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Electric Generating Toy Top

  1. May 19, 2012 #1
    I'm a newbie here... so please be kind.

    I'm working on a physics toy that I thought the group here would enjoy - but I would really love some brain power to help me vet the idea out.

    I've written up the toy for the website Quirky and here is the gist of it:

    The LSX is the worlds longest spinning top. It is now sold only on-line, but I bought mine years ago when it was exclusively sold at FAO Schwartz. It is a specially designed wooden top that can be kept spinning indefinitely by manipulating the surface it is spinning on.
    More info about the top as well as a video of it's use can be found here

    This is an AMAZING toy - and if you don't have one, and you like toys like this - it is well worth the investment. There are plenty of youtube videos where you can see it in action if you want to get a better idea.

    There is another product on the market, that does not work as advertised. It is called the "Green Science Spinning Generator. This uses a poorly crafted top with magnets attached to generate a small amount of electricity when it is spun.
    More info can be found here

    Lets make a top similar to LSX, and add some small Neodymium Magnets to the outer edge.
    Lets take the playing surface board, and add a wire coil within the board (similar to Green Science Spinning Generator) so that as the top spins faster, we can generate some electricity. Perhaps this energy could be used to light up LED lights on the floor of the board itself. Perhaps there could be a series of LED's that start to light as more and more energy is generated (as the top spins faster and faster

    The neat thing here is that, unlike the Green Science product, by manipulating the board - the top can be spun for as long as the user desires - and the speed can also be controlled.

    This would be a very new take on a green/renewable energy/emergency flash light.

    My questions:
    1. Do you foresee any issues with the feasibility of the above?
    2. Do you think this would be able to power up some low energy led lights?
    3. What would it take to get enough out of this to use it as a recharging station for, lets say an iPod?

    Any other thoughts/guidance would be most appreciated.
    Many many thanks,

    Attached Files:

    Last edited: May 19, 2012
  2. jcsd
  3. May 20, 2012 #2
    I am not sure how to test the RMP of the LSX... any advice would be appreciated.
    But I have a feeling we should assume something from 3000-5000 rpm of the top when performing calculations. This is based on the published data on the Levitron which can rotate up to 3000rpm - and with the LSX you can accelerate the initial speed significantly as you play with the toy.

    There is an audible 'hum' when the top gets going... and I wonder if that pitch could be used to guestimate the actual rpm?
  4. May 20, 2012 #3


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    Ok. Welcome! :smile:
    Yes. The mating of a working toy with a non-working toy may yield a mule. If the "Green Science Spinning Generator" doesn't work, and your toy is of the same design, then it won't work either. Unless you improve on the design of course.
    Yes. But I would do it in a very dark room.
    A really big top.
    I ran the numbers for a top similar to the working toy and came up with a kinetic energy of ~1 joule, which is enough energy to power a 0.04 watt light bulb for 30 seconds. (assuming magical perfection)

    You might try building a "Multiple Generator" first and extrapolate what it would take for your spinning top to do the same thing. I would build it exactly as specified, and then add additional spacers to put distance between the coils and the magnets. Figure out how much separation you can achieve and still generate enough voltage to power the lights. Then figure out how many coils you would need to attach to your tilty board thingy to make it not suck like the "Green Science Spinning Generator". (It was sad reading the buyers comments. It really sucks when toys don't live up to their promises. Like ordering Sea Monkeys and getting brine shrimp instead. :grumpy: )

    spinning top energy analysis:
    I=2mr^2/5=0.4mr^2 (moment of inertia for a solid sphere)
    E=0.5I*ω^2 (kinetic rotational energy)
    ω is measured in radians per second
    How do you convert rev/min into rad/seconds?
    1 revolution = 2 pi radian
    1 minute = 60 seconds
    1 rev/min * (2 pi radian / 1 revolution ) * (1 min/60s) = rad/sec
    It works out to multiplying rev/min by pi/30 to get rad/sec
    top spins at 3000 rpm
    top weighs 100 grams = 0.1 kg
    radius of top is 0.025 meters
    m=0.1 kg
    ω=3000 * pi/30 = 100 pi = 314
    I = 0.4 * 0.1 kg * 0.025^2 = 0.4 * 0.1 kg * 0.000625 m^2 = 0.000025 kg m^2
    E = 0.5 * 0.000025 kg m^2 * 314^2 = 0.5 * 0.000025 kg m^2 * 98596 = 1.23245 joules
    1 watt = 1 joule / second
    Std led: 2 volts @ 0.02 amps = .04 watts
    1.23 joule / 0.04 watts = 30 seconds
  5. May 20, 2012 #4
    Can't thank you enough for those tips, formulas, and youtube suggestion.
    I'll keep you updated
  6. May 29, 2012 #5
    Another question...
    if the magnet is on the 'spindle' of the top - or the point that is rotating on the board - and it is spinning above the coil of wire- but not crossing the coil - i.e.: the spinning top is centered in the middle of the coil, and the magnet is on the point of the top - will this generate a change in flux to generate electricity?

    Thanks again,
  7. May 30, 2012 #6
    Isn't your idea similar to a powerball? It has a rotating wheel inside a case and it can be sped up by tilting the case back and forth. There are also models that come with a built in generator and LEDs.
    Last edited: May 30, 2012
  8. May 30, 2012 #7
    Thanks for the comment.
    Yes, a power ball with LED's is similar in that it also transfers angular acceleration of a gyro to generate electrical energy. Great point!
    However, this toy is actually a top - spinning on aboard - which has some slightly different nuances to achieve a solution.
    If you have not yet seen this top, take a look at the video here to better understand what I mean.

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