# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: Harrison's H1
From: George Huxtable
Date: 2009 May 7, 11:10 +0100

```Brad wrote-

I must say the one of the more enjoyable parts of my many visits to the UK
was seeing H1 functioning at the Royal Observatory.  Okay, I realize that
makes me an engineering wonk, but I just couldn't take my eyes off of it.
Wonderful instrument.  A marvel.

I was confused, at first, by the odd analog hands and dials.  For example,
the minutes dial goes from 0 to 59 and from 0 to 59 in one revolution, with
a hand that points to both sides (and the same number).  Why would he do
that?  I finally realized that Harrison was balancing the hands.  Rotating
up would take more energy than rotating down.  Therefore, the clock could
speed or slow down, if we had a hand like modern clocks.  Gravity would play
a part.  Solution: give it two hands that point at the same number on either
side of a dial.  Brilliant!

I wish the horologist nothing but the best of luck.  Bring H1 back to life!

==================

comment from George.

To see the dials Brad was referring to, look at-

http://www.nmm.ac.uk/collections/displayRepro.cfm?reproID=D6783%5F2#content

The upper dial is seconds, on the left minutes, on the right hours, and
below, a count of days.

arrangement, though it would have been simple enough to counterbalance the
pointer with a small blob, or put a balance-weight out of sight on its
shaft. The two-minute seconds hand was an arrangement used on
"astronomical" on-land regulator clocks with a pendulum. On such clocks, the
longer the pendulum was, and the more slowly it swung, the greater the
obtainable accuracy . (That wasn't the case for a balance-wheel marine
timekeeper, as Harrison came to realise by the time he got to H4). A 4-times
longer pendulum meant a halved tick rate, which meant that with conventional
escape-wheel arrangement, it would take two minutes rather than one to make
a turn. So that necessitated a seconds-dial that covered two minutes, and
with unchanged gearing, a minute-hand that covered two hours, and then an
hour-hand that covered 2 x 12 hours. It was sensible, then, to provide a
double pointer, and you could read either end. That isn't so sendible for
the hour-hand; because with such a double-pointer, you can't distinguish
between am and pm, but Lecky, for one, and correspondence to this list, for
another, has emphasised how convenient it would be to have such a 24 hour
dial. However, very few chronometers do so. I have seen a picture from the
1920s of H1 which seems to show only a single-ended pointer for its hour
hand, which would have been handy at sea..

The coil spring that's failed is one of the four, of which you can see the
upper two, right at the top of the picture. What I should have mentioned in
my last posting (but didn't realise it then) was that these springs, as well
as many other components, were missing when Rupert Gould made his
restoration (more a reconstruction) in the 1930s, and he had to make
replacements. When he took the task over, none of these clocks was in
working order, and they had been abandoned for many years, though after his
attentions H1, H2, and H3 have been running ever since. H4, which unlike the
others calls for regular oiling, has only been restarted on special
occasions.

Thanks for GregR for posting that link to the Guardian website.

Jim Wilson's reference to jewelling applies only to Harrison's culminating
effort, K4, which was on completely different lines from its predecessors.
The others had no jewels but achieved almost frictionless motion by allowing
the balance-shafts to rest on a pair of intersecting arcs, which could rock
about slightly, and were counterbalanced. It's the regular movent of all
those balance-bobs, in and out, that create the strong impression of the
clock as a sort-of breathing animal.

Apparently, it's possible to see Betts working on H1 from a gallery at the
museum. I imagine the job will take some time.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

--~--~---------~--~----~------------~-------~--~----~
To post, email NavList@fer3.com
To unsubscribe, email NavList-unsubscribe@fer3.com
-~----------~----~----~----~------~----~------~--~---

```
Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)