17 Sep
2007
17 Sep
'07
12:49 a.m.
Date: Sun, 16 Sep 2007 06:57:40 -0700
From: dwight elvey <dkelvey at hotmail.com>
A carbon arc would work as well but I've not seen
these
since they've stopped using these in search lights.
Dwight
Back in elementary school one of the library books had interesting
projects in it. One project was to remove the carbon rods from four
'D' cells. They're about 1/4" - 3/8" in diameter and run the
length
of the cell. It's a bit of a trick to extract them without breaking
them.
Once you have four carbon rods, suspend two in a jar of salt water.
Grip the other two, each with its own wooden clothes pin (the spring
type, not the slot type).
Now steal a heavy duty electrical cord from something like Mommy's
clothes iron. Attach one lead of the cord to one of the carbon rods
in the jar of salt water. Connect the other lead to one of the
carbon rods held by a clothes pin. Now use a spare length of heavy
wire to connect the remaining two carbon rods together.
Plug the cord into the wall.
Now carefully touch the tips of the two clothes pin carbon rods
together and then slowly draw them apart. TADA! Carbon arc.
Vary the salt content in the jar to adjust the power.
I don't recall the instructions saying anything about not looking
directly at the arc. Perhaps this method doesn't generate enough
UV to be useful/harmful? I spent a fair bit of time staring at the
thing. Thirty-five years later I haven't noticed any vision
impairment, but maybe I was young enough for my retina to recover.
It was quite the attention getter at the ES science fair. I suspect
books in grade schools don't contain cool/dangerous projects like
this any more. I only electrocuted myself once or twice by
touching the live bits of the contraption...
Jeff Walther
17 Sep
17 Sep
12:58 a.m.
Jeff Walther wrote:
Back in elementary school one of the library books had
interesting
projects in it. One project was to remove the carbon rods from four
'D' cells. They're about 1/4" - 3/8" in diameter and run the
length of
the cell. It's a bit of a trick to extract them without breaking them.
No talk like this or soon the Safety Police will be knocking at your
door looking for D-cell's.
Jeff Walther
4:22 a.m.
[...]. TADA! Carbon arc.
I don't recall the instructions saying anything
about not looking
directly at the arc. Perhaps this method doesn't generate enough UV
to be useful/harmful?
Maybe, but it seems dubious to me. Perhaps it depends on how much
power is being run through the arc. But I know it is *not* safe to
look at an arc-welding arc without UV protection; my father told of a
time when, in a pinch, he arc-welded using many sunglasses to cut the
light down - but they didn't cut the UV down enough, and he sunburned
his eyes rather badly. He compared it to living with a handful of sand
in each eye. For a week. (Since then when he's had to weld without a
proper welding filter, he's lined it up and then just kept his eyes
closed while the arc is live, trusting to his manual dexterity and
experience to keep the weld where it belongs.)
After hearing that, I've been rather timid around electrical arcs more
vigorous than what you get out of a car spark coil. I'll even look
away when I see welding across the street on a construction site, even
though I know perfectly well inverse square drops it to something safe.
Plasma is plasma, and the light is going to have a corresponding
spectrum. But there's only as much power coming out as goes in.
Without a real measurement, though, I'd be inclined to err on the side
of caution. Perhaps that's just because I value my sight so much.
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5:11 a.m.
Date: Sun, 16 Sep 2007 18:49:46 -0500> To: cctech
at classiccmp.org> From: trag at io.com>
---snip---> Now carefully touch
the tips of the two clothes pin carbon rods > together and then slowly draw them apart.
TADA! Carbon arc.> > Vary the salt content in the jar to adjust the power.> >
I don't recall the instructions saying anything about not looking > directly at the
arc. Perhaps this method doesn't generate enough > UV to be useful/harmful? I spent
a fair bit of time staring at the > thing. Thirty-five years later I haven't
noticed any vision > impairment, but maybe I was young enough for my retina to
recover.> > It was quite the attention getter at the ES science fair. I suspect >
books in grade schools don't contain cool/dangerous projects like > this any more.
I only electrocuted myself once or twice by > touching the live bits of the
contraption...> > Jeff Walther
The light from these arcs would have a lot of UV. The UV just
depends on the temperature of the arc. The mercury vapor
lamp has peeks in its spectrum in the UV. I is different than an
arc. Arcs are just real hot.
I suspect that for any of there projects, they recommend
adult supervision. The only problem with that is that
more adults don't have a clue.
You can get a sun burn from arc welding as well. I was
about 5 feet away and watching a friend do some welding
for me. All I had was goggles and not a full face shield.
I looked funny for about 2 weeks.
Dwight
_________________________________________________________________
Kick back and relax with hot games and cool activities at the Messenger Caf?.
http://www.cafemessenger.com?ocid=TXT_TAGLM_SeptWLtagline
7:57 a.m.
On Sun, 2007-09-16 at 21:11 -0700, dwight elvey wrote:
You can get a sun burn from arc welding as well. I
was
about 5 feet away and watching a friend do some welding
for me. All I had was goggles and not a full face shield.
I got a nice tan from welding up some bits on a car once. I normally
don't tan or sunburn at all. Of course, there probably isn't a lot of
UV in the sun in these latitudes - wherever you are in Britain, you're
at least as far north as the southern tip of Alaska...
Gordon
2:36 p.m.
dwight elvey wrote:
> Date: Sun, 16 Sep 2007 18:49:46 -0500> To:
cctech at classiccmp.org> From: trag at io.com>
You can get a sun burn from arc welding as well. I
was
about 5 feet away and watching a friend do some welding
for me. All I had was goggles and not a full face shield.
I looked funny for about 2 weeks.
When I was in my teens I worked as a fill welder - using high-amp,
large-diameter arc welder to reinforce and fill "tacked" assemblies. In
most of the welding I did, I might spend 20-30 minutes an hour actually
burning rod, but on the fill line it was over 50, and running at *very*
high energy levels.
I had run out of uniform shirts one day and wore an old long-sleeved
dress shirt with a T-shirt under it. When I got home that day, I had
heavy sunburn all over my front, except for where the shirt pockets and
button-basting had been.
For those arc-burned eyes, we always used chilled grated potato
compresses. I have no clue why, but it works wonders to soothe the pain.
Doc
PS - This was all 20 years ago, and there were tape-loop turret lathes
nearby, so it's on topic, right?
*runs*
11 p.m.
woodelf wrote:
Eew, nasty. :^)
Doc
Doc Shipley wrote:
Bear in mind that "computer" was a very vague idea to me at the time
(mid-70s to early 80s). Some of the shops I worked in had automated
lathes and vertical mills that were guided by punched mylar tape. Since
they normally made dozens or hundreds of the same part, the tape was looped.
Now I'd love to know what was in the guts of the thing, but at the
time I could have cared less. I liked them, though - I took the
tape-loop machines pretty much for granted, but now I marvel at their
reliability in markedly hostile conditions. They also made my life a
lot less boring. The automation of very simple, repetitve machining was
much more of a relief than a threat in my mind.
PS - This was all 20 years ago, and there were
tape-loop turret lathes
nearby, so it's on topic, right?
Just what is a tape-loop turret lathe? *runs*
Thows a wet tribble at you. :) 
11:35 p.m.
Date: Sun, 16 Sep 2007 06:57:40 -0700
From: dwight elvey <dkelvey at hotmail.com>
A carbon arc would work as well but I've not
seen these
since they've stopped using these in search lights.
Dwight
Back in elementary school one of the library books had interesting
projects in it. One project was to remove the carbon rods from four Now carefully touch the tips of the two clothes pin
carbon rods
together and then slowly draw them apart. TADA! Carbon arc.
I must admint I have reservations about hand-holding 2 wooden clothes
pegs holding carbon rods conencted ot the mains...
Vary the salt content in the jar to adjust the power.
Or the spacing between the 2 carbon rods in the rheostat.
At least one of my 'electictal things to make at home' books describes
how to make a proper arc lamp with automatic feeding of the carbons as
they burn down.
It was quite the attention getter at the ES science
fair. I suspect
books in grade schools don't contain cool/dangerous projects like
this any more. I only electrocuted myself once or twice by
Alas not...
touching the live bits of the contraption...
I doubt very much if thing I got up to at school would be OK now. Like
making a crude cathode ray tube. OK, it had ot be continuously pumped
(and a rotary pumo doesn't realyl give a hard enough vacuum), but I did
get a spot that could be deflected. Learnt a lot doing things like that.
-tpny
18 Sep
18 Sep
12:39 a.m.
Tony Duell wrote:
I doubt very much if thing I got up to at school would
be OK now. Like
making a crude cathode ray tube. OK, it had ot be continuously pumped
(and a rotary pumo doesn't realyl give a hard enough vacuum), but I did
get a spot that could be deflected. Learnt a lot doing things like that.
How a about now deflecting a tiny spot?. There was a atomic force microscope
somewhere web as a DIY project but I think it vanished overnight.
I think they were claming about $150 or so for the simple equipment.
-tpny
Ben alias woodelf
11:29 p.m.
Jeff Walther wrote:
[snip description of carbon arc, mains power and hand-held clothes pegs
:-)]
I don't recall the instructions saying anything
about not looking
directly at the arc. Perhaps this method doesn't generate enough
UV to be useful/harmful?
Perhaps the odds of surviving long enough for UV exposure to be an issue
turned out to be quite low :-) At least over here in the 240Vac world.
Antonio
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19 Sep
19 Sep
1:01 a.m.
Jeff Walther wrote:
I don't recall the instructions saying anything
about not looking
directly at the arc. Perhaps this method doesn't generate enough
UV to be useful/harmful?
From my misspent youth taking a summer job as a
drive-in
projectionist, carbon arcs were very impressive. Although some stage
spotlights used AC arcs, all of the arcs used in projectors were DC-
powered. Usually by a sizeable MG set (40 HP motor), although the
smaller houses could get by with 3-phase selenium rectifier setups.
Wall-mounted ballast coils and water-cooled electrode holders. The
anode (IIRC) was about 1/2" in diameter and perhaps 18" in length,
while the cathode was much smaller and usually copper-plated. (Most
of the light was radiated from the anode face, so the cathod actually
met the anode at about a 30 degree angle so as not to obscure it).
An anode would last about 2 reels (40 minutes, give or take). Some of
the more clever "cans" used an aperture and phototube assembly to
track the face of the anode and adjust the (motorized) feed speed
accordingly. Because the can was forced-air ventilated, the arc
actually appeared as an upward-pointing flame (I'm sure that was just
the incandescent carbon vapor glowing).
Observation of the arc was always done by looking at the image
projected onto a surface by a pinhole opening. There were "black
glass" observation ports, but you were warned not look through them
for any amount of time. If you had a watch with a luminescent dial,
you could hold it near the black glass window and notice how brightly
the face glowed. That probably was the UV.
One probably could have erased a whole bunch of EPROMs by putting
them inside the can with the arc.... :)
Cheers,
Chuck
2:04 a.m.
New subject: Carbon arcs (was Re: EPROM Erasers?)
[...drive-in projectionist...carbon arcs...]
Because the can was forced-air ventilated, the arc actually appeared
as an upward-pointing flame (I'm sure that was just the incandescent
carbon vapor glowing).
Burning, I'd guess; carbon vapour at just below plasma temperatures is
not going to be shy about combining with oxygen - which itself is
probably not much cooler - from air.
Observation of the arc was always done by looking at
the image
projected onto a surface by a pinhole opening. There were "black
glass" observation ports, but you were warned not look through them
for any amount of time.
I bet!
I'm reminded of reading of someone doing work that involved some
extreme heat sources - testing heat-shielding materials, I think it was
- and there was, out in the middle of a desert somewhere, an
underground torch whose flame emerged from a hole in the ground.
Something like magnesium dust in liquid oxygen, pumped (at well over
its flame propagation speed!) through the nozzle...I forget details.
Someone photograhed it from some miles away (about as close as the
camera would survive) and the picture looks like midnight even though
it was high noon; the torch easily outshone anything as piddly as the
sun. I imagine the ground was glass for some distance around, shortly
after the first burn started....
Not very useful for the home hobbyist with EPROMs to erase. But I
always find extremes interesting....
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3:25 a.m.
New subject: Carbon arcs (was Re: EPROM Erasers?)
der Mouse wrote:
I'm reminded of reading of someone doing work that
involved some
extreme heat sources - testing heat-shielding materials, I think it was
- and there was, out in the middle of a desert somewhere, an
underground torch whose flame emerged from a hole in the ground.
Something like magnesium dust in liquid oxygen, pumped (at well over
its flame propagation speed!) through the nozzle...I forget details.
Aren't there many reports of people able to see the bones in their hands
as clear as day with their eyes closed when within a certain distance of
an atomic bomb flash?
Peace... Sridhar
5:12 a.m.
On 18 Sep 2007 at 19:28, Fred Cisin wrote:
Perhaps the writer gave up his writing career due to
failing eyesight,
before he got around to writing that warning
Perhaps he was a monk detailed with maintaining the arc--remember "A
Canticle for Liebowitz?"
Gotta watch out for them "negative twists of nothingness"... :)
Cheers,
Chuck
4:33 p.m.
And thusly were the wise words spake by Fred Cisin
"Do Not Look Directly Into Laser Beam With Remaining Eye"
Cheers,
Bryan
> I don't recall the instructions saying
anything about not looking
> directly at the arc. Perhaps this method doesn't generate enough
> UV to be useful/harmful?
Perhaps the writer gave up his writing career due to failing eyesight,
before he got around to writing that warning
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