JFK's greatest achievements/Apollo (Was: Deep Apologies to everyone....)

"Jeffrey Hamilton" wrote:

:Pat Flannery wrote:
:
: What made it all possible was the British invention of the Cavity
: Magnetron Tube, which made it possible to build radars that used very
: short wavelengths, and therefore had far better resolution than the
: ones that came before.

The Brits were hardly the only ones to do this. Both Americans and
Germans were also involved. I'd be inclined to say that the Americans
got there first (Dr. A.W. Hull).

:
:It went into some detail and spoke of the "Cavity
:Magnetron Tube" etc. I'm no expert now but I have a slightly better idea
:asto how they developed the various systems for their particular needs.
:Pretty fascinating stuff.
:

I'm always surprised when people don't know this stuff.


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson

Alan Jones wrote:
Toward the end of WW II we also developed a radar guided missile, the
Lark, to counter komikazee attacks. It worked well enough in the lab,
but in the vibration environment of the missile in flight the radar
guidance range was reduced too much to be effective. And of course
the procimity fuse was a major advance.



Britain also worked on a anti-kamikaze missile during the war, called
the Stooge:
http://www.skomer.u-net.com/projects/stooge.htm

Pat
Alan

Jeffrey Hamilton wrote:
Lol, I'll remember that for future reference. Every boy needs at least one
good magnet and I do have an old HD with a few bad sectors, Ill trash it and
give the magnets to my grandson, when he is a litle older.
What's a Magnetron Tube good for ? If I save one for my grandson, is he
likely to nuke the house ? g

Interesting historical relic.
It's also interesting to see that all those microwaves that heat the
food up come out of a hole that is around 3 mm in diameter.
Regarding the hard drive magnets:

1. See if you can get them free from the mountings without heating them
up much; they completely demagnetize if they are heated very much. A lot
of times they are glued down, and you can insert a thin knife blade
between the magnet and the mounting and pry it free.
2. Do not get your fingers between the magnets, as they will clamp
together so hard that you will get severely pinched.
3. Keep them far away from any cathode ray tubes or magnetic memory
storage units, as despite their small size they are like the magnetic
equivalent of a black hole as far as power goes... how they get them to
be in that close of proximity to the hard drive platters and not
completely erase them is beyond me.

Pat

Pat Flannery wrote:

Jeffrey Hamilton wrote:
This is to both posters, I never actually realized _our_ radar had
developed that fast ! From those very large early sites used during the
Battle of Britain, to the relatively smaller naval sets being used to
destroy the Japanese shipping is a pretty steep learning curve.

Radar, like jet engines, was one of those things that all the major powers
developed at about the same time. Everybody had something that they thought
was better than anyone else's, and everybody was keeping it a Deep Secret.


What made it all possible was the British invention of the Cavity
Magnetron Tube, which made it possible to build radars that used very
short wavelengths, and therefore had far better resolution than the ones
that came before.

Actually not, although the Magnetron was important, The U.S. had the
Klystron as a Microwave source and amplifier, and U.S. Receiver technology
was far superior.
The results produced by the Allies were do to an interesting combination of
intense competition combined with cooperation.
The Germans didn't have that - after all, they were _Germans_ and nobody
could equal them... blah, blah, yadda, yadda.
The concepts of how to apply these systems had all been pretty much worked
out, setting up a blueprint that's still followed today.

The fascinating part is when radar was combined with American control
technology and systems integration - this resulted in auto-tracking radars
that would keep themselves pointed at a particular target and stream
information to fire control computers, (Analog at the time, but better than
everything at determining a continuous solution) and Remote Power Control
of the guns. By late 1943, all U.S. Heavy AAA, and all Naval guns with a
caliber of more than 20mm on anything larger than a Sub Chaser were
remotely controlled by the fire control directors, with the gun crews
acting as manual backup.

A cavity magnetron tube still forms the heart of all microwave ovens:
http://www.gallawa.com/microtech/magnetron.html
...and when Britain thought it was in danger of invasion early in WW II
they sent one to the US...sealed in a mysterious black box...that's
where the term "Black Box" first came from.

Actually not - The Brits carrying the experimental Magnetron to the U.S.
also carried what was hoped to be full documentation - for the first day or
so, until they were called onto the carpet to explain why the X-Rays of the
device that they'd carried over didn't match the drawings. The traveling
Boffins didn't know, and didn't know if the differences (like the number of
cavities) were significant. But, within about a week or so, we'd
determined the operating principles, and that the differences weren't
significant.


--
Pete Stickney
The better the Four Wheel Drive, the further out you get stuck.

Jeffrey Hamilton wrote:

One more question if you have a bit of time, what does the 45 or 50 figure
mean in these instances 16"/50 or 16"/45. I do see that it refers to a
50-caliber barrel, but a 45 or 50 caliber is usually refering to a small
arms or a machine gun etc. I've never understood what that signifies.

cheers....Jeff


The caliber of a naval gun refers to the ratio of the length of the
barrel vs the size of the bore. 16"/50 means the length of the barrel
is 50 time the diameter of the bore or 16" X 50 = 800" or 66.67'. 16"/45
only has barrel that is 60' long.

Jay

Pat Flannery wrote:
Regarding the hard drive magnets:
3. Keep them far away from any cathode ray tubes or magnetic memory
storage units, as despite their small size they are like the magnetic
equivalent of a black hole as far as power goes... how they get them to
be in that close of proximity to the hard drive platters and not
completely erase them is beyond me.

For sure keep them away, well away, from magnetic media (like your
floppy disk collection) and CRTs of all sorts.

I spent about 5 years making disk drives for HP. This was 'back
in the day' where our main seller was a 350MB drive that was
5-1/4 inch form factor, full-height, and weighed about 7 pounds.
This was not a home user drive, they were designed to be used in
arrays for commercial or industrial users. I still have some of
the mag-motor magnets. They are crazy strong--if you get careless
and let them touch with smoe part of you in between they will
pinch a piece of your skin off, and if they really slap they will
shatter into glass-sharp fragments that can cut the hell out of
you (the rare earth material is a ceramic).

I used to use them for elementary school "mad scientist" visits.
Singly, they could deflect a compass needle from more than thirty
feet away. But as a pair (they came with a 3/16" plastic block
which went between the halves to make it much easier to separate
them for installation) you had to get much closer to the compass
before the needle would move. As long as the fields are
contained in this way their ability to damage your drive is
reduced.

And, the mag-motor is mounted in the plane of the disk pack.
The magnetic fields are tightly contained between the two halves
(well, to be fussy some of the field is still present laterally,
i.e. in the area of the disks, but very much weaker than between
the halves.

And, it is harder to damage a drive magnetically than you'd think
(the write heads are quite strong and closely focused).

The real risk we used to face was magnetic contamination--
periodically someone would get careless and break a magnet, and
we had to scrap any media which was exposed at the time--tiny bits
of the broken magnet would get on the disk surface and create
little dead spots (not to mention the physical contamination
problems, which would caus head crashes).


Jeff

--
Dying with an empty inbox is NOT the goal!

Pat Flannery wrote:
Jeffrey Hamilton wrote:
Lol, I'll remember that for future reference. Every boy needs at
least one good magnet and I do have an old HD with a few bad
sectors, Ill trash it and give the magnets to my grandson, when he
is a litle older. What's a Magnetron Tube good for ? If I save one for my
grandson, is
he likely to nuke the house ? g

Interesting historical relic.
It's also interesting to see that all those microwaves that heat the
food up come out of a hole that is around 3 mm in diameter.
Regarding the hard drive magnets:

1. See if you can get them free from the mountings without heating
them up much; they completely demagnetize if they are heated very
much. A lot of times they are glued down, and you can insert a thin
knife blade between the magnet and the mounting and pry it free.
2. Do not get your fingers between the magnets, as they will clamp
together so hard that you will get severely pinched.
3. Keep them far away from any cathode ray tubes or magnetic memory
storage units, as despite their small size they are like the magnetic
equivalent of a black hole as far as power goes... how they get them
to be in that close of proximity to the hard drive platters and not
completely erase them is beyond me.

Pat

Good heads-up Pat, on second thought perhaps I won't give my grandson any
magnet, quite _that_ powerful.

cheers....Jeff

jay walsh wrote:
Jeffrey Hamilton wrote:

One more question if you have a bit of time, what does the 45 or 50
figure mean in these instances 16"/50 or 16"/45. I do see that it
refers to a 50-caliber barrel, but a 45 or 50 caliber is usually
refering to a small arms or a machine gun etc. I've never understood
what that signifies. cheers....Jeff


The caliber of a naval gun refers to the ratio of the length of the
barrel vs the size of the bore. 16"/50 means the length of the barrel
is 50 time the diameter of the bore or 16" X 50 = 800" or 66.67'.
16"/45 only has barrel that is 60' long.

Jay

Thankyou Jay.

cheers....Jeff

Jeff Crowell wrote:
Pat Flannery wrote:
Regarding the hard drive magnets:
3. Keep them far away from any cathode ray tubes or magnetic memory
storage units, as despite their small size they are like the
magnetic equivalent of a black hole as far as power goes... how they
get them to be in that close of proximity to the hard drive platters
and not completely erase them is beyond me.

For sure keep them away, well away, from magnetic media (like your
floppy disk collection) and CRTs of all sorts.

I spent about 5 years making disk drives for HP. This was 'back
in the day' where our main seller was a 350MB drive that was
5-1/4 inch form factor, full-height, and weighed about 7 pounds.
This was not a home user drive, they were designed to be used in
arrays for commercial or industrial users. I still have some of
the mag-motor magnets. They are crazy strong--if you get careless
and let them touch with smoe part of you in between they will
pinch a piece of your skin off,

Yes, I found that out. ;-)
Might as well put your finger into a crab's claw.

and if they really slap they will
shatter into glass-sharp fragments that can cut the hell out of
you (the rare earth material is a ceramic).

I note that all of them seem to be plated with a fairly thick metal
covering (nickel?)
Is that for corrosion resistance, or to prevent any chipping of the
ceramic magnet?



The real risk we used to face was magnetic contamination--
periodically someone would get careless and break a magnet, and
we had to scrap any media which was exposed at the time--tiny bits
of the broken magnet would get on the disk surface and create
little dead spots (not to mention the physical contamination
problems, which would caus head crashes).

What exactly are the discs made out of?
They appear to be some fairly low melting point metal with a plating on it.

Pat

Jeff Crowell wrote:
and if they really slap they will
shatter into glass-sharp fragments that can cut the hell out of
you (the rare earth material is a ceramic).

Pat Flannery wrote:
I note that all of them seem to be plated with a fairly thick metal
covering (nickel?)
Is that for corrosion resistance, or to prevent any chipping of the
ceramic magnet?

It's nickel. It's partly for corrosion resistance, but also
to minimize contamination.


The real risk we used to face was magnetic contamination--
periodically someone would get careless and break a magnet, and
we had to scrap any media which was exposed at the time--tiny bits
of the broken magnet would get on the disk surface and create
little dead spots (not to mention the physical contamination
problems, which would cause head crashes).

What exactly are the discs made out of?
They appear to be some fairly low melting point metal with a
plating on it.

Aluminum, in our case (has to be non-ferrous!). We also made
some glass platters for our smaller-diameter drives. I'd
suspect most, if not, all modern platters are aluminum. They
are plated with an iron-containing matrix (then coated with a
lubricating liquid). I don't know the magnetic media's exact
composition, that wasn't my thang at the time (or since, for
that matter).


[Obsmn/sph: HP's "Nighthawk" 3-1/2 inch hard drives were used
in Tomahawk missiles]. May still be, I dunno.



Jeff

--
To a procrastinator, a lie is just the truth waiting to happen.
C. J. Schoenrock