Hi Edley, You are literally bending over backwards to try to justify this design. But the patent does say the time scale and shadow pointer are.."both revolvable about a common axis, said axis to be held in a vertical position during the reading of the dial" (column 1, line 31). So it is a horizontal dial, not equatorial.
As for magnetic variation, it would be possible to allow for this to some degree in the placing of the time zone marks. But the picture makes clear that this was not in fact done, as they are all marked in 15 degree intervals. The patent goes on to claim the watch can be used "over the whole world without any difficulties depending on the number and the kind of the marks" which is utter rubbish as it is totally useless in the tropics, for instance. A southern-hemisphere version could be made by merely reversing the order of the hour numbers - perhaps this is what he had in mind. It is well known that you can very approximately find north by pointing the hour hand of a watch to the sun, mentally bisecting the angle between the hand and noon to find north-south. This invention merely reverses the process - given north-south, find the time. Why you wouldn't put a wristwatch movement inside the case instead of the sundial escapes me. Regards Chris ----- Original Message ----- From: Edley McKnight To: Chris Lusby Taylor ; [email protected] ; [email protected] Sent: Tuesday, March 09, 2010 5:16 AM Subject: Re: Would this dial work? Hi Peter, Chris, Patrick, and all. I agree with Chris if the plane of the watch is positioned horizontally, but from the patent, there is no regard taken for positioning the watch other than to magnetic north. If the central axis of the watch was made parallel with the earth's axis it would then function even better as an equatorial dial. Of course it would have to be held upside down in winter time and would have the times backward. One would also hope that magnetic deviation was not too far off. ( It's about 20 degrees about our area. ) The two threads function much like rotating a knife blade to minimise the shadow thickness. I wonder if many of them were ever made. Best Wishes! Edley. > Hi Peter, Patricket al, > I've had a brief look at the patent which, by the way, dates from > 1953. > It is, as you supposed, an azimuth dial. The two shadow-casting > strings, f, are horizontal, one > above the other. The ring, d, must be turned until their shadows > coincide, in other words when > they indicate the sun's azimuth. The "time" is then indicated on an > equiangular scale that is > carried by a compass needle, so 12:00 is always on magnetic > North-South. > So, as a sundial, it is very primitive. Its only sophistication lies > in the way the time shown can be > offset to indicate any desired timezone. But the time shown will be > accurate only at noon, as it > supposes that the sun's azimuth changes by 15 degrees per hour. > When I first saw the diagram I imagined it was a bifilar dial. I > think you really could make a > passably accurate portable bifilar dial in a very similar manner, > but this is not it. > Regards > Chris > 51.4N 1.3W > > ----- Original Message ----- > From: [email protected] > To: [email protected] > Sent: Tuesday, March 02, 2010 8:48 PM > Subject: Re: Would this dial work? > For those having difficulty accessing the URL a better one for > this would be: > http://www.freepatentsonline.com/2637108.pdf > > Regards > > Patrick > > > > -----Original Message----- > From: Peter Mayer <[email protected]> > To: 'sundial list' <[email protected]> > Sent: Tue, Mar 2, 2010 2:05 pm > Subject: Would this dial work? > > > Hi, > A while ago I came across US Patent 2637108 for a sundial watch > by > Viesturs(http://www.freepatentsonline.com/2637108). The patent > charmingly > suggests that it may be used 'for play and sport, where a good > mechanical watch > is endangered by pressure, sand and water, and therefore not > always adapted to > be carried around. As play and sport are mostly exercised > during sunny weather, > a portable sundial can well replace a mechanical watch on these > occasions". > As may be seen from the copy of the illustration which I've > attached, it > appears to be an equal-angle dial. It has a compass (label b)to > allow N-S > alignment of the dial. The shadow is cast by two vertical > threads (label f). > After some pondering, I have concluded that the sundial may > be a form of > magnetic azimuth dial, but this could well be wrong. > My question is: would this dial work? > > best wishes, > > Peter > > -------------------------- > Peter Mayer > Politics Department > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8303 5606 > Fax : +61 8 8303 3443 > e-mail: [email protected] > CRICOS Provider Number 00123M > ----------------------------------------------------------- > This email message is intended only for the addressee(s) > and contains information that may be confidential and/or > copyright. If you are not the intended recipient please > notify the sender by reply email and immediately delete > this email. Use, disclosure or reproduction of this email > by anyone other than the intended recipient(s) is strictly > prohibited. No representation is made that this email or > any attachments are free of viruses. Virus scanning is > recommended and is the responsibility of the recipient. > > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > > > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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