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Thread: can this sculpture work?

  1. #1 can this sculpture work? 
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  3. #2  
    Veracity Vigilante inow's Avatar
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    Maybe like this:
    http://www.youtube.com/watch?v=j0Qu8cibT9I


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  4. #3  
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    a better picture:



    quite similar but i think with this i could put the cog far the edge of the table
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  5. #4  
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    If the cog is below the table, it can be stable, otherwise it can't.

    Remember that the pulleys don't necessarily turn, it could just rotate as a rigid body, or something in between.
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  6. #5  
    . DrRocket's Avatar
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    Quote Originally Posted by Bender
    If the cog is below the table, it can be stable, otherwise it can't.

    Remember that the pulleys don't necessarily turn, it could just rotate as a rigid body, or something in between.
    Yep. The same basic idea has been used by kids to make "belt hangers" that hang from the molding over a door (open) for decades.

    It is noting more than a notched stick, with the notch cut so that the CG of the system, with a belt in the notch, is located so that the contraption is stable.

    For details see your local Cub Scout.
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  7. #6  
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    the thing is a realized this old idea:

    http://fantasticcontraption.co...ign?designId=8703393

    mixed with this also old idea:



    should work according physics

    edit:

    the concept less radical:

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  8. #7  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Anytime someone comes up with one of these balancing-systems-of-pulleys devices, the first thing they should consider is whether or not it'd simply fall over if it the pulleys were made immobile. If it would, then it still would if the pulleys were allowed to rotate.
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  9. #8  
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    yes as you can see in this drawing even with the pulley fixed it should be drawn into verticallity:
    [/img]
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  10. #9  
    Forum Ph.D. Leszek Luchowski's Avatar
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    To begin with, what is a rigid cable?

    Do you mean it's made of something that won't bend (I mean, not under the amount of force likely to occur in this context)? Like a thick steel rod?

    In this case, what looks like a pulley transmission is in fact one solid rigid body, and the whole device will just turn counterclockwise (in the picture) around its support, that is, the arm resting on the table, until it falls off or until its center of gravity is underneath that support. For the latter to happen, the upper arm would have to end in some sort of hook and not the straight sharp point I see in your picture.

    If the "rigid cable" is a normal string that doesn't stretch significantly but does bend, then the mass on the end of the lower arm will turn the lower pulley clockwise, making it "climb" a little up the right part of the string, and possibly putting some slack into the left part of the string.
    At the same time, the upper pulley and its arm will turn counterclockwise under their own weight _and_ the weight of all the stuff hanging on the string, until they fall off the table (unless, again, the upper arm has a hook).

    I think I know what you are trying to do. You want both pulleys to turn clockwise, so they "climb" upwards as the upper arm is brought to stand on the table. Is this what you want? OK, but, to do that, you need a kind of chassis, at least one beam holding the two axles at a fixed distance from each other, _and_ some way of keeping that beam vertical.

    Good luck, and keep us posted.
    Leszek. Pronounced [LEH-sheck]. The wondering Slav.
    History teaches us that we don't learn from history.
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  11. #10  
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    yeah thanks for the feedback a beam uniting the two pulleys could work

    the thing is that if it starts static from verticallity it will just fall with all in line so this is the idea to solve that problem give it some initial inertia as this:

    http://fantasticcontraption.co...ign?designId=8703393


    the problem with this design is that to achieve resonance with exactitude is imposible cause a microsecond delay would amplify over time

    but with the pulley connection i ensure not only perfct resonance buat also an amplification of the rising cog as it leans

    i tried to simulate this with phun phiscis simulator but is not valid since its string is elastic so both pulleys dont match

    but well i had abandoned this project as imposible but seeing my dad thinks he solved fermats theorem i think i solved the stable inverted pendulum problem and unless shown a flaw im on building it
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  12. #11  
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    Your dad is a bit late

    About your system with initial inertia: it would just tip over as a whole, moving or not.

    If you make it active (as you seem to be doing since you talk about resonance), you are making it needlessly complicated, as a simple inverted pendulum is a common example/exercise in basic control courses. You can even do it with two pendulums:
    http://www.youtube.com/watch?v=8HDDzKxNMEY
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