Mainsprings for a One day strike Terry Clock

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  • #49944
    shermarie
    Participant
    • Topics Started: 3
    • Total Posts: 9

    Hello everyone
    I am working on a Terry Clock Co. one day strike (kitchen/parlor?) clock. The problem I’m having is finding the correct mainsprings. I can find the correct width and thickness but the length is shorter. The chime side is 33″ shorter and the clock side is 15″ shorter. Will these work? Should they be the same size?
    Thank you,
    Sherry

    #64467
    willofiam
    Moderator
    • Topics Started: 75
    • Total Posts: 1437

    Hello Sherry, sounds like the length is going to be way too short, BUT I am not sure exactly what your dealing with. Where are you getting the sizing from? What are the dimension of the width and thickness? How are you determining that they are short? If your measuring the original mainspring what is the issue with those? Do I need more coffee this morning? Have a great day, William

    #64468
    shermarie
    Participant
    • Topics Started: 3
    • Total Posts: 9

    Hi William, i guess I needed to clarify some thing last night 😆
    Wasn’t sure what you needed to know.
    The dimensions are 0.309″W x 0.013″T x 63″L on the strike side
    and on the clock side they are 0.332″W x 0.015″T x 57″L
    I measured the length with a string. The thickness and width with a digital caliper.
    The image of the spring that is a little looser on the outside of it, is because I tried to unwind
    it and measure it 😯 To me the originals look set, or do they look ok to reuse?
    Hope this clarifies things.
    Thanks William and have a wonderful day!!
    Sherry

    #64469
    willofiam
    Moderator
    • Topics Started: 75
    • Total Posts: 1437

    Hi Sherry, @Shermarie wrote:

    The chime side is 33″ shorter and the clock side is 15″ shorter

    I would not use a mainspring with this amount of length difference. I have looked into it a bit and do not see anything that matches exactly though I see that they can be close with length and strength. I usually would go to a bit lighter strength if I cannot be exact. Some may disagree with me so digest all the information you get and make your own good judgement. My reasoning would be that the old mainspring manufacturing process most likely wasnt as good as it is today…ALSO…by performing a good cleaning, a proper bushing job, pivot polishing and burnishing job, pallet faces polished and burnished with a 30 hours clock you would probably be o.k. NOW with all that said I would most likely use the springs you have, If they do not have any flaws, clean them well and re-lubricate, they look o.k….at least from your pictures. I judge wether a mainspring is set or not by the size of the great wheel. If the mainspring is at least 2 to 2.5 times the size of the great wheel…depending on the clock…then I would reuse them. If anything you can get some practice with them and do a final test when it is all together and see how long it runs….By the way when stretching them out for cleaning and inspection, be careful, and pull them straight so as not to distort them sideways. By all means…have fun…William

    #64470
    shermarie
    Participant
    • Topics Started: 3
    • Total Posts: 9

    Good morning William, thanks for you reply. I will go ahead and try these mainsprings to see how
    long they run as you suggested. I can use the practice! Although they are about the same size as
    the great wheels. You said “depending on the clock” what about the clock determines the size of
    the mainspring to the great wheel?
    Thanks for all your help!!
    BTW you are making an awesome clock! Beautiful work!
    Sherry

    #64471
    willofiam
    Moderator
    • Topics Started: 75
    • Total Posts: 1437

    @Shermarie wrote:

    You said “depending on the clock” what about the clock determines the size of
    the mainspring to the great wheel?

    experience I guess….type of escapement, wether it is in a barrel or not, is the mainspring running a chiming mechanism, a feeling i get??? really 87.352 % of the time I reuse the old mainspring if the rest of the mainspring is in good condition…also, I am usually doing a complete overhaul and have reduced friction as much as possible. Mainsprings can be confusing, there is very little information (that I have been able to find) that would tell you exactly what a clock needs, though if you wanted to there are calculations that can be made to determine mainspring sizes.

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shermarieMainsprings for a One day strike Terry Clock