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Pukenui in the Real Far North
The Mariner's Chronometer 
I am the proud owner of a Thomas Mercer chronometer and a Naval Sextant, your books and blogs are a great help in my understand and care of both items. I am a model engineer with a Myford Super 7 and Aciera F3 milling machine + Wolf Jahn watchmakers lathe. Keep up your good work.
Regards
John
Thank you for the excellent site.
I own a Hamilton model 22, and am frankly confused by the necessity of having two chronometers in production during WWII. I’ve read your explanation, which mirrors other explanations, which to me, doesn’t explain the two being produced; After seeing the construction of both, the 21 has a fusee to help regulate the mainsprings force, the 21 a extra-long mainspring which I’m assuming does the same thing. Other than that, the 21c seems to be a more advanced design.
I would think as far as accuracy, the 21 might be more accurate. What am I missing?
The Model 22 was destined for small ships and even large boats where lesser accuracy I suppose was needed, because of their limited endurance. Small boats and ships too tend to be harder on equipment. Think of a large launch slamming into the waves. I know larger vessels can do so as well, but the shocks are cushioned to some extent by the size of the vessel. A chronometer balance is much heavier than a watch balance, though its pivots are only twice the diameter; and they are more prone to break with shocks. The Model 21 must have been more expensive to produce, whereas the technology to produce what is in effect a large pocket watch of high quality already existed. Notwithstanding the long mainspring of the Mod 22, the fusee may well have been much better at delivering constancy of power to a balance that could be made isochronous, whereas the watch regulator of the Mod 22 must inevitably interfere to some extent with isochronicity, since it varies the length of the balance spring. There may be other things that I have not thought of.
Bill.
Thank you Bill, for the explanation. I have enjoyed the discussions here.
Hello Mr. Morris,
I own and have read many times you wonderful book. I just discovered your website/ blog. I’m a long time chronometer collector and am now ready to try becoming a chronometer builder. I would enjoy the opportunity to dialogue with you.
I am in Mountain time ( USA) GMT -6 or 7 and live in Idaho. I’m planning on basing my project around the model 21.
I have an extensive collection and would be pleased to share information and stories.
I would be happy to hear more from you, Peter.
Mr. Morris, I had no idea there was so much to learn about chronometers. I have one and have Questions. On the back it reads – Watch, Gimbal Chronometer, US Army, 2F12802. There is no box or gimbals or the tipsey key. And has only one large hand. A knob at the top moves the hand, and a small pin extrudes on the left side of knob. After gleaning much info regarding chronometers, I’m sure it is not in good repair. What can you tell me about this? I’m not a hobbyist, this was in my husbands things when he passed. Thank you.
Theresa, it sounds like an M22 watch and I guess it looks like the one illustrated here: https://chronometerbook.com/2014/03/
Normally, it would not be possible to turn the hands except by pressing in the small pin while turning the winding know at the top, but it sounds as though the setting mechanism has stuck in the setting position.
It was likely made no earlier than 1941.
Bill
Thanks for your website and sharing all. I’m a french watchmacker who fix also Poljot Marine Chronometer. Your work is very interesting. Here a sharing about detent fabrication from my collegue: http://artsmecaniques.com/fr/chronometre-a-detente-e-dent/
I Have some ruby parts to make the lever if you want.
Best regards! (sorry for my english…)
http://www.artsmecaniques.com
Thank you for the kind comment and the most interesting link to you colleague’s work. Mine is coarse and clumsy be comparison. Please feel free to communicate in French. I can read it well, but write it poorly.
My wife and I will be driving down the valley of the Loire in September and then around the coast of Brittany.
Kind regards
Bill
Dear Mr. Morris,
I have been enjoying your chronometer book and have what seems like a dumb question. How do I set the time on a hundred year old chronometer? Is it as simple as carefully moving the hands in a clockwise direction?
I have inherited a 1912 W. Brocking with an interesting history. Having read ypur cautions, I haven’t done anything more than look at it. It is probably corked. So I want to proceed carefully and would not dare to clean or adjust it myself. It was last cleaned & regulated in 1958 by the Negus brothers of New York.
Thank you very much for any advice.
Best wishes, Bill Matthiesen
Lanesboro, Massachusetts, USA
Sorry, Bill, I missed your question.
The winding key and the square on the end of the minute arbor are usually the same, so by holding the stem of the tipsy key you should be able to set the hands by turning it clockwise. If you simply push the minute hand around with a finger, you risk breaking it.
It is simple and safe to remove the clock from its gimbals and then to unscrew the bezel. You can then tip the movement out into your hand and replace it movement up in the bowl. It it doesn’t drop out, give it a little push with the key. If the balance is corked, removing the wedges doesn’t risk much unless you are very ham fisted. You can then see if it will run by winding it one turn and moving the balance with an artists brush.. If it does run, stop the balance with the brush, replace the wedges, and find someone to overhaul it. Expect to pay up to $500, not because the job is difficult, but because of the mystique surrounding chronometers.