Thomas Mercer

Discussion in 'Chronometers' started by Flametrap, Nov 17, 2017.

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  1. Flametrap

    Flametrap New Member

    Nov 17, 2017
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    I have just bought at Auction a Thomas Mercer marine chronometer. The serial number is 26553 and is in a case marked Henry Browne & Son Ltd. It looks to be in very good condition, and the auctioneer assured me that it worked correctly. However I cannot get it to run. I phoned Thomas Mercer in London, but they were not very helpful. The only thing they suggested was to shake the chronometer vigorously. Surely not the way to treat a precision instrument! This is the first mechanical chronometer that I have owned. As a sailor I have relied on electronics for my navigation. Any remarks and suggestions welcomed especially as to age, and how I can get the lovely thing to work.
    Thanks and regards,
    Flametrap

    IMG_1404.JPG
     
  2. zedric

    zedric Registered User

    Aug 8, 2012
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    You might want to post this to the chronometer section of the message board, where you are sure to get help. You can find this section under watches...
     
  3. Flametrap

    Flametrap New Member

    Nov 17, 2017
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    Thanks, Zedrick, I'll do that.

    Flametrap
     
  4. gmorse

    gmorse Registered User
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    Hi Flametrap, and welcome to the Forum,

    As Zedric has suggested, there is a dedicated chronometer section under Watches, but rather than post this again, the moderators can move it for you, which I've asked them to do on your behalf.

    Although movements with chronometer detent escapements are not necessarily self-starting the suggestion that you 'shake it vigorously' does seem rather ill-advised on Mercer's part. A gentle swing should be all that's needed, but have you checked to see whether the balance has been immobilised with cork wedges or otherwise locked for transporting it?

    Spring detents are very delicate beasts and should be treated with great care and respect. A damaged one will cost many hundreds of pounds to replace.

    Regards,

    Graham
     
  5. Paul Regan

    Paul Regan Registered User

    Mar 4, 2003
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    Flametrap, I see there is an Alan wrench stored next to the winding key. It likely has a transport hack that has the balance locked. At least I hope it is.
    Paul
     
  6. burt

    burt Registered User
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    #6 burt, Nov 18, 2017
    Last edited: Nov 18, 2017
    I think the Alan wrench is to remove the chronometer tub from the gimbals. If you look at the screw heads on the side gimbals you will see both screw and Alan head provisions. I'm looking at a drawing and that's what it looks like. I also don't think Mercer used a similar type locking device as Hamilton but they may have and if you follow these steps you can find out for yourself.. More than likely your chronometer is probably just "corked" This is a simple fix and only requires the instrument tub removed from the gimgals and the bezel unscrewed. The chronometer is then inverted (be careful) dropping the instrument into your hands while carefully holding the edge of the dial with your fingers. Be also careful not to position your fingers where they will touch the chronometer hands. I usually set the hands to 12 o'clock position with the winding key. Now out of the tub you can then check to see if a small piece of cork or folded paper is under the balance wheel. Carefully remove this corking and give the chronometer a slight quick twist with you wrist and it should run. This procedure isn't that hard to do and there also is a good tutorial on "utube" ( it's for a Hamilton but the procedure is the same) that will take you through these steps with an easy to see visual demonstration of what I have put into print. If you wish but be careful you can set the inverted chronometer mechanism dial down (it is designed not to fall in) into the tub which will act as a movement holder. I really think just check for those wedges, remove them and you will be in business. This "corking" was a required process to protect the delicate balance in chronometers when transporting or shipping and the chronometer was not required to be running.Good luck,be careful and please let us know how you make out?

    Mercer's book has your chronometer built 1968.
     
  7. burt

    burt Registered User
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    #7 burt, Nov 18, 2017
    Last edited: Nov 18, 2017
    Here is what we are looking for, either a paper or cork piece under the balance wheel. When removing, carefully with your finger tip or better yet a set of tweezers gently put straight out the "corking" material parallel to the plates. Be very careful NOT to lift up as you can cause damage to the delicate wheel or other parts of the escapement. I would have posted this earlier but couldn't find the picture. This a Negus instrument but should be no different than yours and you can see how the inverted chronometer "sits" in the tub for a holder. Try not to touch the plates or other parts and handle the chronometer by its edges to avoid possible rusting. Just watching these instruments running is a real joy. If you ever need to re-cork the balance notice that the corking material is placed a close as possible to the balance arm where it joins at the wheel. This is the done to avoid any possible damage to the shape of the wheel.

    Negus 1273 002.JPG Negus 1273 005.JPG
     
  8. Paul Regan

    Paul Regan Registered User

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    A picture of the tub bottom would answer the question.
    Paul
     
  9. Flametrap

    Flametrap New Member

    Nov 17, 2017
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    Thank you all for your input. I took the chronometer to a specialist in Nice (South of France). With some difficulty he got it started. On close examination rust on the several steel shafts was the likely cause of the original malfunction. He further noted that the balance wheel had not been immobilised for transport, but happily there was no apparent damage. He has given me a quote for the general overhaul of the instrument, so it is now down to me to see if the sums add up in my favour. I did contact the seller, an auction house in Holland, who described the chronometer as being in " Good Condition". I gave him them the horologist's report, and they agreed to take the chronometer back and refund the purchase price and costs. All I now need to know is what a Thomas Mercer chronometer dated 1968 and in fully restored condition would be worth. I think I need to pose this question to another forum on this board.

    Thanks to all again,

    Flametrap
     

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