field, the brakes use permanent magnets to provide a stationary field. The reaction plate moves through the field, and a current is induced in the reaction fin, thus setting up a secondary magnetic field which reacts with the fixed field. That interaction will tend to cause the reaction fin to accelerate to the synchronous speed of the magnetic field it is moving through. Since that field is not moving, the end result will tend to drag the fin to a stop.

One difficulty is that the magnitude of the current generated in the fin...and hence the magnetic field...is proportional to the speed of the moving fin, so as the vehicle speed approaches zero, so does the braking force. Hence the advancing wheel at the downtrack end of the brake run, used both to bring the train to a full stop, and to drag the train out of the brakes and into the unloading station.

Does that make sense? In a nutshell, it's a LIM, but with permanent magnets instead of an AC coil, so it will tend to drag the train to a stop...and because it uses permanent magnets, no power is required.

--Dave Althoff, Jr.

And in case Dave's explaination doesn't answer your question fully, just think in terms of simple magnets you can buy as toys. Like poles on those magnets repel each other without any electrical current being passed through them. Although the braking system on MF doesn't work exactly the same way, the idea can still be applied.

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James Draeger
'00 CP Trips: 22
C G & C P

I guess it would work if the car created power as it passes. Hmmm. I think we cover this in physics later this year.
Thanks :)
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Millennium Force - world's first and greatist gigacoaster!