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Homework Help: Soda Can Project

  1. Apr 27, 2010 #1
    I have to make some type of mechanical device to put inside an empty soda can that will make it roll on its own (I can do something to the can before setting it down like winding it up or something, but I can't push it or anything). Nothing can extend beyond 5mm on either side of the can and nothing can be battery operated. I'm hoping to get the can to roll at least 15 or so meters, but so far I've only been able to get about 2 meters. Any ideas?
     
  2. jcsd
  3. Apr 28, 2010 #2
    Make A Soda Can Move On Its Own

    I have to make some type of mechanical device to put inside an empty soda can that will make it roll on its own (I can do something to the can before setting it down like winding it up or something, but I can't push it or anything). Nothing can extend beyond 5mm on either side of the can and nothing can be battery operated. I'm hoping to get the can to roll at least 15 or so meters, but so far I've only been able to get about 2 meters. Any ideas?
     
  4. Apr 29, 2010 #3
    Re: Make A Soda Can Move On Its Own

    Shooting from the hip here...
    what about filling it half with water laying it on it's side and freezing it. when you put it down, place it with the imbalance near the top.

    I'm sure there's a way to calculate the effect to determine a rough est. for volume and placement to get the momentum to move it far enough.
     
  5. Apr 29, 2010 #4

    Nabeshin

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    Re: Make A Soda Can Move On Its Own

    This should just lead to oscillations, no?
     
  6. Apr 29, 2010 #5
    Re: Make A Soda Can Move On Its Own

    I wondered that due to the small radius, I was simply going by off weighted tire rolling. the trick is going to be getting the right mass, hence why some calcs may be needed.
     
  7. Apr 29, 2010 #6
    Re: Make A Soda Can Move On Its Own

    oh man, should've seen this with the 5mm restriction. attach a rod thru the can and wind a string with a weight attached to it to the rod. the dropped weight will be a conservation of energy in the form of rotational motion from the moment of inertia.

    although that small drop distance is going to be limiting, the more turns the better so the smaller the rod the better.

    maybe It's not so simple.
     
  8. Apr 29, 2010 #7

    SpectraCat

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    Re: Make A Soda Can Move On Its Own

    I think you want something that will unwind slowly, driving a fairly large mass (say 50 g or so) around in a circle. Mount that on a rod through the center of the can, wind it up and let it go. Do you have to design the mechanism yourself, or can you steal something from an existing device? If it's the latter, then you can just take apart a wind up toy and use the mechanism in there ... even if you can't use it, you might want to do this to get an idea how they are constructed.

    Heck, if you can use an existing device, get one of the "walking" ones, and position it so that it is supported with its "feet" against the inside of the can, making it like a hamster ball.
     
  9. Apr 29, 2010 #8
    Re: Make A Soda Can Move On Its Own

    Rubber band ring going through the center attached to both ends, with a large nut fixed in the middle. Roll the can backwards to wind it up. Older than your grandfather...
     
  10. Apr 29, 2010 #9
    Re: Make A Soda Can Move On Its Own

    We'll there you go! I figured it was something simple.
     
  11. Apr 29, 2010 #10
    Re: Make A Soda Can Move On Its Own

    I've actually already tried the rubber band method. It doesn't get it to roll more than a meter or so. Is there anyway to increase the distance?
     
  12. Apr 29, 2010 #11

    DaveC426913

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    Re: Make A Soda Can Move On Its Own

    Does anyone know the lower limit on the size of an Alcubierre drive?


    :biggrin:
     
  13. Apr 30, 2010 #12
    I suppose a hamster is out of the question?

    Maybe you could fill it with pressurised gas and affix a small outlet nozzle on each circular face pointing normal to the radius, like a Catherine wheel. Failing that, Diet Coke & Mentos?
     
  14. May 1, 2010 #13
    I've thought of possibly using a gyroscope, but I'm not sure how to harness the spinning to make the can roll as well without inhibiting the gyroscope completely. Anyone know how to do that?
     
  15. May 2, 2010 #14
    Okay I've had another thought. Would it work to take the mechanism out of a wind up clock and somehow attach it to the can to make it roll? If so, how might I go about designing that?
     
  16. May 3, 2010 #15
    Can anyone help me? This is due tomorrow and I haven't been able to get the can to move more than a meter.
     
  17. May 3, 2010 #16

    DaveC426913

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    Your best bet is to experiment with the string and a heavy weight (such as a large bolt).

    Note that you want the rig the string double string (i.e. a half inch or so apart) forming a wide "axle", which will give it better leverage.

    Adapt this:

    http://illustrator.davesbrain.ca/images/pic_rollingcan.gif
     
    Last edited: May 3, 2010
  18. May 3, 2010 #17
    Should I use string, or elastics?
     
  19. May 3, 2010 #18

    DaveC426913

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    I dunno, which one works better?

    C'mon. We can't do the whole thing for you...
     
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