Another intersting tale about Harrison and Longitude.

[roughbarked]

 

[Dr. Jon]

I usually find this guy very interesting and this is good story but he has made some serious errors:

1) It was John not George Harrison !!!! George was a Beatle

2) His expalantion of maintaining power shows that that does not understand that Harrison made two inventions that long outlived him:

a) The first is for fusee and other drives using a cable of chain. Winding the chain or cable backs up the gearing in simple arrangements. At Harrison's time this was not an issue for watches since they were not accurate enough for the reversal and loss of time keeping during winding to matter. Early pendulum clocks had a different form of maintianing power, which most makers had abaondoned by Harrison's time.

With his timepieces irregularity during winding, it did matter and he invented "Harrison's maintaining power" It has since been used in most fusee timepieces, and a variant is in Vienna regulator clocks as well as most modern high end weight driven clocks.

b) His second device was not so much an invention but and improvement, the remontoire. This is small spring wound frequently by the mainspring to provide constant force to the escapement. The force is not really constant, it cycles over the run time, but this cycle is the same over the entire run of the mainspring driving it.

It was the essential element for the success of H4, K1, and similar early marine timekeepers, largely obsoleted by free balances such as the ones using a detent escapement. H4 ans K1 had both the fusee maintaining power and a remontoire.

Another Harrison invention he seems to have ignored is the bimetallic temperature compensation device. It remains in use today for thermostats and was essential for marine timekeepers from Harrison's era to the mid 20th century when special alloys replaced it in balance wheels.

Aside from this I found it very well done.

 

[roughbarked]

Yes I noted the George Harrison thing too as well as the omissions.

 

[Dr. Jon]

I finally caught the end and there he refers John Harrison.


Also, and this is not a real error, this video takes the view that Maskelyne was a villain.

He certainly gave Harrison a hard time, but he had a view that is sensible. The method had to be practical and Harrison Timepieces were expensive. Maskelyne promoted Earnshaw and helped him a lot. Recent research has shown that Maskelyne never profited from his methods and was essentially an honest of very difficult broker.

Maskelyne was trying to make navigation affordable. Harrison timepieces cost 500Guineas (G) or about 1/40 of the Longitude Prize, a lot for something that was to go on every ship.

The subsequent Mudge machines cost 150G. Arnold chronometers cost 64G and Earnshaw's, which MAskelyne favored after trialing them, cost 35 until ship operators bid them up over 100.

Also, and this is mistake the docents at Greenwich also make, the mariners and navigators did not set their chronometers by the time ball, as he said in the video.

Once a marine chronometer is going it is almost never set again unless or until it stops. What they did was to compare their chronometers to the time ball or other signal and record the difference.

 

[gmorse]

Hi Jon,

...this video takes the view that Maskelyne was a villain.

I believe that this was largely promulgated by Dava Sobel's book 'Longitude' on Harrison and his long struggles.

Regards,

Graham

 

[Dr. Jon]

Dava's book certainly promoted this view but I think it long predates her book.

A large part of the animus was due to the London chronometer group not liking Earnshaw and vice versa. Earnshaw was an outsider, was charging less and usually his timepeices out performed he others, even when he was not allowed to use the most current balance spring technology, and several owed him money for timepieces he had made for them and they had signed and taken credit for their performance.

This changed my view