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  1. #1

    Default How to design escapement mechanism and pendulum ?

    Hello.

    I start making my own design clock.
    I fail many times and now I have working mechanism but...
    Does not want to work accurately.


    Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails 512_96779035670050zegar5.jpg  
    Last edited by Decodrew; 02-03-2013 at 06:15 AM.

  2. #2
    Registered User Dick Feldman's Avatar
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Decodrew)


    Decodrew,

    Yours is an interesting machine.

    The function of the pendulum and escapement is to act as a regulator. Without a pendulum and escapement, the works will speed. A pendulum of a certain length will regulate the mechanism with a shorter pendulum allowing the mechanism to move faster. A longer pendulum the converse.

    Your can read about the function and properties of the escapement and pendulum in The Modern Clock, by Ward Goodrich. The book was published over a hundred years ago.

    I am curious about the odd shape of your escape wheel. It seems complicated compared to the verge you are using. I do not think you are getting the greatest mechanical advantage with the combination.

    In the video below, note where the teeth land on the verge and note the impulse surfaces as the escape wheel pushes the verge. With this deadbeat escapement the escape wheel moves only in one direction because of the angle the teeth meet the verge surfaces.

    We would like to see and hear more about your clock.

    Best Regards,

    Dick



    *******I also noticed that the pivot on the escape wheel is loose and jumping around. It needs a bushing!********

    Last edited by Dick Feldman; 02-03-2013 at 07:00 PM.

  3. #3

    Default Re: How to design escapement mechanism and pendulum ? (RE: Dick Feldman)

    I'd say your suspension and drive to the pendulum is loaded with friction. Even the way it is, if I understand the drawing, if the pivot point of the pendulum was changed to be on the same axis as the pivot of the anchor, it might have a chance of running. A pivot used in the suspending of the pendulum would not be recommended in my opinion. A knife edge or a suspension spring would be a better choice.

    This is all assuming that I understand your video and drawing.


    Ralph

  4. #4
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Ralph)

    It'd be better if you made the lock surfaces of the pallets deat,
    as in a deadbeat. Draw a circle with its center on the anchors
    arbor. The dead surfaces of the pallets should follow that
    arc.
    Also, what is it driving that has so much flex sideways to allow
    the impulse to wiggle sideways so much?
    Fix those things and it should do better.
    I might flatten the ends of the pallets to match
    closer the ends of the clubs on the escapement.
    Surprisingly, a pointed surface or a slightly larger
    area have about the same amount of friction with
    the same normal force on them. Making it a sharp
    point just increase wear without reducing friction.
    If you widened the inpulse face of the pallets to not
    be a point, you might have to compensate the
    clubs on the escapement a little.
    Tinker Dwight

  5. #5
    Registered User soaringjoy's Avatar
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Tinker Dwight)

    Welcome to the MB, Decodrew and thanks for sharing your project.
    You are not getting adaquate responses, so I'm moving this to the Clock Construction forum.
    Jurgen "tempus nostrum"

  6. #6

    Default Re: How to design escapement mechanism and pendulum ? (RE: soaringjoy)


  7. #7

    Default Re: How to design escapement mechanism and pendulum ? (RE: Decodrew)

    I do not understand> "one-half a tooth space" what is it?
    How to found that on pictures ?
    I drew a circle but I do not know why it has such dimensions?
    Why there should be such angles?

    There is no mathematical formula to calculate, no proportion.
    I do not know why the wheel has to have 15 teeth.
    Can I do 20,30, 40 How to that counts?

  8. #8
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Decodrew)

    The half tooth makes sense when you think about it.
    Each pallet only interfaces with a tooth for half a
    tooth spacing and then goes to the next tooth.
    This is true for recoils as well. Half tooth rotation of
    the escapement on one side and the other half on the other.
    The picture shows an extreme case of a dead beat.
    Most dead beats are for larger number of teeth ( yes
    you can use any number of teeth ). With a larger
    number of teeth, the assemetry of the pallets is usually
    ignored for ease of manufacture. Still, when there are just
    a few teeth and you want them to push right, they are offset.
    Tinker Dwight

  9. #9
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Decodrew)

    I should clearify the statement on tooth count.
    Tooth count on the escapement is part of the total
    ratio between the pendulum and the minute hand.
    I am a little surprised that you could build a clock
    without knowing this??
    lets say you wanted to do a 40 tooth escapement
    and uses a pendulum with a 1 second beat. It would
    do one tooth every 2 seconds or 80 seconds to do
    one rotation. An hour has 3600 seconds. That means
    the ratio of the gears between the minute hand and the
    escapement need to be a 45:1 ratio. Other ratios could
    be used with the 40 tooth escapement but would require
    a different pendulum rate.
    The angles of the impulse faces are what determines the
    impulse angle of the pendulum. The general rule is 2 degrees.
    This is a compromise. Smaller angles would be more accurate
    but harder to do with slop in pivots and such.
    Larger angles allow too much swing that increase circular
    errors and loss do to air friction.
    Tinker Dwight

  10. #10
    Forums Administrator harold bain's Avatar
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Tinker Dwight)

    You might want to read Ward Goodrich's The Modern Clock. Although written over 100 years ago, the information still applies as to how to design a clock escapement. With a dead beat escapement, the anchor should encompass 25 % of the teeth on the escapewheel for optimum performance.
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  11. #11

    Default Re: How to design escapement mechanism and pendulum ? (RE: harold bain)

    Hello.

    I make little mistake, this is counter clock movement on picture.

    I make 30 teeth escapement wheel > teeth space = 360/30 = 12 degrees ( Pendlum lenght should be 100cm ?)
    2,5 teeth space is 30 degrees.
    Ratio of the gears between the minute hand and the escapement 60:1
    And I cant change this. It would ruined symmetry and appearance.

    Attached my old desingn. I cant only little( max 3-5mm) change those dimensions. Pendulum lenght 50 cm (escapement wheel should have 44 teeth ?)
    My upside down escapement


    I can make pendulum max lenght 50cm, so escapement wheel should have 44 teth ? > Did not take advantage of pushing
    And that dont change gear ratio 60:1 ?
    Attached Thumbnails Attached Thumbnails 512_980919215a4536wychwyt.jpg  
    Last edited by Decodrew; 02-20-2013 at 03:52 PM.

  12. #12
    Forums Administrator harold bain's Avatar
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Decodrew)

    The pendulum length is determined as much by the escapewheel tooth count as it is by the other gear tooth counts leading from the motion works to the escapewheel.
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  13. #13
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    Default Re: How to design escapement mechanism and pendulum ? (RE: harold bain)

    You pendulum length for the 30 tooth is about right. I calculate 99.3 cm ( to the center of the bob ).
    For the 44 I get 46.2, not 50.
    I also don't like your pallets. If they match what you have in your drawing, I think
    you'll have way too much drop. It also looks like the tip spacing is wrong and
    I can't tell if your attempting a deadbeat or a recoil.
    I went back and looked at the video. It is suppose to be a deadbeat
    but isn't.
    Tinker Dwight

  14. #14
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Tinker Dwight)

    One last thing. To minimize the friction, the pendulum should swing from
    the center of the anchors pivot, not the escapement wheels. It should
    have a longer crutch. It should be at least 15 or 20% of the pendulum
    length or you'll not be able to keep the slop in pivots and slot on the
    pendulum small enough.
    Tinker Dwight

  15. #15
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    Default Re: How to design escapement mechanism and pendulum ? (RE: Tinker Dwight)

    Since you expect to make a new escapement wheel to give you
    a shorter pendulum, you need to change the size of the clubs
    on your escapement wheel.
    They should be 40% of the circumference spacing between the teeth if you intend
    to keep the pointed pallet ends.They look to be less than 30%.
    The lock surfaces should be dead ( following a circle centered on the
    pivot of the anchor ).
    Tinker Dwight

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