Kundo Kundo Electromagnetic

Discussion in 'Electric Horology' started by whatgoesaround, Oct 29, 2017.

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  1. Berry Greene

    Berry Greene Registered User

    Oct 2, 2017
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    Wow there two sheds! You'll soon have to have 3 sheds at this rate!

    I'm pleased that you have embraced the electronic issues as it will give you a much better "feel" for what actually goes on. I admit it is quite hard to get even one foot on firm ground, so to speak, as even the coil inductance must be changing as the magnetic core swings through it. You might also want to pay some attention to the environment in which the clock operates. Large metal objects which may have some of their own residual magnetism can affect these tiny sporadic fields. {I'm thinking of a metal gas fire surround, or even some local switching such as wires to a thermostat}.

    You might consider acquiring a Multimeter with Inductance (and capacitance) ranges. These do not need to be very expensive as in general tight accuracy is elusive anyway. An approximate figure will usually do. {The specs of Inductors & Capacitors are usually quite wide for most applications}. However it will get you into the right ball-park if your interest carries you there.
    Rgds, BerryG
     
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  2. two sheds

    two sheds Registered User

    Mar 3, 2019
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    Ah well I live in Cornwall and have a large garden (aka "field") so I have extra sheds - up to five so far :).

    Thanks for the note on potential problems with nearby metal things - something else I wouldn't have thought of. Multimeter with inductance range would be interesting - I have an ordinary multimeter so will try to remember to connect it when I change to AA battery to see if it gives a brief indication of the current.

    Thanks again to people who have contributed - am really pleased that it's going tick tick tick still downstairs.
     
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  3. Berry Greene

    Berry Greene Registered User

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    Well I have only 3 sheds and they have many kitchen sinks and not just clock stuff. Indeed I have tried to make them comfortable for the times I am wound up and thrown out on account of the chimes and strikes let alone the tick - tocks. Well done for getting a result and do enjoy your hobby.
    Rgds, BerryG
     
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  4. two sheds

    two sheds Registered User

    Mar 3, 2019
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    Ta :)

    I had another thought. The steel core will presumably have a relative permeability of 1000. So that will multiply the rise time correspondingly so it's not at all negligible. Meaning that the voltage will actually presumably reach maximum value while the contact is being made and the core is being kicked backwards. That would make sense to reduce current consumption to a minimum.

    I'm hoping someone who actually knows will either confirm or deny, but I'd imagine that everyone has probably lost the will to live by now. :(
     
  5. Berry Greene

    Berry Greene Registered User

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    Two Sheds plus 3 - You are getting in quite deep here and need a scientist or a professor! Maybe another shed?

    I ought to know all this but...... can only tell you what I DO know. The permeability of a coil is increased with an iron core. Indeed it can be finely adjusted, as in tuned by adjustment of the core in say a radio although much higher frequencies involved but similar principle.

    That is what makes the dynamics of your clock much more like a motor AND a generator. The armature is moved by the magnetic field set up by the current in the coil supplied by your battery. However, like a balloon its is easy at first but as the field grows it gets harder. {That's the way I imagine it}. The growing field of magnetic force is also cutting its own coil windings and this is given as the reason.
    As the core swings through the coil it becomes a generator. The voltage and current involved is in opposition to that being applied and is called BEMF (Back Electro Motive Force) and this is the reason for the somewhat deceptive figures you get concerning current use. It's lower dynamically that it would be when static.
    To really see what happens you need to view things on an oscilloscope but guessing you might not have one - a trawl around the web will probably produce some images, explanations and even some even better animations.
    I think you will see that there is a time lag involved (phase shift) in the process and we have not yet covered the field collapse - that happens when the switch opens. This is where energy can be recovered into a capacitor. I would (instinctively) place that across the switch to give it somewhere to go and avoid the arcs that might burn the contacts.
    Value of capacitor? Got me there! Well a small flat non-inductive (0.001uF silver mica) to suppress the spikes, but large (means electrolytic and therefore somewhat inductive as it's of coiled up construction), to collect the energy. My guess would be 8 to 32 uF but not critical. These are wired in parallel.
    I am quite willing to be called out wrong on the fine detail here but the broad principles are right. This though is what makes electric Horology much more interesting. The frustration is in seeing the energy at work. You have to imagine so much.
    Regards, BerryG
     
  6. two sheds

    two sheds Registered User

    Mar 3, 2019
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    Me again. The clock seems to be running a couple of minutes a day slow. I initially thought it might be because I had a proper 1.5V battery in so the pendulum had a wider swing. I swapped it for a rechargeable one, though, and it's the same. I've screwed the pendulum weight up as far as it will go but that seems to make no difference. :(

    Any thoughts people? If it was running fast I could add a bit of extra weight to the pendulum but I can hardly take anything off.
     
  7. MartinM

    MartinM Registered User

    Jun 24, 2011
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    Are you sure the suspension spring is correct? Their shape is pretty unique and identifiable.
    Also, try moving the battery away from the clock a few inches using extension wires, just to be sure there isn't some em force at play, caused by the battery's proximity that causes an amplified swing.
     
  8. Berry Greene

    Berry Greene Registered User

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    I've been thinking.......... and thinking........ slept on it....... still thinking. Mmm! I don't want to BS you with how clever I am. My brain can't seem to get a handle on this. "Natural mechanical resonance" he said importantly but to no-one in particular...!
    I think Martin is correct. He usually is. Stiffer suspension? Shorter suspension? Can you alter these easily, successfully?
    Lastly, does it matter? I can usually tell you the real time. It will be very close to Cornish time here in Sussex if you will make allowance for our slightly earlier sunrises!
    Best regards, BerryG
     
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  9. MartinM

    MartinM Registered User

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    IIRC, you were having trouble identifying the positive vs: negative terminals for the battery. Have you (just for giggles) tried reversing them? My right-hand-rule theory was never really solid, but if they use it in rail guns, there must be something to it.
    I'd expect there to be a negative chassis ground out of sheer convention, but who knows?
     
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  10. two sheds

    two sheds Registered User

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    :)

    Well yes indeed. Cornish time is 20 minutes later than Sussex time (I used to live in Sussex and it's actually 20 years but we'll let that pass).

    I put our problems down to the railways in the 1800s having to standardize everything to London time. Bah. Midday is when the sun is overhead that's the definition not 20 to 12 or some other stupid time, you don't fool me. That's when it all started going downhill.
     
  11. two sheds

    two sheds Registered User

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    With this and the last post ... you people are impressive I have to say, and yes you recall correctly I do indeed have no idea whether my positive is positive and my negative is negative :)

    As phase 1 I have moved the battery away from the coil and it does seem to be ok so far (12 hours so difficult to tell yet).

    Failing that I shall try unsoldering/resoldering the battery terminals as phase 2. But I can't see (so far) why having it the wrong way round so that it gave it a bit of a pull at the end of travel rather than a bit of a push would make the swing slightly wider and so the period slightly longer.

    And failing that I shall look at the spring you mention. I can't see it so far but I didn't really look as moving the battery as phase 1 seemed favourite.
     
  12. MartinM

    MartinM Registered User

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    If your spring looks like this one, it should be okay. Some of the later replacements used plastic blocks, but they all seem to work fine.
    #54 Kundo Suspension Spring
     
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  13. Berry Greene

    Berry Greene Registered User

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    I can't tell you how much I regret mentioning the sunrise. We have had torrential rain and high blustery winds ever since.
    I'm on a learning curve myself now with Two Sheds.

    That suspension spring Martin put up is very short and rather non-standard to my eye. To be honest I cannot see why reversing the polarity would make any difference - but with magnetism there are many such weird effects so its well worth a punt.
    I remember that Maxwell guy. Didn't he have a silver hammer?
    As a slight aside but of phenomenal interest and education see this attractive video!

    Restricted to cack-handed viewers only, you will learn what only the gods know.
    Now about this pre-railway time clock ......... I seem to have so many examples of it.....!:mad:......:rolleyes:
    Best regards, BerryG
     
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  14. two sheds

    two sheds Registered User

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    You lot, are as I noted, really impressive. Changing the polarity did indeed work :) .

    Thinking about it, I suppose the magnets repelling at top of swing would have a slightly shorter period than them attracting at top of swing. Just as well since I still can't see that spring.
     

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