Newbie - new project

Discussion in 'Clock Construction' started by Britannicus, Jan 10, 2018.

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  1. Britannicus

    Britannicus Registered User

    Apr 26, 2016
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    Hi all,

    I've spent a year or so fiddling with watches, building a few robots from scratch and have now tried to restore a clock or two... I've built up a reasonable workshop (watchmaker's lathe etc.) and feel I'd like to set myself a real "stretch challenge" -

    I'd like to design a skeleton clock that's maybe a little idiosyncratic and build it over the summer, so I'm doing a bit of research - my criteria are :

    1/ Relatively short pendulum (7200 beat) spring powered clock

    2/ Self made components wherever I can - where I can't I'd like to use refurbished parts and new only as a last resort

    3/ Hour / minute skeleton design (so I can see what I made)

    4/ My own design

    I realise I'm totally ignorant, but the plan is not to be when I've finished !

    In looking at clocks it seems to me that an early design consideration is the ratio of wheels on the drive train. Is there a spreadsheet or tool out there that can work out ratios so I can experiment with differing sizes of wheel in design.

    what I was thinking was maybe :

    ............................................Wheel teeth.........Pinion teeth

    escape wheel...........................60........................16 ( so rotates X 2 per minute)
    third wheel..............................120........................16
    Centre Wheel (minute hand ) 128........................16

    I adapted this from an existing clock , but if my maths serves me OK gives a a reduction of 120 :1

    Then to drive minute from the centre wheel on a 12:1 reduction to use 2 wheels to provide the drop and to give a clockwise rotation of the hour hand.

    ............................................Wheel teeth.........Pinion teeth
    first reduction................................3........................8
    third wheel....................................24......................-


    Is this a good ratio ? - are there better ? - for instance I could get the same from an escape wheel 30 : 8

    There must be more combinations to get the same answer - can someone point me at a tool or the relevant maths to calculate appropriate trains ? can someone point me at a discussion on the right selection - google hasn't really supplied me with something that helps much
     
  2. Jim DuBois

    Jim DuBois Registered User
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  3. Allan Wolff

    Allan Wolff Moderator
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    Mar 17, 2005
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    Welcome! I like your approach of making a clock from your own design. Here are a few random thoughts for your consideration.

    Skeleton clocks are great! Even though you plan to build your own, sometimes seeing what others have done will spark an idea that you will want to try. See if you can locate Derek Robert's books on Skeleton clocks. They are out of print but show up occasionally on auction sites or may be in your library. You might also check out Mark Frank's website My-Time-Machines.net He has an extensive skeleton clock collection and is currently having an extremely complex astronomical clock built. Also check out some of the clock construction projects documented in this forum.

    I have attached the Excel spreadsheet I use for various clock calculations. No instructions provided; it is pretty basic and easy to figure out. There are several tabs for wheel cutting and mainspring stuff.

    I like your use of high (16 leaf) pinion counts. There are benefits but as you have already found out, it also results in rather high tooth counts on your wheels.

    For motion works, the pitch circle diameters of both trains needs to be the same for the wheels to mesh properly. DeCarle explains this very well in "Practical Clock Repairing". There is an example in the spreadsheet that uses a single reduction of 96:8 to get the 12:1 minute/hour reduction and then a pair of identical tooth count wheels to reverse direction so the hands both go clockwise.

    A CAD program is invaluable for designing your own clock. If you can do 3D CAD (I cannot) that would be even better to verify clearances and parts arrangement.

    Please share your progress, both successes and failures, and ask lots of questions. We live for this stuff!!
    Allan
     

    Attached Files:

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  4. Britannicus

    Britannicus Registered User

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    #4 Britannicus, Jan 11, 2018
    Last edited: Jan 11, 2018
    Hi Allan -

    really appreciate your sage advice, and I will definitely keep the forum posted, though this is likely to be a long range project I feel - Currently I use Visio as my design tool, but was thinking to move to more capable CAD.

    I will be asking incessant questions - so be careful what you ask for :) I have already started a bit of a google search for design inspiration - I saw this and rather liked the general look and feel (though possibly a bit less angular and I've no intention of trying to build my own Fusee ! - well not yet anyway :)


    skeleton clock.jpg
     

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