For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it
seems it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and
before I spend the time winding a BF coil and energizing it through a
transformer and variac, does anyone have any ideas what else I could do
or use to attempt to demagnetize this old family friend? (Without
busting the glass that is.)

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Jeff Wisnia wrote:
[...]
I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.
[...]

Somehow? How?

Dave wrote:
Jeff Wisnia wrote:

[...]
I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.
[...]


Somehow? How?


Only thing I can guess is that maybe someone shook the gadget and the
parts rattled against each other. I'm remembering how as a kid holding
an iron rod in your hand and hitting the end with a hammer would shake
up the atoms so they lined up with the earth's magnetic field and the
rod became a weak magnet.

Jeff (Well at least I had an answer...)



--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Jeff Wisnia wrote:


For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it
seems it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and
before I spend the time winding a BF coil and energizing it through a
transformer and variac, does anyone have any ideas what else I could do
or use to attempt to demagnetize this old family friend? (Without
busting the glass that is.)

Any old-school TV repairman will have a
degaussing coil about a foot in diameter
and would probably do the job for free.

Couldn't you just stick a loop of coat-hanger wire in place of the tip
on an electric soldering iron... and pass it over the globe?
I wouldn't think it's magnetized as strongly rare-earth magnets or
anything. LOL
David


"Jim Stewart" wrote in message
...
Jeff Wisnia wrote:


For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it seems
it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and
before I spend the time winding a BF coil and energizing it through a
transformer and variac, does anyone have any ideas what else I could do
or use to attempt to demagnetize this old family friend? (Without busting
the glass that is.)

Any old-school TV repairman will have a
degaussing coil about a foot in diameter
and would probably do the job for free.

Or you could use an electric motor with the rotor removed as your coil.

I wouldn't think it is ferrous for just the reason that you described.
Probably aluminum, copper, brass, paper, plastic, etc. The black will
still absorb heat for the unbalance ref. the white.

k.o.


"Jeff Wisnia" wrote in message
...

For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it seems
it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow got
magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and before
I spend the time winding a BF coil and energizing it through a transformer
and variac, does anyone have any ideas what else I could do or use to
attempt to demagnetize this old family friend? (Without busting the glass
that is.)

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

In article , Jeff Wisnia says...

I don't own a demagnetizer big enough to fit the whole bulb in, and
before I spend the time winding a BF coil and energizing it through a
transformer and variac, does anyone have any ideas what else I could do
or use to attempt to demagnetize this old family friend? (Without
busting the glass that is.)

I guess if this were mine I'd do the following:

1) wind a ten-or-so turn coil out of bare number 12 or 10 house
wire. Space the turns out so they don't touch. Coil to be
just large enough to slip over the radiometer bulb.

2) connect that coil to the largest weller solder gun you own.

3) pull the trigger on the gun when it is far away from the bulb.

4) *Slowly* advance the coil towards the radiometer. The vanes
inside may start jumping around and could possibly break the glass.
Do this step slow and abort if it starts to get too exciting.

5) pass the back and forth over the bulb, don't let go of the
trigger.

6) bring the bulb and the gun apart, to full arms' length
before releasing the trigger.

Don't use insulated wire, the coil will get *hot*. Don't let the
coil touch the glass bulb for the same reason....

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Wrong - lost the vacuum in the bottle. Likely a slow leak and maybe when the internals
got hot it went through the seal. Rather common.

If you think it is magnetized - the vanes are Al or Mg - for light weight. But if you
want - pass it through a loop that is passing AC.

One of those is the color TV - remember - when you turn on the TV there is a Twang sound -
that is the coil getting a shot of juice upon power. Keeps the tube set.

Just put the unit on a wood table or such - at the center of the screen and turn on the set.

Most won't let you do it more than once for a while... Just once or twice is needed over time.

Martin

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Jeff Wisnia wrote:

For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it
seems it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow
got magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and
before I spend the time winding a BF coil and energizing it through a
transformer and variac, does anyone have any ideas what else I could do
or use to attempt to demagnetize this old family friend? (Without
busting the glass that is.)

Jeff



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

"Jeff Wisnia" wrote in message
...

For longer than I can remember we've had a Crookes radiometer sitting on
our kitchen windowsill where it heralds the coming of spring by starting
to turn when the morning sunshines on it through the window.

If you're not familiar with what I'm describing, see this:

http://en.wikipedia.org/wiki/Image:C...radiometer.jpg

This morning I noticed that the radiomether was illuminated, but wasn't
doing its thing. I nudged it and it started turning but stopped in a few
seconds.

I gave it a closer look and saw that the metal "hub" the vanes are
attached to was "stuck to" the side of the bearing needle, and it looks
like it's magnetism and not an out of balance condition because it seems
it will "stick" anywhere around its periphery.

I'm guessing the hub and the needle are both made of steel and somehow got
magnetized.

I don't own a demagnetizer big enough to fit the whole bulb in, and before
I spend the time winding a BF coil and energizing it through a transformer
and variac, does anyone have any ideas what else I could do or use to
attempt to demagnetize this old family friend? (Without busting the glass
that is.)

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Plenty of demagnetizing advice by others. I would use a turn of #12 copper
wire in my soldering gun. It is very common for steel to become weakly
magnetized from the earth's field when left in one position for a long time.
Don Young

Martin H. Eastburn wrote:
Wrong - lost the vacuum in the bottle. Likely a slow leak and maybe when
the internals
got hot it went through the seal. Rather common.

But if that were the case, why would it run for 15 to 30 seconds when
exposed to sunlight and then get "stuck" when the rotating part wobbles
a bit so the "hub" touches the vertical needle and sticks to it as
though it were magnetized?



If you think it is magnetized - the vanes are Al or Mg - for light
weight.

I don't doubt the vanes are made from a lightweight material but it
looks like they are attached to a small metal hub stuck on the bottom of
the glass nipple resting on the top of the needle. It's that hub which
"sticks" against the needle when it stalls out.

I understand that these radiometers work better when there's a very low
pressure in them than they do at a hard vacuum. Something to do with
having the right amount of air molecules inside which get heated by the
dark side of the vanes and give that side a bit of a kick.

I know I can buy a new radiometer for less than $12, but my curious mind
wants to see if demagnetizing would "fix" this one.

But if you
want - pass it through a loop that is passing AC.

One of those is the color TV - remember - when you turn on the TV there
is a Twang sound -
that is the coil getting a shot of juice upon power. Keeps the tube set.

Just put the unit on a wood table or such - at the center of the screen
and turn on the set.

Most won't let you do it more than once for a while... Just once or
twice is needed over time.

I'll probably make a coil or pull a scrap motor apart over the weekend
and see whether I can win this one with demagnitization. G

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

The one we had at home as a kid had a glass hub.

If you have a metal one - did the needle eat it up and finally cut it ?
Have you turned it upside down and such ?


Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Jeff Wisnia wrote:
Martin H. Eastburn wrote:

Wrong - lost the vacuum in the bottle. Likely a slow leak and maybe
when the internals
got hot it went through the seal. Rather common.


But if that were the case, why would it run for 15 to 30 seconds when
exposed to sunlight and then get "stuck" when the rotating part wobbles
a bit so the "hub" touches the vertical needle and sticks to it as
though it were magnetized?



If you think it is magnetized - the vanes are Al or Mg - for light
weight.


I don't doubt the vanes are made from a lightweight material but it
looks like they are attached to a small metal hub stuck on the bottom of
the glass nipple resting on the top of the needle. It's that hub which
"sticks" against the needle when it stalls out.

I understand that these radiometers work better when there's a very low
pressure in them than they do at a hard vacuum. Something to do with
having the right amount of air molecules inside which get heated by the
dark side of the vanes and give that side a bit of a kick.

I know I can buy a new radiometer for less than $12, but my curious mind
wants to see if demagnetizing would "fix" this one.

But if you

want - pass it through a loop that is passing AC.

One of those is the color TV - remember - when you turn on the TV
there is a Twang sound -
that is the coil getting a shot of juice upon power. Keeps the tube
set.

Just put the unit on a wood table or such - at the center of the
screen and turn on the set.

Most won't let you do it more than once for a while... Just once or
twice is needed over time.


I'll probably make a coil or pull a scrap motor apart over the weekend
and see whether I can win this one with demagnitization. G

Jeff



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

In article , Jeff Wisnia says...

I understand that these radiometers work better when there's a very low
pressure in them than they do at a hard vacuum. Something to do with
having the right amount of air molecules inside which get heated by the
dark side of the vanes and give that side a bit of a kick.

That's right. Those things actually run 'backwards.'

If it were momentum transfer going on, the white side of the
vanes would be trailing, because the photons are reflected off
that side, and absorbed on the dark side.

Instead the dark side gets a tad hotter, and the gas molecules
in the envelope get a slightly stronger kick near the black
surface, so the black side of the vane trails.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

If one would like to restore the vacuum, how could one do that and seal
it off at home?

TMT

Where does one buy a NICE one these days?

TMT

Martin H. Eastburn wrote:
The one we had at home as a kid had a glass hub.

If you have a metal one - did the needle eat it up and finally cut it ?
Have you turned it upside down and such ?

The "hub" looks like an inverted subminiature glass test tube about 5/8"
long and 1/8" ID. A little stamped metal X shaped piece with an extruded
center hole is either press fitted or adhesively attached to its open
end. The paddles are attached to the legs of the X.

My radiometer only has two paddles which are attached to opposite legs
of the X. The other two legs are bare, maybe the manufacturer uses them
when they make four paddle models.

What I prolly should have done before I started this thread was to
slowly move a strong magnet towards the radiometer while it was stopped
to see if it caused any movement or tilting of the vane assembly. That
prolly would have told me whether my assumption that magnetization is
making the metal hub "stick" to the needle has any legs to it.

Dumb of me not to think of that, as right in the next room there's a
pretty strong suspension magnet on the little diamagnetic demo I built a
few years ago.

If you've never played with diamagnetics, it's free floating objects
right before your eyes, sort of counterintuitive to what we usually
think about magnets and/or gravity:

http://home.comcast.net/~jwisnia18/jeff/diamag.html

I'll run a magnet test first before I try demagnetizing with my 250 watt
Weller as suggested.

Report later.....

Thanks guys,

Jeff




--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Too_Many_Tools wrote:
Where does one buy a NICE one these days?

TMT


These looks pretty "nice" but cost nearly $50 in your choice of clear or
two colors.

http://scientificsonline.com/product.asp_Q_pn_E_3116000

The plebeian model from the same place is under $12.

http://scientificsonline.com/product...s=p&pn=3060082



Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Jeff Wisnia wrote:

Martin H. Eastburn wrote:

The one we had at home as a kid had a glass hub.

If you have a metal one - did the needle eat it up and finally cut it ?
Have you turned it upside down and such ?


The "hub" looks like an inverted subminiature glass test tube about 5/8"
long and 1/8" ID. A little stamped metal X shaped piece with an extruded
center hole is either press fitted or adhesively attached to its open
end. The paddles are attached to the legs of the X.

My radiometer only has two paddles which are attached to opposite legs
of the X. The other two legs are bare, maybe the manufacturer uses them
when they make four paddle models.

What I prolly should have done before I started this thread was to
slowly move a strong magnet towards the radiometer while it was stopped
to see if it caused any movement or tilting of the vane assembly. That
prolly would have told me whether my assumption that magnetization is
making the metal hub "stick" to the needle has any legs to it.

Dumb of me not to think of that, as right in the next room there's a
pretty strong suspension magnet on the little diamagnetic demo I built a
few years ago.

If you've never played with diamagnetics, it's free floating objects
right before your eyes, sort of counterintuitive to what we usually
think about magnets and/or gravity:

http://home.comcast.net/~jwisnia18/jeff/diamag.html

I'll run a magnet test first before I try demagnetizing with my 250 watt
Weller as suggested.

Report later.....

Thanks guys,

Jeff


Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim light
and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle or
twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

Looking at the hub assembly under magnification, the metal X piece looks
like it's likely made of aluminum.

But, the "sticking" effect was still there, With the rotor well centered
on the needle, if I tilt the bulb slightly so the hole in the metal X
piece stars moving off center with respect to the needle it soon reaches
a point where the rotor will suddenly "jump" the rest of the way so the
hole in the X piece hits the needle with an audible click and sticks
there even when I return the unit to an upright position. I have to
jiggle it until the rotor ends up centered asgain.

I'm thinking now it's probably an electrostatic effect, but I don't know
what may have happened to make it to start happening now. I'm pretty
sure It didn't do that a dozen or so years ago when it was new.

I tried wiping the outside of the bulb with some antistatic fluid we use
on the glass of our photocopier, but that didn't help.

I guess nothing lasts forever.....

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

According to Jeff Wisnia :
Jeff Wisnia wrote:

[ ... ]

Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim light
and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle or
twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

The magnet would equally magnetize the hub and the needle (If
both were not similarly magnetizable, you would not be having this
problem in the first place.)

I think that your first assumption that it was magnetized was
correct, and that your test with the permanent magnet proves or
disproves nothing -- it give the behavior which I would have expected.

Looking at the hub assembly under magnification, the metal X piece looks
like it's likely made of aluminum.

Looking at mine, it looks as though it was stamped out of cheap
tin-plated steel stock (tin can material), with the four arms twisted 90
degrees bent at right angles, stuck through slots in the corners of the
flags, and then bent over to clamp the flags in place. Yes, it could be
aluminum, but it looks more like tin can material, and that would be
cheaper at the time this was manufactured.

However -- mine shows no reaction to a rather strong magnet, so
it must be aluminum in my case at least.

The bearing is a combination of a tiny glass test tube (sorta)
and the upright needle.

FWIW -- mine has a very cheap black plastic base vacuum-formed
from thin plastic. Just barely enough to support the globe.

So -- still try the degaussing -- with a coil from a soldering
gun or various other things which have been suggested.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Jeff Wisnia wrote:

Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim light
and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle or
twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

Looking at the hub assembly under magnification, the metal X piece looks
like it's likely made of aluminum.

But, the "sticking" effect was still there, With the rotor well centered
on the needle, if I tilt the bulb slightly so the hole in the metal X
piece stars moving off center with respect to the needle it soon reaches
a point where the rotor will suddenly "jump" the rest of the way so the
hole in the X piece hits the needle with an audible click and sticks
there even when I return the unit to an upright position. I have to
jiggle it until the rotor ends up centered asgain.

I'm thinking now it's probably an electrostatic effect, but I don't know
what may have happened to make it to start happening now. I'm pretty
sure It didn't do that a dozen or so years ago when it was new.

I tried wiping the outside of the bulb with some antistatic fluid we use
on the glass of our photocopier, but that didn't help.

I guess nothing lasts forever.....

Jeff


Hey! Has anyone suggested that it may be a result of "deforming" the
tip of the needle or the bearing that rests on it???? Some sort of a
"ring" worn in the bearing or some "unspecified" deformation of the
needle.
Some more examination please.
...lew...

Lew Hartswick wrote:
Jeff Wisnia wrote:


Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim
light and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle
or twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

Looking at the hub assembly under magnification, the metal X piece
looks like it's likely made of aluminum.

But, the "sticking" effect was still there, With the rotor well
centered on the needle, if I tilt the bulb slightly so the hole in the
metal X piece stars moving off center with respect to the needle it
soon reaches a point where the rotor will suddenly "jump" the rest of
the way so the hole in the X piece hits the needle with an audible
click and sticks there even when I return the unit to an upright
position. I have to jiggle it until the rotor ends up centered asgain.

I'm thinking now it's probably an electrostatic effect, but I don't
know what may have happened to make it to start happening now. I'm
pretty sure It didn't do that a dozen or so years ago when it was new.

I tried wiping the outside of the bulb with some antistatic fluid we
use on the glass of our photocopier, but that didn't help.

I guess nothing lasts forever.....

Jeff


Hey! Has anyone suggested that it may be a result of "deforming" the
tip of the needle or the bearing that rests on it???? Some sort of a
"ring" worn in the bearing or some "unspecified" deformation of the
needle.
Some more examination please.
...lew...

Doubt it lew, read on....

First, after I posted last night I tried a three turn coil of #12 wire
in my 250 watt Weller gun carefully moved over the bulb while it was on
and removed several feet away before I released the gun's trigger. It
did squat about removing the "sticking" effect.

So, the radiometer and I went to sleep for the night and when we woke up
early this morning we were BOTH back to normal. It was overcast outside
at dawn and there wasn't enough sunlight coming in through the window to
move the radiometer.

But, to my angst and amazement it no longer displayed that "sticking"
effect. I could slowly tilt it to from side to side and the rotor stayed
horizontal until the needle reached the limits of the hole in the X
shaped metal piece. No sudden "jumping" effect anymore.

Poiting a flashlight at it made it start turning.

I'm now strongly leaning toward it being an electrostatic effect and the
charge(s) must have leaked off in the dark overnight.

Maybe there's a photoelectric effect from the coatings on the vanes
which makes the rotor assembly charge up after light hits them for a
while. The "light" sides of the vanes look like they're covered with a
light yellow paint and the "dark" sides look like they're matte black paint.

'Tis interesting to say the least. I've posted to sci.physics to see if
the effect my radiometer displayed is perhaps known and understood by
some of the cognicenti there. Thus far all I've received on that
newsgroup are a couple of useless remarks made by people who sound like
their entire alimentary tracts have somehow become reversed.

Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

On Fri, 07 Apr 2006 23:59:55 -0400, Jeff Wisnia
wrote:

Jeff Wisnia wrote:

Martin H. Eastburn wrote:

The one we had at home as a kid had a glass hub.

If you have a metal one - did the needle eat it up and finally cut it ?
Have you turned it upside down and such ?


The "hub" looks like an inverted subminiature glass test tube about 5/8"
long and 1/8" ID. A little stamped metal X shaped piece with an extruded
center hole is either press fitted or adhesively attached to its open
end. The paddles are attached to the legs of the X.

My radiometer only has two paddles which are attached to opposite legs
of the X. The other two legs are bare, maybe the manufacturer uses them
when they make four paddle models.

What I prolly should have done before I started this thread was to
slowly move a strong magnet towards the radiometer while it was stopped
to see if it caused any movement or tilting of the vane assembly. That
prolly would have told me whether my assumption that magnetization is
making the metal hub "stick" to the needle has any legs to it.

Dumb of me not to think of that, as right in the next room there's a
pretty strong suspension magnet on the little diamagnetic demo I built a
few years ago.

If you've never played with diamagnetics, it's free floating objects
right before your eyes, sort of counterintuitive to what we usually
think about magnets and/or gravity:

http://home.comcast.net/~jwisnia18/jeff/diamag.html

I'll run a magnet test first before I try demagnetizing with my 250 watt
Weller as suggested.

Report later.....

Thanks guys,

Jeff


Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim light
and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle or
twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

Looking at the hub assembly under magnification, the metal X piece looks
like it's likely made of aluminum.

But, the "sticking" effect was still there, With the rotor well centered
on the needle, if I tilt the bulb slightly so the hole in the metal X
piece stars moving off center with respect to the needle it soon reaches
a point where the rotor will suddenly "jump" the rest of the way so the
hole in the X piece hits the needle with an audible click and sticks
there even when I return the unit to an upright position. I have to
jiggle it until the rotor ends up centered asgain.

I'm thinking now it's probably an electrostatic effect, but I don't know
what may have happened to make it to start happening now. I'm pretty
sure It didn't do that a dozen or so years ago when it was new.

I tried wiping the outside of the bulb with some antistatic fluid we use
on the glass of our photocopier, but that didn't help.

I guess nothing lasts forever.....

Jeff

Ah ****ing ha as we academophobes say now and then.

Static attraction can be a problem. My first job was working with
electrostatically suspended gyroscopes.

Try bombarding your radiometer with UV that might ionize the sparse
gas within enough to dissipate static charge.

Don Foreman wrote:

On Fri, 07 Apr 2006 23:59:55 -0400, Jeff Wisnia
wrote:


Jeff Wisnia wrote:


Martin H. Eastburn wrote:


The one we had at home as a kid had a glass hub.

If you have a metal one - did the needle eat it up and finally cut it ?
Have you turned it upside down and such ?


The "hub" looks like an inverted subminiature glass test tube about 5/8"
long and 1/8" ID. A little stamped metal X shaped piece with an extruded
center hole is either press fitted or adhesively attached to its open
end. The paddles are attached to the legs of the X.

My radiometer only has two paddles which are attached to opposite legs
of the X. The other two legs are bare, maybe the manufacturer uses them
when they make four paddle models.

What I prolly should have done before I started this thread was to
slowly move a strong magnet towards the radiometer while it was stopped
to see if it caused any movement or tilting of the vane assembly. That
prolly would have told me whether my assumption that magnetization is
making the metal hub "stick" to the needle has any legs to it.

Dumb of me not to think of that, as right in the next room there's a
pretty strong suspension magnet on the little diamagnetic demo I built a
few years ago.

If you've never played with diamagnetics, it's free floating objects
right before your eyes, sort of counterintuitive to what we usually
think about magnets and/or gravity:

http://home.comcast.net/~jwisnia18/jeff/diamag.html

I'll run a magnet test first before I try demagnetizing with my 250 watt
Weller as suggested.

Report later.....

Thanks guys,

Jeff


Well, when I got home tonight the first thing I did was take a high
energy magnet and move it toward the radiometer, which was in dim light
and not turning.

The magnet had no effect on the vane assembly, it didn't tilt, wiggle or
twitch even when the magnet was right against the glass bulb.

So much for my thinking it was magnetism causing the metal X piece of
the hub to stick to the needle.

Looking at the hub assembly under magnification, the metal X piece looks
like it's likely made of aluminum.

But, the "sticking" effect was still there, With the rotor well centered
on the needle, if I tilt the bulb slightly so the hole in the metal X
piece stars moving off center with respect to the needle it soon reaches
a point where the rotor will suddenly "jump" the rest of the way so the
hole in the X piece hits the needle with an audible click and sticks
there even when I return the unit to an upright position. I have to
jiggle it until the rotor ends up centered asgain.

I'm thinking now it's probably an electrostatic effect, but I don't know
what may have happened to make it to start happening now. I'm pretty
sure It didn't do that a dozen or so years ago when it was new.

I tried wiping the outside of the bulb with some antistatic fluid we use
on the glass of our photocopier, but that didn't help.

I guess nothing lasts forever.....

Jeff


Ah ****ing ha as we academophobes say now and then.

Static attraction can be a problem. My first job was working with
electrostatically suspended gyroscopes.

Try bombarding your radiometer with UV that might ionize the sparse
gas within enough to dissipate static charge.

Matter of fact I did just that with the little tin can, doorbell xformer
and GE "Germicidal UV lampbulb" rig I'd thrown together about 25 years
ago to clear UV eraseable EPROMS. I suspect the glass in the radiometer
bulb blocked the UV, cause it didn't help.

Those 6 volt UV producing bulbs were used in household clothes dryers
around the 50s to 70s. I think they mostly just created a little ozone
which made the clothes smell "fresher". Never did find out eggsacly how
they worked. They look just like an automotive tail lamp bulb of that
era, and had a filament in them. When lit if you "risked one eye" by
glancing at them you'd see a purple glow inside.

Anyway, I'm pretty well convinced it was static attraction, from the way
it "went away by itself" overnight.


Jeff (Who has learned that things which go away by themselves usually
come back by themselves....)

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Jeff (Who has learned that things which go away
by themselves usually
come back by themselves....)

--
Jeffry Wisnia

Isn't that one of Murphy's laws?

Tom