Rhetorical Question

oldgit said:
Absolutely correct, was it a ship wreck in Wales that led Fitzroy to getting the ball rolling. ?
No doubt you are well aware of the excellent book on the subject " Longtitude" and something along the same lines "The Map that changed the World."
Think the clocks at Greenwich are actually copies ?
A fascinating story.
Click to expand...

They weren't copies when I last went there, in about 1981. This was before the popular book, and there was little fuss made of them at the museum, though they were well-known to informed people. I was absolutely amazed at the sight of them; they were so intricate and beautiful, and the jump from H3 to H4 just astonishing. I believe that they have all been fully restored since then, but as far as I remember they were running when I saw them.
 
The museum has just carried out some tests to find out if the clock design was as accurate as claimed.Apparently down in the basement under the main observatory.


"Mr Burgess, with the help of the Charles Frodsham company, based the clock on Harrison’s designs but used modern materials, chiefly duraluminium and invar (a nickel-iron alloy). The mechanism, however, is from Harrison’s instructions.

“This does not claim to be a replica of Harrison’s clock. It claims to be the use of Harrison’s design and concept. It’s important to realise his design goes against everything the establishment has claimed is the best throughout history,” Mr Betts said."

Crying shame when they started charging to visit the place. !
 
oldgit said:
Absolutely correct, was it a ship wreck in Wales that led Fitzroy to getting the ball rolling. ?
No doubt you are well aware of the excellent book on the subject " Longtitude" and something along the same lines "The Map that changed the World."
Think the clocks at Greenwich are actually copies ?
A fascinating story.
Click to expand...

The clocks on display in the free part of the museum are copies, I understand, but faithful to the original. Ther original clocks are on display, but I understand it's in a paid exhibition.

The earlier clocks, H1-H3 have an interesting history. They were in the museum in a deteriorating, non-running condition until the 20th century, when a self-taught enthusiast took on the mammoth task of restoring them to running condition (after WW2, I think - I'd have to look it up). This proved very difficult, a) because Harrison left little documentation and b) because Harrison obviously changed things as he went along - these were, after all, prototypes! In these earlier clocks, Harrison aimed at zero friction in the movement, and used many devices now commonplace (e.g. roller bearings) for the first time. Just determining the order in which the clocks had to be assembled was a major project, and if it wasn't done right, they couldn't be assembled correctly. I understand that making one particular adjustment meant a day stripping the movement down, make the adjustment and then another day to rebuild it...

Because of their low friction design, H1-3 can be run as they are designed not to wear, and have incredibly low friction.

H4, the one on which subsequent chronometers are based, abandoned the low friction part of the design, because the introduction of the balance wheel meant it was no longer necessary for accurate time-keeping. H4 was, of course, reproduced by Larcum Kendall as K1 and K2, the chronometers Cook took on his 2nd voyage. However, the effect of the change in design is that H4 will wear if it runs, and so, although it COULD be run, it is not, to preserve it. Basically, the enormous design changes between H1-3 and H4 produced a chronometer that could be reproduced more-or-less economically by less skilled workers than Harrison! H1 was not completely successful; H3 was the first to be successful on sea trials, but both were complex and difficult to manufacture.

Fortunately, H1-3 are much more fun to watch!
 
Gladys said:
...errr... no they don't. The NMM is free entry, UNLESS there is a special exhibition on, and you may have to pay for that.
Click to expand...

I don’t think that the clocks are in the NMM, Larry. They are in the exhibition at the top of the hill surely? And that does now charge for entry.....
 
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