From: andyh@chaos.cs.brandeis.edu (Andrew J. Huang)
Subject: Re: Flywheel batteries as EV power source
Organization: Brandeis University
Date: Thu, 17 Dec 1992 19:23:29 GMT

In article <1goebdINNik@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes:
>In article <1992Dec16.192456.6261@news.cs.brandeis.edu>, andyh@chaos.cs.brandeis.edu (Andrew J. Huang) writes:
>=In article <1992Dec15.194558.2556@adobe.com> pngai@adobe.com (Phil Ngai) writes:
>=<I have to admit an emotional response to this since I think that
>=flywheels have tremendous potential.>
>The problem isn't with their potential, it's with their kinetic.
Presumably this is a pretty good pun rather than a counterpoint

>=Since the energy is kinetic, a lot of it will end up as particle
>=velocity.
>Partcles of what?

whatever materials are around. e.g. carbon fiber, aluminum housing,
kevlar scattershield, flesh.

>=Some will dissipate into the air as air friction (some hot
>=air as a side effect).
>What air?  The flywheels are supposed to operate in a vacuum.

The air that surrounds the housing.  Yes, within the housing air
friction is designed to be a non-issue, but since we're discussing the
destruction of the housing, there will be air around.

>You seem to've missed something here.  It's called the law of conservation of
>energy.  While energy will go into these paths you can't just say, as you're
>trying to:
>	A lot of it will end up as particle velocity, so now we can
>	ignore that.
	<deletion>
>Er, the amount of energy that escapes is exactly the amount of energy you
>started with.  Law of conservation of energy comes into play.  All the energy
>from the flywheel will have been converted into these other forms...

Yes, it is obvious that energy is conserved and no I do not postulate
a violation of conservation of energy.  But when you take a car going
80mph and hit a bridge, where does all that energy go?  Into bending
the sheet metal, breaking glass, throwing tires etc.  However, is the
bent metal going to hurt you?  My point is that the disintegration of
parts consumes energy, taking kinetic energy and converting it to
heat.  I think that the kinetic energy is likely the more dangerous
form, depending upon the environment.  (Of course heat will kill you
too, but it depends on the temperature).

>It didn't just vanish.  And that's a LOT of energy.  And it got dumped FAST.
>In other words:  BOOM!

Take a 50's Caddy going 100mph.  Put it into many barrels of sand.
Did it go BOOM?

Take a loaded tractor-trailer with bad brakes.  Put it down a mountain
road.  Send it up the "Failed Brakes" escape road.  Did it go BOOM?

I don't claim to _know_ that an explosion of these flywheels is safe.
I have read a report in the press that the manufacturer's TESTING
showed an apparently safe catastrophic failure.  My post was to give
some _possibilities_ about why the failure was safe.  My post was also
to counteract the hysterical reaction "I hope they do lots of crash
testing before letting such a dangerous thing on the roads".  I don't
see the evidence that it is dangerous.  There is some intuition, some
hunches, etc, but this has not been born out by the manufacturer's
_TESTING_.  Whether you believe them or not is another issue.

-andy



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