From: mwilson@ncratl.AtlantaGA.NCR.COM (Mark Wilson)
Newsgroups: sci.electronics,sci.energy,rec.autos.tech
Subject: Re: Flywheel batteries as EV power source
Date: 23 Dec 92 02:08:59 GMT
Organization: NCR Engineering and Manufacturing Atlanta -- Atlanta, GA

In <1992Dec22.200442.25999@socrates.umd.edu> jimbo@socrates.umd.edu (Jim Bogard) writes:

|I remember reading an article in Scientific American or somesuch about
|high-tech flywheels.  One of the designs that stands out in my mind
|was one made of wood laminates and would store a large percentage of
|its energy in deformation.  That is, the thing started out in roughly
|a square shape, then as it spun up, it would flex out into the 
|normal circular shape.  Recalling from Physics, as a rotating mass
|moves in a shorter radius, the rotational momentum must remain 
|constant, so the spinning speed increases - allowing one to tap the
|power available in the return to the original shape.
|Plus, it's not unappealing that the thing was constructed partially
|of wood... projectiles would be easier to contain.

Containing the projectiles is not the problem, containing the energy is.
All of the energy contained within the flywheel at the moment of failure
will be transfered to the containment vessel.  This transfer will take
place in a matter of milli seconds.  Unless the containment is massive
enough to absorb all of that energy without melting or vaporizing, it
will explode.  It does not matter what the flywheel is made of.

I don't know if wood has enough tensil strength to spin fast enough
to store the kinds of energy we have been talking about.

This also sounds like a lot of flexing, has anybody experimented with
how many times the wood can be spun up before it breaks.

|Has anyone considered using springs as an alternative to flywheels?
|It seems to me (very topically) that while the same amount of power
|could be stored in a (unknown adjective - the type of spring used
|in clocks, as opposed to your screen door slammer spring) spring,
|it would be much safer.

The amounts of energy needed are tremendous.  I do not know of any
material that has enough tensil strength to store this much energy in
this manner.

|There would be no high velocity particles to contend with  -

If there is that much tension on the spring, then there will be high
velocity shrapnel to deal with.

Once again, it is not the shrapnel that you have to worry about.  It is
how do you absorb the energy that used to be stored in your storage
device.  If such a spring were to break, the shock wave from the first
break would quite quickly destroy the entire spring, releasing all of
the energy.

|In the event of spring breakage, or uncontrolled release, It seems that
|the actual outward force would be fairly easy to contain.  In addition,
|the spring material (spring steel, or some derivative thereof) could
|be relatively light and less prone to cause ballistic injury.

It's not the projectiles from the storage device that will kill you.
The storage device will be completely vaporized in the first couple
of milli-seconds.  It's the shrapnel from the containment vessel and
intervening pieces of car and passengers that will get you.  This is
assuming that the shock wave from the explosion doesn't reduce you
to pulp first.

|(At least, I'd prefer it to a flywheel with the same amount of energy!)

It's the energy that will kill you, not how it is stored.

-- 
Mob rule doesn't become any prettier, just because the mob start to call itself
a government.
It ain't charity if you are using someone else's money.
Mark.Wilson@AtlantaGA.NCR.com
Newsgroups: sci.electronics