For those who put up with my blathering about what might be screwing up
my 10+ year old radiometer a few weeks ago, here's "the rest of the story."

I gave up and plopped down $8.95 (Plus S&H) for a brand new radiometer.
It's now sitting on the kitchen window sill spinning like an NPR news
anchor when a little bit of sun falls on it.

http://radiometer.hobbytron.com/Radiometer.html

Interestingly, the cardboard disk glued on its base bears eggsackly the
same wording in the same type font as my old one, right down to the
bottom line where the old one declared "Made in China" and the brand new
one says "Made in India".

I tucked the old radiometer away where my heirs will find it and
undoubtedly chuck it out. I just couldn't bring myself to bust it open
to see whether the needle pivot was no longer as sharp as it needed to
be and maybe creating too much friction drag.

I guess I'll never really know just why the old radiometer "wore out".
I'll just have to blame it on old age.

Sort of like what this homo sapiens is finding out about himself, as I
get older everything either dries up, leaks or breaks. G

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Life is like toilet paper; it runs out faster the closer you get to the
end of the roll."

Jeff Wisnia wrote:


For those who put up with my blathering about what might be screwing up
my 10+ year old radiometer a few weeks ago, here's "the rest of the story."

I gave up and plopped down $8.95 (Plus S&H) for a brand new radiometer.
It's now sitting on the kitchen window sill spinning like an NPR news
anchor when a little bit of sun falls on it.

http://radiometer.hobbytron.com/Radiometer.html

Interestingly, the cardboard disk glued on its base bears eggsackly the
same wording in the same type font as my old one, right down to the
bottom line where the old one declared "Made in China" and the brand new
one says "Made in India".

I tucked the old radiometer away where my heirs will find it and
undoubtedly chuck it out. I just couldn't bring myself to bust it open
to see whether the needle pivot was no longer as sharp as it needed to
be and maybe creating too much friction drag.

I guess I'll never really know just why the old radiometer "wore out".
I'll just have to blame it on old age.

Sort of like what this homo sapiens is finding out about himself, as I
get older everything either dries up, leaks or breaks. G

Jeff

I missed that whole thread. Those things need to be in a vacuum high
enough that the free path of the gas inside is long compared to the
dimensions of the rotor (I don't know if that means 100% or 1%, just
'long'). Perhaps it just leaked.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

In article ,
Tim Wescott wrote:

I missed that whole thread. Those things need to be in a vacuum high
enough that the free path of the gas inside is long compared to the
dimensions of the rotor (I don't know if that means 100% or 1%, just
'long'). Perhaps it just leaked.

I missed the thread too, but there are TWO versions of Crooke's that
turn in OPPOSITE directions. At high vacuum, the reflective sides get
more impulse from light and turn away. At low vacuum, the black side
gets hotter and the air molecules leave the hot side faster so the black
side turns away (slower). At some intermediate vacuum the forces
balance and it doesn't turn.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Nick Hull wrote:
In article ,
Tim Wescott wrote:


I missed that whole thread. Those things need to be in a vacuum high
enough that the free path of the gas inside is long compared to the
dimensions of the rotor (I don't know if that means 100% or 1%, just
'long'). Perhaps it just leaked.


I missed the thread too, but there are TWO versions of Crooke's that
turn in OPPOSITE directions. At high vacuum, the reflective sides get
more impulse from light and turn away. At low vacuum, the black side
gets hotter and the air molecules leave the hot side faster so the black
side turns away (slower). At some intermediate vacuum the forces
balance and it doesn't turn.

Oooh -- I want the _pair_. Isn't the impulse from light pressure very
weak, though? Can the high-vacuum version be made cheaply?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html