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Thread: Any guesses on how this works (Indefinately Spinning Top)?

  1. #1 Any guesses on how this works (Indefinately Spinning Top)? 
    Forum Freshman Munk's Avatar
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    http://www.youtube.com/watch?v=6aQBI...eature=related

    I assume the top is a magnet (or a metal that will be attracted to a magnetic field), but I am not sure what the base is (some sort of electromagnet?). In any case, I'm curious about how this thing ticks, so if someone knows or has a good guess, it be appreciated.



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  3. #2  
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    Well, doesn't look like anyone has any ideas...so I broke down and bought one ($10). When I get it, I'll be taking it apart to see whats inside

    In the mean time, I noticed that the top has LEDs that light up once device is switched on, but the base is clearly plastic. This may give some insight into how the device works. I was wondering, anyone think this is possibly a homopolar motor within some sort of WiTricity-like field?


    http://en.wikipedia.org/wiki/Homopolar_motor
    http://en.wikipedia.org/wiki/WiTricity


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  4. #3  
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    http://en.wikipedia.org/wiki/Tesla%27s_Egg_of_Columbus
    http://en.wikipedia.org/wiki/Rotating_magnetic_field

    " Tesla's device used a toroidal iron core stator on which four coils were wound. The device was powered by a two-phase alternating current source (such as a variable speed alternator) to create the rotating magnetic field. The device operated on 25 to 300 hertz frequency. The ideal operating frequency was described as being between 35 to 40 hertz. Reproductions of the device are displayed at the Nikola Tesla Museum in Belgrade, the Technical Museum in Zagreb and in the Ann Arbor Hands-On Museum. "

    There we go!

    I saw it in Zagreb, cool museum.
    Search more on google if you need more information!
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  5. #4  
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    Nailed it. Thank you for the info!
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  6. #5  
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    So I have been doing some research on this thing, and I think I understand the general principals behind how it works. You basically have a series of electromagnets that turn on and off in a specific sequence so that the N/S polarity of the rotates in circles. If I am not mistaken, this is very similar to how an electric motor works, correct?

    I am a pretty big newb to all of this, so I could be way off base. On a side note, does 35-40hz simply mean 35-40 electric "pulses" per second? If so, the ideal frequency for this device would mean that the N/S polarity completely rotates 35-40 times a second?
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    Yes! Tesla used his machine (the egg) to demonstrate the principles of a rotating magnetic field and induction motors, which is used in all AC motors (DC motors use it as well but they use commutators to create oscillating AC current from the DC source).

    Speed of the rotating magnetic field is determined by this formula:

    v = (120 x f) / p

    or you can find

    v = (60 x f) / n

    v = speed, f = frequency, p = number of poles, n = number of pole pairs, 60 (120) is a constant
    (so p = 2n)

    If it is a Synchronous AC Motor, its speed is the same as the speed of the rotating magnetic field (of course, when no torque is present on the rotor) hence Synchronous. If there is a torque present, the speed of the rotor is less then the speed of the stator (rotating magnetic field).
    This difference is referred to as the "slip".

    s = (Vs - Vr)/ Vs

    or sometimes

    s = 100 x (Vs - Vr)/ Vs (percentage of the stator speed)

    s = slip, V = speed (stator, rotor)

    From that you can get the formula for the rotor speed:

    Vr = Vs (1 - s)

    Synchronous AC Motors can have Vs = Vr or Vs > Vr.
    Now there is the induction motor (Asynchronous AC Motor) which always has a slip, and cannot have Vs = Vr, always Vs > Vr, hence Asynchronous.

    Hope this helps!
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  8. #7  
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    Tremendously.

    If I were to build something like this, would a stainless steel "egg" suffice? Wasn't tesla's egg copper?

    ______________


    If I use your formula, I could theoretically use an 18 pole stator with a 220/240 volt input (making use of a 110/120v to 220/240v ac transformer) and get a rotating magnetic field between 33hz and 36hz, right?

    (240 volts x 18 poles) / 120 = 36hz
    (220 volts x 18 poles) / 120 = 33hz

    Or I could use a 42 pole stator with a standard 110/120v input, to get a frequency range of 38.5hz to 42hz...if I am not mistaken

    (120 volts x 42 poles) / 120 = 42hz
    (110 volts x 42 poles) /120 = 38.5hz

    If I wanted to use an 8 pole stator, I would need a power source of between 525-600 volts to reach the range of 35hz to 40hz...but I can't seem to find a transformer that can do this. Do you know where I can find a transformer (preferrably adjustable) that will step up the voltage this high? Also, what else would be needed to make this thing work? Would I just connect the AC directly to the stator, or would something go between them?
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    On second thought, I didn't even take into consideration the fact that the standard 120v AC power supply in the US is single phase, and I would need a 2 or 3 phase power source to create a rotating magnetic field. Do you think a single phase stator could accomplish the same task of rotating an egg (if I give the egg a spin to start it)?

    Man, this is complicated...Now I am looking at having to get a voltage amplifier and potentially a phase converter.

    Am I missing anything?
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  10. #9  
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    But, of course, there are single phase induction motors. There are several ways this can be done.
    http://www.tpub.com/neets/book5/18d.htm
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  11. #10  
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    Indeed, this may be my best bet.

    On a side note, I received this spinning top in the mail today. Soon, I will open it up and take a look around (and perhaps I post a picture or two while I am at it) My hunch is that this is actually a single phase stator itself.
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  12. #11  
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    Sorry for the low quality picture. Basically, what you are looking at is the base (upside down), and the bottom flap folded open. So, it appears that this is indeed some sort of crude stator. Whatever it is, it is not strong enough to make an object spin unassisted. I discovered that the top is plastic, with at least one magnet on the inside. I did not have the correct screwdriver to take that apart, but it did make a paperclip stick to its base so I know for a fact one is in there.

    I tried to spin a non-magnet metallic objecton this base, but I do not think the field was strong enough to keep it spinning, or it wasn't the right kind of field. Anywho, if someone has something else to add, feel free. I see three wires that connect to the copper ring (just looped copper wiring), as well as three wires connected to the center coil...would this be used to produce a multiple phases?
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    Sorry for a long time with no response.

    I think it is the right kind of field as there is only one kind of magnetic field, magnetic.
    It cannot enter the spin unassisted because the object is bad shaped. If it was, for example, shaped like an egg it would first start to wobble around a bit and it would gain some momentum. After that it only uses the rotating magnetic field to keep it rotating.

    That is only mine opinion and feel free to correct me.

    ~Gogind
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  14. #13  
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    Looks like it's an adaptation of this:

    Faraday's Final Riddle; Does the Field Rotate with a Magnet?
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  15. #14  
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    I do not think this toy is a demonstration of the induction motor (rotating magnetic field). It appears to be more of a demonstration of the DC brushless motor. The top contains a radially oriented magnet. When the spinning top (magnet) moves across the center of the bass it induces a current in the coil which switches on a semiconductor device which momentarily powers up the electromagnet, giving the spinning top an extra boost. The energy that the top receives from this boost is much greater than the energy taken from it to switch the semiconductor device on. The switching of course occurs very rapidly (with each revolution).

    This is just my theory of how it works. If I find a source to verify it (or falsify it) I will link to it.
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  16. #15  
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    This looks like the patent for it:

    http://www.delphion.com/details?pn=US03783550__
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  17. #16  
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    hmm...looks like Ill have to make my own rotating magnetic field :?
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  18. #17  
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    Well, I'm back to this project (was side tracked). I am trying to formulate a plan to create something that will spin a stainless steel object. I really do not need this object to start spinning unassisted, so long as it will continue spinning once its in motion.

    So will a single phase stator work for my purposes (theoretically, of course)? If so, what sorts of appliances would have one of these already built into it that I could re-purpose (ceiling fan, blender, etc)?

    This link says that "A three phase motor may be run from a single phase power source. (Figure below) However, it will not self-start. It may be hand started in either direction, coming up to speed in a few seconds. It will only develop 2/3 of the 3-φ power rating because one winding is not used."

    If I understand this correctly, does that I mean I can connect a 3 (or 2) phase stator to a single phase power source (like an AC outlet), and it will still spin an object so long as it is started manually?

    These may sound like simple questions, but I am still trying to figure out if I actually understand the principles at play, or if I am just mistaken.
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