Magnetic Brakes and Heat

Friday, March 7, 2003 11:04 AM
I know that when LIM/LSM are fired, they cause heat, but is heat a product of magnetic brakes as well? Since there is no friction, I don't see how there could be, but I suppose the magnetic currents used to stop the vehicles could cause it.

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Intelligence is a God given gift: Know how to use it.

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Friday, March 7, 2003 11:27 AM
Hmmm... that's a very good question.

An even better question is "What's the voltage that could be generated by the fins on Millennium Force passing through the brakes?"

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- John
Dag, yo
Support Rob in the Great DDR Challenge!

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Friday, March 7, 2003 11:37 AM
Yep. The magnets generate a current inside the fins. The fins have resistance. Heat = current squared times resistance.

Essentially, that's all magnetic brakes do: convert kinetic energy to heat. There aren't any free lunches in physics, you have to convert the energy lost by the train into something.

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Friday, March 7, 2003 11:38 AM
Hmmm....good question. I'm not sure that magnetic brakes are "electromagnets" like LIMS. Aren't they just stationary magnets, non-powered...and physically moved out of the way to disengage rather than be powered?

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- "I used to be in the audio/visual club, but I was kicked out because of my views on Vietnam........and I was stealing projectors" - Homer Simpson

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Friday, March 7, 2003 12:26 PM
Yep. If you run the fins through the static magnets, current is generated in the fins which, as Comatose said, is lost to the resistance of the fin as heat.

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Be polite and ignore the idiots. - rollergator
"faster, cheaper, and more often" that's somebody's new sig -UpsideDawnGrrrl
My shirt in my photo seems to be for "Aging Bull"

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Friday, March 7, 2003 12:30 PM
Some such questions are partially answered at http://www.magnetarcorp.com . One item in their FAQ says:


Do the brakes get hot? No. Although heat is generated in the brake fin, (not the magnets), it is quickly dissipated.

--Dave Althoff, Jr.

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Friday, March 7, 2003 1:14 PM
I've thought for a while that it would be cool to find some spiffy (and useless) gizmo that could be powered by the current generated by the brake fins... just to show off.

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- John
Dag, yo
Support Rob in the Great DDR Challenge!

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Friday, March 7, 2003 1:20 PM
Thanks for the information.

I was reading the Top Thrill Dragster thread over at America Coasters, and someone mentioned that heat caused by the magnetic brakes could cause the brake fins to break into pieces if they were frozen. Apparently, the brake fins are only nickel and copper, and an extreme change in temp. ( From frozen to extremely hot when the train passes over ) would cause them to shatter. Is this true and/or possible?
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Intelligence is a God given gift: Know how to use it.

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Friday, March 7, 2003 2:27 PM
Probably not shatter *KABOOM*, but shatter-crack-the-metal. Since the seasons are pretty spread out (4 seasons a year, how bout that?) I don't think the fins have any danger of cracking/shattering.

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Tommy Penner - YoYoBaybeeMan
The Beginning, The Past, The Present, The Future

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Friday, March 7, 2003 3:58 PM
I don't think they'd shatter. I'd imagine the warmth from each run would slowly warm up the fins rather than rapidly heating and cooling them.

I guess the specific heat (is that the right term? The rate the heat dissapates from the material) of the metal would be pretty important in guessing.

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Be polite and ignore the idiots. - rollergator
"faster, cheaper, and more often" that's somebody's new sig -UpsideDawnGrrrl
My shirt in my photo seems to be for "Aging Bull"

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Friday, March 7, 2003 7:28 PM
If you use the right alloy of copper or aluminum, the metal should be so ductile that cracking would not be a problem.

Actually, the fins heat quite quickly when the train hits the brakes. The cool down period would be much more gradual.

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