Wiinding a coil

Discussion in 'Electric Horology' started by pineneedle, Feb 3, 2005.

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  1. pineneedle

    pineneedle Guest

    Just in case I can't find a coil for my clock and because I "have the want to know", I had some questions for any electricity-knowledgeable person. I'm assuming there is suppose to be about 2 watts going through the coil to create enough of a magnetic field to run my "primitive" synchronous clock. There seems to have been thousands of windings of fine, thread-like wire on the old coil to give it enough ohm resistance to reduce the voltage down to produce those watts. Can you produce the same effect with a few windings of larger wire that has a resistor soldered in place that would reduce the total wattage to 2 watts? Wouldn't that produce the same magnetic alternating field that is needed for the synchronous clock to work? I'm not quite grasping the whole concept of this single coil. I'd sure appreciate you sharing your knowledge.

    Linda
     
  2. Hi Linda,

    That's a good question, taking me altogether too far back in time to my science days.
    The idea of the resistor to reduce the current flowing in the coils is correct, very low current flow is necessary for "always on" applications like a synchronous motor.

    Unfortunately the intensity of the magnetic field produced in a coil of wire is not related to its thickness, but rather to the amount of current flowing in the coil and the number of turns (coils).
    Which translates into no matter how you reduce the current to acceptable levels, you must then have a sufficient number of turns (coils) to give the required magnetic field. At the very low current flow required, thousands of turns of wire are required to form the field coil.

    A good motor rewind shop should be able to make a new coil for you, or advise you of a shop that can.

    Good luck in your quest.

    Ian
     
  3. pineneedle

    pineneedle Guest

    I figured it seemed too easy a solution but I thought I'd give it a shot, that maybe in those days they didn't have access to these little resistors we have today, ha. I've spent hours looking on line for the answer and couldn't find it. Most everything was about primary and secondary winding snd transformers. Thanks so much for answering my question. I'm still holding out hope for a used one.

    Linda
     
  4. swolf

    swolf Registered User
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    Hi Pineedle, I have a coil that is rated 2 to 3 watts. It has a core opening of 5/16x5/16. It is a little fatter than the one in your clock but if there is clearence between the coil and movement parts, It should work.

    Dimensions are;

    Coil hole, 5/16x5/16"
    Length, 15/16"
    Thickness of winding between core and outside
    of coil, 1/4".
    If this opening is too big it can be shimmed with thin wood or toothpicks so it will be tight on you metale armature.

    Email me at swolf369@aol.com.
     
  5. Scottie-TX

    Scottie-TX Registered User
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    Still hangin' in there PINEY! Great. Without getting too far into OHM's law ( no, he wasn't an attorney ), there's this thing called impedance. And it is with respect to alternating current. What comes out of your wall outlet. While you could produce the same impedance with a small amount of wire and resistor that would pass the same amount of current - there would not be sufficient inductance to run the motor. Let's carry your idea a little further. Let's just not use ANY wire! Just a resistor. See? No magnetic field. You got the idea. Keep thinkn' . It's a lotta fun.
     
  6. pineneedle

    pineneedle Guest

    It is amazing how buying a broken clock can mushroom. (I never gave clocks a second thought until I started to decorate a room in art deco and my eBay "deco" search showed a deco-style Gilbert clock.) Now I'm fascinated by these early-electric clocks and how they work as well as the beautiful antique, wind-up ones. I never appreciated them before. This is a great message board.
     
  7. H.Weiland

    H.Weiland Deceased
    Deceased

    Just to make things a little more clear, coils like this one need to have the ability to produce the needed amount of magnetism to drive the rotor of the clock.

    The meaure of this requirement is "Ampere-turns" of the coil in question. This is the measure of the amount of current flowing through the coil times the number of turns of magnet wire. Thus the same amount of ampere-turns might be reached by a few turns of heavy wire, but carring a much greater current, or very many turns of fine wire carring a small amount of current.

    For a fixed amount of ampere-turns product, the higher the input voltage the less current needed but the greater number of turns required.

    In other words, as in the saying, you can't get something from nothing.

    Hope this helps,

    Henry Weiland
     
  8. pineneedle

    pineneedle Guest

    Thanks, Henry. I'm starting to get the full picture. I found a pretty good book on the subject of magnetism and electricity and how it works but not how it actually make a clock run. I think there are going to be plenty of early, electric clocks starting to fail because of their age. One of you knowledgeable persons really ought to write a detailed book on the subject with lots of pictures and different types of electric set-ups. With e-books you don't really even need a publisher, just the software (I think a special Adobe software that can't be copied) and then sell it on Amazon or similar. The info in detail on how a coil applies to making a clock run and how to fix it is pretty lacking in print.
     
  9. Scottie-TX

    Scottie-TX Registered User
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    Since you seem to like it and seem to have a thirst for it, let me tell ya how KOOL it is. Most clock motors are called synchronous motors. Typically the current available in most homes is called 60cycle current. That means, Piney, that the voltage goes from positive to zero to negative, back to zero and returns to positive in a sixtieth of a second or alternates polarity sixty times in a second! See those "fingers" on the rotor? They're called "poles" . By magnetic induction, every one of those poles is given a shove by each pulse created by the alternations of current. But not only are they given a shove, they are also clamped at that speed . Now is it not a coincidence Piney that the seconds division of a clock are SIXTY! Hmmmmmm.
     
  10. Tom Kloss

    Tom Kloss Registered User
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    Lots of information on synchronous clocks in this book. "Electrifying Time by Jim Linz ISBN: 0-7643-1190-5.

    I Believe Henry Warren chose the 60 cycle standard because a minute consists of 60 seconds. The 60 seconds of a minute set the standard of the AC frequency so the 60 cycle standard of the AC could keep the synchronous motor running at the correct speed. Talk about a close loop.
    Yes I am a dinosaur that can’t stop using the word cycles instead of Hertz. AC can be generated at any frequency.

    Tom
     
  11. pineneedle

    pineneedle Guest

    In diagrams I've seen, they show a bar as a pole that gets pushed by the alternating current. So that round piece with notches all around it is the rotor, then? Tell me if I have the rest right. The "fingers" are closer to the source of magnetism and gets pushed when the alternating current goes from positive to negative and then the next one moves into position and this happens 60 times a second (Hertz). So you would have to be careful not to have too strong of coil and strength of magnetism because you only want the fingers to be close enough to be affected by it, or would that matter much? I can see that too weak of one wouldn't push and pull the fingers. Also, some sources I read say that all electrics have worm gears. Mine doesn't have a worm gear. I guess there are always exceptions. I'm going to try and locate that book, thanks.
     
  12. Jeffrey R. Wood

    Jeffrey R. Wood Registered User
    Old Timer

    Resistors work by converting electricity to HEAT. So while your idea is workable in theory, it is impractical because the resulting setup would be inefficient. In an extreme instance, you might end up needing to make air holes in your clock case and installing a little electric fan to blow away the extra heat before it dried out the lubricant! Seriously, though, NuTone and possibly others made doorbells containing synchronous 60-cycle clocks that ran off the 20-volt output of the doorbell transformer. These had fewer turns of a heavier wire and ran just fine. But no transformer is 100% efficient. If you connect a doorbell clock directly to 120 volts AC, the coil will quickly burn out. So it's best to use a coil designed to operate on the intended voltage.
     

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