William Smith Gearless Gravity Arm Clock

Discussion in 'Clock Construction' started by Badabec, Jul 8, 2015.

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  1. Badabec

    Badabec Registered User

    Jan 3, 2015
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    #1 Badabec, Jul 8, 2015
    Last edited: Jul 8, 2015
    Hello, anyone had a go at making this clock?
    I had the impulse mechanism running for two days, stopped it to polish the gravity arm and now do you think I can get it to run?
    The Hipp toggle won't cooperate. Now the pendulum decays until the vane rubs up against the trigger but just won't engage. Every adjustment impacts upon another.
    It doesn't help when you drop the allen key and the vane vibrates down the pendulum rod like one of those child's toys.

    th_MOV00126_zpswtxcqnjq.jpg

    Download video button on right hand side of page
     
  2. Badabec

    Badabec Registered User

    Jan 3, 2015
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    Well, it's going again. There are so many variables it takes a while to understand what each adjustment does. I moved the entire impulse mechanism and back plate down by two inches. I also increased the length of the toggle (for the Hipp) by at least 0.25 inch. A mirror finish to the toggle bearing shaft helped. I found it vital that the trigger cannot rotate anticlockwise past the vertical. I added a small stop to prevent this happening. I also strengthened the trigger spring. Wiring the electromagnets in parallel rather than series really increased the magnetic pull. It has now been running for two days.
    The solar panel is keeping the battery charged.
    I have started work on an oak case. A simple rectangular shallow box with a glazed door.
    It isn't a quiet, the electromagnets re-latch the gravity arm with quite a bang
     
  3. Allan Wolff

    Allan Wolff Moderator
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    Mar 17, 2005
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    Glad you got it going again.
    It should be an accurate clock from what I have read. I've been around a few self winding clocks that use a solenoid to keep a small spring wound. They kept me wound too as I never got used to the bang each time the solenoid pulsed. Perhaps some type of vibration absorbing mount or a rubber stop on the solenoid lever will help reduce the noise.
    Look forward to seeing the case!
    Allan
     
  4. Tom Barosso

    Tom Barosso Registered User
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    Mar 3, 2015
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    Hi-
    I'm curious how you determined the impulse location on the pendulum. I'm considering building a clock with a gravity impulse arm, but reset mechanically.

    I would like to impulse the pendulum as close to the center of percussion as possible but don't know how to locate that. It seems that any formulas I find online are for a pendulum of uniform dimensions, not a rod with a bob on one end. (I could be wrong about that, I find the formulas rather intimidating.) I can find the center of gravity easy enough with my CAD program, which I assume is the starting point, but then I'm stuck.
     
  5. Badabec

    Badabec Registered User

    Jan 3, 2015
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    Hello, it was nothing clever on my behalf, I just followed William Smith's book. I did lower the impulse mechanism mounting plate by 1.5 inches, Bill measured from the top of the pendulum mount, as there are other discrepancies in the book, I tried from the bottom of the mount. Much easier to set up and get running. I also extended the nose of the toggle mount so I could fit a very thin rod across the gap. This stops the vane from flicking upright and stopping the clock. Bill uses a piece of bent wire.
     
  6. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    I'd be curious as to what formulas you are talking about.
    I see from the video that the rod is driven from about the center
    of the rod.
    To my thinking, this would be the least desired point as it is
    exactly over the most flexible point of the rod and most able
    to cause the primary resonance frequency of the rod.
    Any energy applies to the resonance would be lost. That is
    unless the resonant frequency was such that it kicked the bob
    out at the last part of the drive ( not likely with an arbitrary
    rod and bob ).
    As for resonance points, one could most likely assume it was
    a rod that was constrained at both ends.
    I'm also curious as to what controls how far down the ramp
    the roller goes before it ends impulse?
    Tinker Dwight
     
  7. Badabec

    Badabec Registered User

    Jan 3, 2015
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    Hello, on William Smith's clock, the ball bearing roller travels down the ramp until the right angled arm makes electrical contact with the electromagnet armature. This energises the coils which pulls an armature towards the coils. This pushes the arm upwards and re-latches ready for the next toggle action.
    When I first saw the clock, I though the electromagnetic coils pulled the roller onto the ramp to give the impulse. Instead it is gravity which causes the arm to drop once unlatched and the electromagnets re-latch the arm.
    The pendulum rod doesn't really wobble because the roller hits the ramp gently. It only receives an impulse every 90 or so swings. There are two more attachments to be added to the pendulum, they may dampen it a bit. One for the seconds and one for the minutes (hours are via a Dodd daisy wheel).
    I couldn't get any Invar so the pendulum is 6mm carbon fibre rod, just for a change.
    Back from holiday now so I can get back to it.
     
  8. Badabec

    Badabec Registered User

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    Hello, well, its up and running. No dials yet, just a dummy run. Tricky to set up, the usual scenario of adjust one thing and six others will need adjusting. The case is a simple box, cherry backboard, oak frame with walnut cappings top and bottom. It is really a glorified drawer. The solar panel and battery are housed in an oak box at the bottom. A glass door will finish it off.

    http://vid342.photobucket.com/albums/o412/badabec/MOV00142_zpskgbmko5j.mp4

    http://vid342.photobucket.com/albums/o412/badabec/MOV00143_zpskt5pwwvz.mp4



    Apologies for poor quality
     
  9. A. Wood

    A. Wood Registered User
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    Jan 22, 2015
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    I have just noticed this thread and have made the WS design. I am also located in the UK in the south near Newbury so perhaps we could compare notes. Clearly it is some time since the thread started so perhaps I am a little too late.

    A few comments from me. This was my first clock and I am indebted to Bill for the quality of his documentation and videos for getting me up to speed. I did visit him after the Chattanooga Convention and it was a pleasure to meet him and Judy. I was deeply saddened to hear of his death earlier this year.

    The clock takes some getting your head around and is very interactive. There are some minor mistakes in the documentation, the main one that was expensive was the dimension of the motion work plate.

    I found that the seconds arm loaded the pendulum and I replaced it with a very thin piece of piano wire with a ptfe sleeve where it was in contact with the wheel. The sleeve acted like a rotating bearing and improved / reduced the drag.

    After discussion with a maker in the US I replaced the notch mechanism for the minute increment with a pin in the seconds wheel and a different shaped piano wire activation arm. This needs a picture to explain it better.

    I tried to be clever and use bought solenoids but ended up winding them as Bill instructed.

    Once I grasped the interaction of the mechanisms the clock was better to set up. I used a Microset Timer from Brian Mumford to do the fine adjustment and could get over 100 beats between resets.

    I have one outstanding issue. I used nickel silver to make the hands and they are quite heavy. The clock minute hand was jumping two minutes around 'quarter past' to 'half past' and this was the weight of the hand being too heavy to be retained by the pin wheel spring loading. If I increased the spring pressure the pendulum was then heavily loaded and the reset period dropped. I tried adding a counter balancing weight on the other end of the minute hand which has helped but I think I need to make a new lighter set of hands,

    The reset is noisy but I have my brother in law making me a case to damp this down.

    Everyone that sees the clock appear mesmerised by its workings and for my first clock I am really pleased with the result.

    There are probably other aspects I have forgotten but I would be happy to compare further notes with you if of interest.

    Kind regards

    Alan
     

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