h a l f b a k e r yQuis custodiet the custard?
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The chronometer was once the most important piece of equippent on a ship. A good chronometer was the most reliable way to determine longitude. The only other practicable way was to guess at the time, turn the sextant crooked, measure the distance between the moon and a star, and get an approximate
time with which to start over again, and again, and again until a reasonably accurate time was achieved.
Today, with LCD, quartz crystals, GPS, and all sorts of other wizardry, the true chronometer is a thing of the past, except for the proud few who continue to use a sexant.
For those proud few, a chronometer is a must, and not just any chronometer, but a mechanical one, a swiss precision, marine grade clockwork masterpiece, almost capable of going toe to toe with the atomic clocks as far as reliability is concerned.
Speaking of the swiss, they also make some pretty good wrist watches that are "self winding." Self winding watches have counterweights that use some of the motion of your wrist to wind their spring.
Why a chronometer that would be self winding should not be available is a mystery to me. Chronometers are designed to be used on ships, which tend to rock at least a little due to the fact that they spend their time floating on water. While this motion has not been harnessed for electrical power, or other purposes, it should be more than enough to power a good chronometer.
alt.horology
http://groups.googl.../group/alt.horology
The alt.horolgy group via google's interface. [zen_tom, Aug 14 2006]
[link]
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...so you're saying, make a very accurate self-winding clock. |
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You might want to change this to another catagory, unless you are seeking to wind up swiss swimmers. |
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I wasn't too keen on the categories, but I did not see any "Sailing" category. I saw that other boating and sailing posts had been placed under water sports, and since boating and sailing is a water sport... |
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Is there a way to start a new category, or is there a better category that I missed? |
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On land, the reliable power, and constant communication makes knowing the exact time rather unimportant. At sea, where time and navigation are essential, and where power loss and communication loss is more common, there is an actual use for the device. Thus, for lack of a boating and sailing category, I tossed it into water sports, although I wouldn't mind winding up some of those cute syncronized swiss swimmers. |
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Indeed. Next we'll get some wiseguy suggesting a self-winding town clock, for areas prone to earthquakes. |
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now that you mention it, earthquake
windings sound good. although they
would be few and far between for most
places that you think about for
earthquakes. |
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Good idea Tcarson. Sadly, "Eartquake power" isn't getting much positive feedback. |
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I'm sure these are baked all over the place - Omega Seamaster, Tag Heuer Kirium - among many many others. |
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When wanting to know about something horological, I find the alt.horology group populated with some (apparently) knowledgeable folks. I google'd this group with the phrase 'automatic chronometer' to get the names listed above. |
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Chronometer trivia: On ships of the British Navy, two chronometers were carried so that you could tell if one was losing or gaining time. Chronometers had two cases - you opened the outer case to wind them. The standard penalty for opening the inner case while at sea was death, so important were these instruments in determining longitude. |
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Chronometers for use on long sea voyages had to be extremely accurate even by modern consumer-product standards. A +/- 15ppm crystal would have been considered tolerable, but barely. |
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As for carrying two chronometers, I thought that was to allow for the possibility of one failing completely; otherwise, if they run at different speeds there's no way to tell which is right. When chronometers became affordable, ships would carry three. |
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The two chronometers would be compared against each other, and the two times listed in a Rate book. |
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When the differences got sufficiently large, sailors would perform lunar calculations to try and get a better time (while at sea) or they could watch the coast (if near land) where shore stations would perform ball drops (like the ball in New York for New years) to mark time. |
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Most watches have a fairly steady rate of gain or loss, and after sufficient usage, captains could often determine this, and calculate most of it out with a high degree of accuracy. Modern navigation books generally reccomend a similar process. |
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I fully understand using a rate book--if one discovers on an outward voyage that one's clock is running a second per week slow, it's far better to adjust one's calculations than to try to monkey with the clock. But in the absense of external signals, how is one supposed to handle differences in observed (compensated) time measurements? Since it's unlikely that any anomolies will affect the two timekeepers equally and oppositely, going with the "average" time will simply cut in half the error from choosing the one that's wrong. |
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BTW, how hard would it have been to maintain a ship's chromometer at a temperature roughly equal to the boiling point of water? To be sure, the boiling point of water can vary with atmospheric conditions, but trying to design a clock to yield acceptable accuracy in the temperature range 210F to 215F would seem easier than trying to design one for acceptable accuracy from 40F to 110F. |
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Of course, once John Harrison managed a portable timekeeper with acceptable accuracy, that pretty much "solved" the problem, but it's still something I've pondered. |
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I've also wondered whether John Harrison would have built "H4" if, before he built H2, he'd made a simple modification: construct it so the neutral positions of the balance arms are are 45 degrees from the line between their centers (as opposed to being perpendicular). Thus, they'd sit "//" and oscillate between "|-" and "-|". The oscillation would then have had no effect on the moment of inertia about axis connecting the centers of the two rods. |
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