Hi Fritz: Yes, for some vertical dial designs "hovering" gnomons like you described are great. You see them often on near east or near west dials where the gnomon is nearly parallel to the face. Sometimes, though, the building or window frame design doesn't permit their installation, or they are too difficult to install for a non-dialist owner.
The dial I'm making has a "point-in-space" or "nodus-based" gnomon. These can have an advantage over polar axis gnomons because you can design them with only one point of attachment. Most polar axis gnomons need two points of attachment. - If they have support struts, then they have even more. Nodus-based gnomons are usually easier to design, construct and install. Usually they are just a rod that is bolted or screwed into the sundial face or border. If they have a magnet, then you don't need to screw them into the sundial or wall or use bolts. I'm beginning to think that the easiest gnomon to install is a perpendicular nodus-based rod gnomon with a magnetic base. But you are right, there is a time and place for all sorts of gnomon designs, depending on the circumstances. -----Original Message----- From: Fritz Stumpges [mailto:[email protected]] Sent: Friday, January 07, 2011 9:47 AM To: John Carmichael Subject: RE: More on Sundial Magnets Hi again John, I like to try to have the gnomon mount so that it is a little higher up away from the surface of the dial. That way you get a nicer shaped layout than the triangular pie shaped normal dials. This also means that the gnomon mounts somewhere off of the dial face...on some possibly better support structure. Best always, Fritz ________________________________ From: John Carmichael [mailto:[email protected]] Sent: Fri 1/7/2011 5:47 AM To: 'R Wall'; Fritz Stumpges; 'Tony Moss'; [email protected] Subject: RE: More on Sundial Magnets I ordered several different sizes of the rare earth magnets yesterday for testing. They should arrive tomorrow. And I've come up with a magnetic gnomon design. If the tests work out well, I plan on using a magnetic gnomon on this new stained glass sundial that I'm constructing now. I will make a CAD drawing of the design and will share it with you if it is successful. This is the sundial face pattern of the new dial. The gnomon will go in the center of the 1 inch circle that is in the center of the sun at the top. I've come up with a neat idea to prevent slipping and glass cracking. Stay tuned! http://www.flickr.com/photos/jlcarmichael/5321871752/ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of R Wall Sent: Thursday, January 06, 2011 10:14 PM To: Fritz Stumpges; Tony Moss; [email protected] Subject: Re: More on Sundial Magnets Hi all, Everyone who also sent me a private email also had it correct, The "North Pole is Magnetic South". The North pole of the bar magnetic (compass) is the "north-seeking pole". Thanks Fritz, the following is a good link: http://en.wikipedia.org/wiki/North_Magnetic_Pole Thanks all for a bit of fun, Roderick Wall. -----Original Message----- From: Fritz Stumpges Sent: Friday, January 07, 2011 11:13 AM To: Tony Moss ; [email protected] Subject: RE: More on Sundial Magnets Well that could go either way yet! I always thought that the N pole on a magnet really was the North Polarity and that the geographical north pole was actually a South Polarity. Wiki agrees but what's that worth? http://en.wikipedia.org/wiki/North_Magnetic_Pole -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Tony Moss Sent: Thursday, January 06, 2011 2:56 PM To: [email protected] Subject: Re: More on Sundial Magnets On 06/01/2011 20:10, R Wall wrote: > Hi all, > > See if you have the correct answer for this: > > The magnetic polarity of the earth's North Pole, is it North or South. > > You can test it with a correctly marked (N,S) bar magnet suspended on > a cotton string. If the South Pole of the bar magnetic faces North, > then the Earth's North Pole has a Magnetic North polarity. If the > North Pole of the bar magnet faces North the the North Pole has a > magnetic South polarity. > > Roderick Wall. > > In response to a similar question to my teacher in geography I was taught at school that every bar magnet has a 'north seeking' pole i/e. magnetically a 'south' pole. Tony Moss --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1191 / Virus Database: 1435/3362 - Release Date: 01/05/11 --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
