Good idea Tony!
I have a few of these little magnets that I bought at Ace Hardware. They are round, 1 inch in diameter and 1/8 inch thick. Two of them work very well together through a standard piece of glass that is 1/8" thick. I'm sure you can find larger disk magnets- square ones too. Mine are cheap magnets. There might be even stronger ones available somewhere. But since glass is slippery, they can easily slide around on the glass (a big no no for gnomons!). But there is a solution. You can keep the magnets from sliding around by restricting their movement with a border around the outside one that's on the bottom of the gnomon. It could be the lead came of a soldered window or a ring of something (a little curved rod) glued to the window. This will keep the gnomon in the exact proper position. For extra protection, the bottom of the magnets could have a thin piece of rubber glued on. This would prevent the metal magnet from actually touching the glass with a rubber cushion. So if somebody hits the gnomon hard, the metal magnet won't damage the glass. Larry- if you make one of these magnet gnomons for your window dial, will you please photograph it for us to see? John From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Tony Moss Sent: Tuesday, January 04, 2011 6:28 AM To: Sundial Mailing List Subject: Re: Glass on Glass Mosaic Indoor Sundial Windows On 04/01/2011 05:27, John Carmichael wrote: Oh, by the way, on a related subject, I've been thinking about a neat way of firmly attaching a gnomon to a glass sundial that would prevent the glass from breaking if something bumps into the gnomon (i.e. a window washer or house painter) You could attach a gnomon that has a flat steel base to the outside of the glass by placing a magnet on the inside of the glass. I've already tested this and it works great! If somebody bumps into the gnomon, instead of cracking the glass, it simply falls off and you just stick it back on. This method of gnomon attachment is especially easy to do with a perpendicular rod gnomon since it just has one point of attachment. just put a flat steel base on the rod that will attract the magnet. Simple! No drilling, nuts, washers, or soldering needed! Great idea John but I think I would take it a stage further and have a magnet within the base of the gnomon for a mutual strong pull through the thickness of the glass. Ultra-powerful 'rare earth' magnets are easily available these days in a variety of forms. I have a pair which are 1/4" cubes and are impossible to separate by hand with a straight pull. Even sliding them apart is difficult. Google < rare earth magnets > for infor' and availability. Tony Moss
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