In article , John T. McCracken says...

The furnace, stove and water heater are all propane.
The diesel runs a welding machine, which generates enough electricity to run
the well pump, intermittantly, and the evaporative cooler if it's summer. As
well as keep the refridgerator and freezer functioning.

Sounds like a good deal, as long as there's propane in the
tank. Ever consider a propane refrigerator?

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

On Sun, 17 Aug 2003 14:39:07 GMT, Carl Byrns
wrote:

On Sun, 17 Aug 2003 01:36:25 GMT, Gunner
wrote:

On Sat, 16 Aug 2003 21:37:38 GMT, Carl Byrns
wrote:


Now....how much fun would this have been if it happened during a
blizzard in Febuary?
How many millions of people would be popsicles until spring thawed out
their corpses?

A five hour power outage? No big deal- we would do what we always do-
fire up the generator and invite our elderly nieghbors over.
Anyone living in Central New York stocks up enough groceries for three
days (after that the stores are back in action) and those Evil Utility
Companies distribute dry ice for food storage. Some trucking companies
move reefer trailers to shopping mall parking lots so folks can store
their frozen foods. No charge.

Not a 5 hour power outage..lets try a two Day power outage or longer.
Not all power was restored in the East for at least 2 days in some
places, correct?


Beats me. My power was on in 5 hours- no big deal.
We did have an ice storm a few years ago that left some populated
areas without power for a month. In the winter, which can be severe.
No one died from it.

You can't understand winter around here until you've lived through it-
the day can start in the 40's and sunny and be sub-zero with four FEET
of snow by nightfall. This is perfectly normal- we take the Boy Scouts
camping in such weather.

-Carl


I grew up in the Upper Peninsula of Northern Michigan. Average snow
fall 144" IIRC..

I do know something about finding popsicles after the power goes out
for a few days....

Gunner

"What do you call someone in possesion of all the facts? Paranoid.-William Burroughs

Steve Rayner wrote:

Ahem! I made two electric motors, 6 volt DC , from tin can metal, and wire
from old transformers, at 11 years of age!

That's neat. I had some instructions on how to make motors, but
mechanical construction was something I never did well at as a child...
I never seemed to have the right part or tool so I'd have to improvise
and the improvisation would fail and so on. Joining things together was
a *particularly* sore point. From other people's descriptions, I gather
that to everyone but me, glue actually joins stuff. For me, glues always
turn into sticky goo that never quite dries, or it dries but then
doesn't adhere to the surfaces... I hate glue.

The next thing was a battery
radio from junk parts.

I did this! As a kid, electronics and computer software (it was the
80s... showing my age) were my main creative outlets.

I always wanted to do more serious digital electronics, and making
mechanical stuff. I'm working towards this now, but I only ever seem to
have two of the three: time, money, space.

As a kid I had time and space but no money for the correct parts (and I
am now scarred for life; I can't bear to bodge anything. I *have* to get
the correct part to begin with! :-).

When I started working (living in Central London in the .com boom) I had
time and money, but no space, since flats in London are small.

Now I live on the edge of London, I have money and space, but no time,
because everyone I know is getting married or having birthdays or
whatnot all at once, and now that it looks like I might get some free
time, a load of expenses came along and now I have no savings.

Grrr!

No money for proper batteries, so it was powered by
scrounged fire alarm batteries. The batteries had to be replaced in local
industries once a year. Many were still good. They took up all of the space
under my bed. Before either of these projects, at 8 years of age, I came
into some old telephones. My own private telephone system was soon in
service, powered by,.........you guessed it, ..........scrounged fire alarm
batteries!

Nice :-)

You are not alone!

The interesting thing is, I've tended to be attracted to / prove
attractice to girls who grew up with brothers like me.


Steve Rayner.


ABS

In article , Alaric B Snell says...

The department had got a new NMR machine. An NMR machine is a big
superconducting coil, in liquid nitrogen,

Helium, really.

But a kid was killed recently around here, he was in an
NMR (aka, MRI) machine and a tech brought an O2 bottle in
the room because the oxygen line to the kid was getting
flow troubles.

Wrong bottle. It flew into the machine and crushed
the kid's head.

We used to have one magnet (ten tesla) and there was
a paperclip on a string in the pit underneath it, hung
about five feet away from the dewar. As a tell-tale
to say when the magnet was up. When it was, the paperclip
pulled the string straight out, you could twang the string.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

On Sun, 17 Aug 2003 18:52:19 GMT, Gunner
wrote:


I grew up in the Upper Peninsula of Northern Michigan. Average snow
fall 144" IIRC..

I do know something about finding popsicles after the power goes out
for a few days....

There's an article in today's paper about a snowpile in nearby Oswego.
The city plows built up the pile all winter in an unused parking lot.
The last of it melted away Friday.
No ****.

-Carl

Carl Byrns wrote:

There's an article in today's paper about a snowpile in nearby Oswego.
The city plows built up the pile all winter in an unused parking lot.
The last of it melted away Friday.
No ****.

Have you ever seen what is left over after the snow melts? All the
dust and dirt is impressive, though I would like to know how the
shopping cart got in there...
Ken

"jim rozen" wrote in message
...
In article , John T. McCracken says...

The furnace, stove and water heater are all propane.
The diesel runs a welding machine, which generates enough electricity to
run
the well pump, intermittantly, and the evaporative cooler if it's summer.
As
well as keep the refridgerator and freezer functioning.

Sounds like a good deal, as long as there's propane in the
tank. Ever consider a propane refrigerator?

Jim

I've got one, out in the travel trailer. If the power is off for an extended
period, and it rarely is here, we can allways go stay in the RV. A well
stocked RV is probably the ultimate solution. We keep the propane level up
at my house and my folks, who live about 200 yards away.

JTMcC.



==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

In article ,
says...
I grew up in the Upper Peninsula of Northern Michigan. Average snow
fall 144" IIRC..


Pretty close. Around Marquette and Negaunee it's 172 inches on a
normal year. Last winter was a real snowy one, 302 inches. May be a
record.
--
Jim Kovar
Vulcan, Mi

Alaric B Snell wrote:
jim rozen wrote:

In article , Alaric B Snell says...


The interesting thing (from a sci fi fan's point of view) is that
such a system stores energy in the fabric of space - the energy isn't
in the coil, it's in the space in which the coil sits.



And very real energy it is. Anyone who's seen a superconducting
magnet quench (go normal) while up at field, will attest to that.


anecdote

A friend of mine did a stint as a research physicist, and saw a few
interesting things in his time.

The department had got a new NMR machine. An NMR machine is a big
superconducting coil, in liquid nitrogen, which is charged with current
over a period of days until many millions (billions?) of amps are
flowing around it, to create an intense magnetic field. You put a sample
in the field and do stuff to it with RF energy that I won't go into in
order to analyse its chemical composition.

Anyway, they'd just charged the field up on this thing, after many days
of piping in electricity, so they were holding a little demo and
analysing random objects and so on, when the guy who delivers cylinders
of oxygen went past the door with an oxy cylinder on a trolley.

Now, the people who sited the NMR machine didn't know the oxy guy's
route went past the door. And the oxy guy didn't know that, unlike last
week, there was now a superconducting magnet in the room. So everyone
was surprised when the door slammed open to admit an oxygen cylinder
which flew across the room and slammed into the end of the coil.

The magnetic field, up until that point fairly evenly spread around the
room, concentrated itself into the nicely permeable iron cylinder, which
raised the field strength at two points in the coil beyond the field
strength the superconductor could take, so two bits of it stopped
superconducting and started shunting electrical and magnetic energy into
heat - boiling the liquid nitrogen.

This presented a problem. They couldn't bring the ring current down fast
enough to prevent the LN2 boiling off. Once the coolant level fell below
critical, the ring would start shedding energy as heat, thus boiling
away the remainder even faster - leaving a non-superconducting ring
carrying a vast current, which would turn into heat, which would stop
the current, which would cause the energy stored in the magnetic field
to try to turn back into current, which would turn into more heat... it
would probably violently explode.

LUCKILY, they were prepared for this kind of event, and had a
non-ferrous scissor jack to hand. The strongest members of the group
managed to roll the cylinder onto the jack and jack it away from the
ring housing enough to get shoulders behind it and walk it out of the door.
/anecdote

Nice story but I don't believe it. If the magnetic field were
following the inverse square law and the field was strong enough
to pull in the cylinder from the hall, they'd never get it off with
a non-metallic scissor jack. Just my opinion.

In article , John T. McCracken says...


...we can allways go stay in the RV. A well
stocked RV is probably the ultimate solution.

That's cheating! No privations, no roughing it!

We keep the propane level up
at my house and my folks, who live about 200 yards away.

Hmm. The ultimate backup. Inter-tied familial relationships.

Jim

==================================================
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JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Carl -
No problem -

I know and really care for some UP State types - who had to move out
with their job. Nice types.

I blew off my road today - next week i'll lay some blacktop with a hand
tamper.

Living out of town has the hazards from time to time, but the city there
is
always something going on. - not always good. -

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

Yea - the medium sized stuff - otherwise there would not be a door
near by and never have anyone walking anywhere near the field.

I have one degree in Physics. Almost went to Wy for high Energy.

The RF - what they do is resonate the atom in quest - each has their own
frequency - and then flip an electron. This flip is indication that
this is the correct atom and this material the frequency responds to is
what was pre-determined. e.g. one sees the up/down dip on a scope -
and
yea we found some xxx. Been there done that.

Regarding the people - normally they are stripped of all and I mean all
metal.
This means for some a medical inspection of their eyes. Those with pins
in
their legs or plates in their skulls are excluded from work near the
magnet.

NMR is the stuff medical machines came from.
Much has happened in the last 40 years.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

On Mon, 18 Aug 2003 03:16:01 GMT, Eastburn
wrote:

Yea - the medium sized stuff - otherwise there would not be a door
near by and never have anyone walking anywhere near the field.

I have one degree in Physics. Almost went to Wy for high Energy.

The RF - what they do is resonate the atom in quest - each has their own
frequency - and then flip an electron. This flip is indication that
this is the correct atom and this material the frequency responds to is
what was pre-determined. e.g. one sees the up/down dip on a scope -
and
yea we found some xxx. Been there done that.

Regarding the people - normally they are stripped of all and I mean all
metal.
This means for some a medical inspection of their eyes. Those with pins
in
their legs or plates in their skulls are excluded from work near the
magnet.

NMR is the stuff medical machines came from.
Much has happened in the last 40 years.

Martin

Do really high field strengths do anything wierd to the hemoglobin in
ones blood?

Gunner

"What do you call someone in possesion of all the facts? Paranoid.-William Burroughs

Jim Stewart wrote:

Nice story but I don't believe it. If the magnetic field were
following the inverse square law and the field was strong enough
to pull in the cylinder from the hall, they'd never get it off with
a non-metallic scissor jack. Just my opinion.

'twas on a wheeled trolley, and the guy who told me didn't say how far
the core housing was from the door to the corridoor. The field needn't
follow inverse square either - inverse square holds for a uniform field
radiated from a point, which the electrical field around a sphere
approximates. Magnetic fields from coils or rings are usually in funny
shapes that make the field strength plotted as luminous intensity in 3D
look like two flames extending from the ends of the coil. Along the axis
of the coil, field strength is pretty constant in the middle, tapering
off slowly at first as you leave the coil, then more rapidly at a distance.

I'm more surprised about the managing to roll the cylinder onto the jack
than jacking it off[1] - I'd expect the kind of non-ferrous jack they
have lying around an NMR magnet to be pretty sturdy, but breaking the
initial contact would have been pretty tricky. Perhaps the cylinder was
across the opening in the centre of the ring where you put samples in,
so they could slip the jack under that way then lever it over to get the
jack supported against the ring housing, I dunno.

Heck, I'll ask the guy next time I see him :-)

ABS

[1] Huh. Huhuh. He said "jacking off".

"Gunner" wrote in message
news
Do really high field strengths do anything wierd to the hemoglobin in
ones blood?

The iron is in a form which can't form magnetic domains, so it's
completely nonmagnetic. Also there is very little iron in the body
anyway, interestingly enough (I forget just how much).

However, it will radiate a radio signal if excited properly (if I
understand the process right). ;-)

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

Eastburn wrote:
Yea - the medium sized stuff - otherwise there would not be a door
near by and never have anyone walking anywhere near the field.

Indeed... I got the impression it was a logistical failure, that the
cylinder guy and the magnet people didn't know about each other's
activities.

e.g. one sees the up/down dip on a scope -
and
yea we found some xxx. Been there done that.

You found some XXX? What, stashed behind the magnet? :-)

Regarding the people - normally they are stripped of all and I mean all
metal.
This means for some a medical inspection of their eyes. Those with pins
in
their legs or plates in their skulls are excluded from work near the
magnet.

I've had a few NMR scans myself for various reasons. The techs said that
sometimes you do a head scan and the result comes out with the person's
skull all twisted and creepy looking, and it turns out there was an iron
filing caught in their hair or something like that - not big enough to
form a projectile in the field, but it distorts the scanning somewhat!

Martin

ABS

Gunner wrote:

Do really high field strengths do anything wierd to the hemoglobin in
ones blood?

Well, NMR is all about doing wierd things to molecules.

I am not a nuclear physicist, but if you're referring to the normal
effect magnetic fields have on iron, that's a consequence of the
magnetic moments of electrons on the iron atoms, IIRC. Which is why rust
isn't magnetic; when the iron and the oxygen atoms join, the bond is
made by messing with the electron shells, which destroys the magnetic
moment imbalance. I suspect that the bond in haemoglobin has the same
effect. Very few compounds are magnetic.

But there is that wierd frog-levitating trick you can do with huge
magnets. How does that work? IIRC it's something to do with eddy
currents; you're conductive, so if you are falling (under gravity) in a
magnetic field, a current flows through you which makes you into an
electromagnet which creates a field repelling the field you're in so you
float... no, that doesn't sound right. I think it's something funny to
do with the asymmetrical charges in water molecules.

Ah! This explains all!

http://www.exploratorium.edu/snacks/diamagnetism_www/

"Ferromagnetic materials, such as iron, are strongly attracted to both
poles of a magnet.

Paramagnetic materials, such as aluminum, are weakly attracted to both
poles of a magnet.

Diamagnetic materials, however, are repelled by both poles of a magnet.
The diamagnetic force of repulsion is very weak (a hundred thousand
times weaker than the ferromagnetic force of attraction). Water, the
main component of grapes, is diamagnetic.

When an electric charge moves, a magnetic field is created. Every
electron is therefore a very tiny magnet, because electrons carry charge
and they spin. Additionally, the motion of an orbital electron is an
electric current, with an accompanying magnetic field.

In atoms of iron, cobalt, and nickel, electrons in one atom will align
with electrons in neighboring atoms, making regions called domains, with
very strong magnetization. These materials are ferromagnetic, and are
strongly attracted to magnetic poles.

Atoms and molecules that have single, unpaired electrons are
paramagnetic. Electrons in these materials orient in a magnetic field so
that they will be weakly attracted to magnetic poles. Hydrogen, lithium,
and liquid oxygen are examples of paramagnetic substances.

Atoms and molecules in which all of the electrons are paired with
electrons of opposite spin, and in which the orbital currents are zero,
are diamagnetic. Helium, bismuth, and water are examples of diamagnetic
substances.

If a magnet is brought toward a diamagnetic material, it will generate
orbital electric currents in the atoms and molecules of the material.
The magnetic fields associated with these orbital currents will be
oriented such that they repelled by the approaching magnet.

This behavior is predicted by a law of physics known as Lenz's Law. This
law states that when a current is induced by a change in magnetic field
(the orbital currents in the grape created by the magnet approaching the
grape), the magnetic field produced by the induced current will oppose
the change."

Gunner

ABS

In article ,
says...

Don't forget Copper Harbor. They told me the average was 264 inches when I
used to hunt snowshoe rabbits up there, around 1970. I was there in January.
I believe them.

Ed Huntress



Hunting snowshoes *on* snowshoes. That's fun!
--
Jim Kovar
Vulcan, Mi

On Mon, 18 Aug 2003 07:10:33 -0500, Jim Kovar
wrote:

In article ,
says...

Don't forget Copper Harbor. They told me the average was 264 inches when I
used to hunt snowshoe rabbits up there, around 1970. I was there in January.
I believe them.

Ed Huntress



Hunting snowshoes *on* snowshoes. That's fun!

I've done that , your right. I use to use a .22 colt with a scope ,
shot guns with me always make the rabbit look like its been in a shark
attack. My step bro. was really good at leading them just right , I
seem to hit them smack in the middle.

"Alaric B Snell" wrote in message
...
Daniel Haude wrote:
On Sun, 17 Aug 2003 20:09:07 +0100,
Alaric B Snell wrote
in Msg.

A friend of mine did a stint as a research physicist, and saw a few
interesting things in his time.


Well, I'm a physicist and I work with superconducting magnets every day,
so let me set a few things straight about your story.

Disclaimer: it ain't actually my story, I wasn't the guy there, t'was my
physicist mate.

The department had got a new NMR machine. An NMR machine is a big
superconducting coil, in liquid nitrogen,


liquid helium


I could well have misremembered that bit!

[issues about size of magnet and dependent topics]

Hmmm. As I remember it, he was quite explicit about it having taken days
to wind up and the general magnitude of energy involved. Maybe it was
scanning objects rather than just taking averaged chemical analyses of
samples, after all - he was far less specific about *that*.

FWIW, this sounds like a story about the magnet in the Tokamak fusion
reactor at Forrestal Research Center. It was powered by a flywheel-driven
generator, and the room-sized, electric-motor-driven flywheel took several
days to spin up to its operating speed.

Ed Huntress

And lo, it came about, that on Sat, 16 Aug 2003 21:37:38 GMT in
rec.crafts.metalworking , Carl Byrns was inspired to
utter:


In short, we all pull together and we just work around it.

If the power went out in, say, Los Angles on a hot summer evening, how
long before the rioting and looting started?

This would be the "black out" special rioting, as oppose to the run of the
mill routine smash & grab?


--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

And lo, it came about, that on 16 Aug 2003 22:10:18 -0700 in
rec.crafts.metalworking , jim rozen was inspired to
utter:


I'm beginning to see the wisdom of living in
a small cabin with a large franklin stove.
And a big woodpile. Two rooms and a path.

Had an great aunt & uncle living like that. Of course, on baking day, once
the inside temp went over 80 they'd just open the front door, regardless of the
time of year.

I've wanted what I know as a Bavaria Stove. About three by two and five
feet tall, covered in Ceramic Tiles, little firebox at the bottom. Small fire
heats the masonry, and it radiates all day. Nice.


--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

And lo, it came about, that on 17 Aug 2003 17:48:59 -0700 in
rec.crafts.metalworking , jim rozen was inspired to
utter:

In article , John T. McCracken says...


...we can allways go stay in the RV. A well
stocked RV is probably the ultimate solution.

That's cheating! No privations, no roughing it!

It is roughing it. The RV's TV doesn't have a cable connection.

(I was going to say it was BW, but these days, that might be too much of a
stretch.)

--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

And lo, it came about, that on Mon, 18 Aug 2003 03:31:40 -0500 in
rec.crafts.metalworking , "Tim Williams" was inspired
to utter:

Do really high field strengths do anything wierd to the hemoglobin in
ones blood?

The iron is in a form which can't form magnetic domains, so it's
completely nonmagnetic. Also there is very little iron in the body
anyway, interestingly enough (I forget just how much).

I've read reports that some of the inks used in tatoos have enough iron in
them as to make the wearer "contraindicated" for MRIs. Something about
induction heating, I think it said. The researcher said he got some sample
inks and discovered he could move a drop of ink around using a magnet under the
piece of paper. neat, but ...

However, it will radiate a radio signal if excited properly (if I
understand the process right). ;-)

Tim

--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

Also people with metal body replacements, they get hot. Although I have
hear of some new implants that are made differently and will not heat up.


"pyotr filipivich" wrote in message
...
And lo, it came about, that on Mon, 18 Aug 2003 03:31:40 -0500 in
rec.crafts.metalworking , "Tim Williams" was
inspired
to utter:

Do really high field strengths do anything wierd to the hemoglobin in
ones blood?

The iron is in a form which can't form magnetic domains, so it's
completely nonmagnetic. Also there is very little iron in the body
anyway, interestingly enough (I forget just how much).

I've read reports that some of the inks used in tatoos have enough iron in
them as to make the wearer "contraindicated" for MRIs. Something about
induction heating, I think it said. The researcher said he got some
sample
inks and discovered he could move a drop of ink around using a magnet
under the
piece of paper. neat, but ...

However, it will radiate a radio signal if excited properly (if I
understand the process right). ;-)

Tim

--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

"pyotr filipivich" wrote in message
...
And lo, it came about, that on 17 Aug 2003 17:48:59 -0700 in
rec.crafts.metalworking , jim rozen was inspired
to
utter:

In article , John T. McCracken says...


...we can allways go stay in the RV. A well
stocked RV is probably the ultimate solution.

That's cheating! No privations, no roughing it!

It is roughing it. The RV's TV doesn't have a cable connection.

Where I live we don't get TV, unless of course, you have a satelite dish.

JTMcC.



(I was going to say it was BW, but these days, that might be too much of a
stretch.)

--
pyotr filipivich
The cliche is that history rarely repeats herself. Usually she just
lets fly with a frying pan and yells "Why weren't you listening
the first time!?"

I remember hearing stories (not a personal experience) about curing the
coatings on coils of heavy wire in a wire manufacturing and coating plant.
They ran DC current into many of these in series to heat them up. When they
disconnected the power source, the resultant arc from the collapse of the
magnetic field caused some real problems.

They solved it by dumping the energy into a synchronous inverter that put a 3
megawatt surge into the power line. The power company didn't even notice it
apparently.

The work in developing that synchronous inverter was used to manufacture and
market the Gemini inverter, used in many DC windpower installations to use the
power company as a storage system instead of batteries. Now, most wind systems
use 3 phase motors as the generators. Large DC systems are still being used
though with newer inverters giving much better control of the wind machine.
The biggest advantage is that the blades aren't limited to one or two speed
ranges but can vary according to the wind speed.

Earle Rich
Mont Vernon, NH

jim rozen wrote:

In article , Jon Elson says...



They basicaly already have it. Big UPS and multiple Diesel generators.
Very reliable,
time-tested technology.



As a backup for nuclear power plants, this is the way.

However they're not that reliable. About ten years
ago Indian Point Two and Indian Point Three failed
their NRC inspections. One reason they did so, is
that of the several locomotive-sized diesel gensets
on site, all but (I think) one failed to come on
line and accept load, when tested.


From a national security standpoint, alone, anyone who was aware
of the Diesels and other emergency power systems not being tested
at least weekly, should literally be taken out and shot! If not that,
send them down to Guantanamo Bay, with the rest of the "illegal
combatants". Not having sufficient emergency power to maintain
cooling systems at a nuclear power plant is an extreme emergency,
and could lead to radiation release, multi-billion Dollar damage to
the reactor, etc. What happened to the Three Mile Island plant could
easily happen, or be worse, if the pumps stop.

Note that bringing these Diesel generator sets on line and running them
for an hour or so a week isn't even a waste! They would be switched onto
the grid and be generating power for the utility.

Jon

Alaric B Snell wrote:

Jon Elson wrote:

It might be worth while developing some large power store system to
be kept on-site at a nuclear reactor... like the thing we Brits have
in Wales, a large lake up a mountain which water is pumped to when
the grid is underloaded, and used for hydroelectric power when it's
not.

Sadly, building an artificial mountain + lake next to every reactor
might be tricky. Huge flywheels, maybe?



They basicaly already have it. Big UPS and multiple Diesel
generators. Very reliable,
time-tested technology.


No, I mean something that can act as a load if the real load goes
away, to suck up all that energy that's coming out, if the system
depends on load.

Ah. Well, that's a LOT of power. I think the problem is that these
large stations don't operate
properly, over the long term, under very light load. Also, most
mid-size nukes have a single
turbo-alternator set. It could get real tricky if the one
turbo-alternator were to jump in phase
and trip offline while they were trying to sync it to the grid. The
whole station would go down
with a bang. What I think the actually do, although it hasn't been
explained to me by an operator,
is they switch to Diesel backup power (Huge UPSs carry them through for
a few seconds until
the Diesels get running) and then they let the reactor run at whatever
power it was running at
when they tripped offline, and dump the heat into the cooling tower.
Then, they try to figure
out whether they can get back on the grid shortly (just put the
transmission line back on, and
resynch the alternator) or whether there is a major problem on the lines
that will require a
crew to go out and fix something. If there's no way to deliver
significant power to the grid, then
they start ramping the reactor down.

The plant generally consumes 10 to 15% of the energy produced, and as
the reactor is going to
be producing whatever power setting it was at for a matter of hours,
dumping several megawatts
of electrical power is not something you can throw away easily. So,
they throw it away as heat,
which they are doing to about 80% of the thermal energy, anyway. Now,
maybe they could make
Hydrogen or liquid Ammonia whenever the plant goes offline, and sell the
product, since it would
be wasted energy, otherwise.

Jon

Alaric B Snell wrote:

jim rozen wrote:

In article , Alaric B Snell says...


The interesting thing (from a sci fi fan's point of view) is that
such a system stores energy in the fabric of space - the energy
isn't in the coil, it's in the space in which the coil sits.



And very real energy it is. Anyone who's seen a superconducting
magnet quench (go normal) while up at field, will attest to that.


anecdote

A friend of mine did a stint as a research physicist, and saw a few
interesting things in his time.

The department had got a new NMR machine. An NMR machine is a big
superconducting coil, in liquid nitrogen, which is charged with
current over a period of days until many millions (billions?) of amps
are flowing around it, to create an intense magnetic field. You put a
sample in the field and do stuff to it with RF energy that I won't go
into in order to analyse its chemical composition.

No, it is really just hundreds of amps. They have to "ramp up" such a
magnet with a non-superconducting power
supply, with non-superconducting cables, so the currents outside can't
be enormous. Therefore, there's no
way to get enormous currents INSIDE the superconducting part. But, it
doesn't matter, as they just add more
turns of the superconducting wire. The flux can add up to millions of
amp-turns, however.


Anyway, they'd just charged the field up on this thing, after many
days of piping in electricity, so they were holding a little demo and
analysing random objects and so on, when the guy who delivers
cylinders of oxygen went past the door with an oxy cylinder on a trolley.

Now, the people who sited the NMR machine didn't know the oxy guy's
route went past the door. And the oxy guy didn't know that, unlike
last week, there was now a superconducting magnet in the room. So
everyone was surprised when the door slammed open to admit an oxygen
cylinder which flew across the room and slammed into the end of the coil.

The magnetic field, up until that point fairly evenly spread around
the room, concentrated itself into the nicely permeable iron cylinder,
which raised the field strength at two points in the coil beyond the
field strength the superconductor could take, so two bits of it
stopped superconducting and started shunting electrical and magnetic
energy into heat - boiling the liquid nitrogen.

This presented a problem. They couldn't bring the ring current down
fast enough to prevent the LN2 boiling off. Once the coolant level
fell below critical, the ring would start shedding energy as heat,
thus boiling away the remainder even faster - leaving a
non-superconducting ring carrying a vast current, which would turn
into heat, which would stop the current, which would cause the energy
stored in the magnetic field to try to turn back into current, which
would turn into more heat... it would probably violently explode.

LUCKILY, they were prepared for this kind of event, and had a
non-ferrous scissor jack to hand. The strongest members of the group
managed to roll the cylinder onto the jack and jack it away from the
ring housing enough to get shoulders behind it and walk it out of the
door.
/anecdote

Yup, it's an anecdote, all right. Superconducting magnets quench in a
few seconds under these conditions.
And, it doesn't take a gas bottle to do it, a wrench in the wrong place
can affect the field enough, especially
when it is moving at a couple of hundred miles an hour. The cryogens in
the magnet are enough to absorb the
heat generated (remember, the active part of the magnet winding is at
about 4 Kelvins, (4 degrees C above
absolute zero temperature) so it takes a lot of heat to warm it up just
to room temperature.

The danger of an explosion is not the magnet itself, but the double
dewar jackets filled with liquid helium
and liquid nitrogen. When this stuff boils, it generates a LOT of gas.
They have 6" and bigger vent stacks
to carry away the gas, which would otherwise suffocate everyone within a
couple of rooms.

Since the magnet was quenching anyway, there would be nothing to save,
so it would be wise for
everyone to just get the heck out of there. Once the quench starts
(some spot in the winding becomes
a normal conductor) the quench will spread to the rest of the magnet
very quickly, as only a slight rise in temperature
will change the superconductor to normal.

Jon

Daniel Haude wrote:

On Sun, 17 Aug 2003 20:09:07 +0100,
Alaric B Snell wrote
in Msg.



A friend of mine did a stint as a research physicist, and saw a few
interesting things in his time.



Well, I'm a physicist and I work with superconducting magnets every day,
so let me set a few things straight about your story.

First thing: Dimension of magnet. You mention an NMR magnet for chemical
analyes; those would be pretty strong but small. I'm going to substitute
a few facts in your story that would apply to the 14 Tesla magnet I work
with every day.



The department had got a new NMR machine. An NMR machine is a big
superconducting coil, in liquid nitrogen,



liquid helium



which is charged with current
over a period of days



a few minutes, possibly 1 hour. Much longer with an NMR for medical
imaging.



until many millions (billions?)



about one hundred



amps flowing around it, to create an intense magnetic field. You put a
sample
in the field and do stuff to it with RF energy that I won't go into in
order to analyse its chemical composition.

Anyway, they'd just charged the field up on this thing, after many days



a few hours



of piping in electricity, so they were holding a little demo and
analysing random objects and so on, when the guy who delivers cylinders
of oxygen went past the door with an oxy cylinder on a trolley.

Now, the people who sited the NMR machine didn't know the oxy guy's
route went past the door. And the oxy guy didn't know that, unlike last
week, there was now a superconducting magnet in the room. So everyone
was surprised when the door slammed open to admit an oxygen cylinder
which flew across the room and slammed into the end of the coil.



Could indeed happen



The magnetic field, up until that point fairly evenly spread around the
room, concentrated itself into the nicely permeable iron cylinder, which
raised the field strength at two points in the coil beyond the field
strength the superconductor could take, so two bits of it stopped
superconducting and started shunting electrical and magnetic energy into
heat - boiling the liquid nitrogen.



Liquid helium. This event is called a "quench", and -- apart from the
flying gas cylinders -- is a fairly common occurence in high-magnetic
field labs. The field collapses in about one second, all energy gets
dumped into the liquied helium, which in turn evaporates quite
dramatically.



This presented a problem. They couldn't bring the ring current down fast
enough to prevent the LN2 boiling off. Once the coolant level fell below
critical,



which is like immdeiately



the ring would start shedding energy as heat,



By this time the magnet has long gone into non-superconduction.



thus boiling
away the remainder even faster - leaving a non-superconducting ring
carrying a vast current, which would turn into heat, which would stop
the current, which would cause the energy stored in the magnetic field
to try to turn back into current, which would turn into more heat... it
would probably violently explode.



This sounds as if some sort of chain reaction is taking place. This is not
the case. In reality, the magnet goes normal, heats up (to about 60K in my
experience), and a few cubic meters of helium try to get through the
safety valves in a hurry (quite dramatically, actually). Of course there's
now quite a bit of pressure inside the helium vessel which could rupture
if it's not well designed.



LUCKILY, they were prepared for this kind of event, and had a
non-ferrous scissor jack to hand.



Complete bull****.



The strongest members of the group
managed to roll the cylinder onto the jack and jack it away from the
ring housing enough to get shoulders behind it and walk it out of the door.



Totally impossible.

Facts:

A large superconducting magnet, like a medical imaging NMR, is strong
enough to attract ferromagnetic materials like an oxygen cylinder from a
few meters away. If this were to happen (and it has happened), the
cylinder would shoot through the room and destroy the magnet. The
unavoidable quench would be the least dramatic aspect of this scenario.


Up to this last tiny bit, everything you have replied is absolutely
perfect. The large
medical MRIs, due to the weight of the magnet, dewars and cryogens
alone, as well
as the magnetic fields, the requirement that things be incredible stable
for the MRI
imaging process to work, etc. require the magnet housings to be massive
structures.
I know of several medical MRIs in my area that have been hit by Oxygen
bottles of
various sizes, as well as carts, instruments, gurneys and a floor
polisher! As far as
I know (I have a very good friend who works on many of them) all of the
magnets basically
survived the assault. All of them suffered total destruction of the
plastic "beauty"
covers, and a great mess to the shim and gradient coils that are inside
the main magnet
coil. But, as far as I remember, he said no magnet itself needed to be
replaced.
These incidents still can cause several hundred thousand Dollar repair
bills, as it
is almost always hospital negligence that caused the incident.

At any rate, there's no such thing as a quench stopped mid-way. A quench
is a quench, and when it's over, both the magnetic field and the helium
are gone. Even if we imagined an object stuck to the magnet like you
described, the magnet supports wouldn't be able to withstand the force and
break, destroying the helium vessel from the inside.

Your story is full of holes. A modern laboratory (non-medical) NMR magnet
has no appreciable stray field anyway. I can barely stick a wrench to the
outside of mine when it's at 14T.


Right, we have a bunch of NMR magnets here, but he may have been talking
about some physics research gear, which might have a strong external field.
But, his story is obviously one of those that has been retold a few too
many times!

Jon

Alaric B Snell wrote:

By this time the magnet has long gone into non-superconduction.


Why? The material is only above critical field strength in two points,
and the ring is otherwise totally bathed in cryogenic fluid. Does the
heat from the two 'normal' points conduct through the ring enough to
heat the whole thing up that fast, so the cryocoolant is boiling all
over the surface?

Yes, the heat produces is quite large, and the superconducting material
is JUST barely below the
threshold temperature. It takes only a little heat to raise the
surrounding windings above critical
temperature. Also, a quirk of cryogenics is that materials lose their
specific heat (gradually) near
absolute zero. So, the entire magnet has the same specific heat as a
pound or two of copper, even
though it weighs tons!



This sounds as if some sort of chain reaction is taking place. This
is not
the case.


That depends on what you class as a chain reaction, but heating the
magnet in one place kills the superconductivity there, which release
more heat, which in turn heats adjacent bits of the magnet and/or
depletes the coolant level thus indirectly heating other bits, no? I'd
call that a chain reaction because there's positive feedback involved
- are we just debating definitions, or is there some other mechanism
by which an affect on one small region of the ring propogates to
quench the whole thing that *isn't* positive feedback?

Yes, there is a chain reaction sort of thing to it, as the warming
spreads, more of the magnet becomes
non-superconducting. It spreads very quickly.


But if it were a larger magnet, as I suspect must be the case,
couldn't it support a case where two points on the ring were shedding
energy? After all, those two points - having resistance all of a
sudden - would not actually be getting that much current at all

No, because of the need to use external power supplies to ramp up the
magnetic field, all superconducting magnets
I've seen are just one big coil, therefore all in series. So, all parts
of the winding are FORCED to carry the same
current as all other parts.

; presumably energy shedding would only actually occur along the thin
interface between super- and normal- conductivity. Would the heat
generation along that surface really be sufficient to raise the
temperature enough to cause Tc breakdown in the adjacent
superconducting material in a self-propogating wave that would flash
across the whole ring in no time at all? From my mate's description,
the cryocoolant was absorbing a lot of heat energy from the two points
of contact, by boiling off, but it couldn't sustain that rate of
absorption for long before running out of liquid.

Yes, it will propagate very quickly. It is helped by the loss of the
property of specific heat at these temperatures.


Anyway - I'm not trying to challenge your knowledge of the magnets you
work with here - it's just that any impossibilities are more likely to
be due to me forgetting or misremembering important details than the
story being bad to begin with - this guy did end up with a PhD in high
energy physics from Oxford for his part in building a neutrino
detector, while I just study this stuff out of curiousity!

Yup, sounds like it was a nuclear physics detector magnet, really big,
even bigger than a medical MRI magnet.

There's a pretty well-known incident at Johnson&Johnson's Technicare
division, I believe (now absorbed by GE),
where a forklift truck was picked up and pulled into an MRI magnet at
their facility where they built the things.
I vaguely remember the truck operator and a technician were both killed
in that incident. That magnet was
pretty well trashed, of course.

Jon

Jon Elson wrote:

No, it is really just hundreds of amps. They have to "ramp up" such a
magnet with a non-superconducting power
supply, with non-superconducting cables, so the currents outside can't
be enormous. Therefore, there's no
way to get enormous currents INSIDE the superconducting part. But, it
doesn't matter, as they just add more
turns of the superconducting wire. The flux can add up to millions of
amp-turns, however.

Ok, cool.

*thinks*

How does one define the energy content of a ramped-up magnet? The
problem with superconductors is that I'm familiar with nice ohmic
devices. Big current round the coil, but no voltage, so no power
transfer - that's fine, it's a uniform energy density and it's not changing.

But how does one work out an energy from that? I feel the inductance of
the coil must be involved somewhere...


Jon


ABS

Jon Elson wrote:
Now,
maybe they could make
Hydrogen or liquid Ammonia whenever the plant goes offline, and sell the
product, since it would
be wasted energy, otherwise.

Purify aluminium :-)

Or run a particle accelerator. Do a bit of particle physics while you're
at it, like.

Or feed it to a dorm full of pyromaniac physics undergraduates, who will
try to build the Worlds Biggest Fusor or scale up one of those
electromagnetic can crushers to build a Container Ship Crusher or something.


Jon


ABS

In article , Alaric B Snell says...

But how does one work out an energy from that? I feel the inductance of
the coil must be involved somewhere...

U (stored energy in field) = 1/2 L i*2

You can work this out but that's the answer.

It's analagous to the 1/2 C V*2 for energy stored
in the electric field of a capacitor.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

I should mention - that after years of saying ME TOO - I got DSL.
That was maybe a year ago now.

Around the house, I have hardware and naturally GeBe - or 802.11G which
is A and B. One computer only gets B level - sniffle.

Hope to install a Sat soon - to have half the house wired both ways
so when the storm blows away the cable, maybe the show or game will be
on the sat. Likely never will happen. Naturally.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

What it is is really RF modulation around the sample that is held in
a strong field.

Consider the field as a bias and the RF the hunt and search sweep.

The blood could be modulated - however, the frequency is kept from it
less have the protein to cook :-)

It seems that collections of stuff have resonate frequencies that are
signature quality. This is much like mass spec stuff - atomic level
modulation.

It has always made me nervous thinking of the quality level and what
could happen in any of these big machines. Even X-Ray can be really
bad if the machine broke down and overdosed...

Such is life in the high tech medical route - one takes ones chance.
Either a blind knife operation or a full up front and understood
operation.

Blood - that is the scare - modulate it just right, and a lot of you
wiggles.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

On Mon, 18 Aug 2003 07:10:33 -0500, Jim Kovar
wrote:



Hunting snowshoes *on* snowshoes. That's fun!
Not when you dip the muzzle of the 20 gauge in the snow just before
you see the bunny!
Gerry :-)}
London, Canada

Hairpin ?

Normally the patent is scanned prior to the machine - but I suspect
there are times when xxx happens - often does. Nice input.

The samples I played with in the labs - early 60's - was the size of
ones pinkie finger.

We didn't want to have much larger unit in those days - some exotic
materials
really cost!

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

"Eastburn" wrote in message
...
The thought here isn't like a magnet - but the electron shells are
controlled when the atom is pulsed with it's specific frequency.
The atom absorbs energy from the RF source (scope dip) and then flexes
it out (scope peak). The scope is measuring the source voltage.
Current
flow draws down the voltage and the reflex pumps it up.

So it causes a dip in the voltage, then after a certain period, gives it
back? Kinda like SWR in a long line I think?

As for the coil, I presume that's a big parallel resonant tank circuit,
both LN or LHe cooled (superconducting)? I would presume they use LN
since there's hi-temp superconductors these days...

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms