Negus Chronometer Key Mystery

Discussion in 'Chronometers' started by David D'Apice, Mar 28, 2020.

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  1. David D'Apice

    David D'Apice Registered User
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    Mar 22, 2012
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    Well, I can't say I've seen one of these before -- here's the key to my Negus Chronometer -- it looks as if it had a ratchet or pawl inside the lid, now, something's missing and they glued the whole thing together so there was no more ratchet action. I'm hoping somebody has an image of what the click looked like in this thing -- and I'm not even sure that the long flat clickspring was right. Any images would be of great help. The original cap to this has a pair of dolphins that are gilded -- quite lovely. If I can make a pawl, and locate two screws that are long missing, I can put the whole thing back together. Wish me luck. This is a new land to me --- hope everyone is staying safe and healthy. IMG_1570.jpg IMG_1571.jpg
     
  2. gmorse

    gmorse Registered User
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    Hi David,

    Yes, this is a 'tipsy key', designed so that it's impossible to wind the instrument the wrong way, even if the operator 'has drink taken', hence the name!

    It looks as though there should be a click in one post and its spring on the other; I suggest the click would be on the right-hand post and the spring on the left in your pictures.

    Regards,

    Graham
     
  3. David D'Apice

    David D'Apice Registered User
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    Graham -- I've sketched something here --- let me know what you think. The little brass original spring is pretty fatigued -- I might consider making a new one. Not sure how to temper brass, but the click I'm drawing looks nice.

    IMG_1572.jpg
     
  4. Paul Regan

    Paul Regan Registered User
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    I agree with Graham. Would love to see the rest of the key if possible and the chronometer as well.
    Paul
     
  5. gmorse

    gmorse Registered User
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    Hi David,

    The click is just right, but the spring doesn't need to be brass, steel will be better, and also can be straighter, not bent under at the end.

    Regards,

    Graham
     
  6. David D'Apice

    David D'Apice Registered User
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    Guys -- thanks for your input -- here's the key --- Graham, I believe the spring is shaped as it is because it can't interfere with the screw that holds the dolphins on --- I suppose if went around the outside of it.
    IMG_1575.jpg IMG_1576.jpg
     
  7. gmorse

    gmorse Registered User
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    Hi David,

    Yes, like this, although it would be more elegant to cut the spring out of steel plate rather than bend a piece of old mainspring. The terminal curve needs to be shallow enough to allow the click to rise clear of the ratchet teeth, and the nose of the click has to clear the fixing screw when it's raised. The closer to the click pivot the spring bears on the click, the less the spring needs to be curved to allow the click to rise.

    IMG_1572_edit.jpg

    Regards,

    Graham
     
  8. David D'Apice

    David D'Apice Registered User
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    Graham - you are brilliant --- I'm wondering if they bent the original spring backward to create a pawl of its own -- and that failed --- probably after the original pawl was long gone. If I were to flatten the original spring, I bet it'd line up just like your drawing. This reminds me of the sort of spring one would find on one of those gun black powder flasks. In the illustration we've both created, I'm thinking that by turning the ratchet slightly clockwise, I could, in effect, shorten the length of the pawl.
     
  9. gmorse

    gmorse Registered User
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    Hi David,

    Much the same considerations apply when making a new fusee click.

    Regards,

    Graham
     
  10. David D'Apice

    David D'Apice Registered User
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    Perhaps more like so! IMG_1577.jpg
     
  11. gmorse

    gmorse Registered User
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    Hi David,

    Plenty of clearance there!

    Regards,

    Graham
     
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  12. David D'Apice

    David D'Apice Registered User
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    Seems like it was probably pretty thick piece of stock. I'm wishing I had a french click thick enough to start with, but I can certainly start from scratch with a jeweler's saw!
     
  13. Paul Regan

    Paul Regan Registered User
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    Thanks for showing the key David. Looks like Graham has you on the right track! For all the use that this is going to receive, you could make the click out of brass and the spring out of steel.

    Anybody ever see a chronometer key like that? Quite fascinating.
    Paul
     
  14. Tom McIntyre

    Tom McIntyre Technical Admin
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    Maybe with dolphins, it is a French chronometer. :)
     
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  15. David D'Apice

    David D'Apice Registered User
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    Here's my latest prototype --- a work in progress ---- thanks to you guys -- I hear evidence of a ratchet sound, which is encouraging -- handmade from 1/8" steel. So far, so promising! IMG_1610.jpg
     

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