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 <bow...@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 > > <rich...@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 > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.