[time-nuts] A different timenuts interest

Eugen Leitl eugen at leitl.org
Thu Jul 22 10:04:36 EDT 2010


On Wed, Jul 21, 2010 at 10:40:48PM -0400, Bob Bownes wrote:
> Silly me, I just realized you need to compensate for the change in
> length with temperature.

You could use an Invar wire.
 
> This sounds like a great project!
> 
> 
> On Wed, Jul 21, 2010 at 10:26 PM, Bob Bownes <bownes at gmail.com> wrote:
> > There is at least one in DC, at the Smithsonian iirc.
> >
> > RPI, where I went to college, had one in the 3 story stairwell in the
> > library. Don't know if it is still there.
> >
> > I remember one someplace in London too.
> >
> > Someone mentioned temperature compensation. What would you need to
> > compensate for? Temp change in the wire wouldn't effect the rotation
> > as far as I can tell. Swing length might be different based on temp of
> > the wire I guess, but with a long pendulum, I think the magnet is
> > going to way overcome that issue.
> >
> > The one @ RPI had issues due to air movement in the shaft, but that's
> > a different problem.
> >
> > I suppose the right method is to use a GPS disciplined oscillator and
> > the appropriate divider to drive the magnet under the floor. :) To cut
> > down in draft induced drift and jitter, you'd have to put the whole
> > thing in a vacuum though!
> >
> >
> >
> > On Wed, Jul 21, 2010 at 10:13 PM, Richard (Rick) Karlquist
> > <richard at karlquist.com> wrote:
> >>
> >>
> >> Hal Murray wrote:
> >>
> >>> Several years ago, I found a web site for a commercial place that made
> >>> them for museums.  (I forget why I was looking for that sort of stuff.)  You
> >>> might find interesting stuff/ideas via google but I didn't find a similar
> >>> site with a bit of searching.
> >>>
> >>
> >> The Museum of Science and Industry in Chicago had one when I lived
> >> there in the 1960's.
> >>
> >> Rick N6RK
> >>
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> >
> 
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-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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