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Center of Gravity

Discussion in 'The Okie Corral' started by bocaboca, Apr 30, 2012.

  1. bocaboca

    bocaboca

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    I was balancing my r/c heli blades using a fulcrum to find the CG. Easy enough.. when the blade is level I'm on the CG. But, that's only going left and right..... isn't the TRUE CG when you find the balance point both left and right and front and back? shouldn't both points be at the same spot regardless of what your trying to balance.
     
  2. droidfire

    droidfire

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    In a perfect world, yes. Temperature can change this, uneven expansion, and the shape of the object itself can make it difficult to determine the balance point.

    I've been wanting a tiny entry-level rc heli for a while, it looks like a lot of fun but haven't been able to justify it in light of other things I need at the moment.

    My birthday is coming up, so i'm looking forward to getting one of these to play with then.
     

  3. GarySTL

    GarySTL NRA Life Member

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    Not at all. Wings/blades are an airfoil and are generally thicker about 1/3 of the way back from the leading edge. This moves the fore/aft CG towards the leading edge. Take a broken blade, I'm sure you have some, and cut a piece about 2-3" long. See where the fore/ aft balance point is.


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  4. GarySTL

    GarySTL NRA Life Member

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    To make my self clearer, the overall CG is at one place on the blade, but the fore/aft CG is not on the blade centerline.


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  5. EMTCOP

    EMTCOP

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    Get an MCPx!!!
     
  6. icantpick

    icantpick Señor Member

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    The CG is the CG, if it seems to be moving about, it's just an illusion.
     
  7. JimmyN

    JimmyN

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    It doesn't have to be, it doesn't rotate in that axis. You balance to eliminate vibration so the blades need to be equal weight on each side of the hub, but the hub doesn't spin top to bottom so CG in the top to bottom axis isn't important.

    Glue a lead washer to the top side of the hub. That would definitely move the CG to that side, but does it cause any vibration? Nope. Glue the lead washer to the bottom side of the hub, in fact add two washers and try it. Does it cause any vibration? Nope.

    If it's not rotating in that axis there is no need to balance it.