[HN Gopher] Interesting features of John Harrison's sea clocks
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Interesting features of John Harrison's sea clocks
Author : surprisetalk
Score : 90 points
Date : 2023-11-24 07:52 UTC (1 days ago)
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(TXT) w3m dump (incoherency.co.uk)
| panki27 wrote:
| These old ship clock were the peak of engineering at the time.
| Accuracy was very much a necessity, being one second off London
| time means a 4 mile error when determining position IIRC.
| anfractuosity wrote:
| Thought this was very interesting -
| https://www.theguardian.com/science/2015/apr/19/clockmaker-j...
|
| It mentions - "scientists revealed that a clock that had been
| built to the clockmaker's exact specifications had run for 100
| days during official tests and had lost only five-eighths of a
| second in that period."
|
| While "a typical quartz clock or wristwatch will gain or lose 15
| seconds per 30 days"
| (https://en.wikipedia.org/wiki/Quartz_clock#Accuracy). You can
| get temperature compensated quartz watches etc. though, which
| perform better apparently, but found it pretty interesting that a
| mechanical clock can best standard quartz technology.
| BiteCode_dev wrote:
| That's certainly hasn't been my experience, all my watches have
| kept an accuracy if a few seconds over a year.
| labcomputer wrote:
| That greatly undersells the accuracy of quartz watches. An
| individual unit may gain or lose 15 seconds per month (though
| that level of inaccuracy would be unusual), but that given unit
| will _consistently_ gain or lose almost the exact same amount
| of time _every_ month.
|
| After you have measured the relative speed of a given quartz
| movement, it becomes trivial to obtain the correct time (for,
| e.g., navigation purposes).
|
| For what it's worth, the NBS and US Naval Observatory switched
| from mechanical (pendulum) clocks to quartz during the Great
| Depression.
| bigdave42 wrote:
| I wonder if this is the first example of government IT project
| specification failure?
|
| What the navy wanted was a simple way to calculate a ship's
| position - which is exactly what they ended up with. What they
| didn't anticipate is that each device would cost twice as much as
| the ship it was going on.
| greggsy wrote:
| That just increases the cost of the ship. It has become part of
| the ship's navigation system. Not really a failure, just a
| justifiably expensive enhancement.
| ldmosquera wrote:
| If you're interested in the subject, the book "Longitude" by Dava
| Sobel (mentioned in Resources) is a very good read with lots of
| historical perspective on how these clocks were built.
| daoboy wrote:
| Seconded! It is a wonderful book. Also an easy read and not
| very long.
| hilbert42 wrote:
| I can't agree more, I've not seen a better book on the
| subject and Sobel's writing makes it an enjoyable read (I
| still have my copy of it).
| throw0101b wrote:
| Made into a four-part mini-series with Jeremy Irons and Michael
| Gambon:
|
| * https://en.wikipedia.org/wiki/Longitude_(TV_series)
|
| * https://en.wikipedia.org/wiki/Longitude_(book)
| jstanley wrote:
| Very enjoyable (albeit long) and available on YouTube:
| https://www.youtube.com/watch?v=LHvt48S9l4w
| ethanbond wrote:
| I was lucky enough to come across this book in elementary or
| middle school and found it absolutely mind blowing. In
| retrospect it exposed me to what are still among the most
| important ideas sloshing around my brain:
|
| 1. The realization of how much of the world has to be
| "invented." Latitude and longitude didn't strike me as an
| invention, but they are, and more interestingly longitude
| specifically is a conceptual invention that more or less had to
| sit downstream of a rather immense physical invention
| (Harrison's clocks).
|
| 2. "The world has a surprising amount of detail": as evidenced
| by looking at H1, H2, etc... there's a lot you have to account
| for to achieve the apparently simple task of measuring time
| aboard a ship.
|
| 3. The social components to invention/discovery/progress: The
| competitions, funding/lack thereof, the need for "evangelism"
| around the different approaches, the need to find patrons (VC's
| basically) to create a breakthrough, etc.
|
| This book would make a great gift to an intellectually-inclined
| young person in your family!
| deutschepost wrote:
| There is a great Map Men Episode about the Longitude Problem[1]
|
| [1] https://www.youtube.com/watch?v=3mHC-Pf8-dU
| lloydatkinson wrote:
| Also worth checking out the authors other posts and projects
| mikewarot wrote:
| I had no idea that Harrison's clocks were so complex. His
| obsession with friction and changing conditions _was clearly
| necessary, in retrospect_ , but WOW. The extensive use of "anti-
| friction" wheels, and even portions of a wheel, is very cleaver,
| but at some point the things look like he's trying to win the
| clockmakers version of an Obfuscated C contest[1].
|
| No wonder the Longitude Board gave him such grief. It must have
| seemed like he was deliberately trying to hide secrets from them.
| Unless you understood how important friction and temperature were
| in causing the drift of clocks at that time, it would have all
| seemed like unnecessary complexity.
|
| [1] https://ioccc.org/
| JKCalhoun wrote:
| Perhaps winning an Obfuscated Clock contest would keep copycats
| at bay and allow you a contract to service the devices for the
| remainder of your life.
| jstanley wrote:
| > like he was deliberately trying to hide secrets from them
|
| It can't have helped that by all accounts he was extremely
| verbose in spoken communication, and almost impenetrable in
| written communication.
| JKCalhoun wrote:
| Fascinated by "lignum vitae" mentioned several times. A little
| googling and I'm even more intrigued by this special wood.
|
| Example, one of the first results to come up:
|
| https://www.core77.com/posts/25224/lignum-vitae-wood-so-bad-...
| jstanley wrote:
| Sadly it is an endangered species so it is illegal to trade
| now, I understand the best way to get it is to buy antique
| crown-green bowls and cut them up.
| hilbert42 wrote:
| Also, lignum vitae used to make good bearings, not only is it
| hard-wearing, 'waterproof' and rot proof when compared to
| most other woods but also it's self-lubricating.
|
| It's a wonderful and useful timber, it's a damn shame it's
| been necessary to add it to the CITES Treaty (as it's such a
| slow grower).
| JKCalhoun wrote:
| Didn't know Crown Green Bowls was a game -- and I assume it's
| the balls that are made from Lignum Vitae.
|
| https://en.wikipedia.org/wiki/Crown_green_bowls
| jstanley wrote:
| Yes, the balls are (historically) lignum vitae. I don't
| know why they're called bowls instead of balls.
| mauvehaus wrote:
| Like many quirks in English, we can blame the French:
|
| https://www.etymonline.com/word/bowls#etymonline_v_32538
|
| Boule is the modern French name for a likely similar game
| (I don't play either). And of course the Italians have
| bocce.
| hilbert42 wrote:
| I saw Harrison's clocks years ago during a visit to Greenwich but
| there was no way I could have fathomed out how they worked from
| such a short visit (even if I were able).
|
| This story surprised me because I'd have thought by now that
| Harrison's clocks would have been analyzed to the nth degree and
| copies of them made given their historical significance.
|
| In recent years we've seen considerable efforts made in trying to
| reverse engineer the Antikythera mechanism so it's surprising a
| similar effort hasn't gone into a full understanding of these
| wonderful clocks, especially given that we have them both intact
| and in good combination.
|
| It seems to me we should not only have a full mechanical
| understanding of these clocks together with a good rationale for
| why Harrison tackled the problem as he did but also that an x-ray
| fluorescence (XRF) analysis should be done on the metals used in
| their construction.
|
| Assuming Harrison used the best materials available in the
| Eighteenth Century then an XRF analysis would give us a better
| understanding of the composition of those materials and of their
| production but also of the metrology methods in use in Harrison's
| time.
| tbensky wrote:
| Happy to see this post on HN. As a college prof, I've spend many
| years studying the history of 1700s navigation and taking student
| groups to Greenwich to see and study H1 (H2, H3 and H4). I love
| these clocks and all of the stories behind them. The serious
| enthusiast will find a lot of technical details on the Harrison's
| clocks in this book https://www.amazon.com/Marine-Chronometers-
| Greenwich-Catalog... and this one https://www.amazon.com/Marine-
| Chronometer-Its-History-Develo.... I've also collected all of my
| pedagogy on 1700s navigation into a this book:
| https://www.amazon.com/Longitude-Time-Navigation-Tom-Bensky-...
| where I dive somewhat into the innards of H1. To answer another
| post: H1 has been fully disassembled and reassembled with XRF
| done throughout.
| hilbert42 wrote:
| _"...fully disassembled and reassembled with XRF done
| throughout._
|
| Well, hopefully, that answers my point about the clocks'
| materials and an XRF analysis. Did that reveal anything of
| significance?
|
| From points/questions raised by James Stanley and my ignorance
| of this recent work it seems these facts ought to be more
| widely known. (Ouch, the price of _Marine Chronometers at
| Greenwich_ unfortunately has to mean that information is
| confined to Diehards.)
| jstanley wrote:
| Is there a way to buy your "Longitude, Time and Navigation"
| book as a physical book?
| hyperthesis wrote:
| If he made the most accurate clock in the world, how would he
| know?
|
| The prize here was for most accurate _at sea_ , so compare with
| more accurate land clocks. But in general?
|
| _If salt should lose its savour, with what shall it be salted?_
|
| _... tried feeling bits of himself to see where he might be
| hurt. Wherever he touched himself, he encountered a pain. After a
| short while he worked out that this was because it was his hand
| that was hurting._ a
| jstanley wrote:
| I think he watched for a particular star to disappear behind
| his neighbour's chimney, from a fixed vantage, on the
| understanding that this should always take exactly 1 day, and
| by measuring how many seconds have elapsed on your clock you
| know how well your clock has kept time over the previous day.
| lizknope wrote:
| After reading Dava Sobel's book 20 years ago I made sure to go to
| Greenwich to see the clocks when I was in London in 2005. They
| are both amazing engineering and works of art.
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