I tested my cheapo magnets with double pane glass (1/4" thick) and the bonding force was a lot weaker- not strong enough to hold a small rod gnomon.
Art Krenzel's super strong Neodymium magnets would surely work. He told me about this company that sells supper strong magnets at http://www.kjmagnetics.com They advertise them as the world's strongest magnets. They have just what we need! They're called "Mounting Magnets". The top piece is cup shaped and fits nicely over the bottom magnet so they won't slip around. The top non-rustable stainless steel piece even comes with a threaded hole that you could screw a threaded gnomon rod into!!! And, they come in all sizes- including metric These things are PERFECT! Here is a sample of one of them. See: http://www.kjmagnetics.com/proddetail.asp?prod=MMS-D-XC They also have rubber, plastic and teflon coated magnets! See: http://www.kjmagnetics.com/products.asp?cat=164 Important Safety Warning! Read Before You Order and Use the Magnets Handling them with care is necessary to prevent personal injuries, property damages and magnet damages. 1. Neodymium magnets are brittle; they can be broken or can splinter in a collision. One should wear gloves and protective glasses when handling these magnets, because splinters could disengage and fly from the magnets. 2. Normal Neodymium magnets will lose their magnetic properties if heated above 175°F (80° C). Higher temperature rare earth neodymium magnets are available in our store. 3. The strong magnetic fields of neodymium magnets can damage items such as television, computer monitors, credit cards, bank cards, computers, diskettes and other data carriers, video tapes, mechanical watches, hearing aids, loud speakers and VCRs. Pace-makers may be damaged or switch to "Test Mode" in the presence of a strong magnetic force, if a pace-maker is in use, keep a minimum of 3 feet distance. 4. You should avoid having constant contact with magnets of any size and keep a distance of at least 3 feet to large magnets. 5. Children should not be allowed to handle neodymium magnets as they can be dangerous. Small magnets pose a choking hazard and should never be swallowed or inserted into any part of the body. 6. Under no circumstances should you try to cut, saw or drill the Neodymium magnets! Not only would the magnet break, but the resulting dust from the magnet is very flammable. Neodymium magnets should never be burned, as burning them will create toxic fumes. -----Original Message----- From: Mike Shaw [mailto:[email protected]] Sent: Tuesday, January 04, 2011 4:29 PM To: John Carmichael Cc: Sundial List Subject: Re: Glass on Glass Mosaic Indoor Sundial Windows John Nobody has mentioned double glazing yet. I assume that you don't bother with that in Arizona. Will the magnets still be OK to use through two thicknesses of glass with an air space between? Mike Shaw 53.37N 3.02W www.wiz.to/sundials --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
