Repairs to Hour wheel / Cannon pinion bridge from longcase

Discussion in 'Clock Repair' started by ChrisCam, Jan 14, 2020.

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  1. ChrisCam

    ChrisCam Registered User
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    #1 ChrisCam, Jan 14, 2020
    Last edited: Jan 14, 2020
    Hi,
    Every time I have something to repair I haven't done before I ferret around looking at the alternatives before deciding rightly or wrongly on a coarse of remedy.

    I am faced with repairing / replacing this 18th century hour wheel / cannon pinion bridge which looks very much like it was previously repaired with soft solder. The movement is not of much value but nonetheless deserves a decent repair.

    You can by replacement parts but whether they will suffice is another matter. Just in case they wont has anyone any suggestions on repairing or even making a new one. Any methods warmly received as I never cease to be amazed at the generosity of some forum members.

    One tool I have not yet used is silver soldering. I only have 2 small torches but they are capable to silver solder. Maybe the Smith Little torch is the way to go it's just in the UK the cost of the tanks are a bit excessive.

    i have a lathe and mill and am willing to give any reasonable method a go as I work on the philosophy that a lot of parts cannot be sourced to machine skills are a very good asset to have.

    if attempting to make this part the most obvious issue is bending brass and how one should tackle this.

    Chris

    broken bridge2.jpg
     
  2. David S

    David S Registered User
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    I had a similar problem on a very old movement that had lots of issues. The bridge looked like it perhaps had been replaced at one point with very thin sheet brass and attached to the plate with two screws that didn't appear to be period. The bridge was very thin section and looked like it wasn't going to last.
    I like to preserve as much of the original as possible so decided to just sister another plate underneath it with more contact area.
    front of movement.jpg reinforced bridge side.jpg reinforced bridge top.jpg

    I ended up replacing my two screws with brass rivets.

    David
     
  3. wow

    wow Registered User
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    You may also want to consider cutting a piece of mainspring about 1/2 inch long and the width of the bridge and use silver bearing solder to splice the brass. I would put the steel part under the bridge and, when done, it can be cleaned up where it is hardly seen.
     
  4. ChrisCam

    ChrisCam Registered User
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    #4 ChrisCam, Jan 14, 2020
    Last edited: Jan 14, 2020
    Hi David,
    Thanks for that I can see your arguments in this particular case. I'm thinking of how bendable is brass and can I silver solder with my little torches? Also I photographed the broken piece in the wrong position and have now uploaded the correct one which shows the break right on the corner. Sorry David and Will.
    Chris
    chris
     
  5. Bruce Alexander

    Bruce Alexander Registered User
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    I think I would just fabricate a new bracket piece and try to reuse the Cannon.
    Wonder how or why that broke.
     
  6. ChrisCam

    ChrisCam Registered User
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    Hi Bruce,
    I think the answer to your question may be dodgy old brass: see photo.
    I was wondering how they got the top ring to stay on but the cannon has a slight taper and a bit of loctite 680 will help keep it there. I have googled bending brass and for sharp bends annealing is essential. I would then think riveting the cannon on will work harden some of the brass but to be sure once bent possibly some hammering for this purpose:???::???:
    Chris

    bottom cannon.jpg ring outer.jpg
     
  7. peanuts

    peanuts Registered User

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    Chris
    Have you considered using your mill to machine the part from a brass block, thus avoiding the need to bend? I've never done that myself, but I'm curious as to how effective that would be.
    Simon
     
  8. novicetimekeeper

    novicetimekeeper Registered User

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    The original would have been cast, not made from sheet which had to be cast anyway. rolling mills were invented in the 18th century but were not widely in use until nearer the middle of the 19th century.
     
  9. ChrisCam

    ChrisCam Registered User
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    Hi Simon,
    The plus would be the brass would not be annealed so would be stronger. Downside from a 12mm thick brass bar 90% would be wasted. However I would not totally dismiss the idea at this stage so thanks for that idea.
    Chris
     
  10. Bruce Alexander

    Bruce Alexander Registered User
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    Hi Chris,

    Those are some good photos. Thanks.

    Dodgy, 18th Century Brass, eh? I see what you mean.

    Is there a crack in the Cannon too? If so, I would be reluctant to attempt its removal from the original bracket piece.

    Perhaps silver solder would be the way to go. You might start a conversation with Shutterbug or Jerry Kieffer for some suggestions along those lines.

    Bruce
     
  11. ChrisCam

    ChrisCam Registered User
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    Hi Bruce,
    No the cannon seems OK but what you can see is where a flat piece of brass was rolled together to form the cannon, in other words a joint. i might be tempted purely for the learning curve to make a new one and silver solder so S.B and Jerry's input would be appreciated.
    Chris
     
  12. Bruce Alexander

    Bruce Alexander Registered User
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    Okay.
    I thought it looked like cast brass and was glad to see that Novice, (and Simon) weighed in as well.
    I can only say that in my shop and in my hands I would look into acquiring the tools and ability to silver solder the piece.
    I think this thread may be helpful to you as far as basic information is concerned: Need help with broken parts of Ships Clock
    Please let us know what you decide to do to solve the problem.
    Good luck with it Chris.
    Bruce
     
  13. shutterbug

    shutterbug Moderator
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    If you're considering hard silver solder, you really need a dual solder system with oxygen. A single torch might reach melting temp eventually, but the whole part will be annealed by then, and weakened. With a small torch and dual tanks you can reach melting temp quickly in just a small area.
     
  14. David S

    David S Registered User
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    Although I would try to save the original by doing something like Wow suggested, or trying to silver braze it. You should also be able to form one from brass strip. I have a selection of 2" strips from 0.010 to 0.080" of brass that I got from work years ago that came in rolls and we fed into punch presses to make all sorts of components. What ever brass grade it is I have been able to form parts similar to yours with very small radii at the corners.

    Perhaps 260 brass would work? Where is Glenhead when we need him?

    David
     
  15. novicetimekeeper

    novicetimekeeper Registered User

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    If it is being replaced you can buy cast brass blanks of various sizes of both backcocks and bridges.
     
  16. ChrisCam

    ChrisCam Registered User
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    Update based on all posts...thank you

    My take to date is different grades of brass can with stand acuite bending differently.

    Simons idea of milling now seems (the more I think of it )a good idea based on opportunity cost (time and money spent on alternatives).

    That said until I have silver soldered I cannot hold a valid opinion.

    Using brass angled metal and brass rivets is also a valid alternative. Yes the early bridges were cast but it may be the case they lacked modern equipment and bending via annealing now is a viable alternative.

    Chris
     
  17. JimmyOz

    JimmyOz Registered User

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    I am late into this, however why not file the top of the broken part flat and the end of the bridge flat, get a square bit of brass soft solder the three bits toghether and then pin them, 2 through the top and 2 through the side, file it to the same shape as the other side. This will keep as much of the original clock as possible and since the bridge has no stress should do the job.
     

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